JP7547741B2 - Water heating system - Google Patents

Description

The present invention relates to a water heating system.

In recent years, factories and other business establishments have been working to utilize unused heat discarded from various facilities in order to reduce emissions of carbon dioxide, a greenhouse gas. As such, as shown in Patent Documents 1 and 2, an unused heat utilization system (feedwater heating system) has been proposed that heats boiler feedwater using a heat pump circuit that uses waste hot water as a heat source, thereby reducing the amount of fuel used by the boiler.

JP 2013-210118 A JP 2014-169819 A

The feedwater heating systems described in Patent Documents 1 and 2 can be applied not only to heating boiler feedwater but also to heating water in various production processes. The system according to Patent Document 1 is configured to circulate a heat source fluid (waste hot water) through an evaporator and a heat recovery heat exchanger in that order, and to circulate feedwater (cold water) through a heat recovery heat exchanger, a subcooler, and a condenser in that order. With this configuration, the system according to Patent Document 1 has succeeded in significantly increasing the COP (coefficient of performance: energy consumption efficiency) compared to conventional heat pump systems without a heat recovery heat exchanger and a subcooler. On the other hand, this system has a problem that the heat recovery heat exchanger becomes ineffective when the temperature of the heat source fluid becomes relatively low (for example, 40°C or lower).
In contrast, the system disclosed in Patent Document 2 is configured to circulate the heat source fluid (waste hot water) through the heat recovery heat exchanger and then the evaporator. With this configuration, in the system disclosed in Patent Document 2, if the temperature of the heat source fluid is higher than the feed water, the effectiveness of the heat recovery heat exchanger can be maximized. Although the system disclosed in Patent Document 2 enables heat recovery with a high COP for heat source fluids in a wide temperature range, further efficiency improvement is desired for business establishments that have set high carbon dioxide emission reduction targets.

The present invention was made in consideration of the above problems, and aims to achieve even greater efficiency in a water heating system that uses both a heat pump circuit and a heat recovery heat exchanger.

The present invention relates to a vapor compression heat pump circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in a ring shape by a refrigerant circulation line, and in which heat is extracted by the condenser when the compressor is driven; a heat recovery heat exchanger; a heat source fluid line for circulating a heat source fluid through the heat recovery heat exchanger and the evaporator in that order; a water supply line for circulating water through the heat recovery heat exchanger and the condenser in that order; and a water supply flow rate adjustment means provided on the water supply line, the water supply pump having a rotation speed controllable by an inverter; a flow rate control valve capable of proportional control, a suction temperature sensor that detects the suction temperature of the gas refrigerant flowing into the compressor, a steam pressure sensor that detects the steam pressure of the gas refrigerant flowing out of the evaporator, a hot water outlet temperature sensor that detects the outlet temperature of the feed water flowing out of the condenser, and control means for controlling the expansion valve and the feed water flow rate adjustment means, wherein the control means adjusts the valve opening of the expansion valve by feedback control while the compressor is operating, and adjusts the drive frequency of the feed water pump or the valve opening of the flow rate adjustment valve. a feedback control of the opening degree of the expansion valve, the evaporation temperature of the liquid refrigerant is obtained from the pressure detected by the steam pressure sensor, and the evaporation temperature is subtracted from the temperature detected by the suction temperature sensor to calculate the degree of superheat of the gas refrigerant as a feedback value, and an operation amount of the expansion valve is calculated by a PID calculation algorithm so that this calculated degree of superheat becomes a target degree of superheat; and a feedback control of the drive frequency of the feedwater pump or the opening degree of the flow control valve, the temperature detected by the outlet hot water temperature sensor is used as a feedback value, and an operation amount of the feedwater pump or the flow control valve is calculated by a PID calculation algorithm so that this detected temperature becomes a target outlet hot water temperature, the target outlet hot water temperature can be set between an upper limit value and a lower limit value, and the lower limit value is a value obtained by adding a predetermined value to the temperature of the feedwater after flowing out of the heat recovery heat exchanger and before flowing into the condenser, so that the refrigerant flowing out of the condenser becomes a supercooled liquid state.

It is also preferable that the heat source fluid line is configured to perform heat exchange between the heat source fluid and the feed water in a counterflow manner in the heat recovery heat exchanger, and then perform heat exchange between the heat source fluid and the liquid refrigerant in a counterflow manner in the evaporator.

It is also preferable that a heat source temperature sensor is provided to detect the temperature of the heat source fluid before it flows into the evaporator, and the control means sets the target degree of superheat according to the temperature detected by the heat source temperature sensor.

Furthermore, when the control means determines that the fluctuation in the temperature detected by the heat source temperature sensor is large, it is preferable to increase the target degree of superheat.

Furthermore, it is preferable that the control means reduces the target degree of superheat when it determines that the temperature detected by the heat source temperature sensor is stable.

It is also preferable to provide one or two bypass lines for bypassing the feed water to the heat recovery heat exchanger and/or bypassing the heat source fluid to the heat recovery heat exchanger, and a preheating mode switching means for switching between a feed water preheating mode in which the feed water and the heat source fluid are circulated simultaneously to the heat recovery heat exchanger, and a preheating stop mode in which at least one of the feed water and the heat source fluid is circulated through the bypass line.

It is also preferable that the system includes a pre-heat exchanger feed water temperature sensor that detects the temperature of the feed water before it flows into the heat exchanger for heat recovery, and a pre-heat exchanger heat source temperature sensor that detects the temperature of the heat source fluid before it flows into the heat exchanger for heat recovery, and the control means compares a first detection temperature by the pre-heat exchanger feed water temperature sensor with a second detection temperature by the pre-heat exchanger heat source temperature sensor, and controls the pre-heat mode switching means to execute the feed water pre-heat mode when the first detection temperature is lower than the second detection temperature, and controls the pre-heat mode switching means to execute the pre-heat stop mode when the first detection temperature is higher than the second detection temperature.

It is also preferable that the control means has a signal input unit that receives a preheat mode designation signal that designates the type of the water supply preheat mode or the preheat stop mode, and a preheat mode switching control unit that controls the preheat mode switching means to execute the water supply preheat mode or the preheat stop mode in accordance with the preheat mode designation signal input to the signal input unit.

According to the present invention, it is possible to achieve even higher efficiency in a water heating system that uses a heat pump circuit and a heat recovery heat exchanger in combination.

1 is a diagram showing a schematic diagram of a water heating system according to one embodiment of the present invention; FIG. 2 is a block diagram showing a control unit of the embodiment. 11 is a graph showing fluctuations in temperature detected by a heat source temperature sensor. FIG. 11 is a diagram showing a settable range of target outlet heated water temperature in the embodiment. FIG. 2 is a Mollier diagram for explaining a heat pump cycle. FIG. 11 is a state transition diagram of the water flow mode switching control in the embodiment. 5 is a flowchart showing a flow of a process for setting a target degree of superheat in the embodiment. 5 is a flowchart showing a flow of preheating mode switching control in the embodiment. FIG. 10 is a diagram showing a schematic diagram of a supply water heating system according to a modified example of the above embodiment.

A preferred embodiment of the water heating system 1 of the present invention will be described below with reference to the drawings. Note that in this specification, "line" is a general term for a line, such as a flow path, a pathway, or a pipe, through which a fluid can flow.

Figure 1 is a diagram showing a schematic configuration of a water heating system 1 according to this embodiment. As shown in Figure 1, the water heating system 1 is a system that supplies water W1 heated by a heat recovery heat exchanger 40 and a heat pump circuit 10 as hot water W2 to a hot water demand point.

More specifically, the water supply heating system 1 of this embodiment includes a make-up water tank 70 for storing make-up water W used as water supply W1, a heat recovery heat exchanger 40 and a heat pump circuit 10 for heating the water supply W1, a hot water tank 60 for storing the heated water supply W1 as hot water W2, and a heat source water tank 50 for storing heat source water W5 as a heat source fluid.
In addition, the water supply heating system 1 of this embodiment is equipped with a water supply line L1 that circulates the water supply W1 through the heat recovery heat exchanger 40 and the condenser 12 of the heat pump circuit 10 in that order, a return line L2 that circulates the hot water W2 in the hot water tank 60 upstream of the heat recovery heat exchanger 40, a bypass line L3 that bypasses the water supply W1 from the heat recovery heat exchanger 40, a hot water supply line L4 for supplying the hot water W2 in the hot water tank 60 to a hot water demand point, and a heat source fluid line L5 that circulates the heat source water W5 as a heat source fluid through the heat recovery heat exchanger 40 and the evaporator 14 of the heat pump circuit 10.

The make-up water tank 70 is a tank that stores make-up water W used as the supply water W1 to be heated by the heat recovery heat exchanger 40 and the heat pump circuit 10, and is connected to a water supply line L1.

The heat recovery heat exchanger 40 is an indirect heat exchanger that performs indirect heat exchange between the feed water W1 flowing through the water supply line L1 and the heat source water W5 flowing through the heat source fluid line L5. More specifically, the heat recovery heat exchanger 40 performs heat exchange between the feed water W1 before passing through the condenser 12 of the heat pump circuit 10 and the heat source water W5 before passing through the evaporator 14 of the heat pump circuit 10.
The supply water W1 in the water supply line L1 passes through the heat recovery heat exchanger 40 and the condenser 12 in this order, and the heat source water W5 in the heat source fluid line L5 passes through the heat recovery heat exchanger 40 and the evaporator 14 in this order.

The heat pump circuit 10 is a vapor compression type heat pump circuit in which a compressor 11, a condenser 12, an expansion valve 13, and an evaporator 14 are connected in a circular manner by a refrigerant circulation line L9, and heat is extracted by the condenser 12 when the compressor 11 is driven. A refrigerant R flows through this refrigerant circulation line L9.
The compressor 11 has an electric motor 15 as a drive source, and compresses gaseous refrigerant R such as fluorocarbon gas into high-temperature, high-pressure refrigerant R. The condenser 12 condenses and liquefies the refrigerant R from the compressor 11 by dissipating heat to feed water W1 sent through a water supply line L1. The expansion valve 13 passes the refrigerant R sent from the condenser 12, thereby reducing the pressure and temperature of the refrigerant R. The evaporator 14 absorbs heat from heat source water W5 sent through a heat source fluid line L5, and evaporates the refrigerant R sent from the expansion valve 13.
In this way, in the heat pump circuit 10, the refrigerant R absorbs heat from the outside and vaporizes in the evaporator 14, while the refrigerant R radiates heat to the outside and condenses in the condenser 12. Using this principle, the heat pump circuit 10 pumps heat from the heat source water W5 in the evaporator 14, and heats the supply water W1 in the water supply line L1 in the condenser 12.

The refrigerant circulation line L9 of the heat pump circuit is provided with an intake temperature sensor 17 that detects the intake temperature of the gas refrigerant R flowing into the compressor 11, and a vapor pressure sensor 18 that detects the vapor pressure of the gas refrigerant R flowing out of the evaporator 14.

Here, the expansion valve 13 constitutes a refrigerant flow rate adjustment means that adjusts the flow rate of the refrigerant R flowing through the refrigerant circulation line L9 of the heat pump circuit 10. Specifically, the expansion valve 13 is configured as a proportional control needle valve, and the flow rate of the refrigerant R can be adjusted by changing the stroke of the needle valve through control of the rotation speed of the driving stepping motor and adjusting the valve opening.

The hot water tank 60 is a tank that stores the supply water W1 heated by the heat recovery heat exchanger 40 and the heat pump circuit 10 as hot water W2.
The hot water W2 stored in the hot water tank 60 can be circulated and heated. Specifically, the hot water W2 in the hot water tank 60 can be merged with the water supply line L1 through the return line L2, passed through the heat recovery heat exchanger 40 and the condenser 12 again through the water supply line L1, where it is heated, and returned to the hot water tank 60.
The hot water tank 60 is provided with a hot water temperature sensor 61 that detects the temperature of the hot water W2 in the hot water tank 60. The hot water tank 60 is also provided with a water level detector 62 that detects the water level in the hot water tank 60. In this embodiment, the water level detector 62 is configured with an electrode-type water level detector that includes a plurality of electrodes. Specifically, two electrodes 621 and 622 of different lengths are inserted and held with their lower ends at different height positions. In this embodiment, the electrodes 621 and 622 are inserted into the hot water tank 60 with their lower ends lowered in height position in order. Each of the electrodes 621 and 622 detects the presence or absence of the water level at its lower end depending on whether its lower end is immersed in water or not.
In this embodiment, the control unit 100 performs switching control of the water flow mode, which will be described later, using the detection results of the hot water temperature sensor 61 and the water level detection unit 62. The content of this control will be described in detail later.

The heat source water tank 50 stores heat source water W5 as a heat source fluid for the heat pump circuit 10. For example, waste hot water from a factory is used as the heat source water W5. The heat source water tank 50 is provided with an overflow line (not shown) that allows a predetermined amount of heat source water to overflow. The heat source water tank 50 is also provided with a water level detection unit (not shown) for monitoring whether the heat source water has fallen below a predetermined low water level.

The water supply line L1 is connected to the make-up water tank 70 on its upstream side and to the hot water tank 60 on its downstream side. In the water supply line L1, from the upstream side, a water supply pump 21, a first check valve 23, a first water supply temperature sensor 24, a three-way valve 25 arranged at the bypass line branch, a heat recovery heat exchanger 40, a second water supply temperature sensor 26, a condenser 12, and an outlet hot water temperature sensor 27 are arranged in this order.

The rotation speed of the water supply pump 21 can be controlled by an inverter. By changing the rotation speed of the water supply pump 21, the flow rate of water supply to the hot water tank 60 via the water supply line L1 can be adjusted in the case of a one-time water flow mode described below. In other words, the water supply pump 21 constitutes a water supply flow rate adjustment means in the one-time water flow mode.
The first check valve 23 is provided upstream of a junction with a return line L2 (described later) to prevent the hot water W2 from flowing into the make-up water tank 70 in a circulating water flow mode (described later).
The first feed water temperature sensor 24 is a pre-heat exchanger feed water temperature sensor that detects the temperature of the feed water W1 before it flows into the heat recovery heat exchanger 40. This first feed water temperature sensor 24 is provided upstream of the branching portion of the bypass line L3.
The three-way valve 25 is disposed at a branching portion of the bypass line L3. The three-way valve 25 is a means for switching whether or not the feed water W1 is to be bypassed from the heat recovery heat exchanger 40, and constitutes a preheating mode switching means. The bypass line L3 is a bypass line for bypassing the feed water W1 from the heat recovery heat exchanger 40.
The second feed water temperature sensor 26 is a feed water temperature sensor that detects the temperature of the feed water W1 before it flows into the condenser 12 of the heat pump circuit 10. The second feed water temperature sensor 26 is disposed upstream of the condenser 12, and in this embodiment, is disposed downstream of the heat recovery heat exchanger 40.
The outlet hot water temperature sensor 27 detects the outlet hot water temperature of the heated supply water W<b>1 flowing out from the condenser 12 .

The upstream side of the return line L2 is connected to the hot water tank 60, and the downstream side is connected to the water supply line L1. In addition, the return line L2 is sequentially arranged with a return pump 31 (circulation pump 31) and a second check valve 33 from the upstream side.

The rotation speed of the reflux pump 31 can be controlled by an inverter. By changing the rotation speed of the reflux pump 31, in the case of a circulating water flow mode described below, it is possible to adjust the flow rate of the supply water circulating to return to the hot water tank 60 via the reflux line L2 and the water supply line L1. In other words, the reflux pump 31 constitutes a supply water flow rate adjustment means in the circulating water flow mode.
The second check valve 33 is provided in the return line L2 upstream of the junction of the water supply line L1 and the return line L2 to prevent the make-up water W from the make-up water tank 70 from flowing into the hot water tank 60 in a one-pass water mode described below.

By providing such a water supply line L1 and a reflux line L2, when the water supply pump 21 is operated with the reflux pump 31 stopped, the make-up water W from the make-up water tank 70 can be supplied as supply water W1 to the hot water tank 60 while being heated by passing it through the heat recovery heat exchanger 40 and the condenser 12 in that order. This is called a one-time water flow mode. On the other hand, when the water supply pump 21 is stopped and the reflux pump 31 is operated, the hot water W2 in the hot water tank 60 can be returned as supply water W1 to the heat recovery heat exchanger 40 and the condenser 12 in that order while being reheated, thereby circulating the water stored in the hot water tank 60. This is called a circulation water flow mode. In addition, when both the water supply pump 21 and the reflux pump 31 are stopped, the water flow to the heat recovery heat exchanger 40 and the condenser 12 can be stopped. This is called a water flow stop mode.

That is, in this embodiment, the water supply pump 21 and the reflux pump 31 constitute a water flow mode switching means that switches between a pass-through water flow mode in which water is passed through the condenser 12 without passing hot water W2 through the reflux line L2, a circulating water flow mode in which water is passed through the condenser 12 while passing hot water W2 through the reflux line L2, and a water flow stop mode in which water flow to the condenser 12 is stopped.

The hot water W2 in the hot water tank 60 is then supplied to hot water demand points via a hot water supply line L4.
The hot water supply line L4 is provided with a hot water supply pump 63. An example of a hot water demand point is the use of water supply for a steam boiler. However, the use of the hot water W2 is not limited to a steam boiler. For example, the hot water W2 produced by the water supply heating system 1 of this embodiment may be used for container washing for food, beverages, and medicines, pasteurizer sterilization (sterilization of bottled goods), etc. In this case, the supply of hot water W2 in a high temperature range of about 60°C to 80°C may be required at all times. According to the water supply heating system 1 of this embodiment, in applications where the supply of hot water at a temperature always within a predetermined temperature range is required, for example, in a system in which only the heated water supply W1 is supplied into the hot water tank 60 (a system in which unheated make-up water is not directly supplied into the hot water tank 60), the hot water can be efficiently heated and supplied while maintaining its temperature.

In the heat source fluid line L5, a heat source supply pump 53, a first heat source temperature sensor 54, a heat recovery heat exchanger 40, a second heat source temperature sensor 55, and an evaporator 14 are arranged in this order from the upstream side.
By operating the heat source supply pump 53, the heat source water W5 from the heat source water tank 50 can be circulated through the heat recovery heat exchanger 40 and the evaporator 14 in that order.
The first heat source temperature sensor 54 is a pre-heat exchanger heat source temperature sensor that detects the temperature of the heat source water W5 before it flows into the heat recovery heat exchanger. In this embodiment, the first heat source temperature sensor 54 is provided in the heat source fluid line L5, but this sensor may be provided in the heat source water tank 50.
The second heat source temperature sensor 55 is a heat source temperature sensor that detects the temperature of the heat source fluid that exchanges heat with the refrigerant R in the evaporator 14. In this embodiment, the second heat source temperature sensor 55 detects the temperature of the heat source water W5 before it flows into the evaporator 14. The second heat source temperature sensor 55 is disposed upstream of the evaporator 14, and in this embodiment, it is disposed downstream of the heat recovery heat exchanger 40.

As described above, the heat source fluid line L5 has a connection configuration in which the heat source water W5 flows through the heat recovery heat exchanger 40 and the evaporator 14 in that order.
In this way, by first flowing the heat source water W5 into the heat recovery heat exchanger 40, the amount of preheating of the feed water W1 can be increased, and the heat output of the heat recovery heat exchanger 40 can be increased. Note that the higher the temperature of the heat source water W5, the greater the effect of increasing the heat output.

In addition, as shown in Figure 1, the heat source fluid line L5 is configured so that the heat source water W5 and the feed water W1 are heat exchanged in a counterflow manner in the heat recovery heat exchanger 40, and then the heat source water W5 and the liquid refrigerant R are heat exchanged in a counterflow manner in the evaporator 14.
In this way, by flowing the heat source water W5 through the heat recovery heat exchanger 40 and the evaporator 14 in that order, and flowing it in a counterflow to the flow direction of the supply water W1 in each of the heat recovery heat exchanger 40 and the evaporator 14, the amount of heat recovery can be maximized.

Next, the control unit 100 of the water supply heating system 1 of this embodiment will be described. FIG. 2 is a block diagram of the control unit 100 as a control means of the water supply heating system 1 of this embodiment. The control unit 100 includes a target degree of superheat setting unit 111, a degree of superheat calculation unit 112, a refrigerant flow control unit 113, a target hot water outlet temperature settable range determination unit 121, a target hot water outlet temperature setting unit 122, a water supply flow control unit 123, a water flow mode switching control unit 130, a preheat mode switching control unit 140, a signal input unit 150, and a memory unit 160.

The target superheat setting unit 111 acquires the temperature of the heat source water W5 as the heat source fluid detected by the second heat source temperature sensor 55 as the heat source temperature sensor, and sets the target superheat degree according to the temperature detected by the second heat source temperature sensor 55. For example, when the temperature of the heat source water W5 as the heat source fluid is low, the target superheat degree is set low. This increases the circulation flow rate of the refrigerant R, and the amount of heat recovered can be increased even for the low-temperature heat source water W5.
In this way, by setting an appropriate target degree of superheat according to the temperature of the heat source water W5 as the heat source fluid, it is possible to increase the amount of heat recovered in the evaporator 14 while preventing damage to the compressor 11 due to liquid compression or poor lubrication.

Furthermore, when it is determined that the fluctuation in the temperature detected by the second heat source temperature sensor 55 is large, the target superheat degree setting unit 111 may perform control to increase the target superheat degree.
FIG. 3 is a graph showing the fluctuation of the detected temperature of the second heat source temperature sensor 55, with the vertical axis representing the detected temperature T of the second heat source temperature sensor 55 and the horizontal axis representing time t. For example, as shown in FIG. 3, when the change amount ΔT of the detected temperature T of the second heat source temperature sensor 55 per unit time t0 exceeds a predetermined threshold value ΔT0, it is determined that the fluctuation of the detected temperature of the second heat source temperature sensor 55 is large, and control is performed to increase the target degree of superheat. For example, when ΔT0=5°C and t0=1 min, and there is a fluctuation greater than 5°C/min, control is performed to increase the target degree of superheat. At this time, for example, if the target degree of superheat up to that point was set to 5°C, the target degree of superheat is set to, for example, 10°C. In the example of FIG. 3, the decrease amount ΔT of the detected temperature T per unit time t0 is greater than the predetermined threshold value ΔT0. Therefore, since it is considered that the temperature of the heat source water W5 changes suddenly, the target degree of superheat is changed to, for example, 10°C.

This makes it possible to stably operate the heat pump circuit 10 even when a situation is confirmed in which the temperature of the heat source water W5 serving as the heat source fluid changes suddenly.
For example, even in the case where the temperature of the heat source water W5 drops suddenly due to a sudden change in the temperature, the refrigerant R can be reliably vaporized in the evaporator 14 by setting the target superheat degree to a high value, thereby preventing damage to the compressor 11 due to liquid compression.

Furthermore, when it is determined that the temperature detected by the second heat source temperature sensor 55 is stable, the target superheat degree setting unit 111 may perform control to reduce the target superheat degree.
For example, when the detected temperature T of the second heat source temperature sensor 55 is within a predetermined temperature range for a predetermined time, it is determined that the detected temperature of the second heat source temperature sensor 55 is stable. Also, when the change amount ΔT of the detected temperature T per unit time t0 is below a predetermined threshold value ΔT0 for a predetermined time, it may be determined that the detected temperature of the second heat source temperature sensor 55 is stable. At this time, control is performed to reduce the target degree of superheat. For example, if the target degree of superheat was set to 10°C, the target degree of superheat is changed to, for example, 5°C.

In addition, by setting the lower limit of the target degree of superheat to, for example, 5°C, damage to the compressor 11 due to liquid compression can be prevented. In addition, by setting the upper limit of the target degree of superheat to, for example, 10°C, the circulation flow rate of the refrigerant R can be maintained at or above a predetermined flow rate, and a decrease in the amount of heat recovery can be prevented.

In this way, when the temperature of the heat source water W5 as the heat source fluid is stable, the target degree of superheat can be set to a low value to increase the circulation flow rate of the refrigerant R and increase the amount of heat recovered in the evaporator 14.

In this embodiment, the detection temperature of the second heat source temperature sensor 55 is used as the heat source temperature sensor to set the target degree of superheat, but the first heat source temperature sensor 54 may be used as the heat source temperature sensor that detects the temperature of the heat source water W5 before it flows into the evaporator 14 (heat source temperature before it flows into the evaporator). Although not immediately before it flows into the evaporator 14, the first heat source temperature sensor 54 can also indirectly detect the temperature of the heat source fluid that exchanges heat with the refrigerant R in the evaporator 14, and can confirm a situation in which the temperature of the heat source water W5 changes suddenly. However, it is more preferable to use the second heat source temperature sensor 55 to measure the temperature of the heat source water W5 immediately before it flows into the evaporator 14.

The superheat degree calculation unit 112 calculates the degree of superheat of the refrigerant R flowing into the compressor 11 .
Specifically, the superheat degree calculation unit 112 obtains the evaporation temperature of the liquid refrigerant R from the pressure detected by the vapor pressure sensor 18, and calculates the degree of superheat of the gas refrigerant R by subtracting the evaporation temperature from the temperature detected by the suction temperature sensor 17.

The refrigerant flow rate control unit 113 controls the refrigerant flow rate control means so that the calculated superheat degree (the value calculated by the superheat degree calculation unit 112) becomes the target superheat degree (the value set by the target superheat degree setting unit 111), and adjusts the flow rate of the refrigerant R.
As a specific example of control, it is preferable to employ feedback control in which the calculated degree of superheat calculated in real time by the superheat degree calculation unit 112 is used as a feedback value, and the valve opening degree of the expansion valve 13 is adjusted so that the calculated degree of superheat converges to a target degree of superheat. In addition to proportional control (P control), the feedback control may employ a calculation algorithm for the manipulated variable that combines proportional control with integral control (I control) and/or differential control (D control).

In this way, the superheat degree calculation unit 112 accurately calculates the superheat degree of the gas refrigerant R, and the refrigerant flow rate control unit 113 controls the value to be kept constant, thereby stabilizing the heat output of the condenser 12 to the feed water W1. This reduces fluctuations in the flow rate of the feed water W1 that is heated and supplied as hot water.

The target hot water outlet temperature settable range determination unit 121 obtains the temperature of the supply water W1 before it flows into the condenser 12, detected by the second supply water temperature sensor 26 acting as a supply water temperature sensor, and determines the settable range of the target hot water outlet temperature according to the temperature detected by this second supply water temperature sensor 26.

Fig. 4 is a diagram showing the settable range of the target hot water outlet temperature, which is determined according to the temperature detected by the second supply water temperature sensor 26. The horizontal axis of Fig. 4 is the temperature detected by the second supply water temperature sensor 26 (the supply water temperature before flowing into the condenser), and the vertical axis is the corresponding target hot water outlet temperature.
In this embodiment, the settable range of the target outlet water temperature is the triangular area shown in settable range A. That is, in this embodiment, the target outlet water temperature can be set to a value between an upper limit value and a lower limit value, and the lower limit value is a value obtained by adding a predetermined value to the temperature detected by second feed water temperature sensor 26, and the lower limit value increases as the temperature detected by second feed water temperature sensor 26 increases. More specifically, the lower limit value is a value obtained by adding 15°C to the temperature detected by second feed water temperature sensor 26, and the upper limit value is a fixed temperature, 75°C in this embodiment.

The predetermined value (e.g., 15°C) for setting the lower limit is stored in the storage unit 160 described below. In this case, it is preferable to make it possible to set this predetermined value by external input or the like. Alternatively, a lower limit based on this predetermined value may be stored in the storage unit 160.

In this way, by setting the target hot water outlet temperature to the region shown in settable range A, the system is controlled so that the temperature difference between the water supply W1 on the inlet side and the outlet side of the condenser 12 is sufficiently large, preventing insufficient supercooling of the refrigerant R flowing through the heat pump circuit 10 and suppressing excessive water supply flow rate of the water supply W1 in the control of the water supply flow rate adjustment means by the water supply flow rate control unit 123 described below.

Even if the settable range of the target hot water outlet temperature is a rectangular region with both the upper and lower limit values set to constant values, i.e., even if the lower limit value is constant, if the settable range is set to a region such as that shown in settable range B in FIG. 4, it is possible to prevent insufficient supercooling of the refrigerant R and suppress excessive water supply flow rate of the water supply W1. However, in this case, the range of allowable heat source water temperatures and the settable range of the target hot water outlet temperature are narrowed.

If the target hot water outlet temperature is set to a temperature lower than the lower limit value indicated in the settable range A, for example, if it is not significantly different from the temperature detected by the second water supply temperature sensor 26, there is a possibility that the refrigerant R will not be supercooled enough.

This will be explained using the Mollier diagram (ph diagram) shown in FIG.
The vertical axis of this Mollier diagram is the pressure (p) of the refrigerant, and the horizontal axis is the specific enthalpy (h) of the refrigerant. The Mollier diagram also shows a saturated liquid line Y1 and a saturated vapor line Y2. Such a Mollier diagram can represent the state change of the refrigerant R during the heat pump cycle. The refrigerant R is in a supercooled liquid state (liquid refrigerant R state) to the left of the saturated liquid line Y1, a wet vapor state that is a gas-liquid mixed state between the saturated liquid line Y1 and the saturated vapor line Y2, and a superheated vapor state (gas refrigerant R state) to the right of the saturated vapor line Y2.

In FIG. 5, the solid lines indicated by R (a→b→c→d) indicate the transition of the state of the refrigerant R in a heat pump cycle in an appropriate state.
The gas refrigerant R in a superheated vapor state drawn into the compressor 11 is adiabatically compressed in the compressor 11 to become a gas refrigerant R in a high-temperature, high-pressure superheated vapor state (a→b), then condensed and supercooled in the condenser 12 to become a liquid refrigerant R in a supercooled liquid state (b→c), and then adiabatically expanded in the expansion valve 13 to become a refrigerant R in a wet vapor state (c→d). The refrigerant R in the wet vapor state is then evaporated and heated in the evaporator 14 to become a gas refrigerant R in a superheated vapor state (d→a). The refrigerant R circulates in this cycle. The process (b→c) in FIG. 5 will be described in detail below. The condenser 12 releases the latent heat and sensible heat of the gas refrigerant R to change the gas refrigerant R to a liquid refrigerant R and to supercool the liquid refrigerant R.

Here, if the target hot water outlet temperature is set to a temperature lower than the lower limit value indicated in the settable range A, the temperature difference between the inlet and outlet sides of the water supply W1 of the condenser 12 will be small, and the refrigerant R may not be sufficiently condensed or supercooled in the condenser 12 (b → c'). As a result, the position of "c'" indicating the state of the refrigerant R after passing through the condenser 12 will shift to the right compared to the proper case. That is, the refrigerant R in the "c'" state is insufficiently supercooled. It may also be that the refrigerant R is not sufficiently in a liquid state. In this case, it cannot be said that the heat pump cycle is operating properly.
However, in this embodiment, the lower limit is set to a value obtained by adding a predetermined value to the temperature detected by the second feed water temperature sensor 26, so that the system is controlled so that the temperature difference between the feed water W1 on the inlet side and the outlet side of the condenser 12 is at least greater than a predetermined value, and the above problem does not occur. In other words, the heat pump cycle can be operated in an appropriate state.

The target outlet hot water temperature setting unit 122 sets a target outlet hot water temperature within the above-mentioned settable range of the target outlet hot water temperature according to the temperature detected by the second supply water temperature sensor 26. For example, an arbitrary target outlet hot water temperature can be set within the above-mentioned settable range A based on the requirements of the hot water demand location, etc.
That is, target outlet hot water temperature setting unit 122 acquires the temperature detected by second supply water temperature sensor 26, and can set the target outlet hot water temperature by adding a predetermined value to the acquired temperature detected by second supply water temperature sensor 26, with a higher lower limit value being set as the temperature detected by second supply water temperature sensor 26 increases. This makes it possible to operate the heat pump cycle in an appropriate state, and also makes it possible to widen the setting range for the target outlet hot water temperature.

In addition, the target hot water outlet temperature may be automatically set to a value obtained by adding a predetermined value to the temperature detected by the second water supply temperature sensor 26.

The water supply flow rate control unit 123 controls the water supply flow rate adjustment means so that the temperature detected by the outlet water temperature sensor 27 becomes the target outlet water temperature (the value set by the target outlet water temperature setting unit 122), and adjusts the flow rate of the water supply W1.
As a specific example of control, it is preferable to employ feedback control in which the outlet hot water temperature detected in real time by outlet hot water temperature sensor 27 is used as a feedback value, and the drive frequency of water supply pump 21 or reflux pump 31 is adjusted so that this outlet hot water temperature converges to a target outlet hot water temperature. In addition to proportional control (P control), the feedback control can employ a calculation algorithm for the manipulated variable that combines this with integral control (I control) and/or differential control (D control).

In the one-pass water flow mode described below, the inverter-controllable water supply pump 21 constitutes the water supply flow rate adjustment means, and in the circulating water flow mode, the inverter-controllable return pump 31 constitutes the water supply flow rate adjustment means.

The water supply flow rate adjusting means may be configured in other ways. For example, when the water supply pump 21 and the return pump 31 are configured as pumps that can only be turned on and off, proportionally controllable flow rate adjusting valves may be provided downstream of each pump, and these may serve as the water supply flow rate adjusting means. Alternatively, a proportionally controllable flow rate adjusting valve may be provided downstream of the junction of the water supply line L1 and the return line L2, and this may serve as the water supply flow rate adjusting means.
As an alternative to the supply water pump 21 and the return pump 31, an on-off valve may be provided in the supply water line L1 and the return water line L2, or a three-way valve may be provided at the junction of the supply water line L1 and the return water line L2, and an inverter-controlled pump may be provided downstream of the junction of the supply water line L1 and the return water line L2, which may serve as a supply water flow rate adjustment means.

In this way, by setting an appropriate target hot water outlet temperature according to the temperature of the water supply W1 before it flows into the condenser 12, it is possible to prevent insufficient supercooling in the condenser 12, excessive water supply flow rate, etc.
Furthermore, by setting a lower limit of the range of the target hot water outlet temperature that can be set according to the temperature of the feed water W1 before it flows into the condenser 12, it is possible to reliably prevent insufficient supercooling in the condenser 12 and stabilize the amount of heat recovered in the evaporator 14. Also, it is possible to prevent the flow rate of the feed water W1 from becoming excessive and suppress deterioration of the feed water pump 21 and the like due to overload.

In this embodiment, the temperature detected by the second water supply temperature sensor 26 is used to set the target hot water outlet temperature, but the first water supply temperature sensor 24 may also be used as a water supply temperature sensor that indirectly detects the temperature of the water supply W1 before it flows into the condenser 12 (the water supply temperature before it flows into the condenser). However, in order to perform more stable control, it is preferable to use the second water supply temperature sensor 26 to measure the temperature of the water supply W1 immediately before it flows into the condenser 12.

As explained above, in the feed water heating system 1 of this embodiment, the heat source water W5 is circulated through the heat recovery heat exchanger 40 and the evaporator 14 in that order. The feed water heating system 1 of this embodiment includes a refrigerant flow rate adjustment means that is controlled based on the degree of superheat of the gas refrigerant R flowing into the compressor 11 and adjusts the refrigerant flow rate. The system also includes a feed water flow rate adjustment means that is controlled based on the outlet temperature of the feed water W1 flowing out of the condenser 12 and adjusts the feed water flow rate. The control unit 100 includes a refrigerant flow rate control unit 113 that controls the refrigerant flow rate adjustment means, and a feed water flow rate control unit 123 that controls the feed water flow rate adjustment means.

As a result, by first flowing the heat source water W5 through the heat recovery heat exchanger 40, the heat output of the heat recovery heat exchanger 40 is increased, and the preheat amount of the supply water W1 is increased. Note that the higher the heat source water temperature, the greater the effect of increasing the heat output. When the heat recovery amount of the heat recovery heat exchanger 40 increases, the heat recovery amount of the heat pump circuit 10 can be relatively reduced. In other words, to obtain the same system heat output as when the heat source water W5 is flowed through the evaporator 14 and then the heat recovery heat exchanger 40, the compressor output can be lowered to reduce the power consumption of the heat pump circuit 10.
At this time, by flowing the heat source water W5 through the heat recovery heat exchanger 40 first, the temperature of the heat source water W5 flowing into the evaporator 14 decreases, but by adding further control, i.e., by combining the adjustment of the refrigerant flow rate based on the degree of superheat and the adjustment of the water supply flow rate based on the hot water outlet temperature, the COP of the system can be significantly increased in a configuration in which the heat source water W5 flows through the heat recovery heat exchanger 40 first, due to the multiple effects of, for example, increasing the heat input to the evaporator 14 by adjusting the refrigerant flow rate in accordance with a low superheat setting, and further increasing the heat output of the heat recovery heat exchanger 40 and increasing the heat output of the evaporator 14 by adjusting the water supply flow rate in accordance with a low hot water outlet temperature setting.

The water flow mode switching control unit 130 performs water flow mode switching control to switch between a one-time water flow mode, a circulating water flow mode, and a water flow stop mode. More specifically, the water flow mode switching control unit 130 controls the water supply pump 21 and the reflux pump 31 as water flow mode switching means, and controls switching between a one-time water flow mode in which water is passed through the condenser 12 without circulating hot water W2 through the reflux line L2, a circulating water flow mode in which water is passed through the condenser 12 while circulating hot water W2 through the reflux line L2, and a water flow stop mode in which water flow to the condenser 12 is stopped.

In the one-time water flow mode, the return pump 31 is stopped, while the water supply pump 21 is driven, and the heat source supply pump 53 and the compressor 11 of the heat pump circuit 10 are driven. In the circulating water flow mode, the water supply pump 21 is stopped, while the return pump 31 is driven, and the heat source supply pump 53 and the compressor 11 of the heat pump circuit 10 are driven. In the water flow stop mode, the water supply pump 21 and the return pump 31 are stopped, and the compressor 11 of the heat pump circuit 10 is also stopped. It is also preferable to stop the heat source supply pump 53.

In this embodiment, the water supply pump 21 and the return pump 31 constitute the water flow mode switching means, but the water flow mode switching means may be configured in other ways. For example, the water flow mode switching means may be configured by a three-way valve provided at the junction of the water supply line L1 and the return line L2, and a water supply pump provided downstream of the junction of the water supply line L1 and the return line L2. In this case, the water flow mode is switched by switching the three-way valve and turning the water supply pump on and off.

In this way, by enabling operation in the circulating water flow mode in addition to the one-time water flow mode, the hot water tank 60 can be circulated and heated as necessary to maintain the stored hot water temperature. In addition, in the circulating water flow mode, the return line L2 is used to allow the stored water in the hot water tank 60 to flow in front of the heat recovery heat exchanger 40, so that when the temperature of the heat source water W5 is higher than the temperature of the hot water W2 stored in the hot water tank 60, the hot water W2 flowing as the supply water W1 is heated not only by the condenser 12, but also by the heat recovery heat exchanger 40 before that. This allows for efficient heating.

Here, the water flow mode switching control unit 130 controls the water supply to the hot water tank 60 and can also control the switching of the water flow mode based on the temperature of the hot water W2 in the hot water tank 60.
Specifically, the water flow mode switching control unit 130 controls the water flow mode switching means to execute a one-time water flow mode when new water supply is performed to the confluence of the return line L2, controls the water flow mode switching means to execute a circulating water flow mode when new water supply to the confluence is stopped and the temperature detected by the hot water temperature sensor 61 is below a predetermined set temperature, and controls the water flow mode switching means to execute a water flow stop mode when new water supply to the confluence is stopped and the temperature detected by the hot water temperature sensor 61 is above a predetermined set temperature.

This water flow mode switching control will be described in detail with reference to the state transition diagram shown in FIG. 6A.
During execution of each water flow mode, the water flow mode switching control unit 130 monitors the water level of the hot water W2 in the hot water tank 60 using the water level detection unit 62, and monitors the temperature of the hot water W2 in the hot water tank 60 using the hot water temperature sensor 61. During execution of the water flow stop mode, if the water level exceeds the detection position of the electrode rod 622 of the water level detection unit 62 and the detected temperature of the hot water temperature sensor 61 exceeds a first set temperature (for example, a temperature 2 to 3° C. lower than the target hot water outlet temperature), the water flow mode switching control unit 130 continues the water flow stop mode.

<Event E1>
During the water flow stop mode, if the water level in the hot water tank 60 drops below the detection position of the electrode rod 622 of the water level detector 62, the water flow mode switching controller 130 drives the water supply pump 21 while keeping the return pump 31 stopped. Driving the water supply pump 21 causes new makeup water W to be supplied to the junction of the return line L2, so the water flow mode switching controller 130 drives the heat source supply pump 53 and the compressor 11 to transition to the one-time water flow mode. In the one-time water flow mode, hot water W2 adjusted to a predetermined target hot water outlet temperature is supplied to the hot water tank 60.

<Event E2>
During execution of the transient water flow mode, if the water level in the hot water tank 60 rises and exceeds the detection position of the electrode rod 621 of the water level detection unit 62, the water flow mode switching control unit 130 stops the water supply pump 21 while keeping the return pump 31 stopped. Since stopping the water supply pump 21 stops the supply of new makeup water W to the confluence of the return line L2, the water flow mode switching control unit 130 stops the heat source supply pump 53 and the compressor 11 to transition to the water flow stop mode. In the water flow stop mode, the supply of hot water W2 to the hot water tank 60 is stopped.

<Event E3>
During the water flow stop mode, if the temperature detected by the hot water temperature sensor 61 falls below the set temperature, the return pump 31 is driven while the water supply pump 21 remains stopped. Driving the return pump 31 causes the stored water to be circulated with the supply of new makeup water W to the confluence of the return line L2 stopped, so the water flow mode switching control unit 130 drives the heat source supply pump 53 and the compressor 11 to transition to the circulating water flow mode. In the circulating water flow mode, hot water W2 reheated to a predetermined target hot water outlet temperature is supplied to the hot water tank 60.

<Event E4>
During the execution of the circulating water flow mode, if the temperature detected by the hot water temperature sensor 61 exceeds the set temperature, the water flow mode switching control unit 130 stops the reflux pump 31 while keeping the water supply pump 21 stopped. Then, the heat source supply pump 53 and the compressor 11 are stopped to transition to the water flow stop mode. In the water flow stop mode, the circulation of the hot water W2 to the hot water tank 60 is stopped.

<Event E5>
During the circulation water flow mode, if the water level in the hot water tank 60 drops below the detection position of the electrode rod 622 of the water level detection unit 62, the water flow mode switching control unit 130 stops the reflux pump 31 and drives the water supply pump 21. Driving the water supply pump 21 causes new makeup water W to be supplied to the junction of the reflux line L2, so the water flow mode switching control unit 130 switches to the one-time water flow mode while driving the heat source supply pump 53 and the compressor 11. In the one-time water flow mode, hot water W2 adjusted to a predetermined target hot water outlet temperature is supplied to the hot water tank 60.
In this embodiment, the mode is not switched from the one-time water flow mode to the circulating water flow mode. The mode is switched to the one-time water flow mode when the demand for hot water is high, and this is to give priority to the supply of makeup water W to the hot water tank 60 and quickly restore the water level. In addition, since the outlet hot water temperature in the one-time water flow mode is higher than the hot water temperature stored in the hot water tank 60, the stored hot water temperature can be raised in a short time.

The set temperature for determining whether to continue the water stop mode and the set temperature for determining whether to transition from the water stop mode to the circulating water mode may be the same or different. If they are different temperatures, the latter set temperature is set to a lower temperature than the former set temperature.

In addition, when controlling the switching of the water flow mode described above, the determination of whether new water supply using make-up water W or the like is being performed at the confluence of the return line L2 may be made based on the driving state of the water supply pump 21 (driving command signal or driving feedback signal).
In addition, a flow rate sensor (not shown) may be disposed in the water supply line L1 upstream of the point where it joins with the return line L2, and the determination may be made based on the detection results of this flow rate sensor.

According to the mode switching control according to the state transition diagram of FIG. 6A, when there is sufficient demand for hot water and it is necessary to supply makeup water W, the system can be operated in a one-time water flow mode in which the system COP is maximized. Also, when there is little demand for hot water and it is not necessary to supply makeup water W, the temperature of the stored water in the hot water tank 60 can be raised in a circulating water flow mode when the temperature of the stored water in the hot water tank 60 drops. Also, when there is little demand for hot water and it is not necessary to supply makeup water W, if there is substantially no drop in the temperature of the stored water in the hot water tank 60, the system can wait in a water flow stop mode.

With the configuration described above, hot water W2 at or above the set temperature can be constantly maintained in the hot water tank 60. In addition, the circulating water mode is only executed when the temperature of the stored water in the hot water tank 60 drops, so there is no unnecessary power consumption due to excessive water circulation.

The preheating mode switching control unit 140 performs preheating mode switching control to switch between a water supply preheating mode and a preheating stop mode. More specifically, the preheating mode switching control unit 140 controls the three-way valve 25 as a preheating mode switching means to switch between a water supply preheating mode in which the water supply W1 and the heat source water W5 are simultaneously circulated through the heat recovery heat exchanger 40, and a preheating stop mode in which the water supply W1 is circulated through the bypass line L3.

In this embodiment, the three-way valve 25 constitutes the preheating mode switching means, but the preheating mode switching means may be constituted in other ways. For example, two-way valves may be provided upstream of the junction with the bypass line L3 in the water supply line L1 and in the bypass line L3, and these two-way valves may constitute the preheating mode switching means.

The bypass line is not limited to one that bypasses the supply water W1 from the heat recovery heat exchanger 40, but may be one that bypasses the heat source water W5 from the heat recovery heat exchanger 40. In this case, in the pre-heating stop mode, the heat source water W5 is caused to flow through the bypass line.
In other words, the system is provided with one or two bypass lines that bypass the supply water W1 from the heat recovery heat exchanger 40 and/or the heat source water W5 from the heat recovery heat exchanger 40, and the preheating mode switching means switches between a supply water preheating mode in which the supply water W1 and the heat source water W5 are circulated simultaneously through the heat recovery heat exchanger 40, and a preheating stop mode in which at least one of the supply water W1 and the heat source water W5 is circulated through the bypass line.
This allows the heat recovery heat exchanger 40 to be selectively used depending on the situation.

Here, the preheating mode switching control unit 140 acquires a first detected temperature (supply water temperature before entering the heat exchanger) by the first supply water temperature sensor 24 (supply water temperature sensor 24 before entering the heat exchanger) which detects the temperature of the supply water W1 before it flows into the heat recovery heat exchanger 40, and a second detected temperature (heat source temperature before entering the heat exchanger) by the first heat source temperature sensor 54 (heat source temperature sensor 54 before entering the heat exchanger) which detects the temperature of the heat source water W5 before it flows into the heat recovery heat exchanger 40, and is able to control the switching of the preheating mode based on these first detected temperature and second detected temperature.
Specifically, the preheating mode switching control unit 140 compares the first detected temperature by the first water supply temperature sensor 24 with the second detected temperature by the first heat source temperature sensor 54, and if the first detected temperature is lower than the second detected temperature, controls the preheating mode switching means to execute the water supply preheating mode, and if the first detected temperature is higher than the second detected temperature, controls the preheating mode switching means to execute the preheating stop mode.
By automatically switching the preheating mode in accordance with the supply water temperature and the heat source water temperature in this manner, it is possible to maximize the system COP.

The preheating mode switching control unit 140 can switch the preheating mode switching means between the preheating modes at least when the water flow mode is the circulating water flow mode. In this case, the preheating mode switching control unit 140 may set the preheating mode switching means to the preheating mode when the water flow mode is the passing water flow mode, and may set the preheating mode switching means to the preheating stop mode when the water flow mode is the water flow stop mode.
As a result, for example, in a one-time water flow mode in which makeup water W, which often has a relatively low temperature, is used as the supply water W1, the heat recovery heat exchanger is actively utilized, while in a circulating water flow mode in which stored water in a hot water tank 60, which often has a relatively high temperature, is used as the supply water W1, the heat recovery heat exchanger can be selectively utilized depending on the temperature relationship between the supply water W1 and the heat source water W5.
However, in order to enable efficient heating even under various conditions of make-up water temperature and heat source water temperature, the preheating mode switching control unit 140 may be configured to switch the preheating mode switching means between each preheating mode when the water flow mode is the circulating water flow mode or the one-time water flow mode.

The signal input unit 150 includes a first signal input unit 151 that receives a water flow mode designation signal that designates one of a transient water flow mode, a circulating water flow mode, and a water flow stop mode.
The water flow mode switching control unit 130 controls the water flow mode switching means to execute the one-time water flow mode, the circulating water flow mode, or the water flow stop mode in accordance with the water flow mode designation signal input to the first signal input unit 151. When the water flow mode or the water flow stop mode is executed, the water flow mode switching control unit 130 stops new water supply to the junction of the return line L2 by controlling the water supply pump 21, for example.
This allows, for example, operation in a transient water flow mode where the system COP is maximized by using an external signal indicating the presence of make-up water, or operation in a circulating water flow mode where the temperature of the stored water is maintained by using an external signal indicating no make-up water.

The signal input unit 150 also includes a second signal input unit 152 that receives a pre-heating mode designation signal that designates either the water supply pre-heating mode or the pre-heating stop mode.
The preheating mode switching control unit 140 controls the preheating mode switching means to execute the water supply preheating mode or the preheating stop mode in accordance with the preheating mode designation signal input to the second signal input unit 152 .
This makes it possible to maximize the system COP by manually switching the preheating mode in response to an external signal.

The memory unit 160 stores various information necessary for control, such as various thresholds.

Next, an example of the flow of control by the control unit 100 of this embodiment will be described.

Figure 6B is a flowchart showing an example of the flow of the target superheat degree setting process performed by the target superheat degree setting unit 111 of the control unit 100.

First, when the system is started, the target superheat degree setting unit 111 sets the target superheat degree to a high temperature, for example 10°C, in step S1.

Next, in step S2, it is determined whether the temperature detected by the second heat source temperature sensor 55 is stable and is equal to or lower than a predetermined heat source temperature threshold (e.g., 60°C). If it is determined that the temperature detected by the second heat source temperature sensor 55 is stable (ΔT≦ΔT0, see FIG. 3) and is equal to or lower than the predetermined heat source temperature threshold (step S2: YES), the target degree of superheat is set to a small value, for example, 5°C, in step S3. On the other hand, if it is determined that the temperature detected by the second heat source temperature sensor 55 is not stable or exceeds the predetermined heat source temperature threshold (step S2: NO), the process returns to step S1, and the target degree of superheat continues to be maintained at 10°C.

After setting the target degree of superheat to 5°C in step S3, it is determined in step S4 whether the fluctuation of the detected temperature of the second heat source temperature sensor 55 is large or whether it exceeds a predetermined heat source temperature threshold. If it is determined that the fluctuation of the detected temperature of the second heat source temperature sensor 55 is large (ΔT>ΔT0, see FIG. 3) or if it is determined that it exceeds the predetermined heat source temperature threshold (step S4: YES), the target degree of superheat is increased in step S5, for example, to 10°C. On the other hand, if it is determined that the fluctuation of the detected temperature of the second heat source temperature sensor 55 is not large and is equal to or lower than the predetermined heat source temperature threshold (step S4: NO), the process returns to step S3, and the target degree of superheat is continued to be maintained at 5°C.
This makes it possible to stably operate the heat pump circuit 10 even when a situation is confirmed in which the temperature of the heat source water W5 serving as the heat source fluid changes suddenly.

Next, the preheating mode switching control will be described. The water flow mode switching control is as described above (see FIG. 6A).
6C is a flowchart showing an example of the flow of preheating mode switching control for switching between the water supply preheating mode and the preheating stop mode by the preheating mode switching control unit 140 of the control unit 100. In this example, the preheating mode switching control unit 140 controls the switching of the preheating mode based on the detection results of the first detected temperature (water supply temperature before entering the heat exchanger) by the first water supply temperature sensor 24 (water supply temperature sensor before entering the heat exchanger) and the second detected temperature (heat source temperature before entering the heat exchanger) by the first heat source temperature sensor 54 (heat source temperature sensor before entering the heat exchanger).

In step S11, the preheating mode switching control unit 140 determines whether the circulating water flow mode is being executed. If the circulating water flow mode is being executed (step S21: YES), in step S12, the first detection temperature by the first water supply temperature sensor 24 is compared with the detection result of the second detection temperature by the first heat source temperature sensor 54. If the first detection temperature is lower than the second detection temperature (step S12: YES), in step S13, the water supply preheating mode is executed. On the other hand, if the first detection temperature is not lower than the second detection temperature (step S12: NO), in step S14, the preheating stop mode is executed.

In addition, in step S11, it may be determined whether the one-time water flow mode or the circulating water flow mode is being executed, and if the one-time water flow mode or the circulating water flow mode is being executed, control may be adopted to transition to step S12.

FIG. 7 is a diagram illustrating a modified example of the supply water heating system 1 of the first embodiment.
The condenser 12 of the heat pump circuit 10 in the present embodiment has the functions of condensing and supercooling the refrigerant R. However, as shown in this modified example, the condenser of the heat pump circuit 10 may be divided into a condenser 12A that mainly has the function of condensing the refrigerant R and a supercooler 12B that mainly has the function of supercooling the refrigerant R. In this case, the refrigerant R of the heat pump circuit 10 preferably releases latent heat in the condenser 12A and releases sensible heat in the supercooler 12B. That is, in the condenser 12A, the gas refrigerant R is condensed to become liquid refrigerant R, and the liquid refrigerant R is supplied to the supercooler 12B, where the liquid refrigerant R is further cooled (supercooled).
The subcooler 12B is an indirect heat exchanger that exchanges heat between the feed water W1 sent to the condenser 12A and the refrigerant R flowing from the condenser 12A to the expansion valve 13. The subcooler 12B can subcool the refrigerant R from the condenser 12A to the expansion valve 13 using the feed water W1 to the condenser 12A, and can warm the feed water W1 to the condenser 12A using the refrigerant R from the condenser 12A to the expansion valve 13.
In this way, by using separate heat exchangers for condensing and supercooling the refrigerant R, the design of the heat exchangers is simplified, and costs can be reduced. In addition, a general-purpose heat exchanger can be used.
In addition, in this modified example, it is preferable that the second supply water temperature sensor 26, which serves as a supply water temperature sensor for detecting the temperature of the supply water W1 before it flows into the condenser 12 of the heat pump circuit 10, is arranged upstream of the supercooler 12B.

When the hot water demand point is a steam boiler, or the like, and a drop in the temperature of the hot water W2 in the hot water tank 60 is tolerable to a certain extent, a make-up water line (not shown) may be provided to enable water to be supplied directly from the make-up water tank 70 to the hot water tank 60 without passing through the heat recovery heat exchanger 40 and the heat pump circuit 10. In this case, when the water level of the hot water W2 in the hot water tank 60 falls below the detection position of the electrode rod longer than the electrode rod 622, for example, it is possible to supply make-up water W directly from the make-up water tank 70 to the hot water tank 60 by driving a make-up water pump provided in the make-up water line.

In this embodiment, the heat source water W5 is used as the heat source fluid of the heat pump circuit 10, but the heat source fluid is not limited to the heat source water W5, and various fluids such as air and exhaust gas can be used. It is preferable that the heat source fluid is a fluid that gives heat (sensible heat) to the water supply W1 in the heat recovery heat exchanger 40 while decreasing its own temperature, and that gives heat (sensible heat) to the refrigerant R of the heat pump circuit 10 in the evaporator 14 while decreasing its own temperature.

The driving source of the compressor 11 of the heat pump circuit 10 is not limited to an electric motor. For example, the compressor 11 may be driven by a steam motor that uses steam to generate power, or by a gas engine. In this case, the output of the compressor 11 may be adjusted by adjusting the amount of steam supplied to the steam motor or the amount of gas supplied to the gas engine, thereby adjusting the refrigerant flow rate.

The water heating system 1 of the first embodiment described above provides the following advantages (1A) to (11A).

(1A) The water supply heating system 1 of this embodiment comprises a vapor compression type heat pump circuit 10 in which a compressor 11, a condenser 12, an expansion valve 13 and an evaporator 14 are connected in a ring shape by a refrigerant circulation line L9, and in which warm heat is extracted by the condenser 12 by driving the compressor 11, a heat recovery heat exchanger 40, a heat source fluid line L5 which circulates a heat source fluid through the heat recovery heat exchanger 40 and the evaporator 14 in that order, a water supply line L1 which circulates water W1 through the heat recovery heat exchanger 40 and the condenser 12 in that order, a refrigerant flow rate adjustment means which is controlled based on the degree of superheat of the gas refrigerant R flowing into the compressor 11 and adjusts the refrigerant flow rate, a water supply flow rate adjustment means which is controlled based on the outlet temperature of the water supply W1 flowing out of the condenser 12 and adjusts the water supply flow rate, and a control means which controls the refrigerant flow rate adjustment means and the water supply flow rate adjustment means.
In this way, by first flowing the heat source water W5 as the heat source fluid through the heat recovery heat exchanger 40, the heat output of the heat recovery heat exchanger 40 is increased, and the preheat amount of the feed water W1 is increased. The higher the heat source water temperature, the greater the effect of increasing the heat output. Since the heat recovery amount of the heat recovery heat exchanger 40 increases, the heat recovery amount of the heat pump circuit 10 can be relatively reduced. To obtain the same system heat output as when the heat source water W5 is flowed through the evaporator 14 and then the heat recovery heat exchanger 40, the output of the compressor 11 can be reduced to reduce the power consumption of the heat pump circuit 10.
At this time, by flowing the heat source water W5 through the heat recovery heat exchanger 40 first, the temperature of the heat source water W5 flowing into the evaporator 14 decreases, but by adding further control, i.e., by combining the adjustment of the refrigerant flow rate based on the degree of superheat and the adjustment of the water supply flow rate based on the hot water outlet temperature, the COP of the system can be significantly increased in a configuration in which the heat source water W5 flows through the heat recovery heat exchanger 40 first, due to the multiple effects of, for example, increasing the heat input to the evaporator 14 by adjusting the refrigerant flow rate in accordance with a low superheat setting, and further increasing the heat output of the heat recovery heat exchanger 40 and increasing the heat output of the evaporator 14 by adjusting the water supply flow rate in accordance with a low hot water outlet temperature setting.

(2A) The heat source fluid line L5 of the water supply heating system 1 of this embodiment has a connection configuration in which the heat source fluid and the water supply W1 are heat exchanged in a counterflow manner in the heat recovery heat exchanger 40, and then the heat source fluid and the liquid refrigerant R are heat exchanged in a counterflow manner in the evaporator 14.
In this way, by flowing the heat source water W5 through the heat recovery heat exchanger 40 and the evaporator 14 in that order, and flowing it in a counterflow to the flow direction of the supply water W1 in each of the heat recovery heat exchanger 40 and the evaporator 14, the amount of heat recovery can be maximized.

(3A) The water supply heating system 1 of this embodiment is equipped with an inlet temperature sensor 17 that detects the inlet temperature of the gas refrigerant R flowing into the compressor 11, a steam pressure sensor 18 that detects the vapor pressure of the gas refrigerant R flowing out of the evaporator 14, and an outlet temperature sensor 27 that detects the outlet temperature of the water supply W1 flowing out of the condenser 12, and the control means calculates the evaporation temperature of the liquid refrigerant R from the detected pressure of the steam pressure sensor 18, calculates the degree of superheat of the gas refrigerant R by subtracting the evaporation temperature from the temperature detected by the suction temperature sensor 17, controls the refrigerant flow rate adjustment means so that the calculated degree of superheat becomes a target degree of superheat, and controls the water supply flow rate adjustment means so that the temperature detected by the outlet temperature sensor 27 becomes the target outlet temperature.
In this way, by accurately calculating the degree of superheat of the gas refrigerant R and keeping this value constant, the heat output of the condenser 12 to the preheated feed water W1 is stabilized. This reduces fluctuations in the hot water flow rate. Also, by appropriately increasing the feed water flow rate using the set value of the target hot water outlet temperature, for example, and keeping the flow rate within a constant range, a high heat output can be maintained.

(4A) The water heating system 1 of this embodiment is equipped with a heat source temperature sensor that detects the temperature of the heat source fluid before it flows into the evaporator 14, and the control means sets the target degree of superheat according to the temperature detected by the heat source temperature sensor.
In this way, by setting an appropriate target degree of superheat depending on the temperature of the heat source fluid, it is possible to increase the amount of heat recovered in the evaporator 14 while preventing damage to the compressor 11 due to liquid compression.
For example, when the heat source water temperature is low, the refrigerant circulation flow rate is increased by setting the target degree of superheat low. This makes it possible to increase the amount of heat recovered even with low-temperature heat source water W5. By setting the lower limit of the target degree of superheat to, for example, 5°C, it is possible to prevent damage to the compressor 11 due to liquid compression. Furthermore, by setting the upper limit of the target degree of superheat to, for example, 10°C, it is possible to maintain the refrigerant circulation flow rate at or above a predetermined flow rate and prevent a decrease in the amount of heat recovered.

(5A) The control means of the supply water heating system 1 of this embodiment increases the target degree of superheat when it determines that there is a large fluctuation in the temperature detected by the heat source temperature sensor.
This makes it possible to stably operate the heat pump circuit 10 even when a situation in which the temperature of the heat source fluid changes suddenly is confirmed.
For example, even if the temperature of the heat source fluid drops suddenly, the refrigerant can be reliably vaporized in the evaporator 14 by setting the target superheat degree to a high value, thereby preventing damage to the compressor 11 due to liquid compression.

(6A) The control means of the supply water heating system 1 of this embodiment reduces the target degree of superheat when it determines that the temperature detected by the heat source temperature sensor is stable.
As a result, when the temperature of the heat source fluid is stable, the target degree of superheat can be set to a low value to increase the refrigerant circulation flow rate, thereby increasing the amount of heat recovered in the evaporator 14.

(7A) The water supply heating system 1 of this embodiment is equipped with a water supply temperature sensor that detects the temperature of the water supply before it flows into the condenser 12, and the control means sets the target hot water outlet temperature according to the temperature detected by the water supply temperature sensor.
In this way, by setting an appropriate target hot water outlet temperature according to the temperature of the feed water, it is possible to prevent insufficient supercooling in the condenser 12, an excessive feed water flow rate, and the like.

(8A) The water supply heating system 1 of this embodiment is equipped with a water supply temperature sensor that detects the temperature of the water supply before it flows into the condenser 12, and the target hot water outlet temperature can be set to a value between an upper limit and a lower limit, and the lower limit is a value obtained by adding a predetermined value to the temperature detected by the water supply temperature sensor, and the higher the detected temperature of the water supply temperature sensor, the higher the value.
In this way, by setting the lower limit of the range of target hot water outlet temperatures that can be set according to the feed water temperature, it is possible to reliably prevent insufficient supercooling in the condenser 12 and stabilize the amount of heat recovered in the evaporator 14. In addition, it is possible to prevent the feed water flow rate from becoming excessive and suppress deterioration of the feed water pump 21 due to overload.

(9A) The water supply heating system 1 of this embodiment includes one or two bypass lines for bypassing the water supply W1 from the heat recovery heat exchanger 40 and/or bypassing the heat source fluid from the heat recovery heat exchanger 40, and a preheating mode switching means for switching between a water supply preheating mode in which the water supply W1 and the heat source fluid are circulated simultaneously through the heat recovery heat exchanger 40, and a preheating stop mode in which at least one of the water supply W1 and the heat source fluid is circulated through the bypass line.
As a result, by bypassing the heat recovery heat exchanger 40 under conditions where the heat recovery heat exchanger 40 cannot perform its function, the pressure loss of the supply water W1 and/or the heat source water W5 can be reduced, and the system COP including the supply water pump 21 and the heat source supply pump 53 can be improved.

(10A) The water supply heating system 1 of this embodiment includes a water supply temperature sensor 24 before entering the heat exchanger for detecting the temperature of the water supply W1 before flowing into the heat exchanger 40 for heat recovery, and a heat source temperature sensor 54 before entering the heat exchanger for detecting the temperature of the heat source fluid before flowing into the heat exchanger 40 for heat recovery. The control means compares a first detected temperature by the water supply temperature sensor 24 before entering the heat exchanger with a second detected temperature by the heat source temperature sensor 54 before entering the heat exchanger, and controls the preheating mode switching means to execute a water supply preheating mode if the first detected temperature is lower than the second detected temperature, and controls the preheating mode switching means to execute a preheating stop mode if the first detected temperature is higher than the second detected temperature.
By automatically switching the preheating mode in accordance with the supply water temperature and the heat source water temperature, the system COP can be maximized.

(11A) The control means of the water supply heating system 1 of this embodiment has a signal input unit 150 that receives a preheating mode designation signal that designates the type of water supply preheating mode or preheating stop mode, and a preheating mode switching control unit 140 that controls the preheating mode switching means to execute the water supply preheating mode or the preheating stop mode in accordance with the preheating mode designation signal input to the signal input unit 150.
By switching the pre-heating mode manually in response to an external signal, the system COP can be maximized.

The water heating system 1 of the first embodiment described above also provides the following advantages (1B) to (8B).

(1B) The water heating system 1 of this embodiment includes a vapor compression heat pump circuit 10 in which a compressor 11, a condenser 12, an expansion valve 13, and an evaporator 14 are connected in a ring shape by a refrigerant circulation line L9, and in which heat is extracted by the condenser 12 when the compressor 11 is driven, a heat recovery heat exchanger 40, a heat source fluid line L5 that circulates a heat source fluid through the heat recovery heat exchanger 40 and the evaporator 14, a water supply line L1 that circulates water W1 through the heat recovery heat exchanger 40 and the condenser 12 in this order, and a refrigerant circulation line L2 that circulates the water W1 generated by the condenser 12. The system includes a hot water tank 60 for storing the generated hot water W2, a return line L2 for returning the hot water W2 in the hot water tank 60 to the upstream side of the heat recovery heat exchanger 40, a water flow mode switching means for switching between a one-time water flow mode in which the hot water W2 is passed through the condenser 12 without passing through the return line L2, a circulating water flow mode in which the hot water W2 is passed through the condenser 12 while passing through the return line L2, and a water flow stop mode in which the flow of water to the condenser 12 is stopped, and a control means for controlling the water flow mode switching means.
In this way, by enabling operation in the circulating water flow mode in addition to the passing water flow mode, it is possible to maintain the stored hot water temperature by circulating heating of the hot water tank 60 as necessary. In the circulating water flow mode, since the stored water is configured to flow in front of the heat recovery heat exchanger 40, efficient heating is possible when the stored water temperature is lower than the heat source water temperature.

(2B) The water supply heating system 1 of this embodiment is equipped with one or two bypass lines for bypassing the water supply W1 from the heat recovery heat exchanger 40 and/or bypassing the heat source fluid from the heat recovery heat exchanger 40, and a preheating mode switching means for switching between a water supply preheating mode in which the water supply W1 and the heat source fluid are circulated simultaneously through the heat recovery heat exchanger 40, and a preheating stop mode in which at least one of the water supply W1 and the heat source fluid is circulated through the bypass line.
This allows the heat recovery heat exchanger 40 to be selectively used depending on the situation.

(3B) The control means of the supply water heating system 1 of this embodiment is capable of switching the preheating mode switching means between the supply water preheating mode and the preheating stop mode at least when in the circulating water flow mode.
This makes it possible, for example, to proactively utilize the heat recovery heat exchanger 40 in the pass-through water mode, and selectively utilize the heat recovery heat exchanger 40 in the circulating water mode.

(4B) The heat source fluid line L5 of the supply water heating system 1 of this embodiment has a connection configuration in which the heat source fluid flows through the heat recovery heat exchanger 40 and the evaporator 14 in that order.
As a result, the heat source water W5 as a heat source fluid is first flowed through the heat recovery heat exchanger 40, thereby increasing the amount of preheating of the feed water W1 and increasing the heat output of the heat recovery heat exchanger 40. The higher the heat source water temperature, the greater the effect of increasing the heat output.

(5B) The water supply heating system 1 of this embodiment is equipped with a hot water temperature sensor 61 that detects the temperature of the hot water W2 in the hot water tank 60, and the control means controls the water flow mode switching means to execute a one-time water flow mode when new water supply is being performed to the confluence of the return line L2, controls the water flow mode switching means to execute a circulating water flow mode when new water supply to the confluence is stopped and the temperature detected by the hot water temperature sensor 61 is below the set temperature, and controls the water flow mode switching means to execute a water flow stop mode when new water supply to the confluence is stopped and the temperature detected by the hot water temperature sensor 61 is above the set temperature.
As a result, when there is sufficient demand for hot water and it is necessary to supply makeup water W, the system can be operated in a one-time water flow mode in which the system COP is maximized. Also, when there is little demand for hot water and it is not necessary to supply makeup water W, the temperature of the stored water in the hot water tank 60 can be raised in a circulating water flow mode when the temperature of the stored water drops.

(6B) The water supply heating system 1 of this embodiment is equipped with a water supply temperature sensor 24 before entering the heat exchanger for detecting the temperature of the water supply W1 before it flows into the heat exchanger 40 for heat recovery, and a heat source temperature sensor 54 before entering the heat exchanger for detecting the temperature of the heat source fluid before it flows into the heat exchanger 40 for heat recovery, and the control means compares a first detected temperature by the water supply temperature sensor 24 before entering the heat exchanger with a second detected temperature by the heat source temperature sensor 54 before entering the heat exchanger, and if the first detected temperature is lower than the second detected temperature, controls the preheating mode switching means to execute the water supply preheating mode, and if the first detected temperature is higher than the second detected temperature, controls the preheating mode switching means to execute the preheating stop mode.
By automatically switching the preheating mode in accordance with the supply water temperature and the heat source water temperature, the system COP can be maximized.

(7B) The control means of the water supply heating system 1 of this embodiment includes a first signal input unit 151 that receives a water flow mode designation signal that designates either a one-time water flow mode, a circulating water flow mode, or a water flow stop mode, and a water flow mode switching control unit 130 that controls the water flow mode switching means to execute the one-time water flow mode, the circulating water flow mode, or the water flow stop mode in accordance with the water flow mode designation signal input to the first signal input unit 151, and the water flow mode switching control unit 130 stops new water supply to the confluence of the return line L2 when the circulating water flow mode or the water flow stop mode is executed.
This allows the system to operate in a one-time flow mode where the system COP is maximized by using an external signal indicating that makeup water is being supplied, or to keep the stored water warm in a circulation mode by using an external signal indicating that makeup water is not being supplied.

(8B) The control means of the water supply heating system 1 of this embodiment has a second signal input unit 152 that receives a preheating mode designation signal that designates either the water supply preheating mode or the preheating stop mode, and a preheating mode switching control unit 140 that controls the preheating mode switching means to execute the water supply preheating mode or the preheating stop mode in accordance with the preheating mode designation signal input to the second signal input unit 152.
This makes it possible to manually switch preheating modes in response to an external signal, for example, and maximize the system COP.

The water heating system 1 of the first embodiment described above also provides the following advantages (1C) to (7C).

(1C) The water supply heating system 1 of this embodiment comprises a vapor compression type heat pump circuit 10 in which a compressor 11, a condenser 12, an expansion valve 13 and an evaporator 14 are connected in a ring shape by a refrigerant circulation line L9, and in which the compressor 11 is driven to extract heat in the condenser 12, a refrigerant flow rate adjustment means for adjusting the flow rate of refrigerant R flowing through the heat pump circuit 10, a heat source temperature sensor for detecting the temperature of the heat source fluid that exchanges heat with the refrigerant R in the evaporator 14, and a control means for controlling the refrigerant flow rate adjustment means, and the control means sets a target degree of superheat in accordance with the temperature detected by the heat source temperature sensor, and controls the refrigerant flow rate adjustment means so that the degree of superheat of the refrigerant R flowing into the compressor 11 becomes the target degree of superheat.
In this way, by setting an appropriate target degree of superheat depending on the temperature of the heat source fluid, it is possible to increase the amount of heat recovered in the evaporator 14 while preventing damage to the compressor 11 due to liquid compression.
For example, when the heat source water temperature is low, the refrigerant circulation flow rate is increased by setting the target degree of superheat low. This makes it possible to increase the amount of heat recovered even if the heat source fluid is low-temperature heat source water W5. By setting the lower limit of the target degree of superheat to, for example, 5°C, it is possible to prevent damage to the compressor 11 due to liquid compression. Furthermore, by setting the upper limit of the target degree of superheat to, for example, 10°C, it is possible to maintain the refrigerant circulation flow rate at or above a predetermined flow rate and prevent a decrease in the amount of heat recovered.

(2C) The control means of the supply water heating system 1 of this embodiment increases the target degree of superheat when it determines that there is a large fluctuation in the temperature detected by the heat source temperature sensor.
This allows the heat pump circuit 10 to operate stably even if a situation in which the temperature of the heat source fluid changes suddenly is confirmed.
For example, even if the temperature of the heat source fluid drops suddenly, the refrigerant can be reliably vaporized in the evaporator 14 by setting the target superheat degree to a high value, thereby preventing damage to the compressor 11 due to liquid compression.

(3C) The control means of the supply water heating system 1 of this embodiment reduces the target degree of superheat when it determines that the temperature detected by the heat source temperature sensor is stable.
As a result, when the temperature of the heat source fluid is stable, the target degree of superheat can be set to a low value to increase the refrigerant circulation flow rate, thereby increasing the amount of heat recovered in the evaporator 14.

(4C) The water supply heating system 1 of this embodiment is equipped with an inlet temperature sensor 17 that detects the suction temperature of the gas refrigerant R flowing into the compressor 11, and a vapor pressure sensor 18 that detects the vapor pressure of the gas refrigerant R flowing out from the evaporator 14, and the control means calculates the evaporation temperature of the liquid refrigerant R from the pressure detected by the vapor pressure sensor 18, and calculates the degree of superheat of the gas refrigerant R by subtracting the evaporation temperature from the temperature detected by the suction temperature sensor 17, and controls the refrigerant flow rate adjustment means so that the calculated degree of superheat becomes the target degree of superheat.
In this way, by accurately calculating the degree of superheat of the gas refrigerant R and further keeping this value constant, the heat output of the condenser 12 to the preheated feed water W1 is stabilized. This reduces fluctuations in the hot water flow rate.

(5C) The water supply heating system 1 of this embodiment is equipped with a water supply flow rate adjustment means for adjusting the water supply flow rate flowing through the condenser 12, and an outlet water temperature sensor 27 for detecting the outlet water temperature of the water supply W1 flowing out from the condenser 12, and the control means controls the water supply flow rate adjustment means so that the detected temperature of the outlet water temperature sensor 27 becomes the target outlet water temperature.
This allows the water W1 to always be heated to a desired temperature and dispensed.

(6C) The water supply heating system 1 of this embodiment is equipped with a water supply temperature sensor that detects the temperature of the water supply W1 before it flows into the condenser 12, and the control means sets the target hot water outlet temperature according to the temperature detected by the water supply temperature sensor.
In this way, by setting an appropriate target hot water outlet temperature according to the temperature of the supply water W1, it is possible to prevent insufficient supercooling in the condenser 12, excessive supply water flow rate, and the like.

(7C) The water supply heating system 1 of this embodiment is equipped with a water supply temperature sensor that detects the temperature of the water supply W1 before it flows into the condenser 12, and the target hot water outlet temperature can be set to a value between an upper limit and a lower limit, and the lower limit is a value obtained by adding a predetermined value to the temperature detected by the water supply temperature sensor, and the higher the detected temperature of the water supply temperature sensor, the higher the value.
In this way, by setting the lower limit of the range of target hot water outlet temperatures that can be set according to the feed water temperature, it is possible to reliably prevent insufficient supercooling in the condenser 12 and stabilize the amount of heat recovered in the evaporator 14. In addition, it is possible to prevent the feed water flow rate from becoming excessive and suppress deterioration of the feed water pump 21 due to overload.

The above describes a preferred embodiment of the water heating system of the present invention, but the present invention is not limited to the above embodiment and can be modified as appropriate.

1 Water supply heating system 10 Heat pump circuit 11 Compressor 12 Condenser
12A Condenser
12B Supercooler
13 Expansion valve (refrigerant flow rate adjustment means)
14 Evaporator 17 Suction temperature sensor 18 Steam pressure sensor 21 Water supply pump (water supply flow rate adjustment means, water flow mode switching means)
24 First feed water temperature sensor (feed water temperature sensor before heat exchanger inflow, feed water temperature sensor)
25 Three-way valve (preheating mode switching means)
26 Second supply water temperature sensor (supply water temperature sensor)
27 Outlet water temperature sensor 31 Circulation pump (supply water flow rate adjustment means, water flow mode switching means)
40 Heat recovery heat exchanger 50 Heat source water tank 53 Heat source supply pump 54 First heat source temperature sensor (heat source temperature sensor before flowing into heat exchanger, heat source temperature sensor)
55 Second heat source temperature sensor (heat source temperature sensor)
60 Hot water tank 61 Hot water temperature sensor 62 Water level detection unit 63 Hot water supply pump 70 Make-up water tank 100 Control unit 111 Target degree of superheat setting unit 112 Superheat degree calculation unit 113 Refrigerant flow rate control unit 121 Target hot water outlet temperature settable range determination unit 122 Target hot water outlet temperature setting unit 123 Water supply flow rate control unit 130 Water flow mode switching control unit 140 Preheating mode switching control unit 150 Signal input unit 151 First signal input unit 152 Second signal input unit L1 Water supply line L2 Circulation line L3 Bypass line L4 Hot water supply line L5 Heat source fluid line L9 Refrigerant circulation line R Refrigerant (gas refrigerant, liquid refrigerant)
W Make-up water W1 Water supply W2 Hot water W5 Heat source water (heat source fluid)

Claims (8)

a vapor compression heat pump circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in a ring shape by a refrigerant circulation line, and heat is extracted by the condenser when the compressor is driven;
A heat recovery heat exchanger;
a heat source fluid line through which a heat source fluid flows through the heat recovery heat exchanger and the evaporator in this order;
a water supply line through which water flows through the heat recovery heat exchanger and the condenser in this order;
A water supply flow rate adjusting means provided in the water supply line, the water supply pump being capable of controlling the rotation speed by an inverter, or a flow rate adjusting valve being capable of proportional control;
A suction temperature sensor that detects a suction temperature of the gas refrigerant flowing into the compressor;
A vapor pressure sensor that detects the vapor pressure of the gas refrigerant flowing out from the evaporator;
a temperature sensor for detecting a temperature of the water flowing out from the condenser;
a control means for controlling the expansion valve and the water supply flow rate adjustment means,
The control means
During operation of the compressor, a valve opening degree of the expansion valve is adjusted by feedback control, while a drive frequency of the feedwater pump or a valve opening degree of the flow rate control valve is adjusted by feedback control,
In the feedback control of the valve opening degree of the expansion valve, the evaporation temperature of the liquid refrigerant is obtained from the pressure detected by the vapor pressure sensor, and the degree of superheat of the gas refrigerant is calculated by subtracting the evaporation temperature from the temperature detected by the suction temperature sensor to set the degree of superheat as a feedback value. An operation amount of the expansion valve is calculated by a PID calculation algorithm so that the calculated degree of superheat becomes a target degree of superheat.
In the feedback control of the drive frequency of the water supply pump or the valve opening degree of the flow rate control valve, the temperature detected by the outlet hot water temperature sensor is used as a feedback value, and the operation amount of the water supply pump or the flow rate control valve is calculated by a PID calculation algorithm so that the detected temperature becomes a target outlet hot water temperature .
The target outlet temperature can be set between an upper limit value and a lower limit value,
The lower limit value is a value obtained by adding a predetermined value to the temperature of the feed water after it flows out of the heat recovery heat exchanger and before it flows into the condenser so that the refrigerant flowing out of the condenser becomes a supercooled liquid state .
Water heating system. The water heating system according to claim 1, wherein the heat source fluid line is configured to exchange heat between the heat source fluid and the water supply in a counterflow manner in the heat recovery heat exchanger, and then exchange heat between the heat source fluid and the liquid refrigerant in a counterflow manner in the evaporator. a heat source temperature sensor for detecting a temperature of the heat source fluid before the heat source fluid flows into the evaporator;
The supply water heating system according to claim 1 , wherein the control means sets the target degree of superheat in accordance with a temperature detected by the heat source temperature sensor. The water heating system of claim 3, wherein the control means increases the target degree of superheat when it is determined that the fluctuation in the temperature detected by the heat source temperature sensor is large. The water heating system according to claim 3 or 4, wherein the control means reduces the target degree of superheat when it is determined that the temperature detected by the heat source temperature sensor is stable. one or two bypass lines for bypassing water to the heat recovery heat exchanger and/or for bypassing a heat source fluid to the heat recovery heat exchanger;
and a preheating mode switching means for switching between a feed water preheating mode in which the feed water and the heat source fluid are simultaneously circulated through the heat exchanger for heat recovery and a preheating stop mode in which at least one of the feed water and the heat source fluid is circulated through the bypass line.
The water heating system according to any one of claims 1 to 5 . a feed water temperature sensor before flowing into the heat exchanger for heat recovery, which detects the temperature of the feed water before flowing into the heat exchanger;
a heat source temperature sensor before flowing into the heat exchanger for heat recovery, which detects the temperature of the heat source fluid before flowing into the heat exchanger for heat recovery;
The control means
A first detected temperature by the heat exchanger inlet water temperature sensor is compared with a second detected temperature by the heat exchanger inlet heat source temperature sensor;
When the first detected temperature is lower than the second detected temperature, the preheating mode switching means is controlled to execute the water supply preheating mode;
When the first detected temperature is higher than the second detected temperature, the pre-heating mode switching means is controlled to execute the pre-heating stop mode.
The water heating system according to claim 6 . The control means
a signal input unit that receives a preheating mode designation signal that designates the type of the water supply preheating mode or the preheating stop mode;
The water supply heating system of claim 6, further comprising a preheating mode switching control unit that controls the preheating mode switching means to execute the water supply preheating mode or the preheating stop mode in accordance with the preheating mode designation signal input to the signal input unit.

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