JP5355016B2 - Refrigeration equipment and heat source machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To resolve a problem in a refrigeration apparatus taking intermediate cooler cooled side liquid approach wherein a coefficient of performance COP is deteriorated accompanied by an increase of an compressor input caused by a refrigerant injected into an intermediate chamber of a multi-stage compressor. <P>SOLUTION: The heat source machine 100 is equipped with a refrigerant compressor 10 having a low stage compression mechanism 11 and a high stage compression mechanism 12, a condenser 20 cooling the refrigerant compressed by the compressor 10, a bypass pipe 14 injecting one part of the refrigerant diverged from a main stream of the refrigerant cooled by a heat exchanger 20 between the low stage compression mechanism 11 and the high stage compression mechanism 12 as a sub-stream, an expansion valve 41 provided in the bypass pipe 14 and expanding the sub-stream of the refrigerant, an intermediate cooler 40 cooling the main stream of the refrigerant by using the sub-stream of the refrigerant expanded by the expansion valve 41, and a control circuit 50 increasing an opening of the expansion valve 41 according to an increase of a temperature difference between the main stream of the refrigerant and the sub-stream expanded by the expansion valve 41 and limiting the opening of the expansion valve 41 based on a degree of the superheat of the expanded sub-stream. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a refrigeration apparatus having a multistage compression apparatus and a heat source apparatus.

In order to improve the coefficient of performance COP, a two-stage compression refrigeration apparatus using an economizer cycle is conventionally known (for example, see Patent Document 1).

Japanese Unexamined Patent Publication No. 7-190520 (FIG. 1)

Here, the opening of the electronic expansion valve for the intermediate cooler is the difference between the cooling side refrigerant outlet gas temperature of the intermediate cooler and the saturated gas temperature corresponding to the compressor intermediate chamber pressure (hereinafter referred to as the intermediate cooler cooling side outlet superheat degree). Considering the control by the difference between the cooled refrigerant liquid temperature of the intermediate cooler and the saturated liquid temperature corresponding to the compressor intermediate chamber pressure (hereinafter referred to as the intermediate cooler cooled liquid approach), the following problems There is.
Since the two-stage compressor type refrigeration system has a wide operating pressure range, the compressor suction refrigerant has a large fluctuation in density, the refrigerant mass flow rate of the refrigeration system fluctuates greatly, and the mass flow rate of the refrigerant passing through the intercooler also fluctuates greatly. To do. For this reason, in the operation state deviating from the design point, the cooling capacity of the intermediate cooler is relatively excessive or excessive. In addition, when the opening degree of the electronic expansion valve for the intermediate cooler is controlled by the degree of superheat on the outlet side of the intermediate cooler, the refrigerant flow rate of the intermediate cooler becomes excessive in the operation state where the capacity of the intermediate cooler is excessive. However, there is a problem that the coefficient of performance COP decreases with an increase in compressor input. In addition, when the opening degree of the electronic expansion valve is controlled by the degree of superheater cooling side outlet superheating, there is a problem that it is very difficult to set a control constant if the refrigerant flow rate varies greatly.
On the other hand, when the opening of the electronic expansion valve is controlled by the intercooler cooled side liquid approach, it is relatively easy to set the control constant, but in the operation state where the capacity of the intercooler is too small, The refrigerant flow rate in the cooler becomes excessive, the coefficient of performance COP decreases with the increase in compressor input, and the separation efficiency of the oil separator decreases due to the decrease in the compressor discharge refrigerant temperature, resulting in the exhaustion of lubricating oil. Damage could have occurred.

  The present invention has been made to solve the above-mentioned problems, and a main object is to control an electronic expansion valve used as an expansion valve for an intercooler to obtain a highly efficient refrigeration apparatus.

The refrigeration apparatus according to the present invention includes a compressor having a multistage compressor, a condenser that condenses the refrigerant compressed by the compressor, an evaporator-side expansion valve that expands the refrigerant condensed by the condenser, The evaporator which evaporates the refrigerant expanded by the evaporator side expansion valve and flows to the compressor, and the multistage compression by branching a part from the main flow of the refrigerant flowing from the condenser to the evaporator side expansion valve as a substream. A bypass pipe that is injected between the apparatuses, an expansion valve that is provided in the bypass pipe and expands the subflow of the refrigerant, and a main flow of the refrigerant is cooled by using the subflow of the refrigerant expanded by the expansion valve. Control means for controlling the opening degree of the expansion valve based on the degree of superheat of the expanded subflow when the temperature difference between the intermediate cooler and the main flow of the refrigerant and the subflow expanded by the expansion valve is larger than a target region And with A.

The heat source apparatus according to the present invention includes a compressor having a low-stage compressor and a high-stage compressor, a heat exchanger that cools the refrigerant compressed by the compressor, and a mainstream of the refrigerant cooled by the heat exchanger a bypass pipe for injecting between the low-stage compressor part of the branched refrigerant as a side stream and the high-stage compression device from an expansion valve for expanding the side stream of the coolant is provided in the bypass pipe, An intermediate cooler that cools the main flow of the refrigerant using the subflow of the refrigerant expanded by the expansion valve, and a temperature difference between the main flow of the refrigerant and the subflow expanded by the expansion valve is larger than a target area And a control means for controlling the opening degree of the expansion valve based on the degree of superheat of the expanded substream.

Further, the control means, wherein when the degree of superheat of the expanded sidestream is below a first predetermined value, limits the increase in the opening degree of the expansion valve, the degree of superheat is below the first predetermined value The opening degree of the expansion valve is decreased when it is equal to or smaller than a second predetermined value.

  Further, the control means changes start conditions for limiting the opening of the expansion valve according to the temperature of the refrigerant discharged from the compressor.

  The control means increases the opening of the expansion valve when the temperature of the refrigerant discharged from the compressor exceeds a predetermined temperature, regardless of the opening limit of the expansion valve. .

  Further, another bypass pipe having an on-off valve is provided in parallel with the bypass pipe, and the refrigerant cooled by the intermediate cooler bypasses the load side device and is interposed between the low-stage compressor and the high-stage compressor. It is characterized by injecting.

  According to the refrigeration apparatus and the heat source apparatus according to the present invention, even if the operating state of the refrigeration cycle changes, the refrigerant flow rate of the intermediate cooler can be appropriately controlled, and the increase in the compressor input is suppressed, so that a highly efficient refrigeration A device can be obtained.

Embodiment 1 FIG.
FIG. 1 shows a configuration diagram of a two-stage refrigeration apparatus according to an embodiment of the present invention.
The refrigerant compressor 10 is a two-stage compressor incorporating two low-stage compression mechanisms 11 and a high-stage compression mechanism 12 connected via a compressor intermediate chamber 13, and its discharge pipe is connected to a condenser 20. ing. The condenser 20 is a heat exchanger that cools and condenses the high-temperature and high-pressure refrigerant gas compressed by the refrigerant compressor 10, and generates heat between the gas refrigerant of the refrigerant compressor 10 and the secondary refrigerant supplied from the outside. It is a device that performs the exchange. As an example of the secondary refrigerant, water is used in a case where the refrigeration apparatus is used for hot water supply. Further, the object to be heat-exchanged by the condenser 20 is not limited to water, but may be other refrigerants, or a combination of a heat exchanger and a fan that exchanges heat between the air sent from the fan and the refrigerant. It does not matter.

An intermediate cooler 40 is connected to the outlet side pipe of the condenser 20, and the outlet pipe of the intermediate cooler 40 branches into two. Here, one pipe is connected to the intermediate cooler 40 via the expansion valve 41 for the intermediate cooler, and the outlet of the intermediate cooler 40 is connected to the compressor intermediate chamber 13. This pipe is called a bypass pipe 14, and a part of the refrigerant condensed in the condenser 20 is allowed to flow to the refrigerant compressor 10 as a substream of the refrigerant. The refrigerant flowing through the bypass pipe 14 is expanded by the intermediate cooler expansion valve 41 and becomes a low-temperature refrigerant and is returned to the intermediate cooler 40. The intercooler 40 has a function of further cooling the refrigerant main stream from the condenser 20 by performing heat exchange between the low-temperature reflux refrigerant (substream) and the refrigerant from the condenser 20 (main stream). Is. In the example of FIG. 1, the bypass pipe 14 is connected to the downstream side of the intermediate cooler 40, but the bypass pipe 14 is connected to the upstream side, that is, between the condenser 20 and the intermediate cooler 40, You may comprise so that the substream which flows through the piping 14, and the main stream after a branch may be heat-exchanged.

  The other pipe is a main pipe through which the main flow of the refrigerant flows, and is connected to the evaporator 30 via the evaporator expansion valve 31. The evaporator expansion valve 31 expands the main flow of the refrigerant to a low pressure and low temperature and flows it to the evaporator 30. The evaporator expansion valve 31 can be an electronic expansion valve whose opening degree can be adjusted according to the load. For example, the opening degree so that the suction superheat degree of the refrigerant compressor 10 becomes a predetermined value (or range). Is adjusted (superheat control). Note that other control methods may be employed for the opening degree control, or a throttle device with a fixed opening degree may be used.

  The outlet of the evaporator 30 is connected to the suction port of the refrigerant compressor 10. The evaporator 30 exchanges heat between the refrigerant expanded by the evaporator expansion valve 31 and air or another secondary refrigerant, and cools the air or other secondary refrigerant (heats the primary refrigerant). It is. For example, when heat exchange is performed using air heat, a heat exchanger having a fan and fins can be used, and in the case of a system exchanging heat with water, a plate heat exchanger or the like is used. It is possible.

  The control circuit 50 (control means) controls the opening degree of the expansion valve 41 based on the detection values of the various sensors 51 to 55 using a control board having a microcomputer. The control circuit 50 may have a function of controlling the entire refrigeration apparatus other than the expansion valve 41 or the entire heat source apparatus 100. The temperature sensor 51 is a temperature sensor that detects the temperature of the refrigerant discharged from the refrigerant compressor 10, and is installed in the discharge pipe. The temperature sensor 52 and the pressure sensor 53 are sensors that detect the temperature and pressure of the discharge gas of the intercooler 40, and are used to detect the degree of superheat of the discharge gas. The temperature sensor 54 is a temperature sensor provided on the outlet side piping of the expansion valve 41, and is used to detect a compressor-saturated chamber temperature equivalent saturated liquid temperature. Needless to say, the saturation temperature may be calculated from the detected pressure using a pressure sensor instead of the temperature sensor 54.

  The refrigeration apparatus is divided into a load side apparatus (evaporator 30) and a heat source apparatus 100 that supplies cold heat to the load side apparatus. The evaporator expansion valve 31 is often incorporated in a load side device, but can also be provided on the heat source unit side. As the load side device, various devices such as a refrigeration / refrigeration warehouse and an air conditioning facility are selected according to the application, and connected to the heat source device 100.

The operation of the intercooler expansion valve 41 of the present embodiment will be described below. FIG. 2 shows a control flow of the expansion valve 41 for the intercooler by the control circuit 50.
During the operation of the refrigeration apparatus, the control circuit 50 reads the detection values of the various sensors and adjusts the opening degree of the intercooler expansion valve 41 based on the detection values. First, the control circuit 50 reads the temperature of the cooled side liquid of the intermediate cooler of the expansion valve 41 for the intermediate cooler and the saturated liquid temperature corresponding to the compressor intermediate chamber pressure from the temperature sensors 54 and 55 connected to each pipe, and detects them. Calculate the temperature difference. When the temperature difference in the intercooler cooled side liquid approach is smaller than the target area, the control circuit 50 transmits a control signal for reducing the opening degree to the intercooler expansion valve 41, and expands the intercooler expansion. The opening degree of the valve 41 is controlled to be smaller than the current opening degree (step S3). For example, when the intercooler expansion valve 41 is of a type driven by a stepping motor, this control signal is a pulse signal of the number of times corresponding to the adjustment opening. When the opening degree of the expansion valve 41 for the intermediate cooler is reduced, the amount of refrigerant flowing on the cooling side (diversion side) of the intermediate cooler 40 is reduced, so that the amount of cooling in the intermediate cooler 40 can be reduced.

  When the temperature difference is within the target range, the control circuit 50 maintains the opening degree of the intercooler expansion valve 41 at the current opening degree. And when the opening degree process of step S2 and S3 is complete | finished, it returns to step S1 again and repeats the same process.

On the other hand, if the temperature difference is larger than the target area, the process proceeds to step S4. In step S4, it is determined whether the current state of the refrigeration cycle matches the start condition of the opening degree control of the intercooler expansion valve 41. The control circuit 50 is specifically, a medium between the condenser cooling side outlet superheat degree is calculated from the detected value of the temperature sensor 52 and pressure sensor 53 (the difference between the saturation temperature and the detected temperature of the pressure), the degree of superheat When the degree of superheat is higher than a preset degree of superheat (opening up prohibition superheat, for example, 10 ° C.), control is performed to increase the degree of opening of the expansion valve 41 for the intermediate cooler in order to increase the cooling amount (step S5).

Further, when the degree of superheat is smaller than the degree of opening degree prohibition superheat, the control circuit 50 suppresses the amount of refrigerant flowing into the compressor intermediate chamber 13 of the refrigerant compressor 10, and a large amount of refrigerant flows into the refrigerant. The intercooler expansion valve 41 is controlled so that the input load of the compressor 10 does not become excessive (steps S6, S2, S3). First, the control circuit 50, the degree of superheat of the measured degree of superheat reaches a predetermined determines greater than (opening down start superheat, 5 ° C. For example). If larger , the control circuit 50 suppresses the increase of the opening degree of the expansion valve 41 for the intercooler and maintains the current opening degree even though the liquid approach is larger than the target range (step S2). On the other hand, if the measured degree of superheat is smaller than the degree of opening degree reduction starting superheat, the control circuit 50 performs control to make the opening degree of the intercooler expansion valve 41 smaller than the current opening degree (step S3).

As described above, in this embodiment, when the degree of superheater outlet superheat is equal to or less than a preset value during the opening degree control of the electronic expansion valve by the intercooler cooled side liquid approach, the electronic expansion valve The increase in the opening degree is prohibited to prevent an increase in the intermediate cooler refrigerant flow rate, or the opening degree is reduced to decrease the intermediate cooler refrigerant flow rate. That is, the coefficient of performance COP can be improved by controlling the amount of refrigerant flowing into the cooling side pipe of the intermediate cooler based on the degree of superheat at the outlet of the intermediate cooler. In particular, in a situation where the input to the intermediate chamber of the compressor is excessive, it is possible to actively reduce the opening of the expansion valve 41 for the intermediate cooler and effectively improve the coefficient of performance under the same conditions.

  Further, in the present embodiment, when operating with the target intercooler cooling side liquid approach, even in operating conditions where the intercooler capacity becomes too small such that the intercooler cooling side outlet superheat degree is 0 ° C, Since the intermediate supercooler cooling side outlet superheat degree can be kept above a certain value, oil depletion due to a sudden drop in compressor discharge temperature can be prevented. The target intercooler cooling side liquid approach is a temperature range defined by 0 to the upper limit temperature (for example, 9 ° C.), and the width is set to an appropriate width so that the frequency of opening adjustment is not excessive. Is done.

In addition, it is desirable to set the opening degree down start superheat degree lower than the opening degree up prohibition superheat degree.
In addition, since the coefficient of performance COP begins to drop when droplets begin to mix with the refrigerant at the outlet of the intermediate cooler, it is desirable that the degree of superheat degree for prohibiting the opening increase be 5 to 10 ° C. or higher.

Although this embodiment has shown an example of a two-stage compression refrigeration apparatus, it is used for other refrigeration apparatuses having an economizer circuit, such as a single-stage compression refrigeration apparatus and a compression refrigeration apparatus that performs compression of three or more stages. Also good.
In this embodiment, the electronic expansion valve is used as the pressure reducing means. However, other pressure reducing means such as an ejector or an expander may be used.

Embodiment 2. FIG.
In this embodiment, the control of the electronic expansion valve for the intercooler of Embodiment 1 changes the opening restriction start condition when the compressor discharge temperature is equal to or higher than a preset value, and the opening degree up prohibition superheat degree In addition, control for changing the setting of the degree of superheat at the start of opening reduction to a lower temperature is added. Fig. 3 shows the control flow. 3, the same reference numerals as those in FIG. 2 represent the same or corresponding processes, and different processes will be mainly described below.

  When the control circuit 50 determines that the temperature difference measured in step S1 is larger than the target range, the control circuit 50 reads the compressor discharge refrigerant temperature from the temperature sensor 51 provided in the discharge pipe of the refrigerant compressor 10. When the compressor discharge refrigerant temperature is equal to or higher than a predetermined set temperature, the control circuit 50 reduces the opening degree up prohibition superheat degree and the opening degree down start superheat degree from the current set value by a predetermined temperature (for example, 1 ° C.). Is performed (step S11). On the other hand, if the compressor discharge refrigerant temperature is not equal to or higher than a predetermined set temperature, the control circuit 50 does not change the current set value. As described in the first embodiment, the control circuit 50 controls the opening degree of the intermediate cooler expansion valve 41 based on the degree of superheat of the intermediate cooler refrigerant side outlet.

  In this way, the control circuit 50 changes the refrigerant temperature supplied from the intercooler 40 when the compressor discharge refrigerant temperature is overheated by changing the opening degree up prohibition superheat degree and the opening degree down start superheat degree based on the discharge temperature. The temperature can be lowered and the compressor discharge refrigerant temperature can be lowered. Here, if the purpose is only to lower the discharge temperature, it can be performed by controlling the operating frequency of the refrigerant compressor 10 or adjusting the opening of the expansion valve 31 for evaporation. However, when adjusting with the evaporator expander 31, it is affected by the load of the evaporator 30 downstream thereof, and the adjusted refrigerant needs to pass through the low-stage compressor 11 and the high-stage compressor 12. Therefore, more indirect discharge temperature control must be performed. In contrast, in the present embodiment, since the refrigerant supplied to the middle of the low-stage compression mechanism 11 and the high-stage compression mechanism 12 is controlled, the discharge temperature can be controlled more directly, and the compressor It is possible to achieve both the effects of being able to effectively suppress excessive refrigerant inflow into the intermediate chamber 13.

The intermediate cooler cooling side outlet refrigerant becomes saturated liquid state, in order to prevent the compressor discharge temperature decreases sharply, taking into account the measurement error of the temperature sensor, opening down start superheat example, 5 ° C. or higher Is desirable.

Embodiment 3 FIG.
In the present embodiment, the control of the compressor intermediate chamber refrigerant injection is added to the control of the expansion valve 41 for the intermediate cooler of the second embodiment. FIG. 4 shows a configuration diagram of the refrigeration apparatus of the present embodiment. FIG. 5 shows the control flow. 4 and 5, the same reference numerals as those in FIGS. 1 to 3 represent the same or corresponding parts. Hereinafter, a description will be given focusing on differences from the first and second embodiments.

  This refrigeration apparatus includes an intermediate chamber refrigerant injection valve 60 on the downstream side of the intermediate cooler 40 and on the upstream side of the evaporator expansion valve 31. The intermediate chamber refrigerant injection valve 60 is provided so that a part of the refrigerant cooled by the intermediate cooler 40 can be supplied to the compressor intermediate chamber 13 of the refrigerant compressor 10, and is controlled to be opened and closed by the control circuit 50. It is what is done.

Next, the operation will be described. In FIG. 5, the process of step S21 corresponds to the processes of steps S1, S4, S6, S10, and S11 of FIG. 3, and the connection points P1 to P4 correspond to the connection points P1 to P4 of FIG. That is, how the control circuit 50 controls the opening degree of the expansion valve 41 on the basis of the intermediate cooler cooling side outlet superheat degree (and / or compressor discharge temperature) as described in the second embodiment. Is determined (step S21), and the control of opening up (step S5) / opening maintenance (step S2) / opening down (step S3) is performed.
Here, when control of opening degree maintenance (step S2) / opening degree down (step S3) is performed, the control circuit 50 checks (again) whether the compressor discharge temperature is equal to or higher than a predetermined set temperature. (Step S22) When it is determined that the compressor discharge temperature is lower than the predetermined temperature, the intermediate chamber refrigerant injection valve 60 is closed (Step S23), and when it is determined that the temperature is equal to or higher than the set temperature, the intermediate chamber refrigerant injection is performed. A control signal for opening the valve 60 is transmitted. Receiving this control signal, the intermediate chamber refrigerant injection valve 60 injects the refrigerant into the compressor intermediate chamber 13, so that the discharge temperature of the refrigerant compressor 10 can be lowered.

When the superheat degree of the compressor suction refrigerant is high, the refrigerant discharge refrigerant temperature is overheated even in the operation state in which the supercooler outlet side superheat degree maintains the opening degree of the intermediate cooler 41 or reduces the opening degree. May end up.
Even in such a case, in the present embodiment, the refrigerant can be injected into the compressor intermediate chamber 13 to lower the compressor discharge refrigerant temperature, thereby preventing the compressor from being damaged.
Further, since the refrigerant is injected into the compressor intermediate chamber 13 by the intermediate chamber refrigerant injection valve 60 only when the compressor discharge temperature is overheated, an excessive decrease in the compressor discharge refrigerant temperature is prevented, and the compressor is increased by increasing the refrigerant circulation amount. It is possible to prevent an increase in input and prevent a decrease in the coefficient of performance COP.

  In the present embodiment, the refrigerant is supplied to the compressor intermediate chamber 13 using the intermediate chamber refrigerant injection valve 60, but other means such as a combination of an electromagnetic valve and a capillary tube may be used.

  In the present embodiment, the refrigerant injection flow rate is determined by the intermediate chamber refrigerant injection valve 60. For adjusting the refrigerant injection flow rate, flow rate adjusting means using a capillary tube, an orifice, an expansion valve, etc., and supply of these refrigerants A plurality of systems may be used, and a flow rate adjusting means for switching by an electromagnetic valve or other means may be used in combination.

In the present embodiment, the refrigerant is supplied to the compressor intermediate chamber 13, but the refrigerant may be supplied into the high-stage compression mechanism 12.

As another control example of the present embodiment, the conditions for starting the refrigerant injection into the compressor intermediate chamber 13 may be a case where all of the following conditions are satisfied.
(1) The refrigerant compressor 10 is in operation.
(2) The compressor suction pressure is less than a preset value (for example, 0.15 MPa).
(3) The compressor discharge refrigerant temperature is equal to or higher than a preset value (for example, 85 ° C.).

Furthermore, the condition for terminating the refrigerant injection into the compressor intermediate chamber 13 may be a case where any of the following conditions is satisfied.
(1) The refrigerant compressor 10 is stopped.
(2) The compressor suction pressure is not less than a preset value (for example, 0.15 MPa).
(3) The compressor discharge refrigerant temperature is less than a preset value (for example, 75 ° C.).

  When the compressor discharge pressure is lower than the compressor intermediate chamber pressure, the compressor overheat prevention control by the intermediate chamber refrigerant injection valve 60 may not be performed. This is to prevent the refrigerant from flowing back into the piping system connected from the compressor intermediate chamber 13 and to prevent the compressor from burning.

Two or more of Embodiments 1 to 3 may be combined.

  The refrigeration apparatus according to the present invention can be used for a highly efficient refrigeration apparatus having an intercooler.

It is a block diagram of the freezing apparatus in Embodiment 1 of this invention. It is a control flowchart in Embodiment 1 of this invention. It is a control flow figure in Embodiment 2 of the present invention. It is a block diagram of the freezing apparatus in Embodiment 3 of this invention. It is a control flow figure in Embodiment 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Refrigerant compressor, 11 Low stage compression mechanism, 12 High stage compression mechanism, 13 Compressor intermediate chamber, 14 Bypass piping, 20 Condenser, 30 Evaporator, 31 Expansion valve for evaporator, 40 Intermediate cooler, 41 For intermediate cooler Expansion valve, 50 control circuit, 51, 52, 54, 55 Temperature sensor, 55 Pressure sensor, 60 Refrigerant injection valve for intermediate chamber, 100 Heat source machine

Claims (6)

A compressor having a multi-stage compression device;
A condenser for condensing the refrigerant compressed by the compressor;
An evaporator-side expansion valve that expands the refrigerant condensed by the condenser;
An evaporator that evaporates the refrigerant expanded by the evaporator side expansion valve and flows the refrigerant to the compressor;
A bypass pipe that branches from the main flow of the refrigerant flowing from the condenser to the evaporator side expansion valve as a sub flow and injects between the multistage compression devices;
An expansion valve provided in the bypass pipe to expand the side flow of the refrigerant;
An intercooler that cools the main flow of the refrigerant using the subflow of the refrigerant expanded by the expansion valve;
Control means for controlling the opening degree of the expansion valve based on the degree of superheat of the expanded subflow when the temperature difference between the main flow of the refrigerant and the subflow expanded by the expansion valve is larger than a target area; Refrigeration equipment. A compressor having a low-stage compressor and a high-stage compressor;
A heat exchanger for cooling the refrigerant compressed by the compressor;
A bypass pipe for injecting a part of the refrigerant branched from the main flow of the cooled refrigerant heat exchanger between the low stage compressor and the high-stage compressor as a side stream,
An expansion valve provided in the bypass pipe to expand the side flow of the refrigerant;
An intercooler that cools the main flow of the refrigerant using the subflow of the refrigerant expanded by the expansion valve;
Control means for controlling the opening degree of the expansion valve based on the degree of superheat of the expanded subflow when the temperature difference between the main flow of the refrigerant and the subflow expanded by the expansion valve is larger than a target area; Heat source machine.   The control means limits an increase in the opening degree of the expansion valve when the degree of superheat of the expanded substream is equal to or less than a first predetermined value, and the second degree of superheat is less than the first predetermined value. The heat source device according to claim 2, wherein the opening degree of the expansion valve is decreased when the value is equal to or less than a predetermined value.   4. The heat source apparatus according to claim 2, wherein the control unit changes a start condition for restricting an opening of the expansion valve according to a temperature of a refrigerant discharged from the compressor. 5.   When the temperature of the refrigerant discharged from the compressor exceeds a predetermined temperature, the control means increases the opening of the expansion valve regardless of the opening limit of the expansion valve. The heat source machine according to any one of claims 2 to 4. Wherein the bypass pipe with the other bypass pipe having an on-off valve in parallel provided, injected between the intermediate cooler with cooled refrigerant to bypass the load side apparatus the low stage compressor and the high-stage compressor The heat source machine according to claim 5, wherein

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