JP6433709B2 - Turbo refrigerator, control device therefor, and control method therefor - Google Patents

Description

  The present invention relates to a turbo refrigerator, a control device thereof, and a control method thereof.

  Conventionally, a turbo refrigerator 100 as shown in FIG. 9 is known. The turbo refrigerator 100 includes a main circuit of a refrigeration cycle in which a two-stage turbo compressor 102, a condenser 103, an economizer 104, a main expansion valve 105, and an evaporator 107 are sequentially connected. The gas refrigerant compressed in the turbo compressor 102 and having a high temperature and high pressure is sent to the condenser 103. The condenser 103 is a plate heat exchanger, and heats the hot water up to a predetermined temperature by exchanging heat between the hot water circulating in the hot water circuit 111 and the gas refrigerant.

  The refrigerant condensed and liquefied in the condenser 103 is supplied to the economizer 104. The economizer 104 exchanges heat between the liquid refrigerant from the condenser 103 (a liquefied refrigerant flowing in the main circuit) and the refrigerant diverted from the main circuit and depressurized by the sub-expansion valve 113, and the main circuit uses the latent heat of vaporization of the refrigerant. It is a plate type refrigerant / refrigerant heat exchanger for supercooling a liquid refrigerant flowing inside. Further, the economizer 104 includes a gas circuit for injecting the gas refrigerant evaporated by supercooling the liquid refrigerant into the intermediate-pressure compressed refrigerant from the intermediate suction port 102C of the two-stage turbo compressor 102. The main expansion valve 105 expands the supercooled refrigerant through the economizer 104 and supplies it to the evaporator 107. The evaporator 107 is a plate-type heat exchanger, and evaporates the refrigerant by exchanging heat between the refrigerant led from the main expansion valve 105 and the heat source water circulated through the heat source water circuit 115, and the latent heat of evaporation causes the refrigerant to evaporate. Cool the heat source water.

The refrigerant, as a measurement means for measuring the temperature and pressure of the hot water and heat source water, 2-stage turbo compressor 10 2 of the suction port 102A, the discharge port 102B, the intermediate suction port 102C, a pressure gauge 141, 142, 143 and thermometer 131, 132, 133 are provided, the inlet and outlet of the hot water circuit 111, the inlet and outlet of the heat source water circuit 1 15, thermometer 135,136,137,138 are provided each of the main expansion valve 105 A thermometer 134 is provided at the inlet.

JP 2012-77971 A

It is known that a thermometer generally used for a turbo refrigerator or the like as well as the above-described turbo refrigerator 100 has poor responsiveness and causes a delay of several minutes. This is because the temperature measurement unit cannot be directly inserted into the pipe for safety and ease of maintenance. For example, FIG. 10 shows a configuration example of a thermometer. FIG. 10A shows an example in which a resistance temperature detector with a protective tube (a thermometer having a double structure) is inserted into the pipe, and FIG. 10B shows the temperature by welding a thermometer to the outer wall of the pipe. It shows an example of indirectly measuring.
And since the response of a thermometer is bad as mentioned above, the following problems arise.
For example, taking the turbo chiller 100 shown in FIG. 9 as an example, when a sudden temperature change occurs in the hot water circulating in the hot water circuit 111 (for example, condensation is caused by a large amount of water being added to the hot water by the user). For example, when the temperature of the inlet side hot water of the vessel 103 rapidly decreases, it is necessary to quickly grasp this temperature change and throttle the opening of the main expansion valve 105 and the sub expansion valve 113. However, since the control of the main expansion valve 105 and the sub-expansion valve 113 is delayed due to the measurement delay of the thermometer, the opening degree of the expansion valve becomes excessive compared to the actual temperature, and the evaporator 107 and the economizer 104 cannot evaporate completely. The liquid refrigerant was sucked into the two-stage turbo compressor 102, and the two-stage turbo compressor 102 might be damaged.

  The present invention has been made in view of such circumstances, and provides a turbo chiller, a control device thereof, and a control method thereof that can alleviate a control delay of an expansion valve caused by a measurement delay of a thermometer. For the purpose.

  A first aspect of the present invention includes a main circuit of a refrigeration cycle in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected to circulate a refrigerant, and an inlet temperature of a heat medium flowing into the condenser. It is applied to a turbo chiller comprising first temperature measuring means for measuring the temperature, second temperature measuring means for measuring the outlet temperature of the heat medium flowing out from the condenser, and pressure measuring means for measuring the condensation pressure. A control device for correcting the temperature measured by the first temperature measuring means and the second temperature measuring means; and the heat medium inlet temperature and the heat medium outlet temperature corrected by the temperature correcting means. An expansion valve control means for controlling the opening degree of the expansion valve, and the temperature correction means includes a condensation temperature acquisition means for acquiring a condensation temperature from the condensation pressure acquired by the pressure measurement means, and a current From the condensation temperature A temperature difference calculating means for calculating a temperature difference by subtracting a condensing temperature before a predetermined period; a determining means for determining whether an absolute value of the temperature difference is equal to or greater than a preset threshold; and the temperature difference And a correction unit that adds the temperature difference to each of the temperatures measured by the first temperature measuring unit and the second temperature measuring unit when the absolute value of the temperature is equal to or greater than the threshold value. Device.

  According to the above aspect, the condensation temperature based on the condensation pressure is acquired by the condensation temperature acquisition means, and the temperature difference between the current condensation temperature and the condensation temperature before a certain period is calculated by the temperature difference calculation means. Then, it is determined by the determining means whether the absolute value of the temperature difference is equal to or greater than a predetermined threshold value. When the absolute value of the temperature difference is equal to or greater than the threshold value, the first temperature measuring means and the second temperature measurement are corrected by the correcting means. The temperature is corrected by adding a temperature difference to each temperature measured by the means. Thereby, it becomes possible to catch a temperature change early, and it becomes possible to relieve the measurement delay of a temperature measurement means. And the control of the expansion valve using the corrected temperature is performed by the expansion valve control means, so that the control delay of the expansion valve due to the measurement delay by the first temperature measuring means and the second temperature measuring means is reduced. Is possible.

  In the turbo chiller control device, the certain period may be set to a period in which the refrigerant makes a round of the main circuit.

  By setting the constant period, it is possible to accurately grasp the fluctuation of the inlet temperature of the heat medium.

  The turbo chiller is provided between the condenser and the expansion valve, and exchanges heat between the liquid refrigerant flowing through the main circuit and the refrigerant diverted from the main circuit and decompressed by the sub expansion valve, A heat exchanger that supercools the liquid refrigerant flowing through the main circuit, and a gas circuit that returns the liquid refrigerant flowing through the main circuit and the refrigerant that has finished heat exchange to the compressor in the heat exchanger, In the control device, the expansion valve control means may perform opening control of the sub expansion valve using the heat medium inlet temperature and the heat medium outlet temperature corrected by the temperature correction means.

  Thus, by controlling the sub expansion valve using the corrected temperature, the control delay of the sub expansion valve caused by the measurement delay by the first temperature measuring means and the second temperature measuring means can be alleviated. It becomes possible.

One aspect as a reference example of the present invention is that a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected, a main circuit of a refrigeration cycle in which a refrigerant circulates, and heat source water flowing into the evaporator A heat source water inlet temperature measuring means for measuring the inlet temperature of the heat source water, and a heat source water outlet temperature measuring means for measuring the outlet temperature of the heat source water flowing out of the evaporator. The evaporation temperature is calculated such that a ratio of a value obtained by subtracting the evaporation temperature from the heat source water inlet temperature to a value obtained by subtracting the heat source water inlet temperature from the heat source water outlet temperature matches a target ratio at a stable time. A turbo chiller control device comprising: an evaporation temperature correction means; and an expansion valve control means for controlling an opening degree of the expansion valve using an evaporation pressure obtained from the evaporation temperature corrected by the evaporation temperature correction means. is there.

  According to this aspect, the ratio of the value obtained by subtracting the evaporation temperature from the heat source water inlet temperature to the value obtained by subtracting the heat source water inlet temperature from the heat source water outlet temperature by the evaporation temperature correction means matches the target ratio at the stable time. Such an evaporation temperature is calculated. Then, by reflecting the evaporation temperature calculated by the evaporation temperature correction means in the valve opening control of the expansion valve, it is possible to avoid the valve opening of the expansion valve from becoming excessive.

A second aspect of the present invention is a turbo refrigerator provided with the above-described control device.

According to a third aspect of the present invention, a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected, a main circuit of a refrigeration cycle in which refrigerant circulates, and an inlet temperature of a heat medium flowing into the condenser It is applied to a turbo chiller comprising first temperature measuring means for measuring the temperature, second temperature measuring means for measuring the outlet temperature of the heat medium flowing out from the condenser, and pressure measuring means for measuring the condensation pressure. A control method for correcting a temperature measured by the first temperature measuring unit and the second temperature measuring unit, and a heat medium inlet temperature and a heat medium outlet temperature corrected in the temperature correction step. An expansion valve control step for controlling the opening of the expansion valve, and the temperature correction step includes a condensing temperature acquisition step for acquiring a condensing temperature from the condensing pressure acquired by the pressure measuring means, and a current From the condensation temperature A temperature difference calculating step of calculating a temperature difference by subtracting a condensing temperature before a predetermined period; a determination step of determining whether or not an absolute value of the temperature difference is equal to or greater than a preset threshold; and the temperature difference And a temperature correction step of adding the temperature difference to the respective temperatures measured by the first temperature measuring means and the second temperature measuring means when the absolute value of the turbo chiller is equal to or greater than the threshold value. Is the method.

One aspect as a reference example of the present invention is that a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected, a main circuit of a refrigeration cycle in which a refrigerant circulates, and heat source water flowing into the evaporator A heat source water inlet temperature measuring means for measuring the inlet temperature of the heat source, and a heat source water outlet temperature measuring means for measuring the outlet temperature of the heat source water flowing out of the evaporator. The evaporation temperature is calculated such that a ratio of a value obtained by subtracting the evaporation temperature from the heat source water inlet temperature to a value obtained by subtracting the heat source water inlet temperature from the heat source water outlet temperature matches a target ratio at a stable time. A method for controlling a turbo chiller comprising: an evaporation temperature correction step; and an expansion valve control step for controlling the opening of the expansion valve using an evaporation pressure obtained from the evaporation temperature corrected in the evaporation temperature correction step. is there.

  According to the present invention, there is an effect that the control delay of the expansion valve due to the measurement delay of the thermometer can be reduced.

It is the figure which showed schematic structure of the turbo refrigerator which concerns on 1st Embodiment of this invention. It is a functional block diagram of a control device concerning a 1st embodiment of the present invention. It is the figure which showed the flowchart of the process performed by the present flow volume calculating part. It is the flowchart which showed the process performed by the main expansion valve opening calculating part. It is the flowchart which showed the process performed by the sub expansion valve opening calculating part. It is a figure for demonstrating control of the control apparatus which concerns on 1st Embodiment of this invention. It is the figure which showed an example of the time transition of the heat source water inlet temperature Tswi measured by the temperature sensor, the heat source water outlet temperature Tswo measured by the temperature sensor, the evaporation temperature ET converted from the evaporation pressure Ps, and the compressor discharge temperature. is there. It is a functional block diagram of the control apparatus which concerns on 2nd Embodiment of this invention. It is the figure which showed one structural example of the conventional turbo refrigerator. It is the figure which showed one structural example of the thermometer.

[First Embodiment]
Hereinafter, a turbo chiller, a control device thereof, and a control method according to a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of a turbo refrigerator according to the first embodiment of the present invention. As shown in FIG. 1, a turbo refrigerator 1 includes a closed circuit refrigerant main circuit 8 in which a compressor 2, a condenser 3, an economizer 4, a main expansion valve 5, and an evaporator 7 are sequentially connected. I have.

  The compressor 2 is a multistage centrifugal compressor that is driven by an inverter motor 6. In addition to the suction port 2A and the discharge port 2B, the compressor 2 has an intermediate suction port 2C provided between the first impeller and the second impeller. The low-pressure gas refrigerant sucked from the suction port 2A is sequentially centrifugally compressed by the rotation of the first impeller and the second impeller, and the compressed high-pressure gas refrigerant is discharged from the discharge port 2B.

  The high-pressure gas refrigerant discharged from the discharge port 2 </ b> B of the compressor 2 is guided to the condenser 3. The condenser 3 is, for example, a plate heat exchanger, and exchanges heat between the high-pressure gas refrigerant supplied from the compressor 2 and hot water (heat medium) circulating in the hot water circuit, whereby the hot water is reduced to a predetermined temperature. Raise the temperature. The refrigerant condensed and liquefied in the condenser 3 is supplied to the economizer 4.

  The economizer 4 exchanges heat between the liquid refrigerant that flows in the refrigerant main circuit 8 and the refrigerant that is diverted from the refrigerant main circuit 8 and decompressed by the sub-expansion valve 9, and the refrigerant main circuit 8 is generated by the latent heat of vaporization of the refrigerant after decompression. It is a plate type refrigerant / refrigerant heat exchanger for supercooling a liquid refrigerant flowing inside. The economizer 4 also includes a gas circuit 10 for injecting gas refrigerant (intermediate pressure refrigerant) evaporated by supercooling the liquid refrigerant into the intermediate pressure compressed refrigerant from the intermediate suction port 2C of the compressor 2. Thus, an intermediate cooler type economizer cycle is configured.

  The refrigerant supercooled through the economizer 4 is expanded by passing through the main expansion valve 5 and supplied to the evaporator 7. The evaporator 7 is a heat exchanger (for example, a plate heat exchanger), and evaporates the refrigerant by exchanging heat between the refrigerant introduced from the main expansion valve 5 and the heat source water circulating in the heat source water circuit 15. The heat source water is cooled by the latent heat of evaporation.

The turbo refrigerator 1 includes a temperature sensor 12 that measures a hot water inlet temperature Thwi that is the temperature of hot water flowing into the condenser 3, and a temperature sensor 13 that measures a hot water outlet temperature Thwo that is the temperature of hot water that flows out of the condenser 3. provided in the refrigerant outlet side of the condenser 3, the temperature sensor 14 that measures the condenser exit temperature Tc, is provided between the Econo miser 4 and the main expansion valve 5 in the refrigerant main circuit 8, the main expansion valve inlet temperature A temperature sensor 19 that measures Tecoh, a temperature sensor 16 that measures an intermediate-pressure refrigerant temperature Tm that is the temperature of the intermediate-pressure refrigerant that flows through the gas circuit 10, and a heat source water inlet temperature Tsw that is the temperature of the heat source water that flows into the evaporator 7 A temperature sensor 17 for measuring and a temperature sensor 18 for measuring a heat source water outlet temperature Tswo which is a temperature of the heat source water flowing out of the evaporator 7 are provided. Further, the turbo refrigerator 1 includes a pressure sensor 20 that measures a condensation pressure (compressor discharge pressure) Pd, a pressure sensor 21 that measures an intermediate pressure refrigerant pressure Pm that is the pressure of the intermediate pressure refrigerant flowing through the gas circuit 10, and evaporation. A pressure sensor 22 for measuring pressure (compressor suction pressure) Ps is provided.

The measurement values of the various sensors are transmitted to the control device 30 and used for compressor speed control, opening control of the main expansion valve 5 and the sub-expansion valve 9, and the like.
The control device 30 is, for example, a computer, and communicates with a main storage device such as a CPU (Central Processing Unit) and a RAM (Random Access Memory), an auxiliary storage device, and an external device to communicate information. Equipment.
The auxiliary storage device is a computer-readable recording medium, such as a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, or a semiconductor memory. Various programs are stored in the auxiliary storage device, and various processes are realized by the CPU reading and executing the program from the auxiliary storage device to the main storage device.

FIG. 2 is a functional block diagram of the control device 30. As shown in FIG. 2, the control device 30 includes a temperature correction unit 31 and an expansion valve control unit 32.
The temperature correction unit 31 corrects the hot water inlet temperature Thwi and the hot water outlet temperature Thwo. That is, as described above, a measurement delay occurs in the temperature sensors 12, 13 and the like. The temperature correction unit 31 is a configuration for correcting a measurement delay caused by the temperature sensors 12 and 13.
Specifically, the temperature control unit 31 includes a condensation temperature acquisition unit 41, a temperature difference calculation unit 42, a determination unit 43, and a correction unit 44.

The condensation temperature acquisition unit 41 acquires the condensation temperature CT from the condensation pressure Pd measured by the pressure sensor 20. Specifically, the condensing temperature acquisition unit 41 has correspondence information (function or table) in which the condensing pressure Pd and the condensing temperature CT are uniquely associated, and the condensing pressure Pd is used using this correspondence information. To obtain the condensation temperature CT.
The temperature difference calculation unit 42 calculates the temperature difference ΔCT by subtracting the condensation temperature obtained before a certain period from the current condensation temperature obtained by the condensation temperature acquisition unit 41. Here, the fixed period corresponds to, for example, a period in which the refrigerant makes a round of the refrigerant main circuit 8, and is obtained by dividing the refrigerant charging amount [kg] by the refrigerant circulation amount [kg / min]. Note that a period in which a predetermined margin (margin) is taken into consideration for this value may be a fixed period.

  The determination unit 43 determines whether or not the absolute value | ΔCT | of the temperature difference ΔCT is equal to or greater than a preset threshold value. The threshold is, for example, a value derived from a change rate determined by the specification of the main expansion valve 5. For example, the change rate of the main expansion valve 5 is 10 [%] / 60 [sec] at the maximum, the hot water inlet temperature Thwi is about 70 [° C.], the hot water outlet temperature Thwo is 80 [° C.], and the above-mentioned fixed period is 30 [sec]. Is determined by the following equation (1).

  Threshold = (10 [%] × 10 [° C.] × 30 [sec] / 60 [sec]) + α = 0.5 + α [° C.] (1)

  Here, α is a margin (margin) and may be a fixed value, or may be a value determined according to a value in parentheses in the above equation (1).

  When the absolute value | ΔCT | of the temperature difference is equal to or greater than the threshold value, the correction unit 44 adds the temperature difference ΔCT to the hot water inlet temperature Thwi and the hot water outlet temperature Thwo, thereby setting the hot water inlet temperature Thwi and the hot water outlet temperature Thwo. to correct.

  The expansion valve control unit 32 calculates the expansion valve opening using the corrected hot water inlet temperature Thwi and the corrected hot water outlet temperature Thwo during the period in which the temperature correction is performed by the temperature correction unit 31, During a period when the temperature is not corrected by the temperature correction unit 31, the expansion valve opening is calculated using the hot water inlet temperature Thwi and the hot water outlet temperature Thwo measured by the temperature sensors 12 and 13. Hereinafter, the expansion valve control unit 32 will be described.

  The expansion valve control unit 32 includes, for example, a current flow rate calculation unit 51, a set flow rate calculation unit 52, a main expansion valve opening degree calculation unit 53, and a sub expansion valve opening degree calculation unit 54. In addition, about expansion valve control, it is not limited to the method shown below, A well-known various control method is employable. In this case, when the hot water inlet temperature Thwi and the hot water outlet temperature Thwo are used as parameters, if the temperature correction unit 31 performs temperature correction, the corrected hot water inlet temperature Thwi and hot water outlet are corrected. The temperature Thwo shall be used.

The current flow rate calculation unit 51 performs flow rate calculation using the hot water inlet temperature Thwi and the hot water outlet temperature Thwo as parameters. FIG. 3 shows a flowchart of processing executed by the current flow rate calculation unit 51. As shown in FIG. 3, the current flow rate calculation unit 51 calculates the current heating capability Qcon [kW] using the hot water inlet temperature Thwi and the hot water outlet temperature Thwo (step SA1). Subsequently, the condenser flow rate Gcon [kg / s] is calculated using the following equation (2) (step SA2).

  Gcon = Qcon / (Hd−Hc) (2)

In the equation (2), Hd is the discharge enthalpy [kJ / kg], and Hc is the condenser outlet enthalpy [kJ / kg].
Subsequently, the current flow rate Geva of the main expansion valve 5 is calculated using the following equation (3) (step SA3).

Geva = (Gcon-Gmo-Goc) / (1 + x) (3)
Here, x = (Hc−Hecoh) / (Hecom−Hc) (4)

  In Equation (3), Gcon is a condenser flow rate [kg / s], Gmo is a motor cooling flow rate [kg / s], and Goc is an oil cooling refrigerant flow rate [kg / s]. In the equation (4), Hc is the condenser outlet enthalpy [kJ / kg], Hecoh is the main expansion valve inlet enthalpy [kJ / kg], and Hecom is the intermediate suction gas enthalpy [kJ / kg].

  Next, the current flow rate calculation unit 51 calculates the current flow rate Geco of the sub expansion valve 9 using the condenser flow rate Gcon (step SA4). Specifically, the calculation is performed using the following equation (5).

  Geco = x × Geva (5)

In the equation (5), x is as described in the above equation (4). Geva is the current flow rate Geva of the main expansion valve calculated in the above equation (3).
The current flow rate Geva of the main expansion valve and the current flow rate Geco of the sub expansion valve calculated in this way are output to the main expansion valve opening degree calculation unit 53 and the sub expansion valve opening degree calculation unit 54.

The set flow rate calculation unit 52 calculates the set flow rate Geva ^* of the main expansion valve 5 and the set flow rate Geco ^* of the sub expansion valve 9. Here, the calculation by the set flow rate calculation unit 52 differs only in that the preset hot water outlet set temperature Thwo ^* is used instead of the hot water outlet temperature Thwo in the calculation formula used in the current flow rate calculation unit 51 described above. The others are the same. Therefore, detailed description is omitted.
The set flow rate Geva ^* of the main expansion valve 5 and the set flow rate Geco ^* of the sub expansion valve 9 are output to the main expansion valve opening calculation unit 53 and the sub expansion valve opening calculation unit 54.

The main expansion valve opening degree calculation unit 53 includes the current flow rate Geva of the main expansion valve 5 calculated by the current flow rate calculation unit 51, the current flow rate Geco of the sub expansion valve 9, and the main expansion valve 5 set by the set flow rate calculation unit 52. The feedforward opening degree command is calculated by performing feedforward control using the set flow rate Geva ^* of the sub-expansion valve 9 and the set flow rate Geco ^* of the sub-expansion valve 9, and the feedback opening degree by performing feedback control using the evaporator end temperature. By calculating the command and adding them together, an opening command is generated.
FIG. 4 is a flowchart showing processing executed by the main expansion valve opening degree calculation unit 53.
First, in the feedforward control, the current opening degree Cveva of the main expansion valve 5 is calculated using the current flow rate Geva of the main expansion valve and the pressure difference ΔP2 (= Pd−Ps) between the condensation pressure and the evaporation pressure as parameters. (Step SB1). Next, the set opening Cveva ^* of the main expansion valve is calculated using the set flow rate Geva ^* of the main expansion valve 5 and the differential pressure ΔP2 as parameters (step SB2).
Then, an opening degree command OP_FF in the feedforward control is calculated by apportioning the current opening degree Cveva and the set opening degree Cveva ^{* of} the main expansion valve 5 (step SB3).

In the feedback control, the opening degree command OP_FB is calculated such that the temperature difference ΔTswo between the heat source water outlet temperature Tswo and the evaporation temperature ET converted from the evaporation pressure Ps in the evaporator 7 coincides with the target value ΔTswo ^* ( Step SB4). For example, the opening degree command OP_FB in the feedback control is calculated by performing PID control on the difference between the temperature difference ΔTswo and the target value ΔTswo ^* .

When the opening command OP_FF based on feedforward control and the opening command OP_FB based on feedback control are calculated in this way, the final opening command OP = OP_FF + OP_FB is calculated by adding them (step SB5).
And the opening degree of the main expansion valve 5 is controlled based on this opening degree command OP.

The sub-expansion valve opening calculation unit 54 calculates the current flow rate Geva of the main expansion valve 5 calculated by the current flow rate calculation unit 51, the current flow rate Geco of the sub-expansion valve 9, and the main expansion valve 5 set by the set flow rate calculation unit 52. The feed-forward opening degree command is calculated by performing feedforward control using the set flow rate Geva ^* of the secondary expansion valve 9 and the set flow rate Geco ^* of the sub-expansion valve 9, and feedback is performed by performing feedback control using the main expansion valve inlet temperature Tecoh. The opening degree command OPeco is generated by calculating the opening degree command and adding them together.
FIG. 5 is a flowchart showing a process executed by the sub expansion valve opening degree calculation unit 54.
First, in the feedforward control, the current flow rate Geco of the secondary expansion valve 9 and the differential pressure ΔP1 (= Pd−Pm) between the condensation pressure Pd and the intermediate pressure Pm are used as parameters, and the current opening degree Cveco of the secondary expansion valve 9 is used. Is calculated (step SC1). Next, the set opening degree Cveco ^* of the sub expansion valve 9 is calculated using the set flow rate Geco ^* of the sub expansion valve 9 and the differential pressure ΔP1 as parameters (step SC2).
Then, a command value OPeco_FF in the feedforward control is calculated by apportioning the current opening Cveco and the set opening Cveco ^{* of} the sub-expansion valve 9 (step SC3).

In the feedback control, the main expansion valve inlet temperature target value Tecohset (= ΔT2 + MT) is set by adding a preset economizer outlet temperature difference ΔT2 to the sub-expansion valve inlet temperature MT (step SC4). Next, an opening degree command OPeco_FB is calculated to make the current main expansion valve inlet temperature Tecoh coincide with the main expansion valve inlet temperature target value Tecoh ^* (step SC5). For example, the opening degree command OPeco_FB in the feedback control is calculated by performing PID control on the difference between the current main expansion valve inlet temperature Tecoh and the main expansion valve inlet temperature target value Tecoh ^* .

  When the command value OPeco_FF by feedforward control and the command value OPeco_FB by feedback control are calculated in this way, the final opening command OPeco = OPeco_FF + OPeco_FB is calculated by adding them (step SC6). And the valve opening degree of the sub expansion valve 9 is controlled based on this opening degree command OPeco.

It will now be described with reference to FIG. 6 about the operation of the control device 30.
FIG. 6 is a diagram for explaining the control of the control device 30 according to the present embodiment.
6, before the change in the hot water inlet temperature Thwi occurs at time t1, since the hot water inlet temperature Thwi represents a stable numerical, the temperature difference is calculated by the temperature difference calculation section 42 of the temperature correction part 31 The absolute value | ΔCT | is close to zero. Therefore, in the determination unit 43, it is determined that the absolute value | ΔCT | of the temperature difference is less than the threshold value, and the temperature correction by the correction unit 44 is not performed.

On the other hand, when the hot water inlet temperature Thwi rapidly decreases at time t1, the condensing pressure Pd decreases rapidly with this, and the condensing temperature acquired by the condensing temperature acquisition unit 41 decreases. As a result, the absolute value | ΔCT | of the temperature difference calculated by the temperature difference calculation unit 42 is a relatively large value. As a result, the determination unit 43 determines that the absolute value | ΔCT | of the temperature difference is equal to or greater than the threshold value, and the correction unit 44 performs temperature correction. Accordingly, ΔCT (negative value) is added to the hot water inlet temperature Thwi measured by the temperature sensor 12 and the hot water outlet temperature Thwo measured by the temperature sensor 13, respectively, and the hot water inlet temperature Thwi and the corrected downward descent are added. The expansion valve control unit 32 performs flow rate calculation and opening degree calculation using the hot water outlet temperature Thwo. Thereby, for example, the sub-expansion valve 9 is controlled in a direction in which the valve opening becomes smaller (period of time t1 to t2 in FIG. 6). In the conventional opening control of the sub-expansion valve, the valve opening is calculated using the temperature measured by the temperature sensors 12, 13, that is, the temperature with a measurement delay, so the hot water inlet temperature Thwi actually decreases. Nevertheless, the sub-expansion valve 9 is controlled to open, which causes the compressor 2 to suck in the liquid.

As described above, according to the turbo chiller and the control apparatus and control method thereof according to the present embodiment, the condensation temperature is acquired based on the condensation pressure, and the temperature between the current condensation temperature and the condensation temperature before a certain period of time. If the absolute value of the difference | ΔCT | is equal to or greater than a predetermined threshold value, the temperature is corrected by adding the temperature difference ΔCT to the hot water inlet temperature Thwi and the hot water outlet temperature Thwo measured by the temperature sensors 12 and 13, respectively. The control delay of the expansion valve due to the measurement delay by the temperature sensors 12 and 13 can be alleviated. Thereby, it becomes possible to avoid the liquid refrigerant suction of the compressor 2.

  In the present embodiment, the expansion valve is prevented from opening too much by correcting the hot water inlet temperature Thwi and the hot water outlet temperature Thwo. For example, the change rate of the opening degree of the sub expansion valve 9 is specified in the specification. By adopting a method of keeping the pressure below a predetermined rating, it is possible to avoid sucking liquid refrigerant in the compressor.

[Second Embodiment]
Hereinafter, a turbo chiller, a control device thereof, and a control method thereof according to a second embodiment of the present invention will be described with reference to the drawings.
In the first embodiment described above, the hot water inlet temperature Thwi and the hot water outlet temperature Thwo are corrected. However, in this embodiment, in addition to or instead of this, the evaporation temperature ET in the evaporator 7, Then, the evaporation pressure Ps is corrected. As a result, the accuracy of expansion valve control is further improved.

  In the first embodiment, when the hot water inlet temperature Thwi changes, the effect appears in the condensation pressure Pd relatively early, so the temperature correction is performed using the condensation temperature CT converted from the condensation pressure Pd. However, with regard to the evaporator 7, it has been clarified through experiments that when the heat source water inlet temperature Tswi falls, the effect does not appear early in the evaporating pressure Ps. FIG. 7 shows temporal transitions of the heat source water inlet temperature Tswi measured by the temperature sensor 17, the heat source water outlet temperature Tswo measured by the temperature sensor 18, the evaporation temperature ET converted from the evaporation pressure Ps, and the compressor discharge temperature. An example is shown.

As shown in FIG. 7, it can be seen that the change in the evaporation temperature ET converted from the evaporation pressure Ps is slower than the change in the heat source water inlet temperature Tswi and the heat source water outlet temperature Tswo. Therefore, in the evaporator 7 can not adopt the same manner as the evaporator 7 such correcting the heat source water inlet temperature Ts w i and the heat source water outlet temperature Tswo using evaporation pressure Ps.
Here, when FIG. 7 is analyzed, when stable, the difference ΔTe between the heat source water inlet temperature Tswi and the evaporation temperature ET (equivalent value of the evaporation pressure Ps), the heat source water inlet temperature Tswi and the heat source water outlet temperature Tswo. It was found that the ratio K to the difference ΔTs is equal. In other words, it has been found that the following expression holds.

  K = ΔTe / ΔTs = (Tswi-ET) / (Tswi-Tswo) = constant (6)

Therefore, in this embodiment, may be set to the value of the ratio K in a stable state as a target ratio K ^*, always by the ratio K corrects the evaporation temperature ET so that the target ratio K ^*, promptly The change in the heat source water inlet temperature Tswi was reflected in the expansion valve control.

FIG. 8 is a functional block diagram of the control device 35 according to the present embodiment. As shown in FIG. 8, the control device 35 further includes an evaporation temperature correction unit 33 in addition to the configuration of the control device 30 shown in FIG. 2.
Evaporating temperature correction unit 33 holds the value of the ratio K in a stable state as a target ratio K ^*, so that the ratio K becomes a target ratio K ^*, corrects the evaporation temperature. In other words, the evaporation temperature ET is calculated by substituting the heat source water inlet temperature Tswi, the heat source water outlet temperature Tswo, and the previously held target ratio K ^* into the following equation (7) derived from the above equation (6). To do.

ET = Tswi- (Tswi-Tswo) K ^* (7)

Then, the evaporation temperature ET is converted into an evaporation pressure Ps, and this evaporation pressure Ps is used for expansion valve control. That is, the main expansion valve opening calculation unit 53 and the sub expansion valve opening calculation unit 54 use the evaporation pressure Ps based on the evaporation temperature ET calculated by the evaporation temperature correction unit 33 to use the main expansion valve opening command OP and A sub-expansion valve opening command OPeco is calculated.
Here, for example, when the evaporation temperature ET decreases due to a decrease in the heat source water inlet temperature Tswi, the evaporation pressure Ps also decreases. In the feed forward control of the opening command of the main expansion valve 5 (steps SB1 to SB3 in FIG. 4), when the evaporation pressure Ps decreases, the main expansion valve front-rear differential pressure ΔP2 = Pd−Ps becomes a large value. As a result, the current flow rate Cveva and the set flow rate Ceva ^* of the main expansion valve are reduced, and the opening command OP_FF for feedforward control of the main expansion valve is reduced.
In the feedback control (step SB4 in FIG. 4), an opening degree command OP_FB is calculated so that the temperature difference ΔTswo between the heat source water outlet temperature Tswo and the evaporation temperature ET in the evaporator 7 matches the target value ΔTswo ^* . Here, the temperature difference ΔTswo does not act in the direction in which the main expansion valve 5 opens because it can be said to be substantially constant even if the heat source water inlet temperature Tswi varies (see FIG. 7). From the above, by reflecting the evaporation temperature ET by the evaporation temperature correction unit 33 in the valve opening degree control of the main expansion valve 5, it is possible to avoid the main expansion valve 5 from opening too much, and the liquid refrigerant of the compressor 2 Inhalation can be avoided.

In the embodiment described above, the control devices 30 and 35 applied to the turbo refrigerator 1 having the configuration shown in FIG. 1 have been described. However, the turbo refrigerator 1 to which the control device of the present invention is applied is illustrated in FIG. The configuration shown in FIG. For example, a turbo chiller that does not have a configuration related to the economizer 4, specifically, a configuration in which the economizer 4, the secondary expansion valve 9, the gas circuit 10, the temperature sensor 16, and the pressure sensor 21 are omitted in FIG. Applicable to turbo chillers. In this case, in the opening degree control of the main expansion valve 5, the above calculation may be performed with the flow rate flowing through the sub expansion valve 9 being zero.
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.

DESCRIPTION OF SYMBOLS 1 Turbo refrigerator 2 Compressor 3 Condenser 5 Main expansion valve 7 Evaporator 8 Refrigerant main circuit 9 Sub expansion valve 12-14, 16-18 Temperature sensor 20-22 Pressure sensor 30 Controller 31 Temperature correction part 32 Expansion valve control Unit 33 Evaporation temperature correction unit 41 Condensation temperature acquisition unit 42 Temperature difference calculation unit 43 Determination unit 44 Correction unit 51 Current flow rate calculation unit 52 Set flow rate calculation unit 53 Main expansion valve opening degree calculation unit 54 Sub expansion valve opening degree calculation unit

Claims (5)

A compressor, a condenser, an expansion valve, and an evaporator are sequentially connected, and a main circuit of a refrigeration cycle in which refrigerant circulates, and first temperature measuring means for measuring an inlet temperature of a heat medium flowing into the condenser And a control device applied to a turbo chiller comprising second temperature measuring means for measuring the outlet temperature of the heat medium flowing out from the condenser, and pressure measuring means for measuring the condensation pressure,
Temperature correction means for correcting the heat medium inlet temperature and the heat medium outlet temperature measured by the first temperature measurement means and the second temperature measurement means;
Expansion valve control means for controlling the opening degree of the expansion valve using the heat medium inlet temperature and the heat medium outlet temperature corrected by the temperature correction means,
The temperature correction means includes
Condensation temperature acquisition means for acquiring the condensation temperature from the condensation pressure acquired by the pressure measuring means;
Temperature difference calculating means for calculating a temperature difference by subtracting the condensation temperature before a certain period from the current condensation temperature;
Determination means for determining whether or not the absolute value of the temperature difference is equal to or greater than a preset threshold;
A turbo refrigeration comprising: correction means for adding the temperature difference to the respective temperatures measured by the first temperature measurement means and the second temperature measurement means when the absolute value of the temperature difference is equal to or greater than the threshold value. Machine control device.   The turbo chiller control device according to claim 1, wherein the certain period is set to a period during which the refrigerant makes a circuit of the main circuit. The turbo chiller is provided between the condenser and the expansion valve, and exchanges heat between the liquid refrigerant flowing through the main circuit and the refrigerant diverted from the main circuit and decompressed by the sub expansion valve, A heat exchanger that supercools the liquid refrigerant flowing through the main circuit, and a gas circuit that returns the liquid refrigerant flowing through the main circuit in the heat exchanger and the refrigerant that has finished heat exchange to the compressor,
The turbo chiller according to claim 1 or 2, wherein the expansion valve control means controls the opening degree of the sub expansion valve using the heat medium inlet temperature and the heat medium outlet temperature corrected by the temperature correction means. Control device. The turbo refrigerator provided with the control apparatus in any one of Claims 1-3 . A compressor, a condenser, an expansion valve, and an evaporator are sequentially connected, and a main circuit of a refrigeration cycle in which refrigerant circulates, and first temperature measuring means for measuring an inlet temperature of a heat medium flowing into the condenser And a control method applied to a turbo chiller comprising a second temperature measuring means for measuring the outlet temperature of the heat medium flowing out from the condenser, and a pressure measuring means for measuring the condensation pressure,
A temperature correction step of correcting the temperature measured by the first temperature measurement means and the second temperature measurement means;
An expansion valve control step for controlling the opening of the expansion valve using the heat medium inlet temperature and the heat medium outlet temperature corrected in the temperature correction step,
The temperature correction step includes
A condensation temperature acquisition step of acquiring a condensation temperature from the condensation pressure acquired by the pressure measuring means;
A temperature difference calculation step of calculating a temperature difference by subtracting the condensation temperature before a certain period from the current condensation temperature;
A determination step of determining whether the absolute value of the temperature difference is equal to or greater than a preset threshold;
A turbo refrigeration including a temperature correction step of adding the temperature difference to each temperature measured by the first temperature measurement means and the second temperature measurement means when the absolute value of the temperature difference is equal to or greater than the threshold value. How to control the machine.

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