JP6958019B2 - Low temperature cold water device - Google Patents

Description

The present invention relates to a low temperature cold water device including a compressor, a condenser (high temperature side heat exchanger), an electronic expansion valve, and an evaporator (low temperature side heat exchanger).

Generally, a cooling device that utilizes a phase change of a refrigerant includes a compressor that sucks and compresses the refrigerant, a condenser that condenses and liquefies the compressed refrigerant, and an expansion valve that expands the condensed and liquefied refrigerant. And an evaporator that evaporates the expanded refrigerant.
In the conventional refrigeration cycle, the measurement obtained by subtracting the saturation temperature (also referred to as "evaporation temperature") at the pressure of the refrigerant sucked into the compressor from the temperature of the refrigerant sucked into the compressor (also referred to as "refrigerant temperature"). There is known a constant superheat degree control that controls an expansion valve so that the superheat degree becomes a predetermined target superheat degree set in advance (see Patent Document 1).

Japanese Unexamined Patent Publication No. 2001-248919

However, when the degree of superheat is constantly controlled, the evaporation temperature fluctuates when the refrigerant temperature fluctuates. For example, the refrigerant temperature is high when the operating rate of the compressor is high, and low when the operating rate of the compressor is low. Similarly, the refrigerant temperature becomes high when the outside air temperature is high, and becomes low when the outside air temperature is low. Then, when the superheat degree is constantly controlled, the evaporation temperature fluctuates due to factors such as the operating rate of the compressor and the outside air temperature, and there is a problem that stable operation cannot be performed.
Further, when the degree of superheat is constantly controlled, when the outside air temperature is low, the refrigerant temperature becomes low and the evaporation temperature also becomes low, so that the evaporation temperature in the evaporator becomes low and heat is exchanged with the refrigerant in the evaporator. The liquid to be cooled (for example, water) may freeze.
Therefore, stable operation is possible in which the evaporation temperature does not fluctuate due to factors such as the operating condition of the compressor and the outside air temperature, and for example, the temperature to be cooled (for example, water) that exchanges heat with the refrigerant in the evaporator does not freeze at a low temperature. A cold water device is required.

The present invention is a low-temperature cooling water device provided with a compressor, a condenser (high-temperature side heat exchanger), an electronic expansion valve, and an evaporator (low-temperature side heat exchanger), depending on factors such as the operating condition of the compressor and the outside air temperature. Provided is a low-temperature cooling water device that enables stable operation in which the evaporation temperature does not fluctuate, obtains efficient and stable cooling capacity, and does not freeze, for example, a liquid to be cooled (for example, water) that exchanges heat with a refrigerant in an evaporator. The purpose is to do.

The present invention includes a compressor that sucks and compresses the refrigerant, a condenser that condenses and liquefies the refrigerant discharged by the compressor, an electronic expansion valve that decompresses the refrigerant condensed and liquefied by the condenser, and the electrons. It includes an evaporator that evaporates the refrigerant decompressed by the expansion valve, a refrigerant temperature measuring unit that measures the temperature of the refrigerant that has passed through the evaporator, and an opening degree control unit that controls the opening degree of the electronic expansion valve. In the low-temperature cooling water device, the opening degree control unit controls the opening degree of the electronic expansion valve so that the evaporation temperature of the refrigerant passing through the evaporator matches a predetermined target evaporation temperature set in advance. Regarding low temperature cooling water equipment.

Further, the target evaporation temperature is preferably set so that the outlet of the evaporator is in the evaporation region of the refrigerant.

Further, the target evaporation temperature is preferably set to a compressor suction temperature at which the cooling capacity of the refrigerator including the compressor and the condenser is substantially maximized.

Further, a liquid gas heat exchanger for heat exchange between the refrigerant liquefied by the condenser and the refrigerant vaporized by the evaporator is provided, and the electronic expansion valve has passed through the liquid gas heat exchanger. It is preferable to reduce the pressure of the refrigerant.

The evaporator is a double tube heat exchanger, and the liquid gas heat exchanger may be a plate type heat exchanger.

The refrigerant temperature measuring unit includes a refrigerant temperature sensor unit that measures the temperature of the refrigerant sucked into the compressor, and a refrigerant pressure measuring unit that measures the pressure value of the refrigerant sucked into the compressor. An evaporation temperature conversion unit may be provided in which the saturation temperature at the refrigerant pressure value measured by the refrigerant pressure measuring unit is used as the evaporation temperature.

In the opening degree control unit, the measured superheat degree calculated based on the temperature of the refrigerant sucked into the compressor and the evaporation temperature is determined by the outside air temperature and the heat load of the evaporator as the operating rate of the compressor. The opening degree of the electronic expansion valve may be controlled so as to be equal to the target degree of superheat set by.

According to the present invention, by controlling the electronic expansion valve so that the evaporation temperature matches the preset target evaporation temperature, stable operation in which the evaporation temperature does not fluctuate due to factors such as the operating condition of the compressor and the outside air temperature It is possible to provide a low-temperature cooling water device that enables efficient and stable cooling capacity, and does not freeze, for example, a liquid to be cooled (for example, water) that exchanges heat with a refrigerant in an evaporator.

It is a figure which shows the outline of the low temperature cold water apparatus of this embodiment. It is a figure which shows the example which sets an appropriate target superheat degree according to the outside air temperature in the low temperature cooling water apparatus of this embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing an embodiment of a low-temperature cold water device 100 of the present invention. The low-temperature cooling water device 100 of this embodiment is a steam compression type low-temperature cooling water device.
The low-temperature cold water device 100 includes a refrigerator 1 having a compressor 1A and a condenser 1B, a liquid gas heat exchanger 3, an electronic expansion valve 5, and an evaporator 7 (also referred to as “low temperature side heat exchanger”). A refrigerator intake gas temperature sensor 12, a refrigerator intake gas pressure sensor 14, and a control unit 30 are provided.
These are the electronic expansion valve 5 and the evaporator 7 (“low temperature side heat exchanger”) from the refrigerator 1 (compressor 1A, condenser 1B) via the liquid gas heat exchanger 3 via the refrigerant flow path 21. It is connected to the refrigerator 1 (also referred to as the compressor 1A, the condenser 1B) in sequence so as to return to the refrigerator 1 (compressor 1A, condenser 1B) via the liquid gas heat exchanger 3 again. Perform refrigeration cycles of refrigerant compression, condensation, expansion and evaporation.
More specifically, the refrigerant is compressed to a high temperature and high pressure in the compressor 1A in the state of low temperature and low pressure refrigerant gas to become a superheated steam state, and the high temperature and high pressure state refrigerant gas is in a state of constant pressure in the condenser 1B. The heat is dissipated and becomes a refrigerant liquid in the state of a high-pressure and low-temperature supercooled liquid. The high-pressure and low-temperature refrigerant liquid discharged from the refrigerator 1 passes through the liquid gas heat exchanger 3 and exchanges heat with the cooled liquid in the evaporator 7 (low-temperature side heat exchanger) to the refrigerator 1. Heat exchange is performed with the returning refrigerant, resulting in a cooler state.
The high-pressure and low-temperature refrigerant liquid that has passed through the liquid-gas heat exchanger 3 is rapidly depressurized by the electronic expansion valve 5 to become a low-temperature and low-pressure refrigerant liquid (two layers of gas and liquid), and the evaporator 7 Enter (low temperature side heat exchanger). The refrigerant, which has become a cold / low pressure refrigerant liquid, exchanges heat with the liquid to be cooled (for example, water) in the evaporator 7 (low temperature side heat exchanger) at a constant pressure, resulting in two phases of gas and liquid. In this state, the liquid is discharged from the evaporator 7 (low temperature side heat exchanger).
The gas-liquid two-phase refrigerant gas discharged from the evaporator 7 (low temperature side heat exchanger) passes through the liquid gas heat exchanger 3 and is discharged from the condenser 1B as a high-pressure and low-temperature supercooling liquid. By exchanging heat with the refrigerant liquid in the state of, it is completely gasified and circulated so as to return to the compressor 1A in the state of low temperature and low pressure refrigerant gas.
Next, the components included in the low-temperature cooling water device 100 will be described in detail.

The compressor 1A adiabatically compresses the low-temperature low-pressure refrigerant gas into a high-temperature high-pressure gas. The refrigerant in the high temperature and high pressure gas state in the compressor 1A is preferably sent to the condenser 1B via an oil separator (not shown) that separates and removes the oil contained in the refrigerant from the compressor 1A. The type of the compressor 1A is not particularly limited, and for example, a scroll compressor may be used.

The condenser 1B condenses the refrigerant that has been adiabatically compressed in the compressor 1A to become a high-temperature and high-pressure gas into a high-pressure and low-temperature refrigerant liquid. The condenser 1B of this embodiment is an air-cooled heat exchanger including, for example, a fan 11. The condenser 1B may be a water-cooled heat exchanger. The refrigerant that has become a high-pressure and low-temperature refrigerant liquid in the condenser 1B is sent to the liquid gas heat exchanger 3.

The liquid gas heat exchanger 3 is vaporized by a refrigerant flow path in which the high-pressure and low-temperature refrigerant liquefied by the condenser 1B is sent from the condenser 1B to the electronic expansion valve 5, and an evaporator 7 (low-temperature side heat exchanger). The refrigerant (in the state of two layers of gas and liquid that is not completely vaporized) is provided in the refrigerant flow path that is returned from the evaporator 7 (low temperature side heat exchanger) to the refrigerator 1 (compressor 1A). Heat is exchanged between the high-pressure and low-temperature refrigerant liquefied by the condenser 1B and the refrigerant vaporized by the evaporator 7 (low-temperature side heat exchanger). A plate heat exchanger may be used as the liquid gas heat exchanger 3.
More specifically, in the liquid gas heat exchanger 3, the refrigerant vaporized by the evaporator 7 (low temperature side heat exchanger) (for example, around 0 degrees) is liquefied by the condenser 1B while being returned to the compressor 1A. It exchanges heat with a high-pressure and low-temperature refrigerant (for example, around 30 degrees Celsius) on the way to be sent to the electronic expansion valve 5. By doing so, the high-pressure and low-temperature refrigerant that is being liquefied by the condenser 1B and sent to the electronic expansion valve 5 can be further cooled and sent to the electronic expansion valve 5. Further, the refrigerant returning from the evaporator 7 (low temperature side heat exchanger) to the compressor 1A can be completely gasified and returned to the compressor 1A in the state of the refrigerant gas, that is, the low temperature and low pressure gas.
As a result, when the refrigerant to be heat-exchanged in the evaporator 7 (low temperature side heat exchanger) is not completely evaporated and is discharged from the evaporator 7 (low temperature side heat exchanger) in a gas-liquid two-phase state. Even so, in the liquid gas heat exchanger 3, heat exchange is performed with a high-pressure and low-temperature refrigerant (for example, around 30 degrees Celsius) that is being liquefied by the condenser 1B and sent to the electronic expansion valve 5. , It can be sucked into the refrigerator 1 (compressor 1A) in a completely gasified state.

The electronic expansion valve 5 is an electronic valve whose opening degree can be controlled, and is electrically connected to a control unit 30 described later via a signal line. By adjusting the opening degree of the electronic expansion valve 5 by the control unit 30, the degree of decompression of the pressure of the high-pressure and low-temperature refrigerant liquefied by the condenser 1B can be adjusted. That is, by increasing the degree of decompression of the pressure of the high-pressure and low-temperature refrigerant liquefied in the condenser 1B, the evaporation temperature, which is the saturation temperature of the refrigerant at the pressure, can be further lowered. On the contrary, the evaporation temperature of the refrigerant can be further increased by reducing the degree of depressurization of the pressure of the high-pressure and low-temperature refrigerant liquefied by the condenser 1B. By doing so, it is possible to control the evaporation temperature of the refrigerant.
That is, by controlling the opening degree of the electronic expansion valve 5 by the control unit 30, the evaporation temperature, which is the saturation temperature at the pressure of the high-pressure and low-temperature refrigerant liquefied by the condenser 1B, coincides with the preset target evaporation temperature. Can be done.
By doing so, the refrigerant is discharged from the evaporator 7 (low temperature side heat exchanger) while maintaining the reduced pressure in the electronic expansion valve 5, so that the evaporation temperature of the refrigerant sucked into the compressor 1A is raised. It can be controlled to match the target evaporation temperature. The details of the opening degree control of the electronic expansion valve 5 will be described later.
In this way, the electronic expansion valve 5 lowers the pressure and temperature of the high-pressure and low-temperature refrigerant liquefied by the condenser 1B to bring it into a low-temperature and low-pressure (evaporation temperature matches the target evaporation temperature) refrigerant liquid. Then, it is sent to the evaporator 7 (low temperature side heat exchanger).
By doing so, in the refrigerating cycle of the low-temperature refrigerating water apparatus 100, stable operation can be performed so that the evaporation temperature of the refrigerant gas sucked into the refrigerator 1 matches a predetermined target evaporation temperature set in advance. Refrigeration cycle efficiency is improved. In particular, even when external factors such as the outside air temperature and the heat load change, the operation can be performed so that the evaporation temperature of the refrigerant gas is maintained at a constant evaporation temperature. Further, in a low-temperature chilling device that cools the chilled water temperature to 3 degrees or less by using the liquid to be cooled as water, the water is released by stabilizing the state (temperature, pressure) of the refrigerant in the evaporator 7 (low-temperature side heat exchanger). The risk of freezing can be reduced.

The evaporator 7 (low temperature side heat exchanger) is a heat exchange that removes heat from the surroundings by absorbing and evaporating the refrigerant that has passed through the electronic expansion valve 5 and has become a cold / low pressure refrigerant liquid while maintaining a constant pressure. It is a vessel. The evaporator 7 (low temperature side heat exchanger) is, for example, a heat exchanger that exchanges heat between a refrigerant and a liquid to be cooled (for example, water).
The evaporator 7 (low temperature side heat exchanger) has a refrigerant flow path (primary side flow path) and a cooled liquid flow path (secondary side flow path) without mixing the refrigerant and the cooled liquid. It is a heat exchanger that indirectly exchanges heat, and may be, for example, a double tube heat exchanger.
The refrigerant that has exchanged heat with the liquid to be cooled in the evaporator 7 (low temperature side heat exchanger) does not completely vaporize and passes through the evaporator 7 (low temperature side heat exchanger) in a gas-liquid two-phase state. There is a possibility, but as described above, on the way back to the compressor 1A, the high pressure and low temperature on the way back to the electronic expansion valve 5 are liquefied by the condenser 1B by passing through the liquid gas heat exchanger 10. By exchanging heat with a refrigerant (for example, around 30 degrees), it is completely gasified, that is, it is sucked into the compressor 1A in the state of a low-temperature low-pressure gas.

The low-temperature cold water device 100 is provided with a refrigerator intake gas temperature sensor 12 as a refrigerant temperature measuring unit and a refrigerator suction gas pressure sensor 14 as a refrigerant pressure measuring unit.
The refrigerator intake gas temperature sensor 12 is provided at any position from the outlet of the evaporator 7 (low temperature side heat exchanger) to the suction pipe (refrigerant pipe) from the inlet of the refrigerator 1 (compressor 1A). The temperature of the refrigerant sucked into the refrigerator 1 (compressor 1A) (hereinafter, also referred to as “intake gas temperature”) is measured. When the liquid gas heat exchanger 3 is provided as in the present embodiment, the refrigerator intake gas temperature sensor 12 is the inlet of the refrigerator 1 (compressor 1A) from the outlet of the liquid gas heat exchanger 3 on the refrigerator side. It may be provided at any place up to the suction pipe (refrigerant pipe) leading to the above, and the temperature of the refrigerant (in the gas phase state) may be measured.

The refrigerator suction gas pressure sensor 14 is provided at any position from the outlet of the evaporator 7 (low temperature side heat exchanger) to the suction pipe (refrigerant pipe) leading to the inlet of the refrigerator 1 (compressor 1A). The pressure of the refrigerant sucked into the refrigerator 1 (compressor 1A) (hereinafter, also referred to as “intake gas pressure”) is measured. When the liquid gas heat exchanger 3 is provided as in the present embodiment, the refrigerator intake gas pressure sensor 14 is the inlet of the refrigerator 1 (compressor 1A) from the outlet of the liquid gas heat exchanger 3 on the refrigerator side. It may be provided at any place up to the suction pipe (refrigerant pipe) leading to the above, and the pressure value of the refrigerant (in the gas phase state) may be measured.
Based on the refrigerant pressure value measured by the refrigerator intake gas pressure sensor 14, the evaporation temperature, which is the saturation temperature at the refrigerant pressure, is converted.
By measuring the pressure value of the refrigerant (in the vapor phase state) sucked into the refrigerator 1 (compressor 1A) in this way, the saturation at the pressure value of the refrigerant sucked into the refrigerator 1 (compressor 1A) is achieved. The temperature (evaporation temperature) is measured.

In the low-temperature cold water device 100 of the present embodiment, the evaporation temperature of the refrigerant measured based on the pressure value of the refrigerant measured by the refrigerator suction gas pressure sensor 14 becomes a predetermined target evaporation temperature set in advance. The opening degree of the electronic expansion valve 5 is feedback-controlled so as to match. Details will be described later.

The low-temperature cooling water device 100 described above is used for various purposes, but in this embodiment, it may be a water chiller that cools water in, for example, an evaporator 7 (low-temperature side heat exchanger).
In this case, the liquid to be cooled in the evaporator 7 (low temperature side heat exchanger) is water, and the evaporator 7 (low temperature side heat exchanger) is an indirect heat exchange in which the refrigerant flow path 21 and the water flow path 22 are formed. It is said to be a vessel. Then, the refrigerant from the electronic expansion valve 5 is passed through the refrigerant flow path 21, while the circulating water from the cold water tank (not shown) is passed through the water flow path 22. Therefore, the water flow path 22 of the evaporator 7 (low temperature side heat exchanger) is connected to the cold water tank via the water supply passage 22A and the return passage 22B.
More specifically, a circulation pump 25 is provided in the water supply channel 22A, and by operating the circulation pump 25, water from the cold water tank is sent to the evaporator 7 (low temperature side heat exchanger) via the water supply channel 22A. ), After passing through the water flow path 22 in the evaporator 7 (low temperature side heat exchanger), it is returned to the cold water tank via the return path 22B. In this way, the water in the cold water tank can be circulated between the evaporator 7 (low temperature side heat exchanger) and the heat of vaporization when the refrigerant evaporates in the evaporator 7 (low temperature side heat exchanger). It can be used to cool the circulating water.

Further, the liquid to be cooled by the evaporator 7 (low temperature side heat exchanger) may be used for heat exchange with a heat load (for example, cooling of foodstuffs) and disposed of (running water specification).

The low-temperature cold water device 100 is configured as described above to execute a refrigerating cycle of compression, condensation, expansion, and evaporation of the refrigerant. Further, as described above, in the low temperature cooling water device 100, the control unit 30 determines the evaporation temperature of the refrigerant that has passed through the evaporator 7 (low temperature side heat exchanger) (the refrigerant sucked into the refrigerator 1 (compressor 1A)). The electronic expansion valve 5 is controlled so that the evaporation temperature) matches a predetermined target evaporation temperature.

As shown in FIG. 1, the control unit 30 includes an evaporation temperature conversion unit 31 and an opening degree control unit 32.
The control unit 30 is connected to the refrigerator intake gas temperature sensor 12 and the refrigerator intake gas pressure sensor 14, and controls the opening degree of the electronic expansion valve 5 based on the detection signals of these sensors.

[About evaporation temperature conversion unit 31]
The evaporation temperature conversion unit 31 is the saturation temperature (evaporation temperature) at the pressure value of the refrigerant based on the pressure value of the refrigerant sucked into the refrigerator 1 (compressor 1A) measured by the refrigerator suction gas pressure sensor 14. Is converted. Regarding the conversion of the saturation temperature at the pressure value of the refrigerant, for example, a control table between the refrigerant pressure value and the saturation temperature at the pressure value is set in advance, and the measurement is performed by the refrigerator intake gas pressure sensor 14 based on the control table. The saturation temperature corresponding to the pressure value of the gas sucked into the refrigerator 1 (compressor 1A) may be calculated. Further, a function that takes the refrigerant pressure value as an input and outputs the saturation temperature at the pressure value is set in advance, and the refrigerant sucked into the refrigerator 1 (compressor 1A) measured by the refrigerator intake gas pressure sensor 14 The pressure value may be input to the function to calculate the saturation temperature at the pressure value.
The evaporation temperature conversion unit 31 is not limited to this. For example, an electronic circuit corresponding to the evaporation temperature conversion unit 31 may be created in advance so that the electronic circuit can be used for conversion.

[About the opening control unit 32]
The opening degree control unit 32 controls the opening degree of the electronic expansion valve 5 so that the evaporation temperature of the refrigerant sucked into the compressor 1A matches the target evaporation temperature.
More specifically, the opening degree control unit 32 is an electronic expansion valve so that the evaporation temperature of the refrigerant sucked into the refrigerator 1 (compressor 1A) converted by the evaporation temperature conversion unit 31 matches the target evaporation temperature. The opening degree of 5 is controlled.
Since the efficient operation of the refrigerator 1 is determined by the evaporation temperature, the efficient operation of the refrigerator 1 should be realized by setting the target evaporation temperature to a value at which the efficiency of the refrigerator 1 is considered to be good. Can be done. For example, the target evaporation temperature can be set so that the cooling capacity of the refrigerator 1 is substantially maximized.

Next, the processing content of the opening degree control unit 32 when the electronic expansion valve 5 is configured to be controlled based on the degree of superheat of the refrigerant sucked into the compressor 1A will be described. Here, the degree of superheat of the refrigerant is the refrigerant pressure value (intake gas pressure value) sucked into the refrigerator 1 (compressor 1A) from the temperature (intake gas temperature) of the refrigerant sucked into the refrigerator 1 (compressor 1A). ) Is subtracted from the saturation temperature (evaporation temperature).
Therefore, the evaporation temperature of the refrigerant is equal to the intake gas temperature minus the degree of superheat of the refrigerant. Therefore, when the electronic expansion valve 5 is configured to control based on the degree of superheat of the refrigerant sucked into the compressor 1A, the opening degree control unit 32 determines that the degree of superheat of the refrigerant is "intake gas temperature-target". The opening degree of the electronic expansion valve 5 is controlled so as to match the "evaporation temperature".

FIG. 2 shows an example in which the target value of the superheat degree of the refrigerant (referred to as “target superheat degree”) is changed when the intake gas temperature changes according to the outside air temperature when the target evaporation temperature is set to -8 ° C. Represents. Here, as the outside air temperature, for example, when the condenser 1B includes an air-cooled heat exchanger provided with a fan 11, the suction air temperature of the condenser 1B is assumed.
As shown in FIG. 2, when the outside air temperature is 30 ° C. and the intake gas temperature is 18 ° C., the target superheat degree is set to 26 ° C., and the opening control unit 32 sets the superheat degree to the target superheat degree of 26 ° C. The opening degree of the electronic expansion valve 5 is controlled so as to match.
When the outside air temperature is 25 ° C. and the intake gas temperature is 13 ° C., the target superheat degree is set to 21 ° C., and the opening control unit 32 sets the electron so that the superheat degree matches the target superheat degree 21 ° C. The opening degree of the expansion valve 5 is controlled.
Similarly, when the outside air temperature is 20 ° C. and the intake gas temperature is 8 ° C., the target superheat degree is set to 16 ° C., and the opening control unit 32 sets the superheat degree to match the target superheat degree 16 ° C. The opening degree of the electronic expansion valve 5 is controlled.
By doing so, even if the intake gas temperature changes due to the change in the outside air temperature, the evaporation temperature of the refrigerant sucked into the refrigerator 1 (compressor 1A) matches the target evaporation temperature. Can be controlled to.
The intake gas temperature may fluctuate outside the outside air temperature, for example, depending on the operating rate of the compressor 1A determined by the heat load in the evaporator 7. For example, as factors for changing the heat load in the evaporator 7 (low temperature side heat exchanger), the inlet water temperature supplied from the cold water tank to the evaporator 7 (low temperature side heat exchanger) via the water supply channel 22A, and the circulation pump 25. Fluctuations in the number of revolutions of the inverter or the current value for driving the inverter are expected.
Even in such a case, for example, by setting an appropriate target degree of overheating in response to the operating condition of the compressor 1A, the fluctuation of the heat load in the evaporator 7 (low temperature side heat exchanger), etc., the refrigerator The evaporation temperature of the refrigerant sucked into 1 (compressor 1A) can be controlled so as to always match the target evaporation temperature.

As described above, the low-temperature cooling water device 100 of the present embodiment controls the opening degree of the electronic expansion valve 5 so that the evaporation temperature of the refrigerant that has passed through the evaporator 7 matches a predetermined target evaporation temperature set in advance. The opening degree control unit 32 is provided.
As a result, efficient operation of the refrigerator 1 can be realized. In particular, it enables stable operation in which the evaporation temperature does not fluctuate due to external factors such as the outside air temperature, the operating condition of the compressor 1A, and the fluctuation of the heat load in the evaporator 7, and obtains an efficient and stable cooling capacity, for example. It is possible to prevent the liquid to be cooled (for example, water) that exchanges heat with the refrigerant in the evaporator from freezing.
Further, by controlling the opening degree of the electronic expansion valve 5 so that the evaporation temperature is always constant, a high cooling capacity can be obtained with the low output compressor 1A.

Further, in the low temperature cold water device 100 of the present embodiment, the target evaporation temperature is set so that the outlet (end) of the evaporator 7 is the evaporation region of the refrigerant.
By doing so, the same effect as described above can be achieved.

Further, in the low temperature cooling water device 100 of the present embodiment, the target evaporation temperature can be set so that the cooling capacity of the refrigerator 1 including the compressor 1A and the condenser 1B is substantially maximized.

Further, the low-temperature cold water device 100 of the present embodiment includes a liquid gas heat exchanger 3 that exchanges heat between the refrigerant liquefied by the condenser 1B and the refrigerant vaporized by the evaporator 7.
As a result, even if the refrigerant heat-exchanged in the evaporator 7 is not completely evaporated and is discharged in a gas-liquid two-phase state, the liquid gas heat exchanger 3 is liquefied by the condenser 1B. By exchanging heat with the high-pressure and low-temperature refrigerant (for example, around 30 degrees Celsius), the refrigerator 1 (compressor 1A) can be sucked into a completely gasified state.

Further, in the opening degree control unit 32 of the low temperature chilling water device 100 of the present embodiment, the measured superheat degree calculated based on the temperature and the evaporation temperature of the refrigerant sucked into the compressor 1A is the outside air temperature and the evaporator 7. The opening degree of the electronic expansion valve 5 is controlled so as to be equal to the target degree of superheat set by the heat load.
As a result, an appropriate target superheat degree can be set for each of the outside air temperature and the heat load of the evaporator 7, and the operation can be performed so that the evaporation temperature of the refrigerant always maintains a constant target evaporation temperature.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[Modification 1]
In the present embodiment, the low temperature cooling water device 100 is provided with the refrigerator 1, but the present invention is not limited to this. For example, the refrigerator 1 may be placed separately.

[Modification 2]
In the present embodiment, the low temperature cold water device 100 is provided with the liquid gas heat exchanger 3, but the present invention is not limited to this. The low temperature / cold water device 100 may not include the liquid gas heat exchanger 3.

[Modification 3]
In the present embodiment, the control unit 30 is provided with the evaporation temperature conversion unit 31 and the opening degree control unit 32, but the present invention is not limited to this.
For example, instead of the evaporation temperature conversion unit 31, an evaporation temperature converter (electronic circuit) may be provided. Similarly, the opening degree controller (electronic circuit) may be provided instead of the opening degree control unit 32.

100 Low temperature chiller 1 Refrigerator 1A Compressor 1B Condenser 3 Liquid gas heat exchanger 5 Electronic expansion valve 7 Evaporator 11 Fan 12 Refrigerator Intake gas temperature sensor 14 Refrigerator Intake gas pressure sensor 21 Refrigerant flow path 22 Water flow path 22A Water supply channel 22B Return channel 25 Circulation pump 30 Control unit 31 Evaporation temperature conversion unit 32 Opening control unit

Claims (7)

A compressor that sucks in and compresses the refrigerant,
A condenser that condenses and liquefies the refrigerant discharged by the compressor,
An electronic expansion valve that reduces the pressure of the refrigerant condensed by the condenser, and
An evaporator that evaporates the refrigerant decompressed by the electronic expansion valve, and
A refrigerant temperature measuring unit that measures the temperature of the refrigerant that has passed through the evaporator, and a refrigerant temperature measuring unit.
An opening control unit that controls the opening of the electronic expansion valve and
It is a low-temperature cold water device equipped with
The opening control unit
A low-temperature cold water device that feedback- controls the opening degree of the electronic expansion valve so that the evaporation temperature of the refrigerant that has passed through the evaporator matches a predetermined constant target evaporation temperature. The low-temperature cold water apparatus according to claim 1, wherein the target evaporation temperature is set so that the outlet of the evaporator is in the evaporation region of the refrigerant. The target evaporation temperature is set to be a compressor suction temperature at which the cooling capacity of the refrigerator including the compressor and the condenser is substantially maximized, according to claim 1 or 2. The low temperature cooling water device described. A liquid gas heat exchanger for heat exchange between the refrigerant liquefied by the condenser and the refrigerant vaporized by the evaporator is provided.
The low-temperature cold water device according to any one of claims 1 to 3, wherein the electronic expansion valve reduces the pressure of the refrigerant that has passed through the liquid gas heat exchanger. The evaporator is a double tube heat exchanger,
The low-temperature cold water device according to claim 4, wherein the liquid gas heat exchanger is a plate heat exchanger. The refrigerant temperature measuring unit is
A refrigerant temperature sensor unit that measures the temperature of the refrigerant sucked into the compressor, and
A refrigerant pressure measuring unit for measuring the pressure value of the refrigerant sucked into the compressor is provided.
The low-temperature chilling water apparatus according to any one of claims 1 to 5, further comprising an evaporation temperature conversion unit whose evaporation temperature is the saturation temperature at the refrigerant pressure value measured by the refrigerant pressure measuring unit. The opening control unit
The measured superheat degree calculated based on the temperature of the refrigerant sucked into the compressor and the evaporation temperature is set by the operating rate of the compressor determined by the outside air temperature and the heat load of the evaporator. The low-temperature cooling water device according to any one of claims 1 to 6, which controls the opening degree of the electronic expansion valve so as to be equal to.

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