JP4928357B2 - Cooling system - Google Patents

Description

  The present invention relates to a cooling system, and in particular, has a primary refrigerant circuit in which ammonia (NH 3) or the like is circulated as a medium and a secondary refrigerant circuit in which carbon dioxide (CO 2) or the like is circulated as a medium. The present invention relates to a cooling system that condenses and liquefies carbon dioxide or the like in a secondary refrigerant circuit using cold heat generated in the refrigerant circuit.

  Today, due to the problem of global warming, the adoption of refrigerants with a global warming potential of 0 or nearly zero is required, and there are increasing cases of using natural media such as ammonia, which has been established as a refrigerant. .

  Since the ammonia is harmful to the human body, if ammonia is supplied to the load side as it is, the ammonia diffuses into the fluid to be cooled such as cooling air at the time of leakage, and the danger is high. Therefore, conventionally, there is a configuration in which an ammonia refrigerant circuit is installed in a limited space such as a machine room and brine is used to transfer cold heat to and from a load side cooler.

  However, in the case where cold heat is transferred by brine, the pump for sending the brine requires a large amount of power, increasing the running cost and cannot contribute to energy saving.

  Therefore, in addition to the ammonia refrigerant circuit, a secondary refrigerant circuit using another safe refrigerant such as carbon dioxide is provided, and the cold generated in the ammonia refrigerant circuit is used as cold for condensing the refrigerant in the secondary refrigerant circuit, There is an apparatus configured to supply cold heat generated in a secondary refrigerant circuit to a load side (see, for example, Patent Document 1).

  In the apparatus described above, the liquid refrigerant condensed by the cold heat of the ammonia refrigerant circuit as the primary refrigerant circuit is generally sent to the load-side cooler by a liquid pump, but the refrigerant sent to the cooler by this liquid pump. The amount is basically controlled to be constant.

  By the way, the amount of liquid refrigerant in the cooler changes as the load fluctuates, and in the case of a steady load, the amount of liquid refrigerant in the cooler is maintained properly and stable operation is performed, but when the load decreases The amount of refrigerant evaporated becomes small, and the amount of liquid refrigerant in the cooler increases.

  When the load suddenly increases in the state described above, the evaporating pressure of the refrigerant increases. However, since a certain amount of the liquid refrigerant is fed into the cooler by the liquid pump, the evaporating pressure of the refrigerant further increases and the secondary pressure is increased. The state where the operation in the refrigerant circuit remains unstable is not solved.

  Moreover, the increase in the evaporation pressure of the refrigerant in the secondary refrigerant circuit also affects the evaporation pressure in the primary refrigerant circuit, and the operation of the primary refrigerant circuit becomes unstable.

  Therefore, conventionally, as a means for controlling the amount of refrigerant sent to the cooler to be constant, (a) a flow rate adjusting valve is installed on the cooler side, or (b) an amount of refrigerant held in the cooler by installing a collector Either method of controlling (liquid level) has been adopted.

  In addition, the method of installing the flow rate adjusting valve in (a) includes a method in which a constant amount is always supplied manually using a manual valve, and a flow rate is automatically adjusted by using an automatic control valve. There are two kinds of methods, a method of constantly supplying the energy.

  Of these, the use of a manual valve is the cheapest. However, since the flow rate is constant, if the supply amount becomes too small at the time of load fluctuation, the heat transfer area of the cooler cannot be used effectively, resulting in poor cooling. On the other hand, when the supply amount is excessive, a problem arises in that liquid accumulation occurs in the cooler or the suction pipe, and refrigerant evaporation is hindered.

  On the other hand, the flow rate adjustment using the automatic control valve can detect the pressure and temperature and supply the optimum flow rate according to the load to the cooler, but the cost becomes high.

The method (b) for installing the infusion device holds a certain amount of medium in the cooler by the infusion device, so it can cope with load fluctuations and can effectively use the heat transfer area of the cooler. However, the equipment becomes larger and the installation space is reduced, and the cost is increased.
JP 2003-166765 A

  As described above, the amount of liquid refrigerant in the cooler changes as the load fluctuates. If the supply amount of refrigerant to the cooler becomes too low without being controlled to the optimum amount according to the load, the heat transfer area of the cooler cannot be used effectively and cooling often occurs. On the other hand, if the supply amount is excessive, a liquid pool is generated in the cooler or the suction pipe, and the flow of the evaporated refrigerant gas is hindered, which may cause a cooling failure.

  The present invention should be solved in order to solve the cooling failure caused by the fact that the refrigerant supply amount to the cooler is not optimally controlled according to the load, easily and inexpensively, and to always operate stably. A technical problem arises, and the present invention aims to solve this problem.

The present invention has been proposed to achieve the above object, and the invention according to claim 1 includes a primary refrigerant circuit and a secondary refrigerant circuit in which natural refrigerant is circulated in at least one of the primary refrigerant circuit. A natural refrigerant cooling system in which the refrigerant in the secondary refrigerant circuit is condensed by a cascade condenser by the cold heat generated in the refrigerant circuit and stored in a receiver, and the liquid refrigerant in the receiver is sent to a load-side cooler by a liquid pump,
A liquid level detection sensor for detecting the liquid level of the refrigerant in the receiver is provided, and when a liquid level detected by the sensor is equal to or greater than a preset value, a certain amount of refrigerant is supplied to the cooler. However, in a cooling system including a controller that reduces the refrigerant to the cooler according to a decrease in the liquid amount when the liquid amount is equal to or less than a preset value due to a change in load,
A liquid pump that sends the liquid refrigerant in the receiver into the cooler between the receiver and the cooler, and the controller controls the supply amount of the liquid refrigerant in the liquid pump,
Based on the input of the liquid amount of carbon dioxide in the receiver detected by the liquid amount detection sensor and the pressure in the receiver detected by the pressure gauge and the temperature of the secondary refrigerant circuit detected via the temperature sensor and the processing circuit And
If the amount of liquid in the carbon dioxide receiver detected by the liquid level sensor is greater than or equal to a preset value in a preprogrammed procedure, that is, a control procedure programmed in the microcomputer, When the pump is driven to supply a certain amount of refrigerant to the cooler, and when the liquid volume fluctuates below a preset value due to load fluctuation, etc., the liquid pump the by controlling the driving speed to the procedure as allowed to reduce the refrigerant supply amount to the cooler thus provides a cooling system configured to control.

  According to this configuration, the amount of liquid refrigerant of carbon dioxide in the receiver stored by condensing and liquefying carbon dioxide as the refrigerant is detected by the liquid amount detection sensor, and the detected liquid amount is equal to or greater than a preset value. The controller controls to supply a certain amount of refrigerant to the cooler. On the other hand, when the liquid amount fluctuates below a preset value due to a load change or the like, the controller decreases the amount of refrigerant supplied to the cooler according to the decrease in the liquid amount, and the liquid in the cooler is reduced. Control the amount of refrigerant to be appropriate. Thereby, the heat transfer area of the cooler can be used effectively, and at the same time, obstruction of the refrigerant gas flow due to the liquid pool is prevented.

  According to this configuration, the amount of liquid refrigerant supplied to the cooler can be easily adjusted by controlling the drive rotation speed of the liquid pump with the controller.

According to a second aspect of the present invention, a valve for controlling a supply amount of liquid refrigerant fed into the cooler is provided between the liquid pump and the cooler, and the controller controls the valve to control the liquid refrigerant. The cooling system according to claim 1, wherein the supply amount of the liquid refrigerant is controlled by controlling the supply amount of the liquid refrigerant.

  According to this configuration, when the opening of the valve is controlled by the controller while the liquid pump is driven, the amount of liquid refrigerant supplied to the cooler can be easily adjusted.

  According to the first aspect of the present invention, when the amount of the carbon dioxide refrigerant in the receiver stored by condensing and liquefying carbon dioxide as the refrigerant is detected by a liquid amount detection sensor, Since the amount of liquid refrigerant supplied to the cooler is controlled to appropriately control the amount of refrigerant in the cooler, a cooling system with excellent followability to load fluctuations can be realized. Can do.

  Further, since the operation of the secondary refrigerant circuit using carbon dioxide as a medium is always performed stably, it is not necessary to provide a sufficient margin for the cooling capacity of the primary refrigerant circuit using ammonia as a medium, and the entire system is simplified. Downsizing, downsizing, and low running cost.

  Furthermore, since the configuration is simple and does not require a special configuration, there is an advantage that it can be easily applied to an existing system.

This invention is capable of easily controlling the medium supply amount to the cooler by controlling a driving number of revolutions of the liquid pump controller, in addition to the above effects, the sake of simplification of the control Can do.

According to the second aspect of the present invention, since the amount of medium supplied to the cooler can be easily controlled by controlling the opening degree of the valve with the controller, in addition to the above effect, the control is simplified. can do.

  In order to achieve the purpose of solving the poor cooling caused by the fact that the amount of refrigerant supplied to the cooler is not optimally controlled according to the load at low cost, and enabling stable operation at all times, ammonia is used as a refrigerant. As a primary refrigerant circuit and a secondary refrigerant circuit in which carbon dioxide is circulated as a refrigerant. The cold refrigerant generated in the primary refrigerant circuit condenses and liquefies the refrigerant in the secondary refrigerant circuit. In the cooling system that stores the liquid refrigerant in the receiver to a load-side cooler, the liquid system includes a liquid amount detection sensor that detects the liquid amount of the refrigerant in the receiver, and the liquid amount detected by the sensor Is equal to or greater than a preset value, a certain amount of refrigerant is supplied to the cooler, but the amount of liquid fluctuates with a change in load, and the amount of liquid falls below a preset value. When it was achieved by providing a controller allowed to decrease the supply amount of the refrigerant to the cooler in response to the decrease in liquid volume.

  Embodiments of the cooling system according to the present invention will be described below in detail based on specific examples shown in the accompanying drawings.

The cooling system of this embodiment includes a primary refrigerant circuit 1 that uses ammonia as a refrigerant, a secondary refrigerant circuit 2 that uses carbon dioxide as a refrigerant, and a refrigerant (carbon dioxide) that circulates in the secondary refrigerant circuit 2. And a controller CT for controlling.

  The primary refrigerant circuit 1 includes an ammonia compressor 3, a medium ammonia condenser / receiver 4, an ammonia expansion valve 5, and a carbon dioxide / ammonia gas-cade condenser 6, which are housed in a carbon dioxide / ammonia unit 101. is doing.

  The discharge side of the ammonia compressor 3 is connected to the inlet of the medium ammonia condenser / receiver 4 via an ammonia refrigerant forward pipe 7a. The outlet of the medium ammonia condenser / receiver 4 is connected to the primary side inlet of the carbon dioxide / ammonia gas-cade condenser 6 through an ammonia refrigerant forward pipe 7b provided with an ammonia expansion valve 5 in the middle. The primary side outlet of the carbon dioxide / ammonia gas-cade condenser 6 is connected to the inlet side of the ammonia compressor 3 via the ammonia refrigerant forward pipe 7c.

  The medium ammonia condenser / receiver 4 incorporates a cooling water circuit in which water is circulated, and a cooling water forward pipe 8a is connected to the inlet side of the cooling water circuit and a cooling water return pipe 8b is connected to the outlet side. ing.

  The secondary refrigerant circuit 2 includes a carbon dioxide receiver 9, a carbon dioxide liquid pump 10 (hereinafter referred to as “liquid pump 10”), and a carbon dioxide cooler 11 (hereinafter referred to as “cooler 11”). 11 is accommodated in the load side equipment 102, and the carbon dioxide receiver 9 and the liquid pump 10 are arranged in the carbon dioxide / ammonia unit 101.

  The carbon dioxide receiver 9 includes a liquid level sensor 12 that detects the amount of the carbon dioxide medium that is condensed and liquefied and stored in the carbon dioxide receiver 9 from the height of the liquid level, and the carbon dioxide receiver 9. A pressure gauge 13 for detecting the internal pressure is attached.

  The outlet of the carbon dioxide receiver 9 is connected to the suction port of the liquid pump 10 through the carbon dioxide refrigerant forward pipe 14a. The discharge port side of the liquid pump 10 is connected to the inlet side of the cooler 11 through a carbon dioxide refrigerant forward pipe 14b provided with a carbon dioxide electromagnetic valve 15 in the middle. On the other hand, the outlet side of the cooler 11 is connected to the secondary side inlet of the carbon dioxide / ammonia gas cascade condenser 6 and the inlet side of the carbon dioxide receiver 9 via the carbon dioxide refrigerant return pipe 14c. The liquid refrigerant of carbon dioxide condensed and liquefied by the cascade condenser 6 is returned to the carbon dioxide receiver 9.

  The controller CT constitutes a refrigerant supply amount control means for controlling the supply amount of refrigerant (carbon dioxide) circulating in the secondary refrigerant circuit 2, and is mainly composed of a microcomputer (commonly called "microcomputer"). It is configured as.

  Further, the controller CT includes a liquid amount of carbon dioxide in the carbon dioxide receiver 9 detected by the liquid level gauge 12 and a pressure and temperature sensor 17 in the carbon dioxide receiver 9 detected by the pressure gauge 13 and a processing circuit 18. Each information of the temperature in the secondary refrigerant circuit 2 detected via is input. And based on these each information, the refrigerant | coolant supply amount to the cooler 11 by the liquid pump 10 is controlled according to the procedure programmed beforehand.

  In this case, the controller CT controls the cooler 11 by driving the liquid pump 10 when the amount of liquid in the carbon dioxide receiver 9 detected by the liquid level sensor 12 is equal to or greater than a preset value. Supply an amount of refrigerant. Further, when the amount of liquid fluctuates and falls below a preset value due to a change in the load, etc., the liquid pump 10 is driven to control the rotational speed according to the decrease in the amount of liquid, and the amount of refrigerant supplied to the cooler 10 Decrease. Thereby, the amount of the liquid medium of carbon dioxide supplied into the cooler 10 is controlled so as to be completely gasified at the outlet of the cooler 10.

  Next, the operation of the cooling system configured as described above will be described. On the primary refrigerant circuit 2 side, the ammonia gas compressed by the ammonia compressor 3 is condensed by the medium ammonia condenser / receiver 4, depressurized by the ammonia expansion valve 5, and supplied to the carbon dioxide / ammonia gas-cade condenser 6. The

  On the other hand, the supply amount of the refrigerant (carbon dioxide) to the cooler 11 on the secondary refrigerant circuit 3 side is detected by the liquid level sensor 12 of the carbon dioxide receiver 9, and the liquid amount detected by the liquid level sensor 12 is determined in advance. If it is equal to or greater than the set value, the liquid pump 10 is driven to supply a certain amount of liquid refrigerant to the cooler 11. On the other hand, when the amount of liquid fluctuates with a change in load and falls below a preset value, the liquid pump 10 is driven to control the rotational speed of rotation, and the amount of refrigerant supplied to the cooler 11 is reduced according to the decrease in the amount of liquid. Let me. Further, when the liquid amount becomes a certain amount or more, the liquid pump 10 again feeds a constant amount, and the liquid amount in the carbon dioxide receiver 9 is controlled so as to become a substantially constant amount.

  As a result, the amount of liquid refrigerant held in the cooler 10 is controlled to an appropriate amount for complete gasification at the outlet of the cooler 11, and the heat transfer area of the cooler 11 can be used effectively, Prevents obstruction of refrigerant gas flow due to liquid pool.

  Further, the suction from the cooler 11 to the carbon dioxide receiver 9 is performed by cooling the carbon dioxide gas with the ammonia refrigerant in the carbon dioxide / ammonia gas-cade condenser 6 and changing the phase of the carbon dioxide gas into a liquid. The pressure is reduced at the cooling boundary wall surface of the ammonia gas-cade condenser 6 and suction is performed by the suction action.

  On the other hand, the liquid pump 10 supplies a constant amount of refrigerant liquid to the cooler 11 regardless of load fluctuations, but the liquid level of the carbon dioxide receiver 9 is controlled to be constant by detection of the liquid level sensor 12. Even if the fluctuation occurs, the retained amount of the carbon dioxide medium in the cooler 11 can be kept constant.

  Therefore, according to the cooling system in this embodiment, the liquid amount of the carbon dioxide medium in the carbon dioxide receiver 9 which is stored by condensing and liquefying the carbon dioxide medium is detected by the liquid level sensor 12 which is a liquid amount detection sensor. When the detected liquid amount is greater than or equal to a preset value, a predetermined amount of carbon dioxide medium is supplied to the cooler 11 by the liquid pump 10, but the liquid amount varies in accordance with a change in load or the like and is preset. When the value is equal to or less than the value, the controller CT controls the drive rotation speed of the liquid pump 10, and the amount of the carbon dioxide medium supplied to the cooler 11 by the liquid pump 10 is set according to the decrease in the carbon dioxide receiver 9. Since the amount of liquid refrigerant in the cooler 11 is appropriately controlled, a cooling system with excellent followability to load fluctuations can be obtained.

  Further, since the operation of the secondary refrigerant circuit 2 using carbon dioxide as a medium is always performed stably, it is not necessary to provide a sufficient margin for the cooling capacity of the primary refrigerant circuit 1 using ammonia as a medium, and the entire system. Simplification, downsizing, and low running cost can be expected.

  It should be noted that the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

  For example, in the configuration of the above embodiment, the configuration in which the controller CT drives and stops the liquid pump 10 to control the medium supply amount for sending the refrigerant liquid in the carbon dioxide receiver 9 into the cooler 11 has been described. The liquid pump 10 may be driven at all times, and the controller CT may adjust the opening of the carbon dioxide automatic adjustment valve 15 to control the amount of medium supplied to the cooler 11.

  In the above-described embodiments, the case where ammonia or carbon dioxide is used as the natural refrigerant has been described. However, water may be used as another natural refrigerant, and in one refrigerant circuit, instead of the natural refrigerant, R318 is used. , R245fa, R404A, R410A, R407C, R407E, R507A, R134a, etc. may be used.

The schematic block diagram of the cooling system shown as one embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Primary refrigerant circuit 2 Secondary refrigerant circuit 3 Ammonia compressor 4 Medium ammonia condenser and receiver 6 Carbon dioxide / ammonia gas-cade condenser 9 Carbon dioxide receiver 10 Carbon dioxide liquid pump (liquid pump)
11 Cooler 12 Liquid level sensor (Liquid level detection sensor)
17 Temperature sensor 101 Carbon dioxide / ammonia unit 102 Load side equipment CT controller

Claims (2)

A primary refrigerant circuit and a secondary refrigerant circuit in which natural refrigerant is circulated in at least one of them, and the refrigerant in the secondary refrigerant circuit is condensed by a cascade condenser by cold heat generated in the primary refrigerant circuit and stored in the receiver. A natural refrigerant cooling system that sends liquid refrigerant in the receiver to a load-side cooler by a liquid pump,
A liquid level detection sensor for detecting the liquid level of the refrigerant in the receiver is provided, and when a liquid level detected by the sensor is equal to or greater than a preset value, a certain amount of refrigerant is supplied to the cooler. However, in a cooling system including a controller that reduces the refrigerant to the cooler according to a decrease in the liquid amount when the liquid amount is equal to or less than a preset value due to a change in load,
A liquid pump that sends the liquid refrigerant in the receiver into the cooler between the receiver and the cooler, and the controller controls the supply amount of the liquid refrigerant in the liquid pump,
Based on the input of the liquid amount of carbon dioxide in the receiver detected by the liquid amount detection sensor and the pressure in the receiver detected by the pressure gauge and the temperature of the secondary refrigerant circuit detected via the temperature sensor and the processing circuit And
If the amount of liquid in the carbon dioxide receiver detected by the liquid level sensor is greater than or equal to a preset value in a preprogrammed procedure, that is, a control procedure programmed in the microcomputer, When the pump is driven to supply a certain amount of refrigerant to the cooler, and when the liquid volume fluctuates below a preset value due to load fluctuation, etc., the liquid pump the by controlling the driving speed to the procedure as allowed to reduce the refrigerant supply amount to the cooler Therefore, the cooling system, characterized in that the configuration of controlling. Provided between the liquid pump and the cooler is a valve for controlling the supply amount of the liquid refrigerant sent into the cooler, and the controller controls the valve to control the supply amount of the liquid refrigerant to The cooling system according to claim 1, wherein the supply amount of the liquid refrigerant is controlled.

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