JP2011163713A - Refrigeration system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigeration system capable of achieving stable operation without causing overload and poor cooling in the refrigeration system by controlling a supply amount of carbon dioxide to a cooler to be constant so that evaporation pressure of the cooler becomes constant, even if set temperatures of a plurality of coolers are set to be different from each other depending on each cooler. <P>SOLUTION: In the refrigeration system, an ammonia cycle 11 using ammonia as a medium is combined with a carbon dioxide cycle 12 using carbon dioxide as a medium, the medium of the carbon dioxide cycle 12 is condensed/liquefied by cold generated in the ammonia cycle 11 to be stored in a receiver 15, and the liquefied medium is fed to a plurality of load-side coolers 22 from the receiver 15. A flow rate adjustment valve 21 for adjusting an amount of the liquefied medium supplied to the coolers 22 from the receiver 15 is provided between the receiver 15 and the coolers 22. The flow rate is controlled so that other coolers also have the lowest evaporation pressure of the coolers 22. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a refrigeration system, and more particularly to a refrigeration system that combines an ammonia cycle using ammonia (NH3) as a medium and a carbon dioxide gas cycle using carbon dioxide (CO2, also called "carbon dioxide") as a medium. It is.

  Today, from the viewpoint of global environmental conservation such as prevention of ozone layer destruction and prevention of global warming, the refrigerant in the refrigeration system used for indoor air conditioning and article cooling / freezing is a natural refrigerant instead of conventional chlorofluorocarbon, and ozone destruction Ammonia (NH3) with a coefficient of zero and a global warming coefficient of zero or close to zero has been reviewed, and the use of refrigeration systems that use this ammonia as a refrigerant is increasing.

  However, ammonia is toxic to the human body. Therefore, instead of directly supplying the cold heat of the ammonia cycle to the cooler side, an ammonia cycle is interposed between the cooler and the ammonia cycle by interposing a carbon dioxide gas cycle that uses natural non-toxic carbon dioxide as a refrigerant. A natural refrigerant cooling system in which the cold heat generated in step 1 is supplied to a cooler through a carbon dioxide gas cycle has been practically used (see, for example, Patent Document 1).

  The carbon dioxide gas cycle in the natural refrigerant cooling system described above uses the cold generated by the ammonia cycle as condensed cold heat, liquefies the CO2 medium with this condensed cold heat, and stores it in the CO2 receiver. The CO2 liquid medium is sent to a cooler by a liquid pump, heat exchange is completed by the cooler, and the vaporized CO2 medium is condensed by a CO2 / NH3 cascade condenser and returned to the CO2 receiver.

Japanese Patent Application Laid-Open No. 2002-243350.

  In the conventional refrigeration system described above, there may be a plurality of coolers, and when the set temperatures of the coolers are different, the refrigerator is operated according to the conditions on the lowest temperature side. However, when a high temperature is set, the CO2 evaporating pressure in the cooler becomes a problem, and in some cases, the evaporating pressure becomes higher than the CO2 supply pressure (CO2 pump discharge pressure, CO2 supply pressure due to height difference, etc.). There were problems that caused poor cooling and the like.

  Therefore, even when the set temperature of the plurality of coolers is set to be different for each cooler, the supply amount of carbon dioxide to the cooler is controlled to be constant so that the evaporation pressure of the cooler is constant, A technical problem to be solved in order to provide a refrigeration system capable of realizing stable operation without causing an overload or a cooling failure in the refrigeration system arises, and the present invention solves this problem. With the goal.

The present invention has been proposed to achieve the above object, and the invention according to claim 1 is a combination of an ammonia cycle using ammonia as a medium and a carbon dioxide gas cycle using carbon dioxide as a medium. In the refrigeration system that condenses and liquefies the carbon dioxide gas medium and stores it in a receiver by the cold heat generated in the receiver, and sends the liquefied medium from the receiver to a plurality of load side coolers, the receiver and the cooler A refrigeration system is provided with a flow rate adjusting valve for adjusting the amount of the liquefied medium supplied from the receiver to the cooler, and controls the flow rate so that the other evaporator has the lowest evaporation pressure among the coolers. I will provide a.

  According to this configuration, the amount of the liquefied medium supplied from the receiver to the cooler is adjusted by the flow rate adjusting valve provided between the receiver and the cooler, and the evaporation pressure in the cooler is controlled to be constant. Can do. As a result, even if the set temperature of the object to be cooled in the cooler changes, an increase in the evaporation pressure due to an excessive supply amount of carbon dioxide is prevented, and carbon dioxide is sucked into the cascade condenser, for example, at a constant pressure. That is, even when the set temperature of the cooler is set high or low, the evaporation pressure of the cooler can be controlled to be constant.

  According to a second aspect of the present invention, in the configuration of the first aspect, the carbon dioxide gas cycle includes a temperature sensor that detects a temperature of an object to be cooled that is cooled by each of the coolers, and is detected by the temperature sensor. Provided is a refrigeration system in which the flow rate is controlled by the flow rate adjusting valve in accordance with the temperature of the object to be cooled and the set temperature.

  According to this configuration, the liquefied medium supply amount to the cooler by the flow rate control valve can be adjusted based on the temperature of the object to be cooled and the set temperature to control the set temperature.

  According to a third aspect of the present invention, in the configuration of the first or second aspect, the carbon dioxide gas cycle includes a temperature / pressure sensor for detecting a temperature and a pressure of the refrigerant gas at the outlet of the cooler, and the temperature / pressure is detected. Provided is a refrigeration system in which the flow rate is controlled by the flow rate adjusting valve in accordance with the temperature and pressure detected by a sensor.

  According to this configuration, the liquefied medium supply amount to the cooler by the flow rate control valve is adjusted based on the temperature and pressure of the refrigerant gas at the cooler outlet to control the superheat degree of the cooler to be constant, The stable operation of the system can always be maintained.

  According to a fourth aspect of the present invention, in the configuration according to the first, second, or third aspect, the ammonia cycle is a refrigeration system that detects the pressure of the receiver and controls the capacity of the compressor so as to be within a set pressure range. provide.

  According to this configuration, a plurality of coolers can be operated in different temperature zones with one refrigeration system. In addition, since the carbon dioxide condensation pressure in the cascade condenser is constant, the suction pressure is constant on the ammonia cycle side, and the system as a whole can be operated stably.

    In the first aspect of the invention, even when the set temperature of each cooler is set high or low, the evaporating pressure of the cooler can be controlled to be constant, so that stable operation can always be maintained. .

  According to the second aspect of the present invention, since the liquefied medium supply amount to the cooler by the flow rate control valve is adjusted based on the temperature of the object to be cooled and the set temperature, control is performed so that the set temperature is reached. In addition to the effects of the present invention, a more stable operation can be maintained.

  The invention according to claim 3 is controlled so that the degree of superheat of the cooler becomes constant by adjusting the supply amount of the liquefied medium to the cooler by the flow rate control valve based on the temperature and pressure of the refrigerant gas at the cooler outlet. Therefore, in addition to the effect of the first or second aspect of the invention, a more stable operation can be maintained.

  In addition to the effect of the first, second, or third aspect, the invention described in claim 4 does not cause overload or poor cooling in the refrigeration system when a plurality of coolers are used in one refrigeration system. And stable operation can always be maintained.

The block diagram of the state which connected the two coolers in the refrigerating system shown as one embodiment of this invention.

  The present invention controls the supply amount of carbon dioxide to the cooler so that the evaporating pressure of the cooler is constant even when the set temperature of the multiple coolers is set to be different for each cooler. In order to achieve the object of providing a refrigeration system capable of realizing stable operation without causing overload and poor cooling in the refrigeration system, an ammonia cycle using ammonia as a medium, and carbon dioxide as a medium In the refrigeration system that combines the carbon dioxide gas cycle, condenses and liquefies the carbon dioxide gas medium by the cold heat generated in the ammonia cycle, stores it in the receiver, and sends the liquefied medium from the receiver to the load side cooler. And a flow rate adjustment for adjusting an amount of the liquefied medium supplied from the receiver to the cooler between the receiver and the cooler. It was achieved by providing the valve.

  Hereinafter, the refrigeration system of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of a refrigeration system shown as an embodiment of the present invention. In this figure, this refrigeration system 10 performs only freezing, and is composed of a combination of a high-source side ammonia cycle 11 and a low-source side carbon dioxide gas cycle 12. Moreover, although the following description demonstrates the case where two coolers are drive | operated by one carbon dioxide gas cycle, it is not necessarily limited to 2 units | sets, 3 units | sets or more may be sufficient.

  The ammonia cycle 11 includes an NH 3 compressor 13, an NH 3 condenser 14, an NH 3 receiver 15, an NH 3 expansion valve 16, and a CO 2 / NH 3 cascade condenser 17. Then, the CO2 medium in the carbon dioxide gas cycle 12 is cooled. Further, the ammonia cycle 11 is housed in the CO2 / NH3 unit 101 and installed outdoors or on the roof because the medium is toxic ammonia.

  On the other hand, the carbon dioxide gas cycle 12 includes a CO 2 receiver 18, a CO 2 liquid pump 19, a liquid supply electromagnetic valve 20, a flow rate adjusting valve 21, and a plurality of coolers (evaporators) in addition to the CO 2 / NH 3 cascade condenser 17 described above. ) 22, 22, etc. In the carbon dioxide gas cycle 12, the CO 2 receiver 18 and the CO 2 liquid pump 19 are installed in the CO 2 / NH 3 unit 101. On the other hand, the cooler (evaporator) 22, the liquid supply solenoid valve 20, the flow rate adjusting valve 21, and the like are respectively installed in the cooled chambers 102 a and 102 b of a refrigeration warehouse or the like to cool the cooled chamber 102.

  In the carbon dioxide gas cycle 12, the temperature sensor 23, the temperature controller 24, the CO 2 pressure sensors 25 and 26, the CO 2 temperature sensor 27, the superheat degree controller 28, and the pressure control are provided in the cooled chamber 102. A total of 29 are installed.

Next, the operation of the binary refrigeration system 10 configured as described above will be described. In this system, the operation of the refrigeration operation is performed via the control unit 30 that controls the entire system. The control unit 30 is a microcomputer (commonly called “microcomputer”) as an example, and the control unit 30 stores a program for controlling the entire binary refrigeration system 10 according to a predetermined procedure.

  First, the flow of the NH3 medium in the ammonia cycle 11 will be described. The NH3 refrigerant stored in the NH3 receiver 15 is sent from the NH3 receiver 15 to the NH3 expansion valve 16 as a liquid refrigerant, and expanded to a saturation pressure corresponding to a low temperature required by the NH3 expansion valve 16. It is sent to the NH3 cascade condenser 17 and evaporated by the CO2 / NH3 gascade condenser 17 to become a gas. At this time, the NH3 medium takes heat from a CO2 refrigerant in the carbon dioxide cycle 12 described later, and cools and liquefies the CO2 refrigerant.

  Further, the NH3 refrigerant obtained by cooling and liquefying the CO2 refrigerant in the CO2 / NH3 cascade condenser 17 is compressed by the NH3 compressor 13 to become a high-temperature high-pressure gas. NH3 medium is obtained. The liquefied NH3 medium is stored in the NH3 receiver 15 and used again for cooling. Thereafter, this cycle is repeated.

  On the other hand, in the carbon dioxide gas cycle 12, the CO 2 refrigerant cooled and liquefied by the NH 3 medium in the CO 2 / NH 3 cascade condenser 17 is stored in the CO 2 receiver 15. The CO2 refrigerant stored in the CO2 receiver 15 is sent by the CO2 liquid pump 19 to the cooler 22 through the liquid supply electromagnetic valve 20 and the flow rate adjusting valve 21, and is heated and evaporated by the cooler 22. Then, it goes again to the CO2 / NH3 cascade capacitor 17 side. The gasified CO 2 medium is cooled and liquefied by the NH 3 medium in the CO 2 / NH 3 cascade condenser 17, and then returns to the CO 2 receiver 15. Thereafter, this cycle is repeated.

  In this carbon dioxide gas cycle 12, the supply of the CO2 liquid medium to the cooler 22 is usually performed by detecting the temperature in the cooled chamber 102 (hereinafter referred to as the temperature of the object to be cooled) with the temperature sensor 23, The temperature controller 24 controls the flow rate of the CO2 liquid medium by the flow rate adjusting valve 21 and controls the opening and closing of the liquid supply solenoid valve 20 so that the temperature of the object to be cooled becomes the temperature set in advance by the temperature controller 24. While doing.

  When operating the cooler 22, the CO2 pressure sensor 25 and the CO2 temperature sensor 27 detect the evaporation pressure and temperature state of the CO2 medium gasified in the cooler 22 on the outlet side of the cooler 22. This value is sent to the superheat degree controller 28. The superheat degree controller 28 obtains the superheat degree in the cooler 22 based on the detected pressure and temperature, and the flow rate adjusting valve 21 so that the superheat degree set by the superheat degree controller 28 is constant. And the supply amount of the CO2 medium to the cooler 22 is controlled. Thereby, the superheat degree of the cooler 22 is controlled to be constant, and the operation condition of the entire system is kept substantially constant.

  On the other hand, when the cooler 22 is operated at a temperature higher than the setting conditions of other coolers, the evaporation pressure of the CO2 medium gasified in the cooler 22 is measured on the outlet side of the cooler 22 by a CO2 pressure sensor. 25, and this value is sent to the pressure controller 29. Based on the detected pressure, the pressure regulator 29 controls the flow rate adjustment valve 21 so that the pressure becomes the same as the lowest evaporation pressure among the evaporation pressures corresponding to the set temperatures of the respective coolers 22. The supply amount of the CO2 medium to the cooler 22 is controlled. As a result, the CO2 pressure in the carbon dioxide gas cycle 12 is controlled to be constant, and the operating conditions of the entire system are kept substantially constant.

Therefore, in the refrigeration cycle in this embodiment, even when the set temperature on the cooler 22 side is set to a high temperature, the operating condition of the entire system is made almost constant by controlling the supply amount of the CO2 medium to the cooler 22. Can be maintained. As a result, overload and cooling failure can be prevented, and stable operation can be performed while maintaining the operation conditions of the entire system almost constant.

  Moreover, since the ammonia cycle 11 detects the pressure of the receiver and controls the capacity of the NH3 compressor 13 so as to be within the set pressure range, a plurality of coolers 22 are operated in different temperature zones with one refrigeration system. Can do. Further, since the carbon dioxide condensation pressure in the CO2 / NH3 cascade condenser 17 becomes constant, the suction pressure becomes constant even on the ammonia cycle side, and the system as a whole can be operated stably.

  As a result, even when a plurality of coolers 22 are operated at different temperatures in a single refrigeration system, it is possible to maintain the operating conditions of the entire system substantially constant without causing overload or cooling failure. With this, stable operation can always be performed.

  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.

  As described above, the present invention is not limited to refrigeration in a room to be cooled such as a refrigerated warehouse, but can be applied to, for example, a refrigeration showcase or an air conditioning system.

10 Refrigeration System 11 Ammonia Cycle 12 Carbon Dioxide Cycle 13 NH3 Compressor 14 NH3 Condenser 15 NH3 Receiver 16 NH3 Expansion Valve 17 CO2 / NH3 Cascade Condenser 18 CO2 Receiver 19 CO2 Liquid Pump 20 Liquid Supply Solenoid Valve 21 Flow Control Valve 22 Cooler (Evaporator)
23 Temperature sensor 24 Temperature controller 25 CO2 pressure sensor 26 CO2 pressure sensor 27 CO2 temperature sensor 28 Superheat controller 29 Pressure controller 101 CO2 / NH3 units 102a, 102b Cooled room

Claims (4)

A combination of an ammonia cycle using ammonia as a medium and a carbon dioxide gas cycle using carbon dioxide as a medium, the medium of the carbon dioxide cycle is condensed and liquefied by cold heat generated in the ammonia cycle, and stored in a receiver. In a refrigeration system that sends liquefied media from multiple to the load side coolers,
Between the receiver and the cooler, there is provided a flow rate adjusting valve for adjusting the amount of the liquefied medium supplied from the receiver to the cooler, and other coolers are also set at the lowest evaporating pressure in the cooler. The refrigeration system characterized by controlling the flow rate so that   The carbon dioxide gas cycle includes a temperature sensor that detects the temperature of the object to be cooled by each of the coolers, and is controlled by the flow rate adjustment valve according to the temperature of the object to be cooled and the set temperature detected by the temperature sensor. 2. The refrigeration system according to claim 1, wherein the flow rate is controlled.   The carbon dioxide gas cycle includes a temperature / pressure sensor for detecting the temperature and pressure of the refrigerant gas at the outlet of the cooler, and the flow rate is adjusted by the flow rate adjusting valve according to the temperature and pressure detected by the temperature / pressure sensor. 3. The refrigeration system according to claim 1, wherein the refrigeration system is controlled.   4. The refrigeration system according to claim 1, wherein the ammonia cycle detects the pressure of the receiver and controls the capacity of the compressor so as to be within a set pressure range.

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