JP2008138979A - Refrigeration system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain reliable and stable operation even at a low load time. <P>SOLUTION: The refrigeration system is provided with a refrigerating cycle comprising a compressor 7 driven with a variable capacity, a condenser 9, an expansion valve 13, and an evaporator 15, and a cooling load provided with a cooler 11 including the expansion valve 13 and the evaporator 15, and cooled by a coolant cooled by the cooler 11. The coolers 11 are plurally provided in parallel between the compressor 7 and the condenser 9, an operation capacity is controlled based on a suction pressure of the compressor 7 in the compressor 7, and the number of coolers 11 to be operated is controlled based on the operation capacity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for controlling the operation of a refrigeration apparatus.

  In general, a refrigeration system uses a refrigeration cycle in which a compressor, a condenser, an expansion valve, and an evaporator are connected in order through a refrigerant pipe, and a medium to be cooled such as air that is heat-exchanged with the refrigerant by the evaporator. Refrigeration operation is performed by supplying heat load.

  In such a refrigerating apparatus, a refrigerating apparatus is disclosed in which a plurality of coolers including expansion valves and evaporators are provided in a refrigerator and arranged in parallel, and the number of operating coolers can be switched as appropriate (Patent Document). 1). According to this, for example, it is possible to switch the number of operating coolers as appropriate according to the internal temperature and load fluctuations, so that the cooling capacity can be stabilized.

  By the way, when the capacity of the compressor is constant, when the load required by the evaporator increases, that is, when the internal temperature rises, the suction pressure of the compressor increases, and conversely, it becomes supercooled and the load decreases. , The suction pressure becomes lower. For this reason, in order to efficiently perform the refrigeration operation, for example, it is necessary to appropriately control the operation capacity of the compressor based on the fluctuation of the load.

  On the other hand, for example, a refrigerating apparatus is disclosed in which the suction pressure of a compressor whose frequency is controlled by an inverter is detected and the frequency of the compressor is controlled based on the detected value (see Patent Document 2). ). According to this, since the rotation speed of the compressor can be controlled according to the change of the suction pressure, the cooling capacity of the refrigeration apparatus can be changed according to the load.

JP 63-294478 A (3rd page, FIG. 2) JP 2004-116995 A (page 6, FIG. 3)

  However, for example, in a configuration in which a plurality of coolers including an expansion valve and an evaporator are connected in parallel as in the refrigeration apparatus of Patent Document 2, when the load decreases and the frequency of the compressor decreases, the refrigerant circulation rate Therefore, even if the opening degree of each expansion valve (for example, a temperature type expansion valve) is throttled, the refrigerant does not expand sufficiently, so that the compressor returns due to liquid return or the expansion valve is turned on. There is a risk of causing hunting operation to turn off / off.

  An object of the present invention is to maintain a highly reliable and stable operation even at a low load.

  In order to solve the above-described problems, the present invention is provided with a refrigeration cycle including a compressor, a condenser, an expansion valve, and an evaporator driven with variable capacity, and a cooler including the expansion valve and the evaporator. A cooling load that is cooled by a cooled medium to be cooled, and a plurality of coolers are provided and connected in parallel between the compressor and the condenser, the compressor being the compressor The operating capacity is controlled on the basis of the suction pressure, and the number of operating coolers is controlled on the basis of the operating capacity.

  According to this, for example, even if the load is reduced and the suction pressure of the compressor is reduced, the operating capacity of the compressor is automatically set to be small, so that an appropriate refrigeration capacity is exhibited according to the load fluctuation. And driving efficiency can be improved.

  Further, when the operating capacity of the compressor is reduced, the refrigerant circulation amount is reduced. However, since the number of operating coolers is controlled to be reduced in accordance with the reduction of the operating capacity, the refrigerant flowing through the cooler during operation accordingly. The amount can be increased. In other words, even if the operating capacity of the compressor is reduced, the expansion valve flows with an amount of refrigerant that can perform a predetermined expansion function, so that the valve opening of the expansion valve can be changed following the change in the operating capacity. Can do. Thereby, it is possible to avoid a cooling failure associated with the liquid return operation or the expansion valve hunting operation, and it is possible to maintain a reliable and stable operation.

  In this case, the compressor is driven by an inverter, and the operation frequency is controlled based on the suction pressure. The number of cooler units may be controlled based on the operation frequency.

  A plurality of compressors are provided in parallel and the number of operating units is controlled based on the suction pressure, and the number of operating coolers is controlled based on the number of operating compressors. May be. According to this, for example, the same effect as the above-described invention can be obtained without providing an inverter-driven compressor.

  The cooling load is provided with a temperature sensor for detecting the temperature of the cooling load, and when the temperature detected by the temperature sensor is between the thermo-on temperature at which the compressor starts operating and the thermo-off temperature at which the operation stops. Alternatively, the number of operating coolers may be controlled. That is, for example, when the temperature of the cooling load is equal to or higher than the thermo-on temperature, priority is given to securing the cooling capacity to operate all the coolers, and the number of operating coolers is controlled only when the temperature is between the thermo-on temperature and the thermo-off temperature. As a result, the control efficiency can be improved.

  In addition, when the detected temperature of the temperature sensor reaches the thermo-on temperature, the operation of the compressor is started, and when the time until the thermo-off temperature for stopping the operation of the compressor is shorter than the set time, the next time the compressor is operated, You may make it reduce the operating frequency or operating number of a compressor, and the operating number of a cooler. According to this, for example, when the load is small and the temperature in the container is relatively stable, it is not necessary to increase the operation capacity unnecessarily, so that an energy saving operation can be realized.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a system diagram of a refrigeration apparatus to which the present invention is applied.

  The refrigeration apparatus of the present embodiment includes a condensing unit 1, a refrigerator / freezer 3, and a control device 5.

  The condensing unit 1 houses an inverter compressor 7 and a condenser 9 connected by refrigerant piping. The inverter compressor 7 is configured such that the operating frequency is variably controlled by a command from the control device 5, for example. Two refrigerators 11 are arranged in the refrigerator-freezer 3. Each cooler 11 houses a temperature type expansion valve 13 and an evaporator 15 connected by refrigerant piping. The refrigerant pipe connected to the refrigerant inlet side of each cooler 11 is provided with a refrigerant liquid electromagnetic valve 17.

  A high-pressure refrigerant pipe 19 and a low-pressure refrigerant pipe 21 are connected to the refrigerant outlet side and the refrigerant inlet side of the condensing unit 1, respectively, and two coolers 11 are connected in parallel via these pipes. Thus, a refrigeration cycle is configured. A fan (not shown) that blows air is provided in the vicinity of the condenser 9 and the evaporator 15.

  The low-pressure refrigerant pipe 21 on the suction side of the inverter compressor 7 is provided with a pressure sensor 23 that detects the refrigerant pressure on the suction side of the inverter compressor 7. Inside the refrigerator-freezer 3, a temperature sensor 25 for detecting the internal temperature is provided. Information detected by each sensor is input to the control device 5 through the electrical wiring 27, and based on this input information, the control device 5 instructs the valve opening / closing of the refrigerant liquid electromagnetic valve 17 and the cooler 11. An operation command is output through the electrical wiring 27.

  Next, the operation of the refrigeration cycle in the refrigeration apparatus configured as described above will be described.

  First, in the condensing unit 1, the low-pressure gas refrigerant sucked into the inverter compressor 7 through the low-pressure refrigerant pipe 21 is compressed into a high-temperature and high-pressure refrigerant, and then led to the condenser 9 to be cooled. It is condensed and liquefied. For example, when the two coolers 11 are operated, the liquefied high-pressure refrigerant flows through the high-pressure refrigerant pipe 19 and is branched to the cooler 11 via the refrigerant liquid electromagnetic valve 17.

  The liquid refrigerant that has flowed into the cooler 11 is led to the temperature type expansion valve 13 to be depressurized to become a low-temperature refrigerant, and then sent to the evaporator 15 to exchange heat with the air in the warehouse, and evaporates to low pressure. Gas refrigerant. The low-pressure refrigerant gasified here joins in the low-pressure side refrigerant pipe 21 and is sucked into the inverter compressor 7 and compressed again to circulate through the refrigeration cycle. Moreover, the air cooled in the evaporator 15 is circulated in the warehouse by a fan, and the interior is cooled to a desired temperature.

  Next, an example of basic operation control of such a refrigeration cycle will be described.

  First, in the cooler 11, when the temperature detected by the temperature sensor 25 is equal to or higher than a preset thermo-on temperature for driving the condensing unit 1, all the refrigerant liquid solenoid valves 17 and the coolers 11 are controlled. An operation command is output from the device 5. As a result, the refrigerant liquid electromagnetic valve 17 is opened, and the cooler 11 is in an operating state. Further, when the operation command is output from the control device 5 to the condensing unit 1, for example, when the detected pressure of the pressure sensor 23 becomes equal to or higher than a preset upper limit value, the operation of the inverter compressor 7 is performed. Is started.

  The operation frequency of the inverter compressor 7 is controlled based on the pressure detected by the pressure sensor 23. In this embodiment, when the detected pressure is equal to or higher than the upper limit set value, the operating frequency is increased, and when the detected pressure is less than the upper limit set value and equal to or higher than the lower limit set value, the current operating frequency is maintained. When the value is less than the lower limit set value, the operation frequency is set to be decelerated and the capacity control is performed.

  Subsequently, as the inverter compressor 7 is operated, the internal temperature decreases, and the temperature detected by the temperature sensor 25 decreases to a thermo-off temperature set in advance to stop the condensing unit 1. The operation of the inverter compressor 7 is stopped when the solenoid valve 17 is closed and the detected pressure is lowered to a predetermined set value smaller than the lower limit set value.

  The control device 5 controls the number of operating coolers 11 based on the operating frequency of the inverter compressor 7. FIG. 2 shows an example of the control of the number of operating coolers 11 based on the operating frequency of the inverter compressor 7. As shown in the figure, when the maximum frequency is set to 80 Hz, the inverter compressor 7 operates when two coolers 11 are operated when the frequency is about 41 Hz or more, which is about half the frequency, and one when the frequency is less than 40 Hz. The cooler 11 is set to operate.

  By the way, when the internal temperature is lowered and the load is reduced, the operating frequency of the inverter compressor 7 is lowered as the detected pressure is lowered, and the refrigerant circulation amount is reduced. At this time, depending on the number of operating coolers 11, the amount of refrigerant flowing through each cooler 11 may decrease, and the valve opening by the temperature expansion valve 17 may not be able to follow the change in the operating capacity of the inverter compressor 7. .

  On the other hand, in the present refrigeration apparatus, the number of operating coolers 11 is controlled based on the operating frequency of the inverter compressor 7, so the number of operating coolers 11 is appropriately reduced according to the decrease in operating capacity. Thus, the amount of refrigerant flowing through the cooler 11 can be increased. For this reason, in this refrigeration apparatus, since the expansion function of the temperature type expansion valve 13 can be sufficiently exerted, a failure of the compressor 7 due to the liquid return operation, or hunting in which the valve of the temperature type expansion valve 13 is turned on / off. It is possible to eliminate problems that result in poor cooling such as operation, and to obtain a highly reliable and stable operation state.

  Here, when the cooler 11 is stopped, it is preferable to preferentially stop the cooler 11 having a longer operation time. According to this, since the operation time of each cooler 11 can be made uniform, it can prevent that specific cooler 11 becomes excessive frost formation.

  Control of the number of operating coolers 11 starts when the temperature inside the chamber detected by the temperature sensor 25 is between the thermo-on temperature and the thermo-off temperature, and when the detected temperature of the temperature sensor 25 is equal to or higher than the thermo-on temperature, It is preferable to maximize the number of operating coolers 11. That is, when the internal temperature is equal to or higher than the thermo-on temperature, the detected pressure of the normal pressure sensor 23 is equal to or higher than the upper limit set value, and the operating capacity of the inverter compressor 7 gradually increases. Therefore, all the coolers 11 are operated. In this way, unnecessary on / off operation of the cooler 11 can be suppressed.

  Next, a refrigeration apparatus according to a second embodiment to which the present invention is applied will be described.

  FIG. 3 is a system diagram of the refrigeration apparatus in the present embodiment. This refrigeration apparatus is configured by connecting three compressors in parallel in the condensing unit 1, and the other configuration and operation thereof are the same as those of the first refrigeration apparatus. The compressor 31 used here is not necessarily an inverter compressor, and for example, a compressor having a fixed rotation speed can be used.

  As described above, in the case of a multi-refrigeration apparatus including a plurality of compressors 31, the number of operating compressors 31 is controlled based on the pressure detected by the pressure sensor 23. For example, when the detected pressure is equal to or higher than the upper limit set value, the number of operating compressors 31 is increased, and when the detected pressure is less than the lower limit set value, the operation of the compressor 31 is controlled by reducing the number of operating compressors 31. Similar to the case where the frequency is increased or decreased, the operating capacity of the compressor 31 can be controlled in accordance with a change in load.

  FIG. 4 shows an example of control of the number of operating coolers based on the number of operating compressors. In addition, in order to make description easy, it demonstrates using the example in which the three coolers 11 are installed.

  As shown in FIG. 4, when the number of installed compressors 31 and coolers 11 is the same, according to the change in the number of operating compressors 31 so that the number of operating compressors 31 and the same number of coolers 11 are the same. Control is performed so that the number of operating coolers 11 also changes. For example, when the number of installed compressors 31 is larger than the number of installed coolers 11, such as two compressors 31 and four coolers 11, for example, two compressors 31 are operated. When four coolers 11 are operated, and the number of operating compressors 31 is reduced to one, the number of operating coolers 11 is reduced by two in conjunction with this. Control can be performed so that a predetermined number ratio is obtained.

  As a result, even if the operating capacity of the compressor 31 is reduced, the expansion function of the temperature type expansion valve 13 can be sufficiently ensured, so that the temperature type expansion valve 13 can follow and the liquid to the compressor 31 can be maintained. It is possible to eliminate a problem that causes cooling failure such as a return or a temperature-type expansion valve 17 being turned on / off in a hunting operation, and a stable operation state with high reliability can be obtained.

  In addition, for example, when the internal temperature becomes the thermo-on temperature and the time to reach the thermo-off temperature after the compressor is driven is shorter than a preset time, at the next thermo-on, the inverter compressor operating frequency or Control for reducing the number of operating compressors and the number of operating coolers 11 may be added. According to this, for example, when the cooling load is small and the internal temperature is relatively stable, it is not necessary to increase the operation capacity unnecessarily, so that an energy saving operation can be realized. Note that if the arrival time from when the thermo is on to when the thermo is off is short and the next start-up is set to the minimum capacity, for example, if the internal temperature does not drop below the thermo-on temperature after a certain period of time, this control is immediately released. Return to normal capacity control to prevent insufficient cooling.

  As described above, according to the refrigeration apparatus to which the present invention is applied, the number of operating coolers 11 can be appropriately switched according to the change in the operating capacity of the condensing unit 1, regardless of the state of the load. Reliable and stable operation can be maintained.

  In the above embodiment, the frequency control or the number control as the compressor, the temperature type expansion valve as the expansion valve, and the two units arranged as the cooler are described in parallel. For example, the compressor may have another configuration with variable capacity, or the cooler may have three or more units, both of which are based on the compressor capacity. It goes without saying that the effects of the present invention can be obtained as long as the number of operating units is controlled.

It is a systematic diagram of the freezing apparatus of the 1st Embodiment of this invention. It is a control diagram which shows an example of control of the operation number of a cooler. It is a systematic diagram of the freezing apparatus of the 2nd Embodiment of this invention. It is a control diagram which shows an example of control of the operation number of a cooler.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Condensing unit 3 Refrigerated refrigerator 5 Control apparatus 7 Inverter compressor 9 Condenser 11 Cooler 13 Temperature type expansion valve 15 Evaporator 17 Refrigerant liquid solenoid valve 23 Pressure sensor 25 Chamber temperature sensor 31 Compressor

Claims (5)

A refrigeration cycle comprising a compressor, a condenser, an expansion valve, and an evaporator driven with variable capacity, and a cooler including the expansion valve and the evaporator are provided, and cooling is performed by a cooling medium cooled by the cooler. Cooling load, and
A plurality of the coolers are provided and connected in parallel between the compressor and the condenser,
An operating capacity of the compressor is controlled based on the suction pressure of the compressor, and the operating number of the coolers is controlled based on the operating capacity. The compressor is driven by an inverter, and an operation frequency is controlled on the basis of the suction pressure, wherein the number of the coolers to be operated is controlled on the basis of the operation frequency. The refrigeration apparatus according to 1. A plurality of the compressors are arranged in parallel and the number of operating units is controlled based on the suction pressure, and the number of operating coolers is controlled based on the number of operating compressors. The refrigeration apparatus according to claim 1. The cooling load is provided with a temperature sensor that detects the temperature of the cooling load, and the temperature detected by the temperature sensor is between a thermo-on temperature at which the compressor starts operating and a thermo-off temperature at which the operation stops. The refrigeration apparatus according to any one of claims 1 to 3, wherein the number of operating coolers is controlled. The cooling load is provided with a temperature sensor that detects the temperature of the cooling load. When the temperature detected by the temperature sensor reaches a thermo-on temperature, the compressor starts operating and the thermo-off temperature stops the compressor operation. 3. The operation frequency or the number of the compressors and the number of the coolers to be operated are reduced at the next operation of the compressor when the time until it becomes shorter than a set time. Or the refrigeration apparatus of 3.

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