JP6518467B2 - Refrigeration system - Google Patents

Description

  The present invention relates to a refrigeration system provided with a subcooler, and is particularly suitable for suppressing condensation on refrigerant piping downstream of the subcooler.

  As a conventional freezing apparatus provided with the subcooler, there are some which are described in JP, 2013-142487, A (patent documents 1). According to Patent Document 1, a high-temperature high-pressure gas refrigerant discharged from the compressor is condensed in a condenser, and the condensed liquid refrigerant is further subcooled, and a supercooler (supercooling heat exchanger) is provided. There is. The supercooler is used for the purpose of avoiding the flash gasification without completely condensing the refrigerant in the condenser and for the purpose of improving the refrigeration capacity due to the temperature decrease of the liquid refrigerant.

  In the subcooler, there is provided a liquid refrigerant cooling circuit for supercooling the liquid refrigerant from the main refrigerant pipe flowing through the subcooler by the decompressed refrigerant obtained by extracting and decompressing a part of the high pressure liquid refrigerant flowing through the main refrigerant pipe. Have. Further, the depressurized refrigerant after supercooling of the high pressure liquid refrigerant flowing through the main refrigerant pipe in the subcooler is configured to be injected into an intermediate pressure portion of the compressor.

JP, 2013-142487, A

  In the case of Patent Document 1, the temperature of the refrigerant flowing through the refrigerant pipe downstream of the subcooler may be lowered to the dew point temperature or less by the subcooler, and in this case, condensation occurs in the refrigerant pipe. Conventionally, a heat insulating material is attached to the refrigerant pipe on site to prevent the condensation, but there is a problem that the work load at the time of on-site construction becomes large and the cost due to the use of the heat insulating material is also increased.

  In addition, when using existing refrigerant piping when replacing a product without a subcooler (refrigerator) with a product equipped with a supercooler, installation of a heat insulator may be difficult, In this case, there is a problem that the occurrence of condensation can not be prevented or the amount of cooling in the supercooler must be suppressed so that condensation does not occur, and the refrigeration capacity can not be improved.

  On the other hand, there are also cases where heat insulation construction is performed on the local refrigerant piping where the refrigeration system is installed. In this case, since there is no problem regarding condensation, it is desirable to lower the liquid refrigerant temperature as much as possible to improve the refrigeration capacity. However, in the conventional refrigeration system, sufficient consideration has not been made in improving the refrigeration capacity by controlling the liquid refrigerant temperature low.

  An object of the present invention is to obtain a refrigeration system capable of suppressing the occurrence of condensation even when a heat insulating material is not used for refrigerant piping on the downstream side of the subcooler and also capable of improving the refrigeration capacity.

  In order to achieve the above object, the present invention provides a compressor, a condenser for condensing a refrigerant discharged from the compressor, a supercooler for further supercooling the refrigerant condensed by the condenser, and The refrigerant from the main refrigerant pipe flowing through the supercooler is supercooled by a main refrigerant pipe connecting devices and a decompressed refrigerant obtained by extracting and reducing a part of the high pressure liquid refrigerant flowing through the main refrigerant pipe, and supercooling the refrigerant from the main refrigerant pipe flowing through A liquid refrigerant cooling circuit for injecting the decompressed refrigerant after supercooling into an intermediate pressure portion of a compressor, a supercooling expansion device for controlling and reducing the flow rate of refrigerant flowing through the liquid refrigerant cooling circuit, and The control device for controlling the expansion device for cooling, and the outside air temperature sensor for detecting the outside air temperature, the control device detects the target temperature of the liquid refrigerant downstream of the subcooler, the outside air detected by the outside air temperature sensor Any pre-determined temperature Min to a value given, characterized in that it comprises a condensation suppression mode for controlling the super cooling expansion device on the basis of the target temperature.

  Another feature of the present invention is to connect a compressor, a condenser for condensing the refrigerant discharged from the compressor, a subcooler for further supercooling the refrigerant condensed by the condenser, and these devices After supercooling the refrigerant from the main refrigerant pipe flowing through the subcooler with the main refrigerant piping, and the decompressed refrigerant obtained by extracting and decompressing a part of the high pressure liquid refrigerant flowing through the main refrigerant piping, and after the supercooling A liquid refrigerant cooling circuit for injecting the decompressed refrigerant into the intermediate pressure portion of the compressor, a supercooling expansion device for controlling and depressurizing the flow rate of the refrigerant flowing through the liquid refrigerant cooling circuit, and the expansion for supercooling The control device includes a control device for controlling the device, and the control device reduces the temperature of the liquid refrigerant downstream of the subcooler as much as possible by reducing the dew condensation suppression mode for suppressing condensation of the refrigerant pipe downstream of the subcooler. Liquid temperature operating with high refrigeration capacity An appropriate mode is provided, and in the condensation suppression mode, the target temperature of the liquid refrigerant downstream of the subcooler is a value obtained by giving an arbitrary predetermined difference to the outside air temperature, and for the subcooling based on the target temperature The expansion device is controlled, and in the liquid temperature optimum mode, the opening degree of the supercooling expansion device is increased or decreased in the direction in which the liquid refrigerant temperature is lowered, and the liquid refrigerant temperature is further lowered when the liquid refrigerant temperature is lowered. The operation for increasing or decreasing is repeated, and when the decrease of the liquid refrigerant temperature is stopped or increased, the supercooling expansion device is controlled to maintain the opening state.

  According to the present invention, it is possible to suppress the occurrence of condensation even when the heat insulating material is not used for the refrigerant pipe on the downstream side of the subcooler, and to obtain the effect of obtaining the refrigeration apparatus capable of improving the refrigeration capacity. .

BRIEF DESCRIPTION OF THE DRAWINGS It is a refrigerating-cycle systematic diagram which shows Example 1 of the freezing apparatus of this invention. It is a flowchart which shows the control flow in the case of drive | operating in the condensation suppression mode in the control apparatus shown in FIG. It is a flowchart which shows the control flow in the case of drive | operating in liquid temperature optimal mode in the control apparatus shown in FIG.

  Hereinafter, embodiments of the refrigeration system of the present invention will be described with reference to the drawings.

A first embodiment of the refrigeration system of the present invention will be described with reference to FIGS. 1 to 3.
FIG. 1 is a system diagram of a refrigeration cycle showing Embodiment 1 of the refrigeration system of the present invention, FIG. 2 is a flow chart showing a control flow when operating in the condensation suppression mode in the control device shown in FIG. It is a flowchart which shows the control flow in the case of drive | operating in liquid temperature optimal mode in the control apparatus shown to these.

  In FIG. 1, 100 is a refrigerator which is a heat source device for generating a cold heat source, 200 is a load device connected to the refrigerator 100, and the load device 200 is a low pressure device in this embodiment. explain. The refrigeration cycle apparatus 500 is configured by connecting the refrigerator 100 and the load device (low pressure device) 200 by a liquid side connection pipe 300 and a gas side connection pipe 400. The load device 200 may be a showcase installed in a store such as a refrigerator, a freezer, or a supermarket to cool food etc., or an indoor unit of an air conditioner. In this embodiment, a refrigerator is taken as an example. explain. The present invention can be implemented similarly even when a plurality of low-pressure devices 200 are connected to one refrigerator 100, not limited to one.

  The refrigerator 100 includes a compressor 1 such as a scroll compressor which sucks and compresses a refrigerant, a condenser 2 which condenses and liquefies a gas refrigerant discharged from the compressor 1, and a condenser 2 which condenses the refrigerant. It is configured by a subcooler 3 for further cooling and supercooling the refrigerant, a main refrigerant pipe 31 connecting these devices, and the like.

  Further, the load device (hereinafter also referred to as a low pressure device in the present embodiment) 200 is an expansion valve 4 as pressure reducing means for reducing the pressure of the liquid refrigerant subcooled by the subcooler 3. The gas refrigerant evaporated in the evaporator 5 is again drawn into the compressor 1 of the refrigerator 100 to constitute a refrigeration cycle.

  In the present embodiment, a scroll compressor is described as an example of the compressor 1, but other types of compressors, for example, various other types of compressors such as a screw compressor may be used. good.

  In the present embodiment, the subcooler 3 for supercooling the refrigerant (liquid refrigerant) condensed in the condenser 2 is provided, but from the main refrigerant pipe 31 flowing through the supercooler 3 A liquid refrigerant cooling circuit 32 is provided to subcool the refrigerant. The liquid refrigerant cooling circuit 32 supercools the refrigerant from the main refrigerant pipe 31 flowing through the subcooler 3 with the decompressed refrigerant which is extracted and decompressed a part of the high pressure liquid refrigerant flowing through the main refrigerant pipe 31. The reduced pressure refrigerant after the supercooling is injected into the intermediate pressure portion of the compressor 1, and the liquid refrigerant cooling circuit 32 upstream of the subcooler 3 is a liquid refrigerant cooling circuit. A supercooling expansion device 6 is provided to control and depressurize the flow rate of the refrigerant (liquid refrigerant) flowing through the flow passage 32.

  That is, the liquid refrigerant cooling circuit 32 includes a branch pipe 32a branched from the main refrigerant pipe 31 after passing through the condenser 2, and the supercooling expansion device 6 provided in the branch pipe 32a. . Further, the supercooling expansion device 6 is constituted by an expansion valve capable of opening degree control such as an electronic expansion valve, and is controlled by a control device 30 provided in the refrigeration system 100.

  In the present embodiment, a plate type heat exchanger is used as the subcooling heat exchanger constituting the subcooler 3. The supercooling heat exchanger is not limited to a plate heat exchanger, and various types of heat exchangers such as a double pipe heat exchanger can be used.

  Further, in the present embodiment, in addition to the liquid refrigerant cooling circuit 32, a liquid injection circuit 33 for cooling the compressor 1 is also provided. The liquid injection circuit 33 is for injecting the decompressed refrigerant obtained by extracting and decompressing a part of the high pressure liquid refrigerant flowing through the main refrigerant pipe 31 into the intermediate pressure part of the compressor 1 to cool the compressor 1. The branch pipe 33a branched from the main refrigerant pipe 31 after passing through the condenser 2, and the flow adjustment device 7 for liquid injection provided in the branch pipe 33a and controlling the flow rate flowing through the liquid injection circuit, etc. There is. In the present embodiment, the flow rate adjusting device 7 is also configured by an expansion valve capable of opening degree control such as an electronic expansion valve, and is controlled by the control device 30.

  The flow rate adjustment device 7 provided in the liquid injection circuit 33 is controlled by the control device 30 based on the temperature of the compressor 1 or the temperature of the discharge gas discharged from the compressor 1 or the degree of superheat of the discharge gas. It is controlled. That is, the control is performed based on detection values from a compressor temperature sensor that detects the temperature of the compressor 1 and a discharge gas temperature sensor (not shown) that detects the temperature of discharge gas discharged from the compressor 1. The device 30 is configured to control the flow regulating device 7.

  The downstream side of the liquid refrigerant cooling circuit 32 and the downstream side of the liquid injection circuit 33 are merged, and are connected to the intermediate pressure portion of the compressor 1 through the merged pipe 34 joined. . The intermediate pressure portion is a portion where the refrigerant in the compression process is present, and the refrigerant is injected to the portion via the junction pipe 34 to cool the compressor 1. Note that although it is preferable that the flow rate adjusting device 7 is configured by an electronic expansion valve capable of continuously adjusting the opening degree, fixed flow rate adjustment of a capillary tube or the like having different flow path areas in flow paths provided in parallel The flow rate may be adjusted stepwise by switching the flow path by opening and closing the on-off valve.

  In this embodiment, a liquid refrigerant temperature sensor 10 for detecting the temperature of the liquid refrigerant discharged from the subcooler 3 and an outside air temperature sensor 20 for detecting the outside air temperature are also provided. The detected value at 20 is input to the control device 30. The control device 30 controls the opening degree of the subcooling expansion device 6 of the liquid refrigerant cooling circuit 32 in accordance with detection values from the liquid refrigerant temperature sensor 10 and the outside air temperature sensor 20 and the like. The control device 30 may control the flow rate adjustment device 7 provided in the liquid injection circuit 33 also using the detection values from the liquid refrigerant temperature sensor 10 and the outside air temperature sensor 20. good.

Next, the basic operation of the refrigeration system of the first embodiment configured as described above will be described.
The refrigerant drawn into the compressor 1 is compressed, and the compressed high-temperature, high-pressure gas refrigerant is condensed by heat exchange with, for example, the outside air (outdoor air) in the condenser 2, and all or most of the refrigerant is Become. Thereafter, the refrigerant flows into the subcooler 3 to become a subcooled liquid refrigerant.

  Thereafter, the subcooled liquid refrigerant flows into the low pressure device 200 through the liquid refrigerant pipe 300 and is decompressed by the expansion valve 4. The depressurized gas-liquid two-phase refrigerant flows into the evaporator 5 and exchanges heat with the secondary refrigerant (for example, air in the refrigerator) to remove heat from the secondary refrigerant to cool the secondary refrigerant. And they evaporate themselves. The evaporated refrigerant is again drawn into the compressor 1 of the refrigerator 100 through the gas side refrigerant pipe 400 to form a refrigeration cycle. The secondary refrigerant cooled by the refrigerant in the evaporator 5 is supplied into a refrigerator (low-pressure device) to cool food and the like in the refrigerator.

  In the present embodiment, although the case where the load device is a low pressure device such as a refrigerator has been described, the refrigerant discharged from the compressor 1 can be reversed by reversing the flow of the refrigerant via the four-way switching valve. The load device 200 can also be configured to be heated.

  In the refrigeration apparatus of the present embodiment configured as described above, “condensation suppression mode suppresses condensation of refrigerant piping (main refrigerant piping 31 and liquid side refrigerant piping 300) on the downstream side of the subcooler 3” And the "liquid temperature optimum mode" in which the liquid refrigerant temperature on the downstream side of the subcooler 3 is lowered as much as possible so that it can be operated with a high refrigeration capacity. Each of these modes will be described below.

First, control contents in the above-mentioned "condensation suppression mode" will be described.
The “condensation suppression mode” is selected when it is desired to operate to suppress condensation of refrigerant piping through which the liquid refrigerant downstream of the subcooler 3 flows. In this "condensation suppression mode", a target temperature of the liquid refrigerant is determined such that the refrigerant pipe on the downstream side of the subcooler 3 does not condense. In this embodiment, the target temperature is a value obtained by giving an arbitrary predetermined difference (differential) to the outside air temperature detected by the outside air temperature sensor 20. The control device 30 calculates the target temperature, and controls the expansion device for supercooling 6 based on the target temperature, so that the temperature of the liquid refrigerant downstream of the subcooler 3 becomes the target temperature. It controls to approach.

  The “target temperature of liquid refrigerant” in the “condensation suppression mode” includes not only the target temperature of liquid refrigerant downstream of the subcooler 3 but also the target temperature of refrigerant piping through which the liquid refrigerant flows. The liquid refrigerant temperature sensor 10 shown in FIG. 1 may not only detect the temperature of the liquid refrigerant flowing in the refrigerant pipe but may also detect the temperature of the refrigerant pipe. I use something that detects the temperature.

  The feature of the "condensation suppression mode" in this embodiment is that the target temperature of the liquid refrigerant on the downstream side of the subcooler 3 is a value obtained by giving an arbitrary predetermined difference to the outside air temperature. The target temperature of the liquid refrigerant can also be set arbitrarily by arbitrarily setting. Some conventional ones have the "condensation suppression mode", but in the conventional ones, because the target temperature of the liquid refrigerant is equal to the outside air temperature, the liquid refrigerant temperature is temporarily set due to variations in operating conditions, etc. It is not taken into consideration that the temperature may fall below the outside air temperature, and condensation can not be sufficiently avoided.

  On the other hand, in the above-described embodiment, the target temperature of the liquid refrigerant can be set higher than the outside air temperature by an arbitrarily determined difference by arbitrarily determining the difference as described above. Even when the operating condition in the case of (4) is dispersed, it is possible to suppress the liquid refrigerant temperature from becoming equal to or lower than the outside air temperature, and it is possible to obtain the effect of realizing the operating condition with a margin for condensation. Therefore, the arbitrary difference in the target temperature may be set to a size that can suppress the liquid refrigerant temperature on the downstream side of the subcooler from being equal to or lower than the outside air temperature even if the operating condition in the refrigeration apparatus varies.

  In addition, whether condensation actually occurs on the refrigerant pipe is whether the temperature of the refrigerant pipe is equal to or lower than the dew point temperature determined by the temperature and humidity, not the outside air temperature. In this embodiment, since the target temperature of the liquid refrigerant is a value obtained by giving an arbitrary predetermined difference to the outside air temperature, the difference is determined in consideration of the humidity in the usage environment of the refrigeration apparatus. It is also possible to set a target temperature that is lower than the ambient temperature but higher than the dew point temperature. That is, the temperature of the liquid refrigerant can be controlled as low as possible within the range in which the refrigerant piping does not condense by determining the arbitrary difference so that the target temperature is lower than the outside air temperature and higher than the dew point temperature. Therefore, it is also possible to operate the refrigeration system with higher refrigeration capacity.

  Next, the control flow of the "condensation suppression mode" in this embodiment will be described with reference to FIG. Here, a case where an electronic expansion valve is used as the supercooling expansion device 6 will be described.

  When the condensation suppression mode is started, if the supercooling expansion device (electronic expansion valve) 6 has already been opened to a certain degree, the supercooling expansion device 6 is fully closed first. And (step S1). As a result, the liquid refrigerant temperature on the downstream side of the subcooler 3 can be quickly brought to the outside air temperature or higher, and the occurrence of condensation can be suppressed.

  Next, in step S2, whether or not the liquid refrigerant temperature TL on the downstream side of the subcooler 3 detected by the liquid refrigerant temperature sensor 10 is equal to or higher than the outside air temperature detected by the outside air temperature sensor 20; When the liquid refrigerant temperature TL is less than the outside air temperature (NO), the step S2 is repeated again after the control time (a predetermined time) has elapsed.

  In step S2, when the liquid refrigerant temperature TL is equal to or higher than the outside air temperature (YES), the process proceeds to step S3, and the liquid refrigerant temperature TL and the target temperature of the liquid refrigerant (an arbitrary difference predetermined to the outside air temperature) Compare with the value given). By appropriately adjusting the opening degree of the supercooling expansion device 6 according to the comparison result, the temperature of the liquid refrigerant on the downstream side of the supercooler 3 is caused to reach the target temperature. Details of the process in step S3 will be described later.

  If the supercooling expansion device 6 is already fully closed at the start of the condensation suppression mode, step S2 and subsequent steps may be performed.

  The important point in the present embodiment is that control (step S1) is performed to fully close the electronic expansion valve 7 immediately after the control of the condensation suppression mode is started. That is, the cause of condensation is that the liquid refrigerant is subcooled in the subcooler 3. Since the temperature of the condensed liquid refrigerant is not cooled below the outside air temperature if the subcooler 3 is not provided and the refrigerant is cooled by exchanging heat with the outside air in the condenser 2, the temperature is basically not lower than the outside air temperature. No condensation on the Therefore, once the supercooling expansion device 6 is once fully closed to lose the supercooling effect, a large effect is exhibited from the viewpoint of condensation suppression.

  In addition, immediately after the control of the condensation suppression mode is started, the electronic expansion valve 7 is not fully closed immediately, and the opening degree of the supercooling expansion device 6 is increased or decreased to It is also conceivable to adjust the liquid refrigerant temperature to the outside air temperature (condensation suppression temperature), but when the supercooling expansion device 6 is open, an effect of supercooling the refrigerant is generated. Therefore, as in the present embodiment, it is possible to quickly set the supercooling expansion device 6 to be fully closed once and lose the supercooling effect more quickly than the condensation suppression temperature, which is effective from the viewpoint of condensation suppression. is there.

  In order to increase the temperature of the liquid refrigerant on the downstream side of the subcooler 3 immediately, it is conceivable to physically heat the refrigerant piping by attaching a heater or the like to the refrigerant piping. There is a possibility that the cooling capacity may be reduced.

  Furthermore, from the viewpoint of condensation suppression, it is also conceivable to always fully close the subcooling expansion device 6 so as not to generate the subcooling effect in the subcooler 3. However, in an operation in which the supercooling effect is not always generated, it becomes difficult to operate the refrigeration system with a high refrigeration capacity.

  On the other hand, in the "condensation suppression mode" in the present embodiment, the target temperature (a value obtained by giving an arbitrary predetermined difference to the outside air temperature) of the liquid refrigerant that can suppress condensation is set, By controlling the device 6, it is possible to lower the liquid refrigerant temperature to the target temperature at which condensation does not occur, and in the range where condensation can be reliably suppressed, an effect of operating the refrigeration system with high refrigeration capacity is obtained. That is, as compared with the operation in which the supercooling expansion device 6 is always fully closed, according to this embodiment, the effect of suppressing condensation and operating with a high refrigeration capacity can be obtained.

  If the supercooling expansion device 6 is fully closed immediately after the start of control of the condensation suppression mode, or if the opening degree of the supercooling expansion device 6 is reduced in order to set the liquid refrigerant temperature to the target temperature, Since the refrigerant injection to the intermediate pressure portion of the compressor is stopped or reduced, the temperature rise of the compressor 1 may be caused.

  On the other hand, in the present embodiment, the liquid injection circuit 33 is also provided, and the liquid injection circuit 33 is provided based on the temperature of the compressor 1 or the discharge gas temperature discharged from the compressor 1 or the degree of superheat of the discharge gas. Since the flow rate adjusting device 7 is controlled, the flow rate of the liquid refrigerant injected from the liquid injection circuit 33 into the compressor 1 can be increased as necessary. Therefore, even if it operates in the condensation suppression mode mentioned above, the effect that the temperature rise of the compressor 1 can be suppressed certainly is acquired from this point as well, in this embodiment it is possible to operate with high refrigeration capacity while surely suppressing condensation. An effect is obtained.

Next, details of the process of step S3 shown in FIG. 2 will be described.
In step S2, when the liquid refrigerant temperature TL becomes equal to or higher than the outside air temperature, the process proceeds to step S3. In step S3, the liquid refrigerant temperature TL is compared with the target temperature of the liquid refrigerant, and the degree of opening of the supercooling expansion device 6 is adjusted according to the comparison result. Perform processing to bring the temperature of the liquid refrigerant closer to the target temperature.

  That is, as shown in (1) to (4) of step S3 in FIG. 2, the opening degree change amount of the supercooling expansion device 6 is controlled according to the comparison result of the liquid refrigerant temperature TL and the target temperature. . Α and β shown in step S3 are in an “α <β” relationship at any temperature (° C.). Further, A and B are arbitrary opening change amounts for controlling the opening degree of the supercooling expansion device 6 and have a relation of A <B. In the present embodiment, A and B are the number of pulses for controlling the opening degree of the electronic expansion valve. For example, let α be 1 ° C., β be 3 ° C., A be one pulse, and B be five pulses.

  The case of (1) in step S3 is the case where the liquid refrigerant temperature TL is higher than "target temperature + β (3 ° C. in this example at an arbitrary temperature)". In this case, since the liquid refrigerant temperature TL is relatively high with respect to the target temperature and it is desired to quickly approach the target temperature, the liquid refrigerant temperature needs to have a relatively large supercooling effect. For this reason, the opening degree change amount of the supercooling expansion device 6 is opened for a relatively large B pulse (five pulses in this example), and the liquid refrigerant temperature is rapidly decreased.

  In the case of (2) in step S3, the liquid refrigerant temperature TL is in the range above “target temperature + α (1 ° C. in this example at any temperature)” and below “target temperature + β (3 ° C)” That's the case. In this case, the liquid refrigerant temperature TL is slightly higher than the target temperature, and it is desirable to lower the temperature relatively slowly so that the liquid refrigerant temperature does not fall too low. Therefore, it is necessary to give the liquid refrigerant temperature a supercooling effect smaller than that of the case (1), and the opening change amount of the supercooling expansion device 6 is relatively small A pulse (1 pulse in this example) The valve is opened to slowly reduce the temperature of the liquid refrigerant.

  The case of (3) in step S3 is a case where the liquid refrigerant temperature TL is equal to or higher than the target temperature and in the range below “target temperature + α (1 ° C.)”. In this case, the liquid refrigerant temperature TL has almost reached the target temperature to achieve the control target range. In this case, since the liquid refrigerant temperature is in an appropriate state, the opening degree of the supercooling expansion device 6 is not changed, and the current liquid refrigerant temperature is maintained.

  The case of (4) in step S3 is the case where the liquid refrigerant temperature TL becomes lower than the target temperature, and when the target temperature is set to the outside temperature or lower, there is a possibility of condensation. In this case, since it is necessary to immediately raise the liquid refrigerant temperature, the opening degree of the supercooling expansion device 6 is controlled to once be fully closed, whereby the liquid refrigerant temperature is immediately raised to the outside air temperature or more.

  When the target temperature is set to a temperature relatively higher than the outside air temperature, the liquid refrigerant temperature is close to the outside air temperature in the condenser 2 even if the opening degree of the supercooling expansion device 6 is fully closed. It is also conceivable that the temperature may be cooled down to a temperature below the target temperature. However, in this case, since at least the supercooling effect is lost, there is no problem that dew condensation occurs.

  As described above, in the “condensation suppression mode” of the above-described embodiment, an arbitrary difference in which the target temperature of the liquid refrigerant on the downstream side of the subcooler 3 is predetermined to the outside air temperature detected by the outside air temperature sensor 20 Because the expansion device 6 for supercooling is controlled based on this target temperature, the occurrence of condensation can be suppressed even when the heat insulator is not used for the refrigerant pipe on the downstream side of the subcooler 3 At the same time, it is possible to obtain a refrigeration system capable of improving the refrigeration capacity.

  Next, the "liquid temperature optimum mode" in which the liquid refrigerant temperature on the downstream side of the subcooler 3 is lowered as much as possible to enable operation with a high refrigeration capacity will be described. In this liquid temperature optimum mode, at least the refrigerant pipe on the downstream side of the subcooler 3 is thermally insulated and there is no problem of condensation even if the liquid refrigerant temperature falls below the dew point. This mode is selected when you want to drive with the ability.

  In this liquid temperature optimum mode, the supercooling expansion device 6 is controlled such that the temperature of the liquid refrigerant downstream of the subcooler 3 is as low as possible. That is, when the supercooling expansion device 6 is, for example, an electronic expansion valve, if the opening degree of the supercooling expansion device 6 is too large, the secondary pressure with respect to the primary side pressure in the supercooling expansion device 6 The decrease in pressure on the side decreases. For this reason, the temperature decrease width of the refrigerant flowing through the liquid refrigerant cooling circuit 32 also becomes smaller, and the ability to cool the refrigerant flowing through the main refrigerant piping 31 in the subcooler 3 becomes smaller, and the main refrigerant piping downstream of the subcooler 3 The temperature of the refrigerant flowing through 31 does not decrease.

  On the other hand, if the degree of opening of the supercooling expansion device 6 is too small, the flow rate of the refrigerant passing through the supercooling expansion device 6 decreases too much. The ability to cool the flowing refrigerant is reduced, and the temperature of the refrigerant flowing through the main refrigerant pipe 31 on the downstream side of the subcooler 3 does not decrease.

  Thus, the opening degree of the supercooling expansion device 6 for minimizing the liquid refrigerant temperature on the downstream side of the subcooler 3 has an optimum opening degree according to various operating conditions of the refrigeration system. . In this "liquid temperature optimum mode", in order to minimize the liquid refrigerant temperature on the downstream side of the subcooler 3, the supercooling expansion device 6 is controlled to an optimum opening degree. .

A control flow of the "liquid temperature optimum mode" in the present embodiment will be described with reference to FIG. In the present embodiment, an electronic expansion valve is used as the supercooling expansion device 6 and is controlled by the control device 30.
If the supercooling expansion device (electronic expansion valve) 6 is closed or has an arbitrary opening degree when the liquid temperature optimum mode is started, the opening degree of the supercooling expansion device 6 is first determined in advance To the specified opening degree (step S4). About this regulation opening, for example, it is good to investigate and determine an opening that it is almost appropriate according to some operation conditions at the time of product development. By setting the opening degree to the specified opening first, the temperature of the liquid refrigerant on the downstream side of the subcooler 3 can be made approximately near the minimum under main operating conditions.

  However, even if the preferred specified opening degree of the supercooling expansion device 6 is determined in advance by experiments etc. as described above, the individual dispersion of the supercooling expansion device 6 itself, the freezing device such as the outside air temperature, etc. The liquid refrigerant temperature is often not minimized due to differences in the environmental conditions in which

  Therefore, in the present embodiment, next, in step S5, the opening degree of the supercooling expansion device 6 is controlled to be increased by a predetermined fixed amount, and the temperature of the liquid refrigerant downstream of the subcooler 3 is controlled. It is checked whether it falls or not (step S6). In this step S6, when the liquid refrigerant temperature is lowered (in the case of YES), the direction for increasing the opening degree of the supercooling expansion device 6 is correct, so the process returns to the step S5, and the opening degree is further constant. Increase the amount. By repeating this as long as the liquid refrigerant temperature is lowered, the temperature of the liquid refrigerant on the downstream side of the subcooler 3 can be controlled to be minimized.

  In step S6, when the liquid refrigerant temperature rises (in the case of NO), the process proceeds to step S7. If the liquid refrigerant temperature rises as a result of increasing the opening degree of the supercooling expansion device 6 first from the step S4 to the step S5, the process similarly proceeds to the step S7. Move.

  When the liquid refrigerant temperature rises by increasing the opening degree of the supercooling expansion device 6 (in the case of NO in step S6), the opening degree of the supercooling expansion device 6 is controlled to be decreased In step S7, the opening degree of the supercooling expansion device 6 is controlled to be reduced. As a result, when the temperature of the liquid refrigerant on the downstream side of the subcooler 3 is lowered (in the case of YES in step S8), it is confirmed that the direction to decrease the opening degree of the supercooling expansion device 6 is correct. Returning to step S7, the opening degree is further decreased by a fixed amount. By repeating this as long as the liquid refrigerant temperature is lowered, the temperature of the liquid refrigerant on the downstream side of the subcooler 3 can be controlled to be minimized.

  In step S8, when the drop of the liquid refrigerant temperature stops or turns to increase (NO in step S8), it is determined that the liquid refrigerant temperature is minimum, and the state of the opening is maintained Thus, the control is ended (step S9). As a result, the temperature of the liquid refrigerant downstream of the subcooler 3 can be minimized.

After the step S9, the control device 30 may be configured to control so as to repeat the steps S5 to S9 again after a predetermined time has elapsed.
In the example described above, the opening degree of the supercooling expansion device 6 is controlled to increase at first in step S5, but conversely, the opening degree is controlled to decrease at first. Control may be performed to increase the opening degree at S7.

  Furthermore, for the speed (opening change rate) for increasing or decreasing the opening degree of the supercooling expansion device 6 in the above steps S5 and S7, for example, an appropriate value is investigated by an experiment etc. It is preferable to set the device 30 in advance. If the opening change rate is too fast, the opening changes further in a state where the liquid refrigerant temperature is not stable, and it is conceivable that the liquid refrigerant temperature fluctuates, while if the opening change rate is too slow, This is because it takes too long to minimize the liquid refrigerant temperature.

  It is also conceivable to cause the temperature change of the compressor 1 by opening and closing the supercooling expansion device 6, but in the present embodiment, as described above, the liquid injection circuit for temperature control of the compressor 1 Since 33 is also provided, the temperature rise of the compressor 1 can be suppressed by controlling the flow rate adjusting device 7 of the liquid injection circuit 33 according to the temperature of the compressor 1 or the like.

  In the "liquid temperature optimum mode" of the present embodiment described above, control is first performed to increase or decrease the opening degree of the subcooling expansion device 6, and to further increase or decrease the opening degree when the liquid refrigerant temperature decreases. Control to decrease or increase the degree of opening of the supercooling expansion device in the opposite direction when the temperature of the liquid refrigerant rises, and when the temperature of the liquid refrigerant decreases, the degree of opening is further increased. The control to decrease or increase is repeated, and when the drop of the liquid refrigerant temperature is stopped or increased, it is determined that the liquid refrigerant temperature is minimum, and the state of the opening is maintained and the process is terminated. The temperature of the liquid refrigerant on the downstream side can be controlled to be minimum. Therefore, the effect of further improving the refrigeration capacity of the refrigeration system is obtained.

  In the liquid temperature optimum mode, the opening degree of the supercooling expansion device 6 is increased or decreased in the direction in which the liquid refrigerant temperature decreases, and the opening degree is further increased or decreased when the liquid refrigerant temperature decreases. The supercooling expansion device 6 may be controlled so as to maintain the state of the opening degree when the decrease of the liquid refrigerant temperature is stopped or increased by repeating the operation to be performed. That is, if the opening degree of the supercooling expansion device 6 is increased or decreased in the direction in which the liquid refrigerant temperature decreases and then the liquid refrigerant temperature stops decreasing or turns to rising, the liquid refrigerant temperature at the opening degree at that time Is determined to be minimized.

  In the present embodiment described above, the refrigeration system is provided with the condensation suppression mode and the liquid temperature optimum mode, and these modes are controlled by the control device 30. Further, the condensation suppression mode and the liquid temperature optimum mode can be arbitrarily selected and operated. Therefore, the condensation suppression mode can be selected to suppress condensation, and the liquid temperature optimum mode can be selected and operated to minimize the liquid refrigerant temperature and operate the refrigeration apparatus with a high refrigeration capacity.

  In the above-described embodiment, the refrigeration apparatus is described as having both the condensation suppression mode and the liquid temperature optimum mode. However, any one of the condensation suppression mode and the liquid temperature optimum mode is described. Only the mode may be provided.

  The present invention is not limited to the embodiments described above, but includes various modifications. Further, the above-described embodiments are described in detail to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described.

1: Compressor, 2: Condenser, 3: Subcooler,
4: Expansion valve, 5: Evaporator,
6: Supercooling expander, 7: Flow regulator,
10: Liquid refrigerant temperature sensor, 20: Outside air temperature sensor,
30: Control device,
31: Main refrigerant piping,
32: Liquid refrigerant cooling circuit, 32a: Branch piping,
33: Liquid injection circuit, 33a: Branch piping,
34: Joint piping,
100: heat source device, 200: load device (low pressure device),
300: Liquid side refrigerant piping, 400: Gas side refrigerant piping,
500: refrigeration cycle device.

Claims (5)

A compressor, a condenser for condensing the refrigerant discharged from the compressor, a supercooler for further supercooling the refrigerant condensed by the condenser, and a main refrigerant pipe for connecting these devices;
The refrigerant from the main refrigerant pipe flowing through the subcooler is supercooled by the depressurized refrigerant obtained by extracting and decompressing a part of the high pressure liquid refrigerant flowing through the main refrigerant pipe, and the decompressed refrigerant after the supercooling is compressed A liquid refrigerant cooling circuit injected into an intermediate pressure portion of the compressor, and a supercooling expansion device for controlling and reducing the flow rate of the refrigerant flowing through the liquid refrigerant cooling circuit;
A controller for controlling the subcooling expansion device;
An outside air temperature sensor for detecting the outside air temperature, and a liquid refrigerant temperature sensor for detecting the liquid refrigerant temperature downstream of the subcooler;
Wherein the control device, wherein the target temperature subcooler downstream of the liquid refrigerant, calculated as the value that gave any difference determined in advance on the outside air temperature sensor at the detected outside air temperature,
The arbitrary difference in the target temperature is determined to be a size that can suppress the liquid refrigerant temperature on the downstream side of the subcooler from becoming equal to or lower than the outside air temperature,
A condensation suppression mode for controlling the expansion device for supercooling based on the calculated target temperature is provided, and the control device fully closes the expansion device for supercooling immediately after the control of the condensation suppression mode is started. After that, the supercooling expansion device is controlled such that the temperature of the liquid refrigerant detected by the liquid refrigerant temperature sensor approaches the target temperature;
A liquid injection circuit for injecting into the intermediate pressure portion of the compressor a decompressed refrigerant obtained by extracting and decompressing a part of the high-pressure liquid refrigerant flowing through the main refrigerant pipe; and a flow control device for controlling the flow rate flowing through the liquid injection circuit. The refrigeration apparatus further comprising: A compressor, a condenser for condensing the refrigerant discharged from the compressor, a supercooler for further supercooling the refrigerant condensed by the condenser, and a main refrigerant pipe for connecting these devices;
The refrigerant from the main refrigerant pipe flowing through the subcooler is supercooled by the depressurized refrigerant obtained by extracting and decompressing a part of the high pressure liquid refrigerant flowing through the main refrigerant pipe, and the decompressed refrigerant after the supercooling is compressed A liquid refrigerant cooling circuit injected into an intermediate pressure portion of the compressor, and a supercooling expansion device for controlling and reducing the flow rate of the refrigerant flowing through the liquid refrigerant cooling circuit;
A controller for controlling the subcooling expansion device;
An outside air temperature sensor for detecting the outside air temperature, and a liquid refrigerant temperature sensor for detecting the liquid refrigerant temperature downstream of the subcooler;
The control device calculates a target temperature of the liquid refrigerant downstream of the subcooler as a value obtained by giving an arbitrary predetermined difference to the outside air temperature detected by the outside air temperature sensor,
The arbitrary difference is determined such that the target temperature is lower than the ambient temperature and higher than the dew point temperature .
A condensation suppression mode for controlling the expansion device for supercooling based on the calculated target temperature, and
The control device fully closes the supercooling expansion device immediately after the start of control of the condensation suppression mode, and thereafter the temperature of the liquid refrigerant detected by the liquid refrigerant temperature sensor approaches the target temperature. Control the supercooling expansion device,
A liquid injection circuit for injecting into the intermediate pressure portion of the compressor a decompressed refrigerant obtained by extracting and decompressing a part of the high-pressure liquid refrigerant flowing through the main refrigerant pipe; and a flow control device for controlling the flow rate flowing through the liquid injection circuit. The refrigeration apparatus further comprising: The refrigeration apparatus according to claim 1 or 2 , wherein the control device further includes a liquid temperature optimum mode in which the liquid refrigerant temperature downstream of the subcooler is lowered to operate with a high refrigeration capacity, and the liquid temperature optimum mode In the first place, the operation for increasing or decreasing the opening degree of the supercooling expansion device is repeated, and the operation for controlling the opening degree is further repeated when the liquid refrigerant temperature is lowered, Next, when the liquid refrigerant temperature rises, the opening degree of the supercooling expansion device is decreased or increased in the opposite direction, and when the liquid refrigerant temperature is lowered, the opening degree is further decreased or increased. The operation of controlling the direction is repeated, and when the decrease of the liquid refrigerant temperature stops or increases, the expansion device for supercooling is controlled to maintain the state of the opening degree. The refrigeration apparatus according to claim 1 or 2 , wherein the flow rate adjusting device provided in the liquid injection circuit is based on the temperature of the compressor or the temperature of the discharged gas discharged from the compressor or the degree of superheat of the discharged gas. A refrigeration system characterized in that it is controlled. The refrigeration apparatus according to claim 1 or 2 , further comprising: a pressure reducing means for reducing the pressure of the refrigerant condensed in the condenser downstream of the subcooler; and an evaporator for evaporating the refrigerant in the pressure reducing means. A refrigeration system characterized in that it is connected.

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