WO2019021346A1 - Refrigeration device - Google Patents

Abstract

The refrigeration system includes a refrigerant circuit to which a compressor, a condenser, an expansion valve, and an evaporator are connected, a discharge pressure sensor for measuring the discharge pressure of the refrigerant of the compressor, and a suction pressure for measuring the suction pressure of the refrigerant of the compressor The control unit has a sensor, an ambient temperature sensor that measures the ambient temperature, and a control unit, and the control unit controls the compressor and the expansion valve so that the discharge pressure is higher than the saturation pressure of the ambient temperature by a set high pressure, A preparatory operation is performed in which the suction pressure is lower than the saturation pressure by the set low pressure, and the differential pressure change time from when the preparatory operation is stopped to when the discharge pressure or suction pressure changes to a specified value is measured. If the time is equal to or less than the reference time, it is determined that there is a refrigerant leak.

Description

Refrigeration system

The present invention relates to a refrigeration apparatus that determines the presence or absence of a refrigerant leak from a refrigerant circuit.

Conventionally, a refrigeration cycle apparatus capable of detecting a refrigerant leak is known (see, for example, Patent Document 1). The refrigeration cycle apparatus of Patent Document 1 calculates the amount of refrigerant of each component from the amount of operating state of each component constituting a refrigerant circuit, and calculates the sum of the calculated amounts of refrigerant. Then, the refrigeration cycle apparatus determines the excess or deficiency of the refrigerant amount by comparing the calculated refrigerant amount, which is the sum of the refrigerant amounts, with the appropriate refrigerant amount acquired in advance.

JP, 2010-236714, A

In the refrigeration cycle apparatus of Patent Document 1, when there is a refrigerant leak, fluctuations in the ambient temperature, such as the outside air temperature, affect the refrigerant pressure in the refrigerant circuit, and the refrigerant pressure affects the calculated amount of refrigerant. There is a possibility that it can not be judged well.

The present invention has been made to solve the problems as described above, and provides a refrigeration apparatus capable of accurately determining refrigerant leakage.

The refrigeration apparatus according to the present invention comprises a refrigerant circuit having a compressor, a condenser, an expansion valve, and an evaporator connected thereto, a discharge pressure sensor for measuring a discharge pressure of the refrigerant of the compressor, and suction of the refrigerant of the compressor. The control unit includes: a suction pressure sensor that measures pressure; an ambient temperature sensor that measures an ambient temperature; and a control unit that determines a refrigerant leak using the discharge pressure, the suction pressure, and the ambient temperature. Setting a preparatory operation for controlling the compressor and the expansion valve so that the discharge pressure is higher than the saturation pressure of the ambient temperature by the set high pressure and the suction pressure is lower than the saturation pressure by the set low pressure Operation control means, measuring means for measuring a differential pressure change time until the discharge pressure or the suction pressure changes to a specified value after the preparation operation is stopped, and the differential pressure change time is less than or equal to a reference time is there If those having a determination unit that there is refrigerant leakage, the.

According to the present invention, in the preparatory operation, the discharge pressure and the suction pressure are set based on the saturation pressure of the ambient temperature that is also affected by the pressure of the refrigerant, and the refrigerant leakage determination is performed based on the time-dependent change of the discharge pressure or the suction pressure. It will be. Therefore, the influence of the ambient temperature in the refrigerant circuit on the change in pressure on the refrigerant is suppressed, and the determination accuracy of the refrigerant leak is improved.

BRIEF DESCRIPTION OF THE DRAWINGS It is a refrigerant circuit figure which shows one structural example of the freezing apparatus of Embodiment 1 of this invention. It is a functional block diagram which shows one structural example of the control part shown in FIG. It is a graph which shows a time-dependent change of the refrigerant | coolant pressure in the refrigerant circuit shown in FIG. It is a flowchart which shows the procedure of the refrigerant | coolant leak determination method which the freezing apparatus shown in FIG. 1 performs. It is a figure for demonstrating another determination about the refrigerant | coolant leak determination in Embodiment 1 of this invention. It is a figure which shows an example of the table which the memory | storage part in the freezing apparatus of Embodiment 2 of this invention memorize | stores. It is a flowchart which shows the procedure of the refrigerant | coolant leak determination method which the freezing apparatus of Embodiment 2 of this invention performs. It is a flowchart which shows an example of a procedure of the method of the control part shown in FIG. 1 updating the data of the table shown in FIG. 6 according to a learning function. It is a figure which shows an example at the time of updating the data of the table shown in FIG. It is a refrigerant circuit figure which shows one structural example of the freezing apparatus of Embodiment 3 of this invention. It is a functional block diagram which shows one structural example of the control part shown in FIG. It is a refrigerant circuit figure which shows one structural example of the freezing apparatus of Embodiment 4 of this invention.

Embodiment 1
The configuration of the refrigeration system of the first embodiment will be described. FIG. 1 is a refrigerant circuit diagram showing a configuration example of a refrigeration apparatus according to a first embodiment of the present invention. The refrigeration system 100 has a refrigerant circuit 10 in which a compressor 1, a condenser 2, an expansion valve 3 and an evaporator 4 are annularly connected. The refrigeration system 100 is provided with a fan 18 that supplies air in a space to be air-conditioned to the evaporator 4. The refrigeration system 100 includes a control unit 15 that controls a refrigeration cycle that circulates a refrigerant to the refrigerant circuit 10. The refrigeration apparatus 100 is provided with an output unit 19 that notifies the user of a refrigerant leak. Although not shown, a fan may be provided to supply outside air to the condenser 2.

The compressor 1 has an inverter circuit not shown in the figure. The compressor 1 is a compressor whose operating frequency can be changed by controlling an inverter circuit. The compressor 1 compresses the refrigerant and sends the compressed refrigerant to the condenser 2. The condenser 2 is an air heat exchanger provided in an outdoor unit or the like. The condenser 2 exchanges the heat of the refrigerant compressed by the compressor 1 with the air to condense the refrigerant.

The expansion valve 3 expands the refrigerant condensed by the condenser 2. The evaporator 4 is installed in an air conditioning target space such as the inside of a cold storage warehouse. The evaporator 4 is an air heat exchanger provided in a unit cooler or the like. The evaporator 4 evaporates the refrigerant expanded by the expansion valve 3 to cool the space to be air-conditioned.

A suction pressure sensor 11 is provided at a refrigerant suction port of the compressor 1. The suction pressure sensor 11 measures the suction pressure Pin of the refrigerant drawn into the compressor 1. A discharge pressure sensor 12 is provided at the discharge port of the refrigerant of the compressor 1. The discharge pressure sensor 12 measures the discharge pressure Pout of the refrigerant discharged from the compressor 1. The refrigerator 100 is provided with an outside air temperature sensor 14 as an ambient temperature sensor for measuring the temperature around the refrigerant. The outside air temperature sensor 14 measures the outside air temperature. The refrigerating apparatus 100 is provided with an indoor temperature sensor 16 that measures the temperature of air in the space to be air conditioned.

The output unit 19 has a speaker and a display unit (not shown). When an alarm signal indicating that the output is abnormal is input from the control unit 15, the output unit 19 outputs an alarm sound from the speaker, and causes the display to display the abnormality. The display unit may turn on a lamp indicating that it is abnormal or may display a message indicating the content of the abnormality. When a normal signal indicating no abnormality is input from control unit 15, output unit 19 does not operate the speaker and the display unit. The output unit 19 may have both or one of the speaker and the display unit.

FIG. 2 is a functional block diagram showing one configuration example of the control unit shown in FIG. The control unit 15 includes a storage unit 150 which stores a program, and a CPU (Central Processing Unit) 151 which executes processing in accordance with the program. The control unit 15 is connected to the fan 18, the output unit 19, the compressor 1, and the expansion valve 3 by signal lines. The control unit 15 is connected to the suction pressure sensor 11 and the discharge pressure sensor 12 by signal lines. The control unit 15 is connected to the outside air temperature sensor 14 and the room temperature sensor 16 by signal lines. The connection means may be wireless.

The storage unit 150 is a non-volatile memory such as a flash memory. The storage unit 150 stores the set temperature and the set humidity. The storage unit 150 stores the count number n when it is determined that the probability of the occurrence of the refrigerant leakage is high by the refrigerant leakage determination method described later.

As shown in FIG. 2, the control unit 15 includes an operation control unit 21, a measurement unit 22, a determination unit 23, and an alarm unit 24. The operation control unit 21, the measurement unit 22, the determination unit 23, and the alarm unit 24 are configured in the refrigeration apparatus 100 by the CPU 151 executing the program.

The operation control means 21 controls the refrigeration cycle using measured values acquired from the suction pressure sensor 11, the discharge pressure sensor 12, and the indoor temperature sensor 16, and the set temperature. The operation control means 21 controls the compressor 1, the fan 18 and the expansion valve 3 so that the measured value of the indoor temperature sensor 16 becomes the set temperature. The operation control means 21 stops the operation of the compressor 1 when the measured value of the indoor temperature sensor 16 is in the state of thermo-off that matches the set temperature.

Further, the operation control means 21 instructs the measuring means 22 to monitor the pressure when the refrigerant leak judgment instruction is inputted. Further, the operation control means 21 calculates the saturation pressure using the measurement value obtained from the outside air temperature sensor 14. The operation control means 21 refers to the measured values of the suction pressure sensor 11 and the discharge pressure sensor 12 and controls the compressor 1 and the expansion valve 3 so that the discharge pressure is higher than the saturation pressure of the outside air temperature by the set pressure, A preparatory operation is started in which the suction pressure is lower than the saturation pressure of the outside air temperature by the set pressure. The operation control means 21 maintains this state for a set period if the discharge pressure is higher than the saturation pressure of the outside air temperature by the set pressure and the suction pressure is lower than the saturation pressure of the outside air temperature by the set pressure. When the preparatory operation is performed for a set period, the operation control unit 21 stops the preparatory operation and instructs the measuring unit 22 to start measurement.

The measuring means 22 comprises a timer not shown in the figure. The measuring means 22 monitors the measured values of the suction pressure sensor 11 and the discharge pressure sensor 12 when instructed by the operation control means 21 to monitor the pressure. When the operation control means 21 gives an instruction to start measurement, the measurement means 22 measures time from the instruction to start measurement. Then, when the time taken for the pressure difference between the discharge pressure Pout and the suction pressure Pin to reach the specified value Pdref is measured, the measurement means 22 notifies the measured time to the judgment means 23.

The prescribed value Pdref is stored in the storage unit 150. The specified value Pdref is a value related to the differential pressure between the high pressure and the low pressure in the refrigerant circuit 10. The reference time tref is a time serving as a reference for determining whether or not there is a refrigerant leak from the time change of the refrigerant pressure in the refrigerant circuit 10. The reference time tref is represented by tref = t0 × coefficient, where the time measured with no refrigerant leakage is an initial value t0. The coefficient is, for example, 0.7. The reference time tref is stored in the storage unit 150.

When information on the time measured by the measuring means 22 is received from the measuring means 22, the judging means 23 compares the measured time with the reference time stored in the storage unit 150 to determine whether there is a refrigerant leak or not. . The judging means 23 notifies the alarming means 24 of the judgment result. The determination unit 23 may record the number of refrigerant leak determinations as the count number n, and determine the presence or absence of the refrigerant leak in the plurality of refrigerant leak determinations.

The alarm unit 24 outputs a signal to the output unit 19 in accordance with the determination result notified from the determination unit 23. When the determination result of the determination means 23 indicates that there is a refrigerant leak, the alarm means 24 outputs an alarm signal to the output unit 19. If the determination result is that there is no refrigerant leakage, the alarm means 24 outputs a normal signal indicating that there is no abnormality to the output unit 19.

Next, the principle of the refrigerant leak determination will be described with reference to FIG. FIG. 3 is a graph showing the temporal change of the refrigerant pressure in the refrigerant circuit shown in FIG. The vertical axis of the graph shown in FIG. 3 represents pressure, and the horizontal axis represents time. In FIG. 3, the saturation pressure is represented by AT. In FIG. 3, the solid line on the side higher than the saturation pressure AT indicates the change of the discharge pressure Pout. The solid line on the lower side of the saturation pressure AT indicates the change of the suction pressure Pin. FIG. 3 shows the pressure difference between the saturation pressure AT and the discharge pressure Pout as ΔPout, and the pressure difference between the saturation pressure AT and the suction pressure Pin as ΔPin. The set pressures of the pressure difference ΔPout and the pressure difference ΔPin are, for example, 0.5 [Mpa].

The operation control means 21 starts the operation of the compressor 1 and controls the compressor 1 and the expansion valve 3 to perform a preparatory operation. Then, as shown in FIG. 3, at time t1, the pressure difference ΔPout and the pressure difference ΔPin become the set pressure. The set pressure of the pressure difference ΔPout is referred to as a set high pressure based on the saturation pressure AT. The set pressure of the pressure difference ΔPin is referred to as a set low pressure based on the saturation pressure AT. At time t2 when the set period has elapsed from time t1, the operation control means 21 stops the compressor 1. The measuring means 22 starts measuring the differential pressure change time tm. As time passes, both the discharge pressure Pout and the suction pressure Pin gradually approach the saturation pressure AT.

As shown in FIG. 3, the pressure difference between the high pressure and the low pressure changes with the passage of time while the balance between the discharge pressure Pout and the suction pressure Pin is maintained based on the saturation pressure AT. The change speed vp of this pressure difference differs depending on whether there is a refrigerant leak or not. The change speed vp when there is a refrigerant leak is faster than the change speed vp when there is no refrigerant leak. When the differential pressure change time tm is equal to or less than the reference time tref, the determination means 23 determines that the refrigerant leaks.

Next, the refrigerant leak detection operation of the refrigerating apparatus 100 according to the first embodiment will be described. FIG. 4 is a flow chart showing the procedure of the refrigerant leak determination method executed by the refrigeration system shown in FIG. FIG. 3 is a view for explaining a refrigerant leak determination method performed according to the procedure shown in FIG.

Operation control means 21 operates compressor 1 when a refrigerant leak determination instruction is input (step S101). Then, the operation control means 21 operates the compressor 1 for a certain period of time, and determines whether the thermo-off is not performed (step S102). For example, when it is after the defrosting operation, the temperature difference between the temperature of the space to be air-conditioned and the set temperature becomes large, so the thermo-off state does not occur for the predetermined period. Therefore, when the compressor 1 continues the operation for a predetermined time, the control unit 15 determines that the refrigerant leakage can be determined, and starts the refrigerant leakage determination (step S103). In the non-thermo-off state, a change in pressure in the refrigerant circuit 10 is accurately measured. If it is determined in step S102 that the thermo-off state is established, the control unit 15 determines that the refrigerant leakage can not be correctly determined, and the refrigerant leakage determination is not performed.

The operation control means 21 performs the preparatory operation which controls the operating frequency of the compressor 1 and the opening degree of the expansion valve 3, when it progresses to step S103. In the preparatory operation, the operation control means 21 sets the discharge pressure Pout higher by a set pressure (for example, 0.5 Mpa) than the saturation pressure of the outside air temperature, and the suction pressure Pin by a set pressure than the saturation pressure of the outside air temperature (for example, Make it as low as 0.5Mpa). The operation control means 21 performs the preparatory operation for the setting period in a state where the pressure difference ΔPout becomes the set high pressure and the pressure difference ΔPin becomes the set low pressure (step S104). When the set period (for example, several minutes) elapses, the operation control unit 21 stops the compressor 1 (step S105). By maintaining the preparatory operation for the setting period in a state where a constant pressure difference is generated, the temperature of the air conditioning target space is stabilized, and the state of the refrigerant circuit 10 is also stabilized.

Subsequently, the measuring means 22 starts measuring the differential pressure change time tm until the pressure difference ΔP between the discharge pressure Pout and the suction pressure Pin reaches the specified value Pdref after the preparatory operation is stopped (step S106). ). When the pressure difference ΔP becomes equal to or less than the specified value Pdref (step S107), the measurement means 22 notifies the determination means 23 of the differential pressure change time tm. The determination means 23 determines whether the differential pressure change time tm is less than or equal to the reference time tref (step S108). When the differential pressure change time tm is equal to or less than the reference time tref, the determination unit 23 determines that the refrigerant leaks, and updates the count number n stored in the storage unit 150 (step S109). The determination means 23 determines whether the count number n is 3 or more (step S110). If the count number n is less than 3, the control unit 15 returns to step S101.

As a result of the determination in step S110, when the count number n is 3 or more, the determination unit 23 determines that there is a refrigerant leak (step S112). The determination means 23 outputs an alarm signal to the output unit 19. The output unit 19 outputs an alarm sound and displays that it is abnormal. Note that, in order to suppress the refrigerant leakage to the space to be air-conditioned, the control unit 15 may perform a pump-down operation of closing the expansion valve 3 and liquefying the refrigerant in the refrigerant circuit 10 by the condenser 2 . In this case, in the refrigerant circuit 10, a receiver may be provided between the condenser 2 and the expansion valve 3 for recovering the liquefied refrigerant. On the other hand, as a result of the determination in step S108, if the differential pressure change time tm becomes larger than the reference time tref even once in three times, the determination means 23 sets the count number n to zero (step S111), Finish. Thereby, the determination error is suppressed.

Although the flowchart shown in FIG. 4 shows the case where it is determined that the refrigerant leaks when the count number n is three or more, the count number determined as the refrigerant leak is not limited to three. The user may set the determination unit 23 to determine that the refrigerant leaks when n = 1. The determination accuracy of the refrigerant leak is improved when the number of counts n is more than one.

Here, the refrigeration apparatus 100 has a function of setting an initial value t0 of the reference time tref. After the worker installs the refrigeration system 100, the refrigeration system 100 performs a test operation. At the time of trial operation, the control unit 15 executes steps S101 to S106 shown in FIG. 4 and stores the measured differential pressure change time tm in the storage unit 150 as the initial value t0 of the reference time tref. At this time, the control unit 15 may measure the differential pressure change time tm a plurality of times, calculate an average value of the plurality of differential pressure change times tm, and set the calculated average value as the initial value t0. The determination accuracy is improved by measuring a plurality of times and calculating the average value as the reference time.

As described with reference to FIGS. 3 and 4, the operation control means 21 sets the pressure difference ΔPout and the pressure difference ΔPin as the set pressure with reference to the saturation pressure. Then, the measuring means 22 measures the differential pressure change time tm which is required until the pressure difference ΔP between the discharge pressure Pout and the suction pressure Pin falls to a specified value after stopping the refrigeration cycle. Subsequently, the determination unit 23 determines the presence or absence of the refrigerant leak by comparing the differential pressure change time tm with the reference time tref.

In the refrigeration apparatus 100 of the first embodiment, in the preparatory operation, the discharge pressure Pout and the suction pressure Pin are set based on the saturation pressure of the ambient temperature that is also affected by the pressure of the refrigerant, and the time elapsed of the discharge pressure Pout or the suction pressure Pin The refrigerant leak determination is performed based on the change. As a result, the fluctuation of the pressure difference due to the fluctuation of the operating state is suppressed, and the influence of the ambient temperature in the refrigerant circuit on the change of the pressure on the refrigerant is suppressed. Therefore, the determination accuracy of the refrigerant leak is improved.

Here, the method of using the degree of subcooling (SC) as the parameter of the refrigerant leak determination and the refrigerant leak determination method according to the first embodiment will be compared. Due to the influence of heat input from the outside air to the condenser, such as when the season is summer, the refrigeration system may not be able to accurately measure the degree of subcooling. In this case, the refrigeration system can not stably acquire the data used for the refrigerant leak determination, and the accuracy of the refrigerant leak determination using parameters such as the degree of subcooling may be deteriorated.

On the other hand, the refrigeration apparatus 100 according to the first embodiment uses the differential pressure change time tm reflecting the change speed vp of the pressure difference in the refrigerant circuit 10 based on the saturation pressure as a parameter for determining the refrigerant leak. The refrigerant leak judgment is performed using it. Not only the refrigerant pressure of the refrigerant circuit 10 but also the reference saturation pressure are affected by the ambient temperature, so the influence on these pressures is the same. Therefore, the determination accuracy of the refrigerant leak can be improved. Further, in the first embodiment, the number of parameters is small, and control becomes easy. Further, since the presence or absence of refrigerant leakage is determined using the discharge pressure Pout and the suction pressure Pin, it is not necessary to newly add a sensor, and it is possible to suppress an increase in the cost of the apparatus body.

Further, in the procedure shown in FIG. 4, the refrigeration apparatus 100 performs the refrigerant leakage determination described above without performing the thermo-off, so that the change in pressure difference can be stably measured. Therefore, the determination accuracy of the refrigerant leak is improved.

Further, although the differential pressure change time tm is measured using the discharge pressure Pout and the suction pressure Pin in FIGS. 3 and 4, the refrigerant leak can also be determined using the discharge pressure Pout or the suction pressure Pin. FIG. 5 is a diagram for explaining another determination of the refrigerant leak determination in the first embodiment of the present invention.

The measuring means 22 measures the differential pressure change time tm using one of the pressure difference ΔPout and the pressure difference ΔPin. In this case, the storage unit 150 stores the high pressure specified value HPref as the specified value of the pressure difference ΔPout on the high pressure side, and stores the low pressure specified value LPref as the specified value of the pressure difference ΔPin on the low pressure side. The high pressure specified value HPref and the low pressure specified value LPref are measured in the state where there is no refrigerant leakage. The high-pressure specified value HPref and the low-pressure specified value LPref are shown in FIG.

It is assumed that there is a refrigerant leak in the refrigerant pipe on the high pressure side of the refrigerant circuit 10. In this case, after time t2 shown in FIG. 5, the change in the pressure difference ΔPout becomes remarkable as compared with the change in the pressure difference ΔPin. From time t2, as time passes, the discharge pressure Pout approaches the saturation pressure AT earlier than the suction pressure Pin. Therefore, when the pressure difference ΔPout is used, when there is a refrigerant leak in the refrigerant pipe on the high pressure side of the refrigerant circuit 10, the determination unit 23 can more reliably determine the refrigerant leak.

Subsequently, it is assumed that there is a gap in the refrigerant pipe on the low pressure side of the refrigerant circuit 10 that causes the refrigerant to leak. In this case, since the saturation pressure AT is higher than the suction pressure Pin after time t2 shown in FIG. 5, air flows into the refrigerant pipe. From time t2, as time passes, the suction pressure Pin approaches the saturation pressure AT earlier than the discharge pressure Pout. Therefore, when the pressure difference ΔPin is used, when there is a gap in the low pressure side refrigerant pipe of the refrigerant circuit 10, the determination means 23 can more reliably determine that the refrigerant leaks.

The refrigerant leak appears in the pressure difference ΔP between the discharge pressure Pout and the suction pressure Pin, even if the refrigerant leaks in any of the refrigerant pipe on the high pressure side or the refrigerant pipe on the low pressure side of the refrigerant circuit 10. Therefore, in the refrigerant circuit 10, even if refrigerant leakage occurs in either the high pressure side piping or the low pressure side piping, the refrigerant leakage can be determined by the determination using the pressure difference ΔP between the discharge pressure Pout and the suction pressure Pin. . Further, the determination using both the pressure difference ΔPout and the pressure difference ΔPin may be combined with the determination using one of these pressure differences. The determination accuracy of the refrigerant leak is further improved.

The refrigerant leak determination according to the first embodiment can be performed not only during operation of the refrigeration apparatus 100 but also while the refrigeration apparatus 100 is stopped. When the refrigeration system 100 is in operation, the control unit 15 may determine the refrigerant leakage according to the procedure shown in FIG. When the refrigeration apparatus 100 stops operation for a long time, the control unit 15 may periodically perform the refrigerant leak determination in accordance with the procedure illustrated in FIG. 4. At that time, the control unit 15 starts the operation of the compressor 1 and, after the state of the refrigeration cycle is stabilized, performs the determination of the refrigerant leakage according to the procedure shown in FIG.

In the first embodiment, the control unit 15 may make the refrigerant leak determination by using the scheduling function. In this case, the control unit 15 has a schedule function of performing the refrigerant determination according to the procedure shown in FIG. 4 while the refrigeration system 100 is stopped. During a time period when the user is not using the refrigeration system 100, the control unit 15 operates the schedule function, and performs the refrigerant leak determination according to the procedure shown in FIG. Thereby, even when the user does not use the refrigeration apparatus 100, the refrigeration apparatus 100 can automatically perform the refrigerant leak determination. In addition, even if it is determined that the refrigerant leaks, the control unit 15 may store the result of the refrigerant leak determination in the storage unit 150 without outputting an alarm. In this case, when using the refrigeration apparatus 100, the user operates the control unit 15 to cause the output unit 19 to display the refrigerant leakage determination result stored in the storage unit 150 to know the result of the refrigerant leakage determination. it can. Furthermore, the user may operate the control unit 15 to designate the control unit 15 with a time zone in which the refrigerant leak determination is to be performed. Since the control unit 15 performs the refrigerant leak determination in the time zone designated by the user, it is possible to prevent the decrease in the refrigeration capacity in the time zone in which the user desires to use the refrigeration system 100.

Some refrigeration systems are provided with a solenoid valve between the condenser and the expansion valve, and perform a pump-down operation to close the solenoid valve when the compressor is stopped to prevent the liquid refrigerant from flowing out to the expansion valve side . The refrigerant determination method of the first embodiment can be applied to a refrigeration system that does not perform the pump down operation. The refrigeration system that does not perform the pump-down operation does not stop the refrigeration cycle due to the pump-down operation, and therefore can obtain the differential pressure change time tm by sampling data for several minutes after the compressor is stopped. In the refrigeration apparatus 100 according to the first embodiment, the compressor 1 can change the operating frequency by the inverter circuit, so that the high pressure and the low pressure in the refrigerant circuit 10 can be adjusted during the operation of the compressor 1. As a result, the refrigeration apparatus 100 can set the pressure difference suitable for the refrigerant leak determination in the refrigerant circuit 10.

In the first embodiment, the case where the outside air temperature has an influence on the pressure of the refrigerant is described using the saturation pressure of the outside air temperature as the pressure reference, but the ambient temperature is limited to the outside air temperature. Absent. When the temperature of the air in the room is larger than the outside air temperature, the saturation pressure of the room temperature may be used when the influence of the temperature on the refrigerant circuit 10 is larger than the outside air temperature. For example, when half or more circuits of the entire refrigerant circuit 10 are installed indoors, the room temperature is more suitable as the ambient temperature than the outside air temperature. In this case, the indoor temperature sensor 16 functions as an ambient temperature sensor. However, after the compressor 1 is stopped, the change in the room temperature may be larger than the change in the outside air temperature during measurement of the differential pressure change time tm. The saturation pressure at any one of the ambient temperatures may be selected for each of the refrigeration units 100 from the relationship between the influence of the outside air temperature and the room temperature on the refrigerant and the saturation pressure with less fluctuation.

Second Embodiment
FIG. 6 is a diagram showing an example of a table stored by the storage unit in the refrigeration apparatus of the second embodiment of the present invention. In the second embodiment, the refrigeration system 100 determines a refrigerant leak using a reference value that is different for each temperature range of the outside air temperature. The configuration of the refrigeration system of the second embodiment will be described. In the second embodiment, the detailed description of the same configuration as that of the first embodiment is omitted, and the points different from the first embodiment will be described in detail.

In the refrigeration apparatus 100 according to the second embodiment, the storage unit 150 stores a table in the configuration shown in FIG. As shown in FIG. 6, in the table stored in the storage unit 150, state data and a reference time are associated and recorded. In the table shown in FIG. 6, the outside air temperature is classified into a plurality of temperature zones. And in the table shown in FIG. 6, the state data and the reference time are associated and stored for each of a plurality of temperature zones. In the example shown in FIG. 6, the temperature width of one temperature zone is 5 ° C.

The state data shown in FIG. 6 are, for example, the discharge pressure Pout, the suction pressure Pin, the degree of superheat (SH), and the degree of subcooling (SC). As the reference time, reference times A1 to A6 are described for each temperature zone. As shown in FIG. 6, in each of the reference times A1 to A6, an average value calculated from a plurality of measurement values is multiplied by a coefficient. Further, in the table shown in FIG. 6, the standard deviation of the reference time is stored together with the reference time. In the table shown in FIG. 6, a standard deviation B common to a plurality of temperature zones is stored as the standard deviation.

In the second embodiment, the determination unit 23 refers to the table stored in the storage unit 150 when performing the refrigerant leak determination. Then, the determination means 23 reads out the reference time tref recorded in the temperature zone to which the measured value of the outside air temperature sensor 14 belongs, and performs the refrigerant leak determination using the read out reference time tref. The determination means 23 may determine the refrigerant shortage using the state data.

Next, the operation of the refrigerating apparatus 100 according to the second embodiment will be described. FIG. 7 is a flowchart showing the procedure of the refrigerant leak determination method executed by the refrigeration system of the second embodiment of the present invention. Here, the detailed description about the processing similar to the processing described in FIG. 4 is omitted.

As compared with FIG. 4, the flowchart shown in FIG. 7 adds the process of step S201 between step S107 and step S108. In step S107, the measuring means 22 passes the measured differential pressure change time tm to the judging means 23. When the determination means 23 receives the differential pressure change time tm from the determination means 23, the determination means 23 refers to the measurement value of the outside air temperature sensor 14 and the table shown in FIG. Then, the determination means 23 reads out the reference time tref recorded in the temperature zone to which the measurement value of the outside air temperature sensor 14 belongs (step S201). Thereafter, in step S108, the determination unit 23 compares the read reference time tref with the differential pressure change time tm, and determines whether the differential pressure change time tm is less than or equal to the reference time tref. The subsequent processing is the same as the processing described in FIG.

As shown in FIG. 6, the storage unit 150 stores a reference time tref for each of a plurality of temperature zones with respect to the outside air temperature. The determination unit 23 can reduce the influence of the outside air temperature by performing the refrigerant leak determination using the reference time tref corresponding to the outside air temperature. As a result, the accuracy of the refrigerant leak determination further improves.

With reference to FIG. 6, storage unit 150 has been described as holding the state data and reference time tref for each of a plurality of temperature zones with respect to the outside air temperature. These data may be held. The humidity range of the humidity zone is, for example, 10%. The storage unit 150 stores the reference time tref for each of a plurality of humidity zones with respect to the humidity, so that the influence of the humidity of the outside air of the refrigerant leak determination can be reduced. As a result, the accuracy of the refrigerant leak determination further improves.

Further, when the storage unit 150 stores the table shown in FIG. 6, the determination means 23 substitutes the measured differential pressure change time tm in the following equation (1) in step S107 shown in FIG. Then, the refrigerant leakage may be determined. Specifically, the determination unit 23 substitutes the differential pressure change time tm, the reference time tref and the standard deviation into the equation (1), and determines whether the determination value Dt is close to 0 or not. Determine the presence or absence.

Dt = (differential pressure change time tm-reference time tref) / standard deviation ... (1)
When the outside air temperature belongs to the temperature range of 15 to 20 ° C. shown in FIG. 10, the judgment value Dt is calculated by Dt = (differential pressure change time tm−AA4) / B4.

As an example of the factor that the determination accuracy of the refrigerant leak decreases, disturbance such as manufacturing variation of equipment provided in the refrigeration apparatus 100 can be considered in addition to the outside air temperature. Therefore, in the second embodiment, the determination unit 23 of the control unit 15 accumulates state data and data of the differential pressure change time tm after the refrigerating apparatus 100 is installed, and a reference time suitable for the installed apparatus. The tref is reset in the storage unit 150. As a result, since the characteristic unique to the product is reflected in the reference time tref stored in the storage unit 150, the determination accuracy of the refrigerant leak is improved. Further, even if the piping of the refrigeration system 100 is repaired and the equipment provided in the refrigeration system 100 is changed, the determination unit 23 resets the reference time tref suitable for the equipment installed in the storage unit 150. . After the reference time tref stored in the storage unit 150 is erased once, the corrected reference time tref is set in the storage unit 150, whereby the reference time tref is made appropriate. In this way, the reference time tref can be reset in consideration of the influence of the replacement of the device.

Next, an example of a method of updating the reference time tref will be described. A case where the control unit 15 has a learning function will be described. After the refrigeration system 100 is installed or after the refrigeration system 100 is repaired, the measuring means 22 measures the differential pressure change time tm five times or more. Then, the determination means 23 compares the average value of the measured five or more differential pressure change times tm with the reference time tref stored in the storage unit 150, corrects the reference time tref, and obtains the reference time tref. Update. By updating the reference time tref set when the refrigeration system 100 is shipped after the installation of the refrigeration system 100, it is possible to prevent the reference time tref from becoming an abnormal value.

In this manner, the determination unit 23 stores new data related to the reference time tref in the storage unit 150, compares the stored data with the existing reference time tref, and is most suitable for the refrigeration apparatus 100. The reference time tref is updated to. The determination accuracy of the refrigerant leak can be improved by updating the reference time tref.

Next, an example of a procedure in which the control unit 15 updates data of the table stored in the storage unit 150 in the second embodiment will be described. FIG. 8 is a flow chart showing an example of the procedure of a method in which the control unit shown in FIG. 1 updates the data of the table shown in FIG. 6 in accordance with the learning function.

Here, the detailed description about the processing similar to the processing described in FIG. 4 is omitted. Further, the case where the dip switch for inputting the instruction to reset the reference time tref is provided in the control unit 15 will be described. The instruction to reset the reference time tref is not limited to the dip switch.

After the refrigeration system 100 is installed, when the power is turned on for a test run, the determination unit 23 determines whether an instruction to reset the reference time tref has been input (step S301). When an instruction to reset the reference time tref is input, the determination unit 23 instructs the operation control unit 21 to start the preparatory operation. The operation control means 21 starts the operation of the compressor 1 (step S302). Steps S303 to S305 are similar to steps S102 to S104 described with reference to FIG. 4, and thus detailed description thereof is omitted.

In step S306, the determination unit 23 samples the discharge pressure Pout, the suction pressure Pin, the degree of superheat, and the degree of supercooling within the time K before stopping the compressor 1 and stores the sampled values in the storage unit 150. The time K is, for example, one minute. Subsequently, the determination unit 23 instructs the measurement unit 22 to perform measurement. The measuring means 22 measures the differential pressure change time tm in the same manner as steps S106 to S107 shown in FIG. 4 (steps S307 to S308). Then, the measuring unit 22 records the measured differential pressure change time tm in the storage unit 150 (step S309). The determination means 23 adds 1 to the measurement count number n of the differential pressure change time tm (step S310). Then, the determination unit 23 determines whether the measurement count number n is 5 or more (step S311). If the measurement count number n is less than 5, the determination unit 23 returns to step S301. As a result of the determination in step S311, when the measurement count number n is 5 or more, the determination unit 23 completes data acquisition of the differential pressure change time tm. Then, the determination means 23 calculates an average value of the measured five or more differential pressure change times tm. Furthermore, the determination unit 23 rewrites the reference time tref stored in the storage unit 150 to a value obtained by multiplying the calculated average value by a coefficient (step S312). Further, the determination means 23 calculates the standard deviation of five or more differential pressure change times tm.

FIG. 9 is a diagram showing an example when the data of the table shown in FIG. 6 is updated. The case where the outside air temperature belongs to the range of 15 to 20 ° C. will be described with reference to FIG. In step S306 shown in FIG. 8, the operation control means 21 refers to the temperature zone 15 to 20 ° C. of the table shown in FIG. Then, the operation control means 21 records P1, P2, Sh1, and Sc1 as the discharge pressure Pout, the suction pressure Pin, the degree of superheat (SH) and the degree of subcooling (SC) in relation to the temperature zone 15 to 20 ° C. . In step S312, the determination unit 23 rewrites the value of the reference time tref from A4 to AA4 shown in FIG. 6 in the temperature range of 15 to 20 ° C. In addition, the determination means 23 rewrites the standard deviation of the reference time tref in the temperature range of 15 to 20 ° C. from B to B4 shown in FIG.

As described above, the control unit 15 records the state data for each temperature range of the outside air temperature, and rewrites the average value and the standard deviation of the reference time tref. FIG. 9 shows a case where the average value and the standard deviation of each temperature zone are rewritten with respect to the reference time tref, as compared with FIG. Comparing FIG. 6 with FIG. 9, the average value of the reference time tref is updated from A1 to AA1 in the temperature range of 0 to 5 ° C. In the temperature range of 5 to 10 ° C., the average value of the reference time tref is updated from A2 to AA2.

Although an example of the method of updating the reference time tref to suppress the influence of the outside air temperature on the reference time tref has been described with reference to FIGS. 6, 8 and 9, the method is not limited to the air conditioning target space. It may be applied to the room temperature. The temperature range of the indoor temperature may be classified into a plurality of temperature zones, and the control unit 15 may correct the reference time of each of the plurality of temperature zones in the same manner as in FIG. 6, FIG. 8 and FIG. In this case, the influence of the room temperature on the reference time tref can be suppressed.

Third Embodiment
The refrigeration system of the third embodiment is provided with a hot gas path for defrosting the evaporator.

The configuration of the refrigeration system of the third embodiment will be described. FIG. 10 is a refrigerant circuit diagram showing one configuration example of the refrigeration apparatus of Embodiment 3 of the present invention. FIG. 11 is a functional block diagram showing one configuration example of the control unit shown in FIG. In the third embodiment, the detailed description of the same configuration as that of the refrigeration apparatus described in the first and second embodiments will be omitted.

As shown in FIG. 10, the refrigerating apparatus 100a has a refrigerant circuit 10 in which a compressor 1, a condenser 2, an expansion valve 3 and an evaporator 4 are annularly connected. In the refrigerant circuit 10, a receiver 8 and an electromagnetic valve 6 are provided between the condenser 2 and the expansion valve 3. An accumulator 7 is provided on the refrigerant inlet side of the compressor 1. The refrigeration system 100 a includes a control unit 15 that controls a refrigeration cycle that circulates a refrigerant to the refrigerant circuit 10.

Further, as shown in FIG. 10, a bypass circuit 17 is connected to the refrigerant circuit 10. One of the two connection ports of the bypass circuit 17 is connected between the compressor 1 and the condenser 2, and the other connection port is connected to the refrigerant inlet of the evaporator 4. The bypass circuit 17 serves as a hot gas path for supplying the high temperature and high pressure refrigerant to the evaporator 4. A solenoid valve 5 is provided in the bypass circuit 17. The solenoid valves 5 and 6 are two-way valves. The solenoid valves 5 and 6 are connected to the control unit 15 by a signal line.

When defrosting the evaporator 4, the operation control means 21 of the control unit 15 shown in FIG. 11 switches the electromagnetic valve 5 from the closed state to the open state, and executes hot gas defrosting. Further, the operation control means 21 switches the solenoid valve 6 from the open state to the closed state when executing the hot gas defrosting.

The refrigerating apparatus 100a of the third embodiment is an apparatus provided with a solenoid valve 6 between the liquid receiver 8 and the expansion valve 3 and capable of performing a pump-down operation. When the refrigeration cycle is stopped, the control unit 15 of the third embodiment shifts the timing of switching the solenoid valve 6 from the open state to the closed state without immediately performing the pump-down operation.

The operation of the refrigeration system 100a of the third embodiment will be described. When performing the refrigerant leak determination described in the first embodiment, the operation control unit 21 does not immediately perform the pump-down operation even if the compressor 1 is stopped. The operation control means 21 maintains the solenoid valve 6 in the open state, and the liquid bag is made resistant to the accumulator 7, and the measuring means 22 and the judging means 23 perform the refrigerant leak judgment shown in FIG. 4 or FIG. I do. If the determination means 23 determines that there is a refrigerant leak as a result of the determination, the solenoid valve 6 is switched from the open state to the closed state, and the pump-down operation is performed.

Thus, the determination means 23 confirms the differential pressure change time tm before instructing the operation control means 21 to close the solenoid valve 6. Then, the determination means 23 compares the change speed vp of the pressure difference between the discharge pressure Pout and the suction pressure Pin with the pressure decrease speed on the high pressure side in the normal pump-down operation. The judging means 23 judges that the refrigerant leaks from the high pressure side of the refrigerant circuit 10 when the change speed Vp of the pressure difference is larger than the pressure decrease speed on the high pressure side in the normal pump-down operation. Explain the reason.

In the pump-down operation, if there is no refrigerant leakage, the pressure decrease speed on the high pressure side is slow, and no abnormality appears in the pressure difference change speed vp. On the other hand, when there is a refrigerant leak, when the rate of change in pressure difference vp is compared with the rate of decrease in pressure on the high pressure side during normal pump down operation, these rates are different.

In mixed refrigerants such as non-azeotropic refrigerants, when the refrigerant leaks, the high pressure refrigerant in the mixed refrigerant leaks, so the leakage from the high pressure side appears more prominently, and the refrigerant leakage may be judged more easily it can. As described above, in the third embodiment, when it is determined that there is a refrigerant leak, the refrigeration apparatus 100a can determine whether the leakage is from the high pressure side of the refrigerant circuit 10.

And R32 refrigerant, and R125, and R134a, and R1234yf, a mixed refrigerant of CO _2, and conditions the ratio of R32 XR32 [wt%] is 33 <XR32 <39, the proportion of R125 XR125 [wt%] is The condition that 27 <XR125 <33, the condition that the ratio XR134a [wt%] of R134a is 11 <XR134a <17, the condition the ratio XR1234yf [wt%] of R1234yf is 11 <XR1234yf <17, CO ₂ and conditions the ratio _XCO 2 [wt%] of a 3 _<XCO 2 <9, non-azeotropic as the refrigerant to satisfy all the conditions sum of XR32 and XR125 and XR134a and XR1234yf and XCO ₂ is 100, the In the refrigerant, when the refrigerant leaks, it leaks from the high-pressure refrigerant in the mixed refrigerant. These leaks are more pronounced and refrigerant leaks can be more easily determined. As described above, in the third embodiment, when it is determined that there is a refrigerant leak, the refrigeration apparatus 100a can determine whether the leakage is from the high pressure side of the refrigerant circuit 10.

Further, also in the third embodiment, after performing the hot gas defrosting, the refrigeration apparatus 100a can stop the refrigeration cycle and measure the rate of change in pressure difference vp, so that the refrigerant leakage can be determined with high accuracy.

Furthermore, the refrigeration apparatus 100a of the third embodiment sets a constant pressure difference in the refrigerant circuit 10 with respect to the saturation pressure of the outside air temperature, as in the first embodiment. Thereafter, the refrigeration system 100a performs hot gas defrosting, measures the rate of change in pressure difference vp after the refrigeration cycle is stopped, and determines the refrigerant leakage. Therefore, also in the third embodiment, the same effect as the first embodiment can be obtained.

Fourth Embodiment
In the fourth embodiment, the refrigerant leakage determination described in the first to third embodiments is combined with the refrigerant shortage determination using state data indicating the operating state of the refrigeration cycle during the preparatory operation. In the fourth embodiment, in the first to third embodiments, the case where the refrigerant leakage determination described in the first embodiment is combined with the refrigerant shortage determination will be described.

As described above, the refrigeration apparatus 100 determines the refrigerant leakage using the rate of change Vp of the pressure difference in a state where a constant pressure difference is generated in the refrigerant circuit based on the saturation pressure of the outside air temperature. . In the determination procedure, the measuring unit 22 records the differential pressure change time tm to be measured in the storage unit 150. The determination means 23 is linked to the outside air temperature, and records state data such as the degree of superheat (SH) and the degree of subcooling in the storage unit 150.

The determination means 23 may monitor not only the change rate Vp of the pressure difference but also the high pressure and low pressure in the refrigerant circuit 10 during the operation of the refrigeration cycle, and use information on changes in these pressures for refrigerant leak determination . Further, the determination means 23 may use state data of the degree of superheat and the degree of subcooling with reference to the table shown in FIG. 6 or 9 as well as the change speed Vp of the pressure difference for refrigerant leakage determination. By combining a plurality of determination methods, it is possible to improve the determination accuracy of the presence or absence of refrigerant leakage.

FIG. 12 is a refrigerant circuit diagram showing one configuration example of the refrigeration apparatus of the fourth embodiment of the present invention. The refrigeration apparatus 100b shown in FIG. 12 further includes temperature sensors 31 to 34 as compared to the refrigeration apparatus 100 shown in FIG. The temperature sensor 31 is provided near the refrigerant outlet in the condenser 2. The temperature sensor 31 measures the condensation temperature. The temperature sensor 32 is provided in the vicinity of a refrigerant outlet of the condenser 2 in a refrigerant pipe that connects the condenser 2 and the expansion valve 3. The temperature sensor 32 measures the temperature of the liquid refrigerant.

The temperature sensor 33 is provided near the refrigerant outlet in the evaporator 4. The temperature sensor 33 measures the evaporation temperature. The temperature sensor 34 is provided in the vicinity of the refrigerant suction port of the compressor 1 in a refrigerant pipe that connects the evaporator 4 and the compressor 1. The temperature sensor 34 measures the temperature of the gas refrigerant. The temperature sensors 31 to 34 are connected to the control unit 15 by signal lines.

The operation control means 21 of the control unit 15 calculates the degree of subcooling using measured values obtained from the temperature sensor 31 and the temperature sensor 32 during the preparatory operation. The operation control means 21 also uses the measured values obtained from the temperature sensor 32 and the temperature sensor 33 to calculate the degree of superheat. The operation control unit 21 stores the calculated degree of supercooling and the degree of superheat in the storage unit 150.

If the amount of refrigerant in the refrigerant circuit 10 is insufficient, the discharge pressure Pout and the suction pressure Pin tend to decrease as compared with the case where the amount of refrigerant is normal. The measuring means 22 monitors the discharge pressure Pout and the suction pressure Pin during the preparatory operation of the refrigeration system 100a. Specifically, the measuring unit 22 stores the values of the discharge pressure Pout and the suction pressure Pin in the storage unit 150. The determination means 23 determines that the refrigerant is insufficient when any one of the discharge pressure Pout and the suction pressure Pin to be monitored becomes lower than a predetermined ratio. The fixed rate is, for example, 90% of the normal value. The determination unit 23 stores, in the storage unit 150, alarm information indicating that the refrigerant is insufficient. Subsequently, the control unit 15 performs the refrigerant leak determination in accordance with the procedure shown in FIG. 4 or 7. The determination means 23 determines that the refrigerant is insufficient based on the refrigerant pressure during the preparatory operation of the refrigeration apparatus 100a, and determines that there is a refrigerant leak when the differential pressure change time tm is less than or equal to the reference time tref.

Thus, the determination accuracy of the refrigerant leak is further improved by performing the refrigerant leak determination combining the refrigerant pressure during the preparatory operation of the refrigeration apparatus 100a and the change speed vp of the pressure difference during the stop of the refrigeration cycle.

Subsequently, the case where the refrigerant shortage determination using the degree of superheat is combined with the refrigerant leak determination will be described. When the refrigerant in the refrigerant circuit 10 runs short, the degree of superheat tends to increase. The measuring means 22 monitors the state of the degree of superheat during the preparatory operation of the refrigeration system 100a. Specifically, the measuring unit 22 calculates the degree of superheat every predetermined time, and stores the calculated value of the degree of superheat in the storage unit 150. When the degree of superheat becomes higher than the set value, the determination means 23 determines that the refrigerant is insufficient. The set value is, for example, 1.1 times the normal value. The determination unit 23 stores the alarm information in the storage unit 150. Subsequently, the control unit 15 performs the refrigerant leak determination in accordance with the procedure shown in FIG. 4 or 7. The determination means 23 determines that the refrigerant is insufficient based on the degree of superheat during the preparatory operation of the refrigeration apparatus 100a, and determines that there is a refrigerant leak when the differential pressure change time tm is less than or equal to the reference time tref.

In this manner, the determination accuracy of the refrigerant leakage is further improved by performing the refrigerant leakage determination combining the degree of superheat during the preparatory operation of the refrigeration apparatus 100a and the change speed vp of the pressure difference during the stop of the refrigeration cycle.

Subsequently, the case where the refrigerant shortage determination using the degree of subcooling is combined with the refrigerant leak determination will be described. When the refrigerant in the refrigerant circuit 10 runs short, the degree of subcooling tends to decrease. The measuring means 22 monitors the state of the degree of supercooling while the refrigeration system 100a is in operation. Specifically, the measuring unit 22 calculates the degree of subcooling at regular intervals, and stores the calculated value of the degree of subcooling in the storage unit 150. When the degree of subcooling becomes lower than the set value, the determination means 23 determines that there is a possibility of refrigerant leakage. The set value is, for example, 0.9 times the normal value. Subsequently, the control unit 15 performs the refrigerant leak determination in accordance with the procedure shown in FIG. 4 or 7. The determination means 23 determines that the refrigerant is insufficient based on the degree of supercooling during the preparatory operation of the refrigeration apparatus 100a, and determines that there is a refrigerant leak when the differential pressure change time tm is less than or equal to the reference time tref.

In this manner, the refrigerant leakage determination accuracy is further improved by performing the refrigerant leakage determination combining the degree of supercooling during the preparatory operation of the refrigeration apparatus 100a and the change speed vp of the pressure difference during the refrigeration cycle stop. .

Modification 1
A case will be described in which the refrigerant leakage determination method of the fourth embodiment is combined with the refrigerant shortage determination using the temperature efficiency as an example of the state data during the preparatory operation of the refrigeration apparatus 100a. In the first modification, the configuration of the refrigeration apparatus 100a shown in FIG. 10 provided with the temperature sensors 31 and 32 shown in FIG. 12 will be described. Moreover, the subcooler which is not shown in the figure is provided in the freezing apparatus 100a of the modification 1. The control unit 15 calculates the temperature efficiency ε using the following equation (2).

Temperature efficiency ε = supercooling degree / ΔTA (2)
In the equation (2), the degree of subcooling is calculated by the degree of subcooling = (condensing temperature−liquid refrigerant temperature). The temperature difference ΔTA is calculated by ΔTA = (condensing temperature−ambient temperature). Ambient temperature is the outside air temperature measured by the outside air temperature sensor 14.

When a proper amount of refrigerant is sealed in the refrigerant circuit 10, the refrigerant discharged from the compressor 1 is in a saturated liquid state at the outlet of the condenser 2, and the surplus refrigerant is stored in the liquid receiver 8. On the downstream side of the receiver 8, the refrigerant is further cooled by a subcooler not shown, and the temperature efficiency ε becomes about 0.5 or more. The value of 0.5 depends on the heat exchange performance.

The degree of supercooling fluctuates due to the fluctuation of ΔTA, but the fluctuation of the temperature efficiency ε becomes smaller. When the refrigerant runs short, the refrigerant discharged from the compressor 1 is also in the gaseous state at the outlet of the condenser 2 and in the receiver 8. The refrigerant is in a saturated liquid state in the subcooler or in a gas state in the subcooler. As a result, the degree of subcooling, which is the temperature difference between the condensation temperature and the liquid refrigerant temperature, becomes smaller and the temperature efficiency ε becomes smaller or zero, as compared with the case where the refrigerant circuit 10 is filled with the appropriate amount of refrigerant. It will be close value. Since the temperature efficiency ε has such a property, the control unit 15 can determine the refrigerant shortage using the temperature efficiency ε.

In the first to third embodiments described above, the control unit 15 determines the shortage of the refrigerant using the temperature efficiency ε, and when it is determined that the refrigerant is insufficient, the refrigerant leakage determination described in the first to third embodiments is performed. Good. Also in this case, the effect of improving the determination accuracy of the refrigerant leak can be obtained.

Reference Signs List 1 compressor, 2 condenser, 3 expansion valve, 4 evaporator, 5, 6 solenoid valve, 7 accumulator, 8 receiver, 10 refrigerant circuit, 11 suction pressure sensor, 12 discharge pressure sensor, 14 ambient temperature sensor, 15 Control unit, 16 indoor temperature sensor, 17 bypass circuit, 18 fan, 19 output unit, 21 operation control means, 22 measurement means, 23 determination means, 24 alarm means, 31 to 34 temperature sensors, 100, 100a, 100b refrigeration system, 150 storage units, 151 CPUs.

Claims (11)

A refrigerant circuit to which a compressor, a condenser, an expansion valve and an evaporator are connected,
A discharge pressure sensor that measures the discharge pressure of the refrigerant of the compressor;
A suction pressure sensor that measures a suction pressure of the refrigerant of the compressor;
An ambient temperature sensor that measures the ambient temperature;
A control unit that determines a refrigerant leak using the discharge pressure, the suction pressure, and the ambient temperature;
The control unit
The compressor and the expansion valve are controlled to perform a preparatory operation in which the discharge pressure is higher than the saturation pressure of the ambient temperature by the set high pressure and the suction pressure is lower than the saturation pressure by the set low pressure for a set period Operation control means,
Measurement means for measuring a differential pressure change time until the discharge pressure or the suction pressure changes to a specified value after the preparatory operation is stopped;
And a determination unit that determines that there is a refrigerant leak when the differential pressure change time is equal to or less than a reference time. The measuring means is
The refrigeration apparatus according to claim 1, wherein a time until a pressure difference between the discharge pressure and the suction pressure reaches the specified value is measured as the differential pressure change time. The measuring means is
The refrigeration apparatus according to claim 1, wherein a time until a pressure difference between the discharge pressure and the saturation pressure reaches the specified value is measured as the differential pressure change time. The measuring means is
The refrigeration apparatus according to any one of claims 1 to 3, wherein a time until a pressure difference between the suction pressure and the saturation pressure reaches the specified value is measured as the differential pressure change time. The operation control means performs the preparatory operation a plurality of times,
The measuring means measures the differential pressure change time for each of the plurality of preparatory operations;
The refrigeration apparatus according to any one of claims 1 to 4, wherein the determination means determines that there is a refrigerant leak when any of the plurality of differential pressure change times is equal to or less than the reference time. The control unit includes a storage unit that stores a table in which a plurality of reference times are recorded in association with a plurality of temperature zones of the ambient temperature.
The said determination means determines a refrigerant | coolant leak using the said reference time recorded on the temperature zone to which the measured value of the said ambient temperature sensor belongs with reference to the said table. Refrigeration system. The measurement means measures the differential pressure change time a plurality of times for the temperature zone to which the measurement value of the ambient temperature sensor belongs among the plurality of temperature zones,
The determination means corrects the reference time of the temperature zone to which the measurement value of the ambient temperature sensor belongs, recorded in the table, using the plurality of differential pressure change times measured by the measurement means. The freezing apparatus of Claim 6. The refrigeration apparatus according to any one of claims 1 to 7, wherein the ambient temperature sensor is an outside air temperature sensor that measures an outside air temperature, or a room temperature sensor that measures the temperature of a room in which the evaporator is installed. . The control unit has a storage unit that stores the specified value,
The operation control means performs the preparatory operation multiple times with no refrigerant leakage,
The measuring means measures the differential pressure change time for each of the plurality of preparatory operations;
5. The method according to claim 1, wherein the determination unit calculates the reference time using the plurality of differential pressure change times measured by the measurement unit, and records the calculated reference time in the storage unit. Refrigerating apparatus as described in a paragraph. The control unit has a storage unit that stores state data indicating an operating state of the refrigeration cycle during the preparatory operation;
The determination means
The refrigeration according to any one of claims 1 to 4, wherein if it is determined that the refrigerant is insufficient based on the state data and the differential pressure change time is equal to or less than the reference time, it is determined that the refrigerant leaks. apparatus. The operation control means is
The refrigeration apparatus according to any one of claims 1 to 10, wherein the preparatory operation is started after the defrosting operation is performed on the evaporator.

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