JP6184156B2 - Refrigeration cycle equipment - Google Patents

Description

  The present invention relates to a refrigeration cycle apparatus.

  In order to improve the efficiency of the refrigeration cycle apparatus, it is necessary to improve the heat exchange capacity of the heat exchanger. The simplest method for improving the heat exchange capacity of the heat exchanger is to increase the heat exchange area of the heat exchanger. However, when the heat exchange area of the heat exchanger is increased, the size of the heat exchanger increases, so that the refrigeration cycle apparatus becomes larger and the price of the refrigeration cycle apparatus increases. For this reason, improving the heat exchange efficiency of a heat exchanger as a method for improving the heat exchange capacity of the heat exchanger has been conventionally proposed. By improving the heat exchange efficiency of the heat exchanger, it is possible to achieve both high efficiency and downsizing of the refrigeration cycle apparatus.

  Patent Document 1 discloses a compressor that converts low-pressure refrigerant gas to high pressure, a condenser that converts refrigerant gas from the compressor into high-pressure refrigerant liquid, and a subcool coil that supercools the refrigerant liquid from the condenser. An electronic expansion valve that adjusts the amount of refrigerant liquid that has passed through the subcool coil, an evaporator that evaporates the refrigerant liquid that has passed through the electronic expansion valve, and an accumulator that incorporates the subcool coil and overheats the refrigerant evaporated in the evaporator And a control device for controlling the electronic expansion valve so that the outlet of the evaporator is always kept in a two-phase state is disclosed.

JP-A-2-75858

  In the above refrigeration air conditioner, the heat exchange efficiency of the evaporator is improved by always keeping the evaporator outlet in a two-phase state. However, when the degree of superheat at the evaporator outlet is kept low, it is necessary to prevent the refrigerant liquid from returning to the compressor. For this reason, in the above-described refrigerating and air-conditioning apparatus, a heat exchanger (accumulator with a built-in subcool coil) for superheating the refrigerant sucked into the compressor is provided on the outlet side of the evaporator. Therefore, the above-described refrigeration and air-conditioning apparatus has a problem that the structure becomes complicated and the apparatus becomes large.

  The present invention has been made to solve the above-described problems, and provides a refrigeration cycle apparatus capable of improving efficiency while avoiding the complexity of the structure and the enlargement of the apparatus. Objective.

In the refrigeration cycle apparatus according to the present invention, a compressor, a condenser, an electronic expansion valve, and an evaporator are annularly connected in this order, a refrigerant circuit that circulates refrigerant, and a downstream side of the compressor than the condenser. An oil separator that is provided on the upstream side and separates the oil discharged from the compressor from the refrigerant, and a merging portion that is provided on the downstream side of the oil separator and the evaporator and on the upstream side of the compressor And an oil return circuit that joins the oil separated by the oil separator with the refrigerant at the junction and returns it to the compressor, and joins the oil at the junction and sucks it into the compressor And a control unit that controls the electronic expansion valve based on the degree of superheat of the suction refrigerant, and a suction unit that is provided downstream of the junction and upstream of the compressor, and detects the pressure of the suction refrigerant From the compressor on the downstream side of the pressure sensor and the junction An intake temperature sensor provided on the upstream side for detecting the temperature of the intake refrigerant; a discharge pressure sensor provided on the downstream side of the compressor for detecting the pressure of the discharge refrigerant discharged from the compressor; than the compressor provided on the downstream side, it has a, a discharge temperature sensor for detecting the temperature of the discharge refrigerant, the control unit includes a pressure and temperature of the suction refrigerant, the pressure and temperature of the discharged refrigerant, Based on the compression capacity of the compressor, the temperature rise width of the refrigerant before and after the merge at the merge portion is estimated, and based on the temperature rise width, the refrigerant on the outlet side of the evaporator is in a saturated gas state. The superheat degree target value of the suction refrigerant is set, and the electronic expansion valve is controlled so that the superheat degree of the suction refrigerant approaches the superheat degree target value .

  According to the present invention, the refrigerant that has flowed out of the evaporator is superheated by the high-temperature oil that joins at the joining portion, and is then sucked into the compressor. For this reason, even if the refrigerant on the outlet side of the evaporator is in a saturated gas state, the refrigerant sucked into the compressor can be more reliably superheated without providing a separate heat exchanger on the downstream side of the evaporator. Can do. Therefore, the efficiency of the refrigeration cycle apparatus can be improved while avoiding the complexity of the structure of the refrigeration cycle apparatus and the enlargement of the apparatus.

It is a refrigerant circuit diagram which shows schematic structure of the refrigerating-cycle apparatus 1 which concerns on Embodiment 1 of this invention. It is a flowchart which shows an example of the flow of the opening degree control process of the electronic expansion valve 40 performed by the control part 60 of the refrigerating-cycle apparatus 1 which concerns on Embodiment 1 of this invention. It is a refrigerant circuit diagram which shows schematic structure of the refrigerating-cycle apparatus 2 which concerns on Embodiment 2 of this invention. It is a flowchart which shows an example of the flow of the opening degree control process of the electronic expansion valve 40 performed by the control part 60 of the refrigerating-cycle apparatus 2 which concerns on Embodiment 2 of this invention.

Embodiment 1 FIG.
A refrigeration cycle apparatus according to Embodiment 1 of the present invention will be described. FIG. 1 is a refrigerant circuit diagram showing a schematic configuration of a refrigeration cycle apparatus 1 according to the present embodiment. The refrigeration cycle apparatus 1 according to the present embodiment is used for various industrial machines such as a refrigerator, a freezer, an air conditioner, a refrigeration apparatus, a vending machine, and a water heater. As shown in FIG. 1, the refrigeration cycle apparatus 1 has a refrigerant circuit 100 that circulates refrigerant. The refrigerant circuit 100 has a configuration in which the compressor 10, the condenser 30, the electronic expansion valve 40, and the evaporator 50 are annularly connected in this order by refrigerant piping. The compressor 10 is a fluid machine that sucks and compresses a low-temperature and low-pressure refrigerant and discharges it as a high-temperature and high-pressure refrigerant. The compressor 10 includes a compression mechanism unit that compresses the refrigerant and a drive mechanism unit that drives the compression mechanism unit when electric power is supplied from the outside. In this example, an inverter power source that can change the driving frequency under the control of the control unit 60 described later is used as a power source that supplies power to the drive mechanism unit of the compressor 10. In addition, as a power supply which supplies electric power to the drive mechanism part of the compressor 10, a general commercial power supply with a frequency of 50 Hz or 60 Hz can also be used.

  The condenser 30 is a heat exchanger that condenses the refrigerant discharged from the compressor 10 by heat exchange with an external fluid (for example, air). The electronic expansion valve 40 decompresses and expands the refrigerant condensed in the condenser 30 by a throttling action, and causes the refrigerant to flow out as a low-temperature and low-pressure gas-liquid two-phase refrigerant. The electronic expansion valve 40 is controlled by a control unit 60 described later. The evaporator 50 is a heat exchanger that evaporates the gas-liquid two-phase refrigerant flowing out from the electronic expansion valve 40 by heat exchange with an external fluid (for example, air).

  An oil separator 20 that separates oil (refrigeration oil) discharged from the compressor 10 together with the refrigerant from the refrigerant is provided downstream of the compressor 10 and upstream of the condenser 30 in the refrigerant circuit 100. Yes. An oil return circuit 70 connects between the oil separator 20 and a merging portion 71 provided downstream of the evaporator 50 and upstream of the compressor 10 in the refrigerant circuit 100. The oil return circuit 70 is configured to return the oil to the suction side of the compressor 10 by circulating the oil separated by the oil separator 20 and causing the oil to join the refrigerant at the junction 71. Since the temperature of the oil separated by the oil separator 20 is high, the temperature of the refrigerant combined with the oil at the merging portion 71 is the temperature of the refrigerant before merging with the oil (that is, the refrigerant temperature on the outlet side of the evaporator 50). Than to rise. The compressor 10 sucks refrigerant whose temperature has increased due to the merge with oil.

  The pressure of the refrigerant sucked into the compressor 10 (hereinafter sometimes referred to as “suction pressure”) is downstream of the junction 71 and upstream of the compressor 10 (suction side of the compressor 10). A suction pressure sensor (low-pressure side pressure sensor) 61 for detecting, and a suction temperature sensor 62 for detecting the temperature of refrigerant sucked into the compressor 10 (hereinafter sometimes referred to as “suction temperature”) are provided. Yes. A discharge pressure sensor that detects the pressure of refrigerant discharged from the compressor 10 (hereinafter sometimes referred to as “discharge pressure”) downstream of the compressor 10 (on the discharge side of the compressor 10). A (high pressure side pressure sensor) 63 and a discharge temperature sensor 64 for detecting the temperature of the discharge refrigerant discharged from the compressor 10 (hereinafter sometimes referred to as “discharge temperature”) are provided. The suction pressure sensor 61, the suction temperature sensor 62, the discharge pressure sensor 63, and the discharge temperature sensor 64 are configured to output detected pressure or temperature information to the control unit 60 described later.

  The refrigeration cycle apparatus 1 includes a control unit 60 that controls the compressor 10 and the electronic expansion valve 40 of the refrigerant circuit 100. The control unit 60 includes a CPU, a ROM, a RAM, an input / output port, and the like. The controller 60 changes the driving frequency of the compressor 10 based on the load of the condenser 30 or the evaporator 50, thereby controlling the compression capacity. In addition, the control unit 60 controls the opening degree of the electronic expansion valve 40 based on the degree of superheat of the suction refrigerant that joins the oil at the joining unit 71 and is sucked into the compressor 10. The degree of superheat of the suction refrigerant is calculated based on the suction pressure detected by the suction pressure sensor 61 and the suction temperature detected by the suction temperature sensor 62.

  FIG. 2 is a flowchart illustrating an example of a flow of opening degree control processing of the electronic expansion valve 40 that is executed by the control unit 60 of the refrigeration cycle apparatus 1. As shown in FIG. 2, first, in step S <b> 1, the suction pressure information output from the suction pressure sensor 61, the suction temperature information output from the suction temperature sensor 62, and the discharge pressure output from the discharge pressure sensor 63. , Information on the discharge temperature output from the discharge temperature sensor 64, and information on the compression capacity (for example, drive frequency) of the compressor 10 set by the control unit 60 itself.

  Next, in step S2, the temperature rise width (superheat degree rise width) of the refrigerant before and after joining at the joining portion 71 is estimated based on the suction pressure, suction temperature, discharge pressure, discharge temperature, and compression capacity. The temperature rise width before and after the merging includes the temperature of the refrigerant before merging flowing from the outlet side of the evaporator 50 to the merging part 71 and the refrigerant after merging whose temperature has increased by merging with oil at the merging part 71 ( It is a temperature difference with the temperature of the refrigerant | coolant which the mixed oil mixed. For calculating the temperature rise width of the refrigerant before and after merging, for example, information on the temperature of the oil before merging, the flow rate of the oil before merging, the temperature of the refrigerant after merging, and the flow rate of the refrigerant after merging Is required.

  The temperature of the oil before joining is approximately the same temperature as the discharge temperature of the refrigerant discharged from the compressor 10. Therefore, the temperature of the oil before joining can be estimated based on the discharge temperature detected by the discharge temperature sensor 64.

  The oil flow rate (oil return amount) before merging can be estimated from the pressure difference between the oil separator 20 and the merging portion 71. The pressure of the oil separator 20 is the same as the discharge pressure (high-pressure side pressure) of the refrigerant discharged from the compressor 10. The pressure of the junction 71 is the same as the suction pressure (low pressure side pressure) of the refrigerant sucked into the compressor 10. Therefore, the flow rate of the oil before joining can be estimated based on the discharge pressure detected by the discharge pressure sensor 63 and the suction pressure detected by the suction pressure sensor 61.

  The temperature of the refrigerant after merging is the same temperature as the refrigerant sucked into the compressor 10. Therefore, the suction temperature detected by the suction temperature sensor 62 can be handled as the temperature of the refrigerant after merging.

  The flow rate of the refrigerant after merging (the circulation amount of the refrigerant circulating in the refrigerant circuit 100) is the discharge pressure of the refrigerant discharged from the compressor 10, the suction pressure of the refrigerant sucked into the compressor 10, and the It can be estimated by the compression capacity. Therefore, the flow rate of the refrigerant after merging includes the discharge pressure detected by the discharge pressure sensor 63, the suction pressure detected by the suction pressure sensor 61, and the compression capacity of the compressor 10 set by the control unit 60 itself. Can be estimated.

  As described above, the control unit 60 can estimate the temperature rise width of the refrigerant before and after merging based on each information of the suction pressure, suction temperature, discharge pressure, discharge temperature, and compression capacity acquired in step S1.

  Next, in step S3, the superheat degree target value of the refrigerant sucked into the compressor 10 is set based on the temperature rise range estimated in step S2. In this example, the superheat degree target value of the suction refrigerant is set so that the refrigerant on the outlet side of the evaporator 50 is in a saturated gas state (dry saturated state). The degree of superheat of the refrigerant sucked into the compressor 10 is higher than the degree of superheat of the refrigerant on the outlet side of the evaporator 50 by the above temperature increase width. Therefore, for example, assuming that the superheat degree of the refrigerant on the outlet side of the evaporator 50 is T (for example, 0 ° C.) and the above temperature rise is Δt, the superheat degree target value of the suction refrigerant is set to T + Δt.

  Next, in step S4, the opening degree of the electronic expansion valve 40 is controlled so that the superheat degree of the refrigerant sucked into the compressor 10 approaches the superheat degree target value. Here, the superheat degree of the suction refrigerant is calculated based on the suction pressure and suction temperature information acquired in step S1. As a result, the electronic expansion valve 40 is controlled so that the refrigerant on the outlet side of the evaporator 50 approaches the saturated gas state.

  The processes in steps S1 to S4 are repeatedly executed at a predetermined cycle from the start of the refrigeration cycle apparatus 1 to the stop (step S5).

  As described above, the refrigeration cycle apparatus 1 according to the present embodiment includes the refrigerant circuit 100 in which the compressor 10, the condenser 30, the electronic expansion valve 40, and the evaporator 50 are annularly connected in this order to circulate the refrigerant. The oil separator 20 is provided downstream of the compressor 10 and upstream of the condenser 30 and separates the oil discharged from the compressor 10 from the refrigerant, and downstream of the oil separator 20 and the evaporator 50. Between the merging section 71 provided on the upstream side of the compressor 10 on the side, circulates the oil separated by the oil separator 20, merges with the refrigerant at the merging section 71, and returns to the compressor 10. It has an oil return circuit 70 and a control unit 60 that controls the electronic expansion valve 40 based on the degree of superheat of the refrigerant sucked into the compressor 10 after joining the oil at the junction 71. Is.

  According to this configuration, the refrigerant that has flowed out of the evaporator 50 is sucked into the compressor 10 after being superheated by the high-temperature oil that merges at the merge portion 71. For this reason, even if the refrigerant on the outlet side of the evaporator 50 is in a saturated gas state, the refrigerant sucked into the compressor 10 is more reliably superheated gas without separately providing a heat exchanger on the downstream side of the evaporator 50. Can be Further, the electronic expansion valve 40 is controlled based on the degree of superheat of the refrigerant after being superheated by high-temperature oil that joins at the junction 71. For this reason, it is possible to control the electronic expansion valve 40 based on the degree of superheat of the refrigerant, and to make the refrigerant at the outlet of the evaporator 50 into a saturated gas state. Thereby, since the refrigerant | coolant inside the evaporator 50 can be maintained in a gas-liquid two-phase state, the heat exchange efficiency of the evaporator 50 can be improved. Therefore, according to this Embodiment, the efficiency of the refrigerating cycle apparatus 1 can be improved, avoiding the complexity of the structure of the refrigerating cycle apparatus 1, and the enlargement of an apparatus. Moreover, the energy consumption of the refrigeration cycle apparatus 1 can be reduced by improving the efficiency of the refrigeration cycle apparatus 1. Thereby, an environmental load can be reduced at least when the refrigeration cycle apparatus 1 is used.

  In addition, the refrigeration cycle apparatus 1 according to the present embodiment includes a suction pressure sensor 61 that is provided on the downstream side of the merging portion 71 and upstream of the compressor 10 and detects the pressure of the suction refrigerant, and the merging portion 71. Also, a suction temperature sensor 62 that detects the temperature of the suction refrigerant is provided downstream of the compressor 10 on the downstream side, and a pressure of the discharge refrigerant that is provided downstream of the compressor 10 and discharged from the compressor 10. A discharge pressure sensor 63 that detects the temperature of the refrigerant, and a discharge temperature sensor 64 that is provided downstream of the compressor 10 and upstream of the condenser 30 and detects the temperature of the discharged refrigerant. Based on the pressure and temperature of the suction refrigerant, the pressure and temperature of the discharge refrigerant, and the compression capacity of the compressor 10, the temperature rise width of the refrigerant before and after joining the oil in the joining portion 71 is estimated, and the temperature rise width On the basis of the evaporator 5 The superheat degree target value of the suction refrigerant in which the refrigerant on the outlet side of the refrigerant is in a saturated gas state is set, and the electronic expansion valve 40 is controlled so that the superheat degree of the suction refrigerant approaches the superheat degree target value. is there.

  Further, in the refrigeration cycle apparatus 1 according to the present embodiment, the control unit 60 estimates the temperature of oil before joining with the refrigerant in the joining unit 71 based on the temperature of the discharged refrigerant, and the pressure of the discharged refrigerant, Based on the pressure of the suction refrigerant, the flow rate of the oil before joining with the refrigerant in the joining portion 71 is estimated, and based on the pressure of the discharge refrigerant, the pressure of the suction refrigerant, and the compression capacity of the compressor 10, The flow rate of the refrigerant after merging in the unit 71 is estimated, and the temperature rise width is estimated based on the temperature and flow rate of the oil before merging, the flow rate of the refrigerant after merging, and the suction temperature. Is.

  According to these configurations, it is possible to set a superheat degree target value for setting the refrigerant at the outlet of the evaporator 50 to a saturated gas state without increasing the number of sensors more than necessary. Therefore, the refrigerant at the outlet of the evaporator 50 can be brought into a saturated gas state, and the refrigerant sucked into the compressor 10 can be more reliably superheated.

Embodiment 2. FIG.
A refrigeration cycle apparatus according to Embodiment 2 of the present invention will be described. FIG. 3 is a refrigerant circuit diagram illustrating a schematic configuration of the refrigeration cycle apparatus 2 according to the present embodiment. In addition, about the component which has the same function and effect | action as the refrigerating-cycle apparatus 1 which concerns on Embodiment 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted. As shown in FIG. 3, the refrigeration cycle apparatus 2 is characterized in that the refrigeration cycle apparatus 2 further includes an accumulator 80 provided on the downstream side of the evaporator 50 and the upstream side of the merging portion 71 as compared with the refrigeration cycle apparatus 1. doing. The accumulator 80 is a gas-liquid separator that gas-liquid separates the inflowing refrigerant and causes the gas refrigerant to flow out to prevent liquid back to the compressor 10.

  An accumulator inlet temperature sensor 81 that detects the temperature of the refrigerant on the inlet side of the accumulator 80 (the outlet side of the evaporator 50) is provided downstream of the evaporator 50 and upstream of the accumulator 80. A condenser outlet temperature sensor 31 that detects the temperature of the refrigerant on the outlet side of the condenser 30 is provided downstream of the condenser 30 and upstream of the electronic expansion valve 40. The accumulator inlet temperature sensor 81 and the condenser outlet temperature sensor 31 are configured to output detected temperature information to the control unit 60.

  FIG. 4 is a flowchart illustrating an example of a flow of opening degree control processing of the electronic expansion valve 40 that is executed by the control unit 60 of the refrigeration cycle apparatus 2. As shown in FIG. 4, first, in step S11, it is determined whether or not the degree of supercooling of the refrigerant on the outlet side of the condenser 30 is equal to or greater than a preset reference value. If the degree of supercooling of the refrigerant on the outlet side of the condenser 30 is greater than or equal to the reference value, the process proceeds to step S12. Here, the degree of supercooling of the refrigerant on the outlet side of the condenser 30 depends on the condenser outlet temperature detected by the condenser outlet temperature sensor 31 and the discharge pressure (high pressure side pressure) detected by the discharge pressure sensor 63. Calculated based on In step S12 and steps S13 to S15 executed thereafter, the electronic expansion valve 40 is controlled based on the degree of superheat of the suction refrigerant sucked into the compressor 10 as in the first embodiment. Since each process of step S12-S15 is the same as each process of step S1-S4 of FIG. 2, description is abbreviate | omitted.

  On the other hand, when the degree of supercooling of the refrigerant on the outlet side of the condenser 30 is less than the reference value, the process proceeds to step S16. In step S16, the electronic expansion valve 40 is controlled based on the degree of superheat of the refrigerant on the inlet side of the accumulator 80. In this example, the electronic expansion valve 40 is controlled so that the refrigerant on the inlet side of the accumulator 80 becomes superheated gas. Here, the superheat degree of the refrigerant on the inlet side of the accumulator 80 is calculated based on the accumulator inlet temperature detected by the accumulator inlet temperature sensor 81 and the suction pressure (low pressure side pressure) detected by the suction pressure sensor 61. The

  The processing of steps S11 to S16 (the processing of steps S12 to S15 or the processing of step S16) is repeatedly executed at a predetermined cycle until the refrigeration cycle apparatus 2 is started and stopped (step S17).

  As described above, the refrigeration cycle apparatus 2 according to the present embodiment further includes the accumulator 80 provided downstream of the evaporator 50 and upstream of the junction 71. .

  The refrigeration cycle apparatus 2 according to the present embodiment is provided downstream of the condenser 30 and upstream of the electronic expansion valve 40, and detects the temperature of the refrigerant on the outlet side of the condenser 30. The controller 60 further includes a temperature sensor 31 and an accumulator inlet temperature sensor 81 that is provided downstream of the evaporator 50 and upstream of the accumulator 80 and detects the temperature of the refrigerant on the inlet side of the accumulator 80. If the degree of supercooling of the refrigerant on the outlet side of the condenser 30 is equal to or higher than the reference value, the electronic expansion valve 40 is controlled based on the degree of superheat of the refrigerant sucked into the compressor 10 (steps S12 to S15). ) If the degree of supercooling of the refrigerant on the outlet side of the condenser 30 is less than the reference value, the electronic expansion valve 40 is controlled based on the degree of superheating of the refrigerant on the inlet side of the accumulator 80 (step S16). It is an butterfly.

  In the present embodiment, when the degree of supercooling of the refrigerant on the outlet side of the condenser 30 is greater than or equal to a reference value, the degree of superheating of the refrigerant sucked into the compressor 10 is based on the degree of superheating of the refrigerant sucked into the compressor 10 as in the first embodiment. The electronic expansion valve 40 is controlled. Therefore, according to the present embodiment, the same effect as in the first embodiment can be obtained.

  However, in the configuration as in the present embodiment, the refrigerant on the outlet side of the evaporator 50 is not always in a saturated gas state due to detection errors of each sensor, changes in the operating state of the refrigeration cycle, and the like. May be in a phase state. When the accumulator 80 is installed on the outlet side of the evaporator 50, when the two-phase refrigerant flows into the accumulator 80, the amount of refrigerant that stays in the accumulator 80 may increase. In this case, since the amount of refrigerant staying in the condenser 30 decreases, the performance of the refrigeration cycle apparatus 2 may be deteriorated.

  In the present embodiment, when the degree of supercooling of the refrigerant on the outlet side of the condenser 30 falls below a reference value, the electronic expansion valve 40 is controlled so that the refrigerant on the inlet side of the accumulator 80 is in a superheated gas state. Is done. By performing this control, the liquid refrigerant staying in the accumulator 80 is driven out by the superheated refrigerant flowing into the accumulator 80. Therefore, according to this Embodiment, since the fall of the refrigerant | coolant amount which retains in the condenser 30 can be prevented, the performance of the refrigerating-cycle apparatus 2 can be improved.

  When the liquid refrigerant staying in the accumulator 80 is expelled and the degree of supercooling of the refrigerant on the outlet side of the condenser 30 increases to a reference value or more, the suction refrigerant sucked into the compressor 10 again. The electronic expansion valve 40 is controlled based on the degree of superheat.

Other embodiments.
The present invention is not limited to the above embodiment, and various modifications can be made.
For example, in the above embodiment, the superheat target value of the suction refrigerant is set so that the refrigerant on the outlet side of the evaporator 50 is in a saturated gas state. The refrigerant on the outlet side of 50 may be set so as to be in a two-phase state with a high dryness close to a saturated gas state or a superheated gas state with a low superheat degree close to a saturated gas state.

  In addition, the above embodiments and modifications can be implemented in combination with each other.

  1, 2, refrigeration cycle apparatus, 10 compressor, 20 oil separator, 30 condenser, 31 condenser outlet temperature sensor, 40 electronic expansion valve, 50 evaporator, 60 control unit, 61 suction pressure sensor, 62 suction temperature sensor, 63 discharge pressure sensor, 64 discharge temperature sensor, 70 oil return circuit, 71 junction, 80 accumulator, 81 accumulator inlet temperature sensor, 100 refrigerant circuit.

Claims (3)

A refrigerant circuit in which a compressor, a condenser, an electronic expansion valve, and an evaporator are annularly connected in this order to circulate the refrigerant;
An oil separator that is provided downstream of the compressor and upstream of the condenser, and separates oil discharged from the compressor from the refrigerant;
The oil separator is connected downstream of the evaporator and a merging portion provided upstream of the compressor, and the oil separated by the oil separator is merged with the refrigerant at the merging portion. An oil return circuit for returning to the compressor;
A control unit that controls the electronic expansion valve based on the degree of superheat of the refrigerant that is sucked into the compressor after joining the oil in the joining unit;
A suction pressure sensor that is provided downstream of the merging portion and upstream of the compressor, and that detects the pressure of the suction refrigerant;
An intake temperature sensor that is provided downstream of the junction and upstream of the compressor, and detects the temperature of the intake refrigerant;
A discharge pressure sensor that is provided on the downstream side of the compressor and detects a pressure of a discharge refrigerant discharged from the compressor;
A discharge temperature sensor that is provided downstream of the compressor and detects a temperature of the discharge refrigerant;
I have a,
The controller is
Based on the pressure and temperature of the suction refrigerant, the pressure and temperature of the discharge refrigerant, and the compression capacity of the compressor, the temperature increase width of the refrigerant before and after merging in the merging portion is estimated,
Based on the temperature rise width, set the superheat degree target value of the suction refrigerant in which the refrigerant on the outlet side of the evaporator is in a saturated gas state,
The refrigeration cycle apparatus , wherein the electronic expansion valve is controlled so that the superheat degree of the suction refrigerant approaches the superheat degree target value . The controller is
Based on the temperature of the discharged refrigerant, the temperature of the oil before merging at the merging portion is estimated,
Based on the pressure of the discharged refrigerant and the pressure of the suction refrigerant, the flow rate of the oil before joining at the joining portion is estimated,
Based on the pressure of the discharged refrigerant, the pressure of the suction refrigerant, and the compression capacity of the compressor, the flow rate of the refrigerant after merging in the merging portion is estimated,
Temperature and flow rate of the oil before the merging, and the flow rate of the refrigerant after the merging, on the basis of the temperature of the suction refrigerant, the refrigeration cycle according to claim 1, characterized in that to estimate the temperature rise apparatus. A refrigerant circuit in which a compressor, a condenser, an electronic expansion valve, and an evaporator are annularly connected in this order to circulate the refrigerant;
An oil separator that is provided downstream of the compressor and upstream of the condenser, and separates oil discharged from the compressor from the refrigerant;
The oil separator is connected downstream of the evaporator and a merging portion provided upstream of the compressor, and the oil separated by the oil separator is merged with the refrigerant at the merging portion. An oil return circuit for returning to the compressor;
An accumulator provided downstream of the evaporator and upstream of the junction; and
A condenser outlet temperature sensor which is provided downstream of the condenser and upstream of the electronic expansion valve, and detects the temperature of the refrigerant on the outlet side of the condenser;
An accumulator inlet temperature sensor that is provided downstream of the evaporator and upstream of the accumulator to detect the temperature of the refrigerant on the inlet side of the accumulator;
A control unit that controls the electronic expansion valve based on the degree of superheat of the refrigerant that is sucked into the compressor after joining the oil in the joining unit;
I have a,
The controller is
When the degree of supercooling of the refrigerant on the outlet side of the condenser is greater than or equal to a reference value, the electronic expansion valve is controlled based on the degree of superheating of the suction refrigerant,
When the degree of supercooling is less than the reference value, the electronic expansion valve is controlled based on the degree of superheat of the refrigerant on the inlet side of the accumulator .

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