JP2017096564A - Refrigeration cycle system and liquid back prevention method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a compressor by preventing liquid back with a simple, low-cost, reliable, and excellent in maintainability structure.SOLUTION: A cooling/heating air conditioning system of the invention performs the gas-liquid separation of the gas-liquid mixture inducted in a motor compressor, so that only evaporated coolant is sucked into the motor compressor; an electric type exothermic body 23 is provided at a position of a maximum allowable liquid level H3 of liquid coolant R in an accumulator 12 for storing a predetermined amount of the liquid coolant R; changes in calorific power of the electric type exothermic body 23 are detected by a control part as changes in electric power consumption, when the electric power consumption reaches a prescribed threshold level, the protective operation is performed for lowering the liquid level of the liquid coolant R.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a refrigeration cycle system and a liquid back prevention method that prevent liquid back to a compressor.

  In air conditioning systems used in stores, offices, houses, etc., a pressure vessel accumulator is connected to the suction side of a compressor that compresses and liquefies a gas refrigerant. The accumulator temporarily stores gas-liquid mixed refrigerant gas flowing back from the evaporator to the compressor, performs gas-liquid separation by gravity inside, and causes only the vaporized refrigerant to be sucked into the compressor. As a result, an event called liquid back where the liquid refrigerant is sucked into the compressor as it is is prevented, and damage to the compressor due to liquid compression is avoided.

  As disclosed in Patent Document 1, the accumulator is provided with a liquid level detector at a predetermined liquid level level position so that the capacity of the stored liquid refrigerant does not exceed the capacity. The liquid level detector is exposed in the pressure vessel of the accumulator and touches the liquid refrigerant. When the liquid level reaches the position of the liquid level detector, the detection signal is electrically output. The

  When the control unit of the air conditioning system receives this detection signal, it takes measures such as reducing or temporarily stopping the rotation speed of the compressor, or reducing the opening of the expansion valve, and the liquid level of the liquid refrigerant in the accumulator Protective operation to prevent liquid back by lowering the level. In the air conditioning system of Patent Document 1, the liquid refrigerant is heated to the saturation temperature or higher by raising the temperature of the heating device provided at the bottom of the accumulator, and the liquid level is lowered.

Japanese Patent Laid-Open No. 2001-27460

  However, as disclosed in Patent Document 1, providing a liquid level detector in the pressure vessel of the accumulator causes a complicated structure of the accumulator and an increase in manufacturing cost, as well as liquid level detection that is liable to fail. By using the air conditioner, the reliability of the air conditioning system is reduced. In addition, when the liquid level detector fails, when removing the liquid level detector from the pressure vessel of the accumulator, it is necessary to remove the refrigerant from the entire air conditioning system, and it takes time to refill the refrigerant, resulting in poor maintainability. .

  The present invention has been made in view of the above circumstances, and is a refrigeration cycle system capable of preventing a liquid back and protecting a compressor with a simple, inexpensive, reliable, and maintainable configuration. And it aims at providing the liquid back prevention method.

In order to solve the above problems, the present invention employs the following means.
That is, the refrigeration cycle system according to the present invention includes a compressor that compresses a refrigerant, a condenser that condenses the compressed refrigerant discharged from the compressor, and an expansion that expands the compressed refrigerant condensed in the condenser. A valve, an evaporator that vaporizes the compressed refrigerant expanded by the expansion valve, and a gas-liquid mixed refrigerant that recirculates from the evaporator to the compressor, and temporarily stores the gas and liquid into a liquid refrigerant and a vaporized refrigerant. An accumulator that sucks only the vaporized refrigerant into the compressor, and the accumulator includes a pressure vessel, a refrigerant inflow portion for allowing the gas-liquid mixed refrigerant to flow into the pressure vessel, and the vaporized refrigerant. A refrigerant outflow portion that flows to the compressor side, and an electric heating element provided at a position of the pressure vessel at the highest allowable liquid level level of the liquid refrigerant in the pressure vessel, and The above Control for detecting a change in the amount of heat generated by the pneumatic heating element based on a change in power consumption, and performing a protective operation to lower the liquid level of the liquid refrigerant when the power consumption reaches a predetermined threshold Part.

  In the case of the above configuration, the heat generation amount of the electric heating element provided in the accumulator, that is, the power consumption (for example, current value) is higher than that when the electric heating element is adjacent to the vaporized refrigerant having a small specific heat. It becomes larger when it is adjacent to a large liquid refrigerant. For this reason, when the liquid level of the liquid refrigerant reaches the height of the electric heating element, the power consumption of the electric heating element increases. Therefore, by monitoring the power consumption of the electric heating element by the control unit, it is possible to specify whether the electric heating element is adjacent to the vaporized refrigerant or the liquid refrigerant.

  When the power consumption of the electric heating element reaches a predetermined threshold value, the control unit performs a protective operation for reducing the liquid level of the liquid refrigerant. Specifically, measures such as lowering the rotational speed of the compressor, temporarily stopping, or reducing the opening of the expansion valve are taken to lower the liquid level of the liquid refrigerant in the accumulator. Thereby, a liquid back can be prevented and a compressor can be protected.

  Since the electric heating element is not a sensor, it can be implemented more simply and at a lower cost than the conventional configuration in which a liquid level detector is provided in the accumulator, and the reliability of the refrigeration cycle system is reduced because the failure rate is reduced. improves. Therefore, a simple, inexpensive, and highly reliable configuration can prevent the liquid back from the accumulator and protect the compressor.

  In the above-described configuration, the voltage applied to the electric heating element increases the temperature of the vaporized refrigerant by the heat generated by the electric heating element when the electric heating element is adjacent to the vaporized refrigerant. When the body is adjacent to the liquid refrigerant, it can be considered that the temperature of the electric heating element is lowered by the cold heat of the liquid refrigerant.

  As a result, the calorific value of the electric heating element can warm the vaporized refrigerant, but cannot warm the liquid refrigerant. Conversely, the calorific value is such that the electric heating element is cooled by the liquid refrigerant. Become. Even in this case, the vaporized refrigerant and the liquid refrigerant can be discriminated, so that an increase in the liquid level of the liquid refrigerant can be detected with a minimum amount of electric power, and liquid back can be prevented.

  In addition, since the amount of heat generated by the electric heating element is kept to the minimum necessary, the gas-liquid refrigerant in the accumulator is not heated more than necessary. Therefore, it is possible to prevent the efficiency of the refrigeration cycle system from being reduced due to an excessive degree of superheat being imparted to the refrigerant by the electric heating element.

  In the above configuration, the electric heating element may be a resistance temperature detector that can also be used as a temperature sensor. In this way, in the case of a refrigeration cycle system in which a refrigerant temperature sensor is provided in the accumulator, one electric heating element can be used as both a liquid level detection sensor and a refrigerant temperature sensor. In addition, the system configuration can be simplified to reduce costs and improve reliability.

In the above configuration, the electric heating element may be provided by being inserted from the outside into a recess provided in the pressure vessel and immersing from the outside to the inside of the pressure vessel.
According to this configuration, since the electric heating element can be attached and detached from the outside of the accumulator pressure vessel, for example, when performing maintenance to replace the electric heating element, the refrigerant of the entire refrigeration cycle system is not drained. The maintenance can be greatly improved.

Moreover, since the surface of the electric heating element is immersed in the gas-liquid refrigerant in a wide area through the recess of the pressure vessel, compared to a case where the electric heating element is simply attached to the side wall of the pressure vessel, The heat exchange speed between the electric heating element and the gas-liquid refrigerant can be increased.
As a result, when the liquid level of the liquid refrigerant increases in the pressure vessel and reaches the height of the electric heating element, the time until the power consumption of the electric heating element increases is shortened. For this reason, the time until the start of the protective operation by the control unit is also shortened. Therefore, it is possible to improve control responsiveness, prevent liquid back, and reliably protect the compressor.

  That is, the liquid back prevention method according to the present invention provides a maximum storage amount of the liquid refrigerant in an accumulator that separates the gas-liquid mixed refrigerant that flows back from the evaporator to the compressor into a liquid refrigerant and a vaporized refrigerant in the refrigeration cycle system. An electric heating element is provided at the liquid level, and the change in the amount of heat generated by the electric heating element is detected by a change in the current value to detect that the liquid refrigerant has reached the maximum allowable liquid level. To do.

  According to the above liquid back prevention method, a liquid refrigerant is provided inside the accumulator by a simple method of providing an electric heating element at the liquid level that is the maximum storage amount of the accumulator and monitoring the change in power consumption. It is possible to reliably detect that the liquid level has risen and to perform an operation to lower the liquid level to prevent liquid back and protect the compressor.

  As described above, according to the refrigeration cycle system and the liquid back prevention method according to the present invention, the liquid back is prevented and the compressor is protected by a simple, inexpensive, reliable, and maintainable configuration. be able to.

It is a circuit diagram which shows the basic composition of the air conditioning air conditioning system which concerns on embodiment of this invention. It is a longitudinal cross-sectional view of the accumulator which shows 1st Embodiment of this invention. It is a graph which shows the example of a change of the electric current value in an electric heating element. It is a longitudinal cross-sectional view of the accumulator which shows 2nd Embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a circuit diagram showing a basic configuration of an air conditioning / air conditioning system 1 (an example of a refrigeration cycle system) according to an embodiment of the present invention. This air-conditioning / air-conditioning system 1 is a heat pump air-conditioning / air-conditioning system applied to a residence, office, store, etc., and generally includes an outdoor unit 2 installed outdoors and an indoor unit 3 installed indoors. It has a typical structure.

  The outdoor unit 2 functions as a sealed electric compressor 4 (compressor) that compresses the refrigerant, a four-way valve 5 that controls the flow of the refrigerant, and a condenser that condenses the refrigerant during cooling operation. An outdoor heat exchanger 6 that functions as an evaporator that evaporates the refrigerant during operation, a receiver dryer 7 that removes moisture in the refrigerant, and an expansion valve 8 that expands the refrigerant are connected in this order by a pipe member 10. ing. A pipe member 11 extends from the expansion valve 8 and is connected to the indoor unit 3.

  An accumulator 12 is connected to the suction side of the electric compressor 4, and a cooling fan 13 is provided in the outdoor heat exchanger 6. Furthermore, the control part 14 which controls this air conditioning air conditioning system 1 is installed. The control unit 14 controls the electric compressor 4, the four-way valve 5, and the expansion valve 8 by sending control signals S1, S2, and S3, respectively.

  On the other hand, the indoor unit 3 includes an indoor heat exchanger 15 that functions as an evaporator that evaporates the refrigerant during the cooling operation and functions as a condenser that condenses the refrigerant during the heating operation. ing. A pipe member 11 extending from the outdoor unit 2 is connected to one end of the indoor heat exchanger 15, and a pipe member 17 extending from the other end of the indoor heat exchanger 15 is connected to the four-way valve 5 in the outdoor unit 2. And connected to the accumulator 12.

  When the four-way valve 5 is at the angle shown in FIG. 1, the air-conditioning / air-conditioning system 1 is in a cooling operation mode, and the high-temperature and high-pressure refrigerant that is compressed and discharged by the electric compressor 4 passes through the four-way valve 5 to generate outdoor heat. It flows into the exchanger 6 and becomes a liquid phase by being cooled by exchanging heat with the outside air by the cooling fan 13. Next, after moisture is removed by the receiver dryer 7, it is expanded by the expansion valve 8 and set to an appropriate pressure, and then flows through the pipe member 11 to the indoor heat exchanger 15 of the indoor unit 3, where it is vaporized. As a result, the indoor heat exchanger 15 is deprived of heat, and at the same time, the blower fan 16 is operated, whereby the indoor air is cooled by the indoor heat exchanger 15 and blown out into the room, and is supplied to the room for cooling. The refrigerant evaporated in the indoor heat exchanger 15 is sucked into the electric compressor 4 again through the pipe line member 17, the four-way valve 5, and the accumulator 12.

  When the four-way valve 5 rotates 90 degrees clockwise or counterclockwise from the angle shown in FIG. 1, the air conditioning / air conditioning system 1 enters the heating operation mode. That is, the refrigerant compressed by the electric compressor 4 flows into the indoor heat exchanger 15 through the four-way valve 5 and the pipe line member 17, where it is cooled by being exchanged with the indoor air by the blower fan 16, and is cooled in the liquid phase. It becomes a shape. At this time, the air heated by the heat exchange with the refrigerant is blown into the room by the blower fan 16 and is used for room heating. The refrigerant that has passed through the indoor heat exchanger 15 and has become a liquid phase is expanded by the expansion valve 8 and set to an appropriate pressure, and then the moisture is removed by the receiver dryer 7 before the outdoor heat exchanger. 6, where heat is released to the outside by vaporization, and is sucked into the electric compressor 4 again through the accumulator 12.

[First Embodiment]
FIG. 2 is a longitudinal sectional view showing the first embodiment of the accumulator 12.
The accumulator 12 temporarily stores the gas-liquid mixed refrigerant that recirculates from the outdoor heat exchanger 6 or the indoor heat exchanger 15 to the electric compressor 4 and performs gas-liquid separation by gravity inside, and only the vaporized refrigerant is supplied to the electric compressor 4. And a predetermined amount of liquid refrigerant R is stored. The accumulator 12 includes a tank-shaped pressure vessel 20 having a predetermined internal volume, a pipe-shaped refrigerant inflow portion 21 and a refrigerant outflow portion 22 provided on the top of the pressure vessel 20, an electric heating element 23, A temperature sensor 24 is provided.

  The refrigerant inflow portion 21 is a short pipe member bent at a right angle, an inlet opening 21 a provided at one end thereof is connected to the four-way valve 5, and an outlet opening 21 b provided at the other end is a top plate of the pressure vessel 20. Is opened downward in the upper part of the pressure vessel 20.

  The refrigerant outflow portion 22 is a U-shaped pipe member that is longer than the refrigerant inflow portion 21. An inlet opening 22 a provided at one end of the refrigerant outflow portion 22 opens upward inside the pressure vessel 20, and the other end is the pressure vessel 20. The outlet opening 22 b provided at the other end is connected to the electric compressor 4. An intermediate portion of the refrigerant outflow portion 22 is deeply curved in a U shape so as to protrude downward inside the pressure vessel 20, and the curved portion is located near the bottom of the pressure vessel 20.

  If the height of the outlet opening 21b of the refrigerant inflow portion 21 inside the pressure vessel 20 is H1, the height H2 of the inlet opening 22a of the refrigerant outflow portion 22 is set lower than H1. Further, the height H3 of the electric heating element 23 and the temperature sensor 24 is set to be lower than H2. That is, H1> H2> H3. The installation height H3 of the electric heating element 23 and the temperature sensor 24 is the maximum allowable liquid level of the liquid refrigerant R inside the pressure vessel 20.

  In this accumulator 12, the gas-liquid mixed refrigerant that recirculates from the outdoor heat exchanger 6 or the indoor heat exchanger 15 to the electric compressor 4 flows from the inlet opening 21a of the refrigerant inflow portion 21 and flows down from the outlet opening 21b. Into the pressure vessel 20. The gas-liquid mixed refrigerant is gas-liquid separated by gravity, and the liquid refrigerant R corresponding to the liquid phase is stored in the pressure vessel 20 together with the lubricating oil. Thus, the liquid level R4 of the liquid refrigerant R stored in the pressure vessel 20 is adjusted to be lower than the height H3 of the electric heating element 23 and the temperature sensor 24 during normal operation of the air conditioning / air conditioning system 1. Is done. Therefore, during normal operation, the inlet opening 22a of the refrigerant outflow portion 22 sufficiently protrudes above the liquid level of the liquid refrigerant R.

  The vaporized refrigerant separated from the gas-liquid mixed refrigerant enters the refrigerant outflow portion 22 through the inlet opening 22a, exits through the outlet opening 22b, and is sucked into the electric compressor 4. Thus, the liquid refrigerant R is stored in the pressure vessel 20 and only the vaporized refrigerant is sucked into the electric compressor 4, and the liquid refrigerant R is not sucked into the electric compressor 4.

  The side wall 20a that forms the side surface of the pressure vessel 20 is formed with a recess 20b that is recessed from the outside of the pressure vessel 20 to the inside. The recess 20b is formed, for example, by forming a through hole in the side wall 20a, and inserting and welding a predetermined length of a pipe member 20c having a closed end into the through hole. An electric heating element 23 and a temperature sensor 24 are inserted into the recess 20b from the outside of the pressure vessel 20.

  Since the temperature sensor 24 is not an essential element for carrying out the present invention, it can be omitted. Alternatively, a pressure sensor may be provided together with the temperature sensor 24. By providing the pressure sensor, the pressure in the pressure vessel 20 is detected, and the electric heating element 23 is calculated from the difference between the saturated evaporation temperature of the liquid refrigerant R under the pressure and the actual temperature measured by the temperature sensor 24. It can be determined to some extent whether or not the liquid refrigerant R exists near the installation height H3 of the temperature sensor 24.

  During operation of the air conditioning / air conditioning system 1 configured as described above, electric power is supplied to the electric heating element 23 from the control unit 14 (or from a power supply unit (not shown)) via the harness 23a. At this time, the voltage applied to the electric heating element 23 increases the temperature of the vaporized refrigerant by the heat generated by the electric heating element 23 when the electric heating element 23 is adjacent to the vaporized refrigerant. When it is adjacent to R, it is set to a constant voltage such that the temperature of the electric heating element 23 is lowered by the cold heat of the liquid refrigerant R.

  That is, as shown in FIG. 2, when the liquid level of the liquid refrigerant R stored in the pressure vessel 20 is lower than the height H3 of the electric heating element 23, the electric heating element 23 is adjacent to the vaporized refrigerant. Thus, the vaporized refrigerant in the pressure vessel 20 is warmed by the heat generated by the electric heating element 23. Further, when the liquid level of the liquid refrigerant R reaches the height H3 of the electric heating element 23, the electric heating element 23 is adjacent to the liquid refrigerant R, and the liquid refrigerant having a larger specific heat than the vaporized refrigerant. The electric heating element 23 is cooled by the R heat.

  The control unit 14 detects the change in the heat generation amount of the electric heating element 23 as described above based on the change in the power consumption amount, and when the power consumption amount reaches a predetermined threshold A as shown in FIG. Then, a protection operation for reducing the liquid level of the liquid refrigerant R is performed.

  For example, when the time T1 has elapsed from the start of operation and the liquid level of the liquid refrigerant R in the pressure vessel 20 of the accumulator 12 increases and reaches the height H3 of the electric heating element 23, a constant voltage is supplied. The heating value of the electric heating element 23, that is, the current value starts to rise from the steady value N. This is because the amount of current required to cause the electric heating element 23 to generate heat is greater when it is adjacent to the liquid refrigerant R having a higher specific heat than when it is adjacent to the vaporized refrigerant having a lower specific heat. Because. Therefore, it is possible to specify whether the electric heating element 23 is adjacent to the vaporized refrigerant or the liquid refrigerant R by monitoring the current amount of the electric heating element 23 by the control unit 14. it can.

  When the current value reaches a predetermined threshold A at time T2, the control unit 14 starts the protective operation. Specifically, measures such as reducing or temporarily stopping the rotation speed of the electric compressor 4 or reducing the opening degree of the expansion valve 8 are taken (these are appropriately selected according to the operating conditions), The liquid level of the liquid refrigerant R in the accumulator 12 is lowered. Thereby, liquid back can be prevented and the electric compressor 4 can be protected.

Thereafter, when the current value decreases past the peak value and falls to the threshold value B lower than the threshold value A at time T3, the control unit 14 ends the protection operation. As described above, the threshold B for ending the protective operation is set lower than the threshold A for starting the protective operation because the start and end of the protective operation are performed when the current value fluctuates in the vicinity of the threshold A. This is to prevent frequent repetition (hysteresis).
In FIG. 3, the liquid level of the liquid refrigerant R decreases to the initial value and the current value returns to the steady value N at time T <b> 4. However, during actual operation, the current value is between the steady value N and the threshold value A. Move up and down.

  As described above, the air conditioning / air conditioning system 1 according to the present embodiment performs gas-liquid separation of the gas-liquid mixed refrigerant sucked into the electric compressor 4 and causes the electric compressor 4 to suck only the vaporized refrigerant into the liquid refrigerant in the accumulator 12. The electric heating element 23 is provided at the position of the maximum allowable liquid level H3 of R, and the control unit 14 detects a change in the amount of heat generated by the electric heating element 23 as a change in the power consumption. When A is reached, the protection operation for lowering the liquid level is performed.

  In this configuration, since the electric heating element 23 is not a sensor, it can be implemented more simply and at a lower cost than the conventional configuration in which the accumulator 12 is provided with a liquid level detector. Therefore, the reliability of the air conditioning / air conditioning system 1 can be remarkably improved. Therefore, the electric compressor 4 can be protected by preventing liquid back from the accumulator 12 with a simple, inexpensive and highly reliable configuration.

  The voltage applied to the electric heating element 23 increases the temperature of the vaporized refrigerant by the heat generated by the electric heating element 23 when the electric heating element 23 is adjacent to the vaporized refrigerant. When adjacent to R, the temperature of the electric heating element 23 is set in a range where the temperature of the electric heating element 23 decreases due to the cold heat of the liquid refrigerant R.

  Thereby, the calorific value of the electric heating element 23 can warm the vaporized refrigerant, but cannot warm the liquid refrigerant. Conversely, the calorific value is so weak that the electric heating element 23 is cooled. . Even in this case, the vaporized refrigerant and the liquid refrigerant R can be sufficiently discriminated, so that an increase in the liquid level of the liquid refrigerant R can be detected with a minimum amount of electric power, and liquid back can be prevented.

  Moreover, since the amount of heat generated by the electric heating element 23 is kept to the minimum necessary, the gas-liquid refrigerant in the accumulator 12 is not heated more than necessary. Therefore, it is possible to prevent the efficiency of the air-conditioning / air-conditioning system 1 from being reduced due to an excessive degree of superheat being imparted to the refrigerant by the electric heating element 23.

The electric heating element 23 is provided on the side wall 20a of the accumulator 12 (pressure vessel 20) and inserted from the outside into a recess 20b that immerses from the outside to the inside of the pressure vessel 20. .
According to this structure, since the electric heating element 23 can be attached and detached from the outside of the pressure vessel 20, for example, when maintenance for exchanging the electric heating element 23 is performed, the refrigerant of the entire heating and cooling air conditioning system 1 is used. There is no need to remove it, and the maintainability can be greatly improved.

Moreover, since the surface of the electric heating element 23 is immersed in the gas-liquid refrigerant over a wide area via the recess 20b of the pressure vessel 20, the electric heating element 23 is simply attached to the side wall 20a of the pressure vessel 20. Compared to such a case, the heat exchange rate between the electric heating element 23 and the gas-liquid refrigerant can be increased.
As a result, when the liquid level of the liquid refrigerant R increases in the pressure vessel 20 and reaches the height H3 of the electric heating element 23, the time until the power consumption of the electric heating element 23 increases (see FIG. (Time from T1 to T2 in 3) is shortened. For this reason, the time until the start of the protective operation by the control unit 14 is also shortened. Therefore, the control responsiveness can be improved to prevent the liquid back, and the electric compressor 4 can be reliably protected.

[Second Embodiment]
FIG. 4 is a longitudinal sectional view showing a second embodiment of the accumulator.
The difference between the accumulator 12A and the accumulator 12 of the first embodiment shown in FIG. 2 is that the electric heating element 23A is a resistance temperature detector that can also be used as a temperature sensor. This is two points that the temperature sensor 24 shown is not provided. Since the other components are the same as those of the accumulator 12 shown in FIG.

In this way, by using a resistance temperature detector as the electric heating element 23A, by supplying a constant voltage to the electric heating element 23A as in the case of the first embodiment, the electric heating element 23A is liquidated. It can be used as a liquid level detection sensor for the refrigerant R.
Further, in the case of an air conditioning and air conditioning system in which a refrigerant temperature sensor is provided in the accumulator 12A, temperature data detected by the electric heating element 23A can be sent to the control unit 14 to detect the temperature of the refrigerant.
That is, one electric heating element 23A can be used as both a liquid level detection sensor for liquid refrigerant R and a refrigerant temperature sensor, simplifying the system configuration and reducing costs and improving reliability. Can be planned.

  As described above, according to the refrigeration cycle system and the liquid back prevention method according to the present embodiment, a simple, inexpensive, reliable, and maintainable configuration prevents liquid back and allows the compressor to be installed. Can be protected.

It should be noted that the present invention is not limited to the configuration of the above-described embodiment, and can be appropriately changed or improved. Embodiments with such changes and improvements are also included in the scope of the right of the present invention. And
For example, the recess 20b into which the electric heating elements 23 and 23A are inserted is not necessarily provided on the side wall 20a of the pressure vessel 20, and is, for example, suspended from the top plate of the pressure vessel 20 toward the inside of the pressure vessel 20. The recess 20b may be formed, and the electric heating elements 23 and 23A may be inserted therein.

1 Air conditioning system (refrigeration cycle system)
2 Outdoor unit 3 Indoor unit 4 Electric compressor (compressor)
5 Four-way valve 6 Outdoor heat exchanger (condenser)
7 Receiver dryer 8 Expansion valve 12, 12A Accumulator 14 Control unit 15 Indoor heat exchanger (evaporator)
20 Pressure vessel 20a Pressure vessel side wall 20b Recess 20c Pipe material 21 Refrigerant inflow portion 22 Refrigerant outflow portion 23 Electric heating element 23A Electric heating element (resistance temperature detector)
A Threshold value H3 Maximum allowable liquid level R Liquid refrigerant

Claims (5)

A compressor for compressing the refrigerant;
A condenser for condensing the compressed refrigerant discharged from the compressor;
An expansion valve for expanding the compressed refrigerant condensed in the condenser;
An evaporator for vaporizing the compressed refrigerant expanded by the expansion valve;
An accumulator that temporarily stores a gas-liquid mixed refrigerant that is refluxed from the evaporator to the compressor, separates the gas-liquid mixed liquid into a liquid refrigerant and a vaporized refrigerant, and sucks only the vaporized refrigerant into the compressor. ,
The accumulator is
A pressure vessel;
A refrigerant inflow portion for allowing the gas-liquid mixed refrigerant to flow into the pressure vessel;
A refrigerant outflow portion for flowing the vaporized refrigerant toward the compressor;
An electric heating element provided at a position of the highest allowable liquid level level of the liquid refrigerant in the pressure vessel.
Further, a protective operation for detecting a change in the amount of heat generated by the electric heating element based on a change in power consumption, and lowering the liquid level of the liquid refrigerant when the power consumption reaches a predetermined threshold value. A refrigeration cycle system, comprising:   When the electric heating element is adjacent to the vaporized refrigerant, the voltage applied to the electric heating element raises the temperature of the vaporized refrigerant due to the heat generated by the electric heating element, and the electric heating element 2. The refrigeration cycle system according to claim 1, wherein the refrigeration cycle system is set in a range in which the temperature of the electric heating element is lowered by the cold heat of the liquid refrigerant when adjacent to the refrigerant.   The refrigeration cycle system according to claim 1, wherein the electric heating element is a resistance temperature detector that can also be used as a temperature sensor.   4. The electric heating element according to claim 1, wherein the electric heating element is provided by being inserted from the outside into a recess provided in the pressure vessel and immersing from the outside to the inside of the pressure vessel. Refrigeration cycle system.   In the refrigeration cycle system, an electric heating element is provided at the liquid surface level at which the maximum storage amount of the liquid refrigerant of the accumulator that separates the gas-liquid mixed refrigerant flowing back from the evaporator to the compressor into liquid refrigerant and vaporized refrigerant A liquid back prevention method, wherein a change in the amount of heat generated by the electric heating element is detected by a change in a current value, and the liquid level of the liquid refrigerant reaches a maximum allowable liquid level.

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