JP5908177B1 - Refrigeration cycle apparatus, air conditioner, and control method for refrigeration cycle apparatus - Google Patents

Abstract

A refrigeration cycle apparatus with improved reliability and versatility is obtained. The refrigeration cycle apparatus includes a refrigerant circulation circuit 10 in which a compressor 11, a condenser 12, a first expansion device 13, an evaporator 14, and an accumulator 15 are connected in an annular shape, and a second expansion device in the middle. 21, a bypass passage 20 for bypassing the refrigerant flowing through the portion between the condenser 12 of the refrigerant circulation circuit 10 and the first throttling device 13 to the compressor 11, the condenser 12 of the refrigerant circulation circuit 10, Depending on the amount of refrigerant in the accumulator 15, the internal heat exchanger 30 that exchanges heat between the refrigerant flowing between the first expansion device 13 and the refrigerant that has passed through the second expansion device 21 of the bypass flow path 20. And control means for changing the amount of liquid refrigerant flowing into the compressor 11 via the bypass flow path 20.

Description

  The present invention relates to a refrigeration cycle apparatus, an air conditioner, and a control method for a refrigeration cycle apparatus.

  As a conventional refrigeration cycle apparatus, for example, a compressor, a condenser, a throttling device, an evaporator, and an accumulator are provided with a refrigerant circulation circuit connected in an annular shape, and the outlet pipes of the accumulator have different heights. Some of which are formed with a plurality of small holes located at. The accumulator stores excess refrigerant in the refrigerant circuit. The liquid refrigerant contained in the refrigerant accumulated in the accumulator flows into the outlet pipe through a plurality of small holes and is sucked into the compressor together with the refrigerant (see, for example, Patent Document 1).

JP 2013-124800 A (paragraph [0027] to paragraph [0050], FIG. 1 etc.)

  In the conventional refrigeration cycle apparatus, the amount of liquid refrigerant sucked into the compressor changes depending on the inner diameter of the small hole, the height at which the small hole is formed, and the like. Therefore, when a small hole design error occurs, or when the refrigeration cycle device enters an operating state that is not assumed at the time of design, excessive liquid refrigerant returns to the compressor, increasing the frequency of compressor failure. As a result, there is a problem that reliability is lowered. In addition, it is necessary to design an accumulator for each model, and there is a problem that versatility is low.

  The present invention has been made against the background described above, and provides a refrigeration cycle apparatus with improved reliability and versatility. Moreover, such an air conditioning apparatus is obtained. Moreover, the control method of such a refrigeration cycle apparatus is obtained.

The refrigeration cycle apparatus according to the present invention includes a refrigerant circulation circuit in which a compressor, a condenser, a first throttle device, an evaporator, and an accumulator are connected in an annular shape, and a second throttle device is connected in the middle. A bypass flow path for bypassing the refrigerant flowing through a portion of the refrigerant circuit between the condenser and the first throttle device to the compressor, the condenser of the refrigerant circuit, and the first throttle device An internal heat exchanger that exchanges heat between the refrigerant flowing between the refrigerant and the refrigerant that has passed through the second expansion device of the bypass flow path, and the amount of refrigerant enclosed in the refrigerant circulation circuit The refrigerant amount in the accumulator is estimated by subtracting the refrigerant amount in the condenser and the refrigerant amount in the evaporator, and the opening of the second expansion device is controlled according to the estimated refrigerant amount in the accumulator. The bypass channel And control means for changing the amount of liquid refrigerant flowing into the compressor, the control means when the amount of refrigerant in the accumulator is large compared to when the amount of refrigerant in the accumulator is small. Thus, the frequency of the compressor is lowered.

  In the refrigeration cycle apparatus according to the present invention, the control means changes the amount of the liquid refrigerant flowing into the compressor via the bypass flow path according to the refrigerant amount in the accumulator. Therefore, it is possible to control the amount of liquid refrigerant flowing into the compressor to suppress excessive liquid refrigerant from flowing into the compressor, thereby improving the reliability. Further, since the amount of liquid refrigerant flowing into the compressor can be controlled, the accumulator can be used for a plurality of models, and versatility is improved.

It is a figure for demonstrating the structure of the air conditioning apparatus which concerns on Embodiment 1. FIG. It is a Mollier diagram of the refrigeration cycle in the high efficiency operation mode of the air-conditioning apparatus according to Embodiment 1. It is a Mollier diagram of the refrigeration cycle in the high pressure suppression operation mode of the air-conditioning apparatus according to Embodiment 1. It is a figure for demonstrating the relationship between the flow rate of a refrigerant | coolant, and the thickness of a liquid film. It is a figure for demonstrating the structure of the air conditioning apparatus which concerns on Embodiment 2. FIG. It is a figure for demonstrating the structure of the air conditioning apparatus which concerns on Embodiment 3. FIG. It is a Mollier diagram in case a refrigerant | coolant is HFO1234yf or HFO1234ze.

Hereinafter, a refrigeration cycle apparatus according to the present invention will be described with reference to the drawings.
In the following, the case where the refrigeration cycle apparatus according to the present invention is an air conditioner is described. However, the present invention is not limited to such a case, and the refrigeration cycle apparatus according to the present invention is not an air conditioner. Other refrigeration cycle apparatuses may be used. In the following, the case where the refrigeration cycle apparatus according to the present invention is an air conditioner that performs only heating will be described. However, the refrigeration cycle apparatus according to the present invention is not limited to such a case. And an air conditioner that switches between cooling and cooling. Moreover, the structure, operation | movement, etc. which are demonstrated below are only examples, and the refrigeration cycle apparatus which concerns on this invention is not limited to the case where it is such a structure, operation | movement, etc. In addition, detailed descriptions of the configuration, operation, and the like are appropriately simplified or omitted. In addition, overlapping or similar descriptions are appropriately simplified or omitted.

Embodiment 1 FIG.
Below, the air conditioning apparatus which concerns on Embodiment 1 is demonstrated.
<Configuration of air conditioner>
1 is a diagram for explaining a configuration of an air-conditioning apparatus according to Embodiment 1. FIG.
As shown in FIG. 1, an air conditioner 100 includes a refrigerant circulation circuit 10 in which a compressor 11, a condenser 12, a first expansion device 13, an evaporator 14, and an accumulator 15 are connected in an annular shape. A bypass passage 20 for bypassing the refrigerant flowing through the portion between the condenser 12 and the first throttle device 13 of the refrigerant circulation circuit 10 to the compressor 11, An internal heat exchanger 30 for exchanging heat between the refrigerant flowing through the portion between the condenser 12 of the circulation circuit 10 and the first expansion device 13 and the refrigerant that has passed through the second expansion device 21 of the bypass flow path 20; A refrigeration cycle 1 is provided. The downstream side of the bypass flow path 20 is connected to a portion of the refrigerant circulation circuit 10 between the accumulator 15 and the compressor 11.

  For example, the condenser 12 exchanges heat between the refrigerant in the refrigerant circuit 10 and the water in the water circuit 40. The water circuit 40 supplies hot water to a heat exchanger or the like of the indoor unit using the pump 41 as a drive source.

  The air conditioning apparatus 100 includes a control unit 50. The control unit 50 governs the operation of the air conditioning apparatus 100. The control unit 50 includes a compressor 11, a first throttle device 13, a second throttle device 21, a pump 41, a discharge pressure sensor 51 that detects the pressure of refrigerant on the discharge side of the compressor 11, and a suction side of the compressor 11. An intake pressure sensor 52 that detects the pressure of the refrigerant, an internal heat exchanger outlet temperature sensor 53 that detects the temperature of the refrigerant on the outlet side of the internal heat exchanger 30, an outside air temperature sensor 54 that detects the outside air temperature, and the like are connected. All or part of the control unit 50 may be configured by a microcomputer, a microprocessor unit, or the like, may be configured by an updatable component such as firmware, and is executed by a command from the CPU or the like. It may be a program module or the like. The control unit 50 corresponds to the “control unit” in the present invention.

  When the air conditioner 100 switches between heating and cooling, for example, a flow path switching device such as a four-way valve is connected to the discharge side of the compressor 11 of the refrigerant circulation circuit 10, and the control unit The flow direction of the refrigerant in the refrigerant circuit 10 is reversed by switching the flow path of the flow path switching device by 50.

<Operation of air conditioner>
The controller 50 switches between a high efficiency operation mode, a high pressure suppression operation mode, and a liquid return suppression operation mode.

[High efficiency operation mode]
FIG. 2 is a Mollier diagram of the refrigeration cycle in the high efficiency operation mode of the air-conditioning apparatus according to Embodiment 1.
In the refrigeration cycle 1 in the high-efficiency operation mode, as shown in FIG. 2, the refrigerant discharged from the compressor 11 is in a high-pressure gas state (point A in the figure) and flows into the condenser 12. The refrigerant that has passed through the condenser 12 becomes a supercooled liquid state (point B in the figure) and flows into the internal heat exchanger 30. The refrigerant that has passed through the internal heat exchanger 30 becomes a further supercooled liquid state (point C in the figure) and flows into the first expansion device 13. The refrigerant decompressed by the first expansion device 13 enters a low-pressure gas-liquid two-phase state (point D in the figure) and flows into the evaporator 14. The refrigerant that has passed through the evaporator 14 is in a superheated gas state (point E in the figure), passes through the accumulator 15, and is then sucked into the compressor 11. In addition, the refrigerant that has passed through the condenser 12 and has flowed into the bypass flow path 20 flows into the second expansion device 21. The refrigerant decompressed by the second expansion device 21 enters a low-pressure gas-liquid two-phase state (point F in the figure) and flows into the internal heat exchanger 30. The refrigerant that has passed through the internal heat exchanger 30 is sucked into the compressor 11 in a gas-liquid two-phase state (point G in the figure).

  That is, the control unit 50 adjusts the opening degree of the first expansion device 13 to an opening degree at which the degree of supercooling in the condenser 12 is increased and the COP (coefficient of performance) is maximized. Further, the control unit 50 adjusts the opening degree of the second expansion device 21 to an opening degree at which excessive liquid refrigerant does not return to the compressor 11. The amount of refrigerant sealed in the refrigeration cycle 1 may be an amount that does not allow liquid refrigerant to accumulate in the accumulator 15 under the condition that COP (coefficient of performance) is maximized. When the temperature of the refrigerant on the discharge side of the compressor 11 rises excessively, the control unit 50 may adjust the opening of the second expansion device 21 to an opening that keeps the temperature within a predetermined range.

[High-pressure suppression operation mode]
FIG. 3 is a Mollier diagram of the refrigeration cycle in the high-pressure suppression operation mode of the air-conditioning apparatus according to Embodiment 1.
In the refrigeration cycle 1 in the high-pressure suppression operation mode, as shown in FIG. 3, the refrigerant discharged from the compressor 11 is in a high-pressure gas state (point A in the figure) and flows into the condenser 12. The refrigerant that has passed through the condenser 12 enters a gas-liquid two-phase state (point B in the figure) and flows into the internal heat exchanger 30. The refrigerant that has passed through the internal heat exchanger 30 becomes a supercooled liquid state (point C in the figure) and flows into the first expansion device 13. The refrigerant decompressed by the first expansion device 13 enters a low-pressure gas-liquid two-phase state (point D in the figure) and flows into the evaporator 14. The refrigerant that has passed through the evaporator 14 is in a superheated gas state (point E in the figure), passes through the accumulator 15, and is then sucked into the compressor 11. In addition, the refrigerant that has passed through the condenser 12 and has flowed into the bypass flow path 20 flows into the second expansion device 21. The refrigerant decompressed by the second expansion device 21 enters a low-pressure gas-liquid two-phase state (point F in the figure) and flows into the internal heat exchanger 30. The refrigerant that has passed through the internal heat exchanger 30 is sucked into the compressor 11 in a gas-liquid two-phase state (point G in the figure).

  That is, the control unit 50 sets the opening of the first expansion device 13 to an opening at which the degree of supercooling in the condenser 12 is not provided, that is, an opening at which the refrigerant enters a gas-liquid two-phase state at the outlet of the condenser 12. It adjusts and it adjusts so that the high voltage | pressure side pressure of the refrigerating cycle 1 may become below a predetermined pressure. Further, in order to prevent the controllability from deteriorating due to the refrigerant in the gas-liquid two-phase state flowing into the first expansion device 13, the control unit 50 sets the opening degree of the second expansion device 21 to the internal heat exchanger. 30, the refrigerant cooled by the refrigerant that has passed through the second expansion device 21 of the bypass channel 20 and flowing into the first expansion device 13 is adjusted to an opening degree that becomes a liquid refrigerant. When the refrigerant enters a gas-liquid two-phase state at the outlet of the condenser 12, the amount of refrigerant flowing other than the accumulator 15 of the refrigeration cycle 1 is reduced, and excess refrigerant accumulates in the accumulator 15.

[Liquid return suppression operation mode]
If the refrigerant is excessively accumulated in the accumulator 15 in the high-pressure suppression operation mode, the refrigerating machine oil accumulated in the accumulator 15 is diluted with the refrigerant to have a low concentration, and the amount of liquid refrigerant flowing out from the accumulator 15 increases. The reliability of the compressor 11 is reduced. The refrigeration oil has functions such as lubrication of each part of the compressor 11 and sealing of the compression part of the compressor 11. Therefore, the control unit 50 estimates the refrigerant amount in the accumulator 15 and shifts to the liquid return suppression operation mode before the refrigerant amount in the accumulator 15 becomes too large. A method for estimating the amount of refrigerant in the accumulator 15 will be described later.

  The control unit 50 shifts to the liquid return suppression operation mode, and adjusts the opening degree of the second expansion device 21 to an opening degree at which the refrigerant is in a gas state (overheated gas state) at the outlet of the internal heat exchanger 30. To do. That is, the control unit 50 reduces the opening of the second expansion device 21 when the amount of refrigerant in the accumulator 15 is large, compared with the case where the amount of refrigerant in the accumulator 15 is small, The amount of liquid refrigerant flowing into the compressor 11 is reduced.

FIG. 4 is a diagram for explaining the relationship between the flow rate of the refrigerant and the thickness of the liquid film.
In addition, the control unit 50 still reduces the frequency of the compressor 11 and determines the opening degree of the first expansion device 13 to the outlet of the evaporator 14 when it is determined that the amount of refrigerant in the accumulator 15 is too large. In step 1, the opening is adjusted to such an extent that the refrigerant does not enter the superheated gas state. In other words, the control unit 50 reduces the frequency of the compressor 11 when the refrigerant amount in the accumulator 15 is large, compared with the case where the refrigerant amount in the accumulator 15 is small, and the liquid refrigerant flowing into the accumulator 15. Reduce the amount. As shown in FIG. 4, when the frequency of the compressor 11 is lowered, the flow rate of the refrigerant is reduced, and the shearing force generated at the location where the refrigerant is in a gas-liquid two-phase state is reduced. The thickness of the liquid film to be formed increases. Therefore, the amount of refrigerant stored in the evaporator 14 increases, and the amount of liquid refrigerant flowing into the accumulator 15 decreases.

(Method for estimating the amount of refrigerant in the accumulator)
First, the control unit 50 acquires the temperature of the refrigerant at the outlet of the internal heat exchanger 30 from the detection result of the internal heat exchanger outlet temperature sensor 53.

  Next, the control unit 50 acquires the refrigerant pressure at the outlet of the internal heat exchanger 30 from the detection result of the discharge pressure sensor 51. Instead of the detection result of the discharge pressure sensor 51, the detection result of the temperature sensor that detects the temperature of the refrigerant at the location where the refrigerant of the condenser 12 is in a two-phase state is used, and the saturation pressure obtained from the detection result of the temperature sensor is May be acquired. When the condenser 12 exchanges heat between the refrigerant in the refrigerant circuit 10 and the water in the water circuit 40, the condensation temperature of the refrigeration cycle 1 and the temperature of water flowing out of the condenser 12 are substantially equal. Therefore, instead of the detection result of the discharge pressure sensor 51, the detection result of the temperature sensor that detects the temperature of the water flowing out of the condenser 12 is used, and the saturation pressure obtained from the detection result of the temperature sensor is acquired. May be.

  Next, the control unit 50 acquires the pressure of the refrigerant on the suction side of the compressor 11 from the detection result of the suction pressure sensor 52. Instead of the detection result of the suction pressure sensor 52, the detection result of the temperature sensor that detects the temperature of the refrigerant at the location where the refrigerant of the evaporator 14 is in a two-phase state is used, and the saturation pressure obtained from the detection result of the temperature sensor is May be acquired. When the refrigerant is always present in the accumulator 15, the refrigerant at the outlet of the accumulator 15 is in a gas-liquid two-phase state. Therefore, instead of the detection result of the suction pressure sensor 52, the temperature of the refrigerant at the outlet of the accumulator 15. The detection result of the temperature sensor for detecting the temperature sensor may be used, and the saturation pressure obtained from the detection result of the temperature sensor may be acquired.

  Next, the control unit 50 estimates the exchange heat quantity Qa in the internal heat exchanger 30. The heat exchange amount Q of the heat exchanger is generally expressed by the following equation (1), where A is the heat transfer area, K is the heat transfer coefficient, and ΔT is the temperature difference. The heat transfer area A is determined from the specifications of the internal heat exchanger 30. The temperature difference ΔT is determined from the refrigerant temperature at the outlet of the internal heat exchanger 30 and the saturation temperature obtained from the refrigerant pressure on the suction side of the compressor 11.

[Equation 1]
Q = A × K × ΔT (1)

  The heat transfer coefficient K is proportional to the Reynolds number Re. The Reynolds number Re is generally expressed by the following equation (2), where u is a flow velocity, d is a representative diameter, and v is a kinematic viscosity coefficient. In the internal heat exchanger 30, heat is exchanged between the refrigerant that has passed through the condenser 12 of the refrigerant circulation circuit 10 and the refrigerant that has passed through the second expansion device 21 of the bypass flow path 20, so that the refrigerant circulation of the refrigerant circulation circuit 10 The heat transfer coefficient K can be estimated using the amount Gra, the refrigerant circulation amount Grab of the bypass passage 20, and the relationship between the Reynolds number Re acquired in advance and the characteristics of the internal heat exchanger 30. The refrigerant circulation amount Gra of the refrigerant circuit 10 can be estimated from the refrigerant pressure on the suction side of the compressor 11 and the frequency f of the compressor 11, the refrigerant density is ρs, the stroke volume of the compressor 11 is V, When the volume efficiency of the compressor 11 is ηv, it is expressed by the following equation (3). In addition, the refrigerant circulation amount Grb in the bypass flow path 20 includes the Cv value of the second expansion device 21 obtained from the opening of the second expansion device 21, the differential pressure ΔP before and after passing through the second expansion device 21 of the refrigerant, If the specific gravity of the refrigerant is G and the coefficient is C, it is represented by the following equation (4).

[Equation 2]
Re = u × d / ν (2)

[Equation 3]
Gra = ρs × V × f × ηv (3)

[Equation 4]
Grb = C × Cv × (ΔP / G) ^0.5 (4)

  Next, the control unit 50 estimates the quality (dryness) of the refrigerant at the outlet of the condenser 12. The quality (dryness) can be estimated from the refrigerant pressure at the outlet of the internal heat exchanger 30 and the refrigerant enthalpy at the outlet of the condenser 12. The refrigerant enthalpy h2 at the outlet of the condenser 12 is estimated from the refrigerant enthalpy h1 at the outlet of the internal heat exchanger 30, the exchange heat quantity Qa of the internal heat exchanger 30, and the refrigerant circulation quantity Gra of the refrigerant circulation circuit 10. And is represented by the following equation (5). The enthalpy h1 of the refrigerant at the outlet of the internal heat exchanger 30 is obtained from the pressure and temperature of the refrigerant at the outlet of the internal heat exchanger 30.

[Equation 5]
h2 = h1 + Qa / Gra (5)

  Next, the control unit 50 estimates the amount of refrigerant in the condenser 12. The refrigerant quantity of the condenser 12 can be estimated from the ratio of the liquid refrigerant quantity and the gas refrigerant quantity in the condenser 12. The ratio between the liquid refrigerant amount and the gas refrigerant amount in the condenser 12 can be estimated from the refrigerant pressure at the outlet of the internal heat exchanger 30 and the refrigerant quality (dryness) at the outlet of the condenser 12. . The relationship between the refrigerant pressure at the outlet of the internal heat exchanger 30, the quality (dryness) of the refrigerant at the outlet of the condenser 12, and the refrigerant quantity of the condenser 12 is acquired in advance, and the refrigerant quantity of the condenser 12 is It may be estimated using the relationship.

  Next, the control unit 50 estimates the exchange heat quantity Qb in the evaporator 14. In equation (1), the heat transfer area A is determined from the specifications of the evaporator 14. The temperature difference ΔT is determined from the saturation temperature obtained from the detection result of the suction pressure sensor 52 and the outside air temperature acquired from the detection result of the outside air temperature sensor 54. Moreover, since the heat exchange performance of the evaporator 14 greatly depends on the performance on the air side (fin side), the heat transfer coefficient K may be estimated from the heat exchange performance of the fins. Since the heat exchange performance of the fin is proportional to the amount of air blown from the fan, the relationship between the amount of air blown from the fan and the heat transfer characteristics is acquired in advance, and the heat transfer coefficient K is estimated using the relationship. Good. The amount of air blown from the fan can be converted from the rotational speed of the fan.

  Next, the control unit 50 estimates the quality (dryness) of the refrigerant at the outlet of the evaporator 14. The quality (dryness) can be estimated from the refrigerant pressure on the suction side of the compressor 11 and the refrigerant enthalpy at the outlet of the evaporator 14. The refrigerant enthalpy h3 at the outlet of the evaporator 14 can be estimated from the refrigerant enthalpy h1 at the outlet of the internal heat exchanger 30, the exchange heat quantity Qb of the evaporator 14, and the refrigerant circulation amount Gra of the refrigerant circuit 10. It is represented by the following formula (6).

[Equation 6]
h3 = h1 + Qb / Gra (6)

  Next, the control unit 50 estimates the amount of refrigerant in the evaporator 14. The refrigerant amount of the evaporator 14 can be estimated from the ratio of the liquid refrigerant amount and the gas refrigerant amount in the evaporator 14. The ratio between the liquid refrigerant amount and the gas refrigerant amount in the evaporator 14 can be estimated from the refrigerant pressure on the suction side of the compressor 11 and the quality (dryness) of the refrigerant at the outlet of the evaporator 14. The relationship between the refrigerant pressure on the suction side of the compressor 11, the refrigerant quality (dryness) at the outlet of the evaporator 14, and the refrigerant amount of the evaporator 14 is acquired in advance, and the refrigerant amount of the evaporator 14 is It is good to estimate using the relationship.

  Next, the control unit 50 estimates the amount of refrigerant in the accumulator 15. The amount of refrigerant in the accumulator 15 can be estimated by subtracting the amount of refrigerant in the condenser 12 and the amount of refrigerant in the evaporator 14 from the amount of refrigerant enclosed in the refrigeration cycle 1. That is, the refrigerant amount in the accumulator 15 can be estimated based on the refrigerant amount distribution in the refrigeration cycle 1.

<Operation of air conditioner>
In the air conditioner 100, when the control unit 50 accumulates too much refrigerant in the accumulator 15, the control unit 50 shifts to the liquid return suppression operation mode, and the opening degree of the second expansion device 21 is changed to the refrigerant at the outlet of the internal heat exchanger 30. Is adjusted to an opening degree at which becomes a gas state (overheated gas state). Therefore, before being sucked into the compressor 11, the liquid refrigerant flowing out from the accumulator 15 and the refrigerant in a gas state (overheated gas state) that has passed through the internal heat exchanger 30 are mixed together, and the compressor 11 is mixed. Since it is possible to reduce the quantity of the liquid refrigerant which returns, the reliability of the compressor 11 is improved.

  Moreover, in the air conditioning apparatus 100, when it is determined that the amount of refrigerant in the accumulator 15 is still too much, the control unit 50 reduces the frequency of the compressor 11. Therefore, it is possible to increase the amount of refrigerant stored in the evaporator 14 and reduce the amount of liquid refrigerant that returns to the compressor 11, so that the reliability of the compressor 11 is improved.

Embodiment 2. FIG.
Below, the air conditioning apparatus which concerns on Embodiment 2 is demonstrated.
Note that, in the following, descriptions that overlap or are similar to those of the first embodiment are appropriately simplified or omitted.
<Configuration of air conditioner>
FIG. 5 is a diagram for explaining the configuration of the air-conditioning apparatus according to Embodiment 2.
As shown in FIG. 5, the condenser 12 exchanges heat between the refrigerant in the refrigerant circuit 10 and the water in the water circuit 40. The water circuit 40 supplies hot water to a heat exchanger or the like of the indoor unit using the pump 41 as a drive source.

  The control unit 50 includes a compressor 11, a first throttle device 13, a second throttle device 21, a pump 41, a discharge pressure sensor 51 that detects the pressure of refrigerant on the discharge side of the compressor 11, and a suction side of the compressor 11. An intake pressure sensor 52 that detects the pressure of the refrigerant, an internal heat exchanger outlet temperature sensor 53 that detects the temperature of the refrigerant on the outlet side of the internal heat exchanger 30, an outside air temperature sensor 54 that detects the outside air temperature, and the discharge of the compressor 11 A discharge temperature sensor 55 for detecting the temperature of the refrigerant on the side, an incoming water temperature sensor 56 for detecting the temperature of the water flowing into the condenser 12, a hot water temperature sensor 57 for detecting the temperature of the water flowing out of the condenser 12, and the like are connected. The

<Operation of air conditioner>
(Method for estimating the amount of refrigerant in the accumulator)
First, the control unit 50 acquires the pressure and temperature of the refrigerant on the discharge side of the compressor 11 from the detection result of the discharge pressure sensor 51 and the detection result of the discharge temperature sensor 55. Further, the control unit 50 acquires the temperature Twin of water flowing into the condenser 12 and the temperature Twout of water flowing out of the condenser 12 from the detection result of the incoming water temperature sensor 56 and the detection result of the hot water temperature sensor 57.

  Next, the control unit 50 estimates the exchange heat quantity Qc in the condenser 12. The exchange heat quantity Qc in the condenser 12 can be estimated from the difference between the temperature Twin of the water flowing into the condenser 12 and the temperature Twout of the water flowing out of the condenser 12 and the water flow rate Gw. The specific heat of the water is Cpw, If the density is ρw, it is expressed by the following equation (7). The water flow rate Gw is obtained from the rotational speed of the pump 41. Further, the specific heat Cpw of water and the density ρw of water are obtained from the temperature of the water.

[Equation 7]
Qc = (Twin−Twout) × Gw × Cpw × ρw (7)

  Next, the control unit 50 estimates the quality (dryness) of the refrigerant at the outlet of the condenser 12. The quality (dryness) can be estimated from the refrigerant pressure on the discharge side of the compressor 11 and the refrigerant enthalpy at the outlet of the condenser 12. The refrigerant enthalpy h2 at the outlet of the condenser 12 can be estimated from the refrigerant enthalpy h0 on the discharge side of the compressor 11, the exchange heat amount Qc of the condenser 12, and the refrigerant circulation amount Gra of the refrigerant circuit 10, and the following (8) The refrigerant enthalpy h0 on the discharge side of the compressor 11 is obtained from the pressure and temperature of the refrigerant on the discharge side of the compressor 11.

[Equation 8]
h2 = h0−Qc / Gra (8)

  Next, the control unit 50 estimates the amount of refrigerant in the condenser 12. The refrigerant quantity of the condenser 12 can be estimated from the ratio of the liquid refrigerant quantity and the gas refrigerant quantity in the condenser 12. The ratio between the liquid refrigerant amount and the gas refrigerant amount in the condenser 12 can be estimated from the refrigerant pressure on the discharge side of the compressor 11 and the quality (dryness) of the refrigerant at the outlet of the condenser 12. The relationship between the refrigerant pressure on the discharge side of the compressor 11, the quality (dryness) of the refrigerant at the outlet of the condenser 12, and the refrigerant amount of the condenser 12 is acquired in advance, and the refrigerant amount of the condenser 12 is It is good to estimate using the relationship.

  Next, the control unit 50 estimates the exchange heat quantity Qb in the evaporator 14. In equation (1), the heat transfer area A is determined from the specifications of the evaporator 14. The temperature difference ΔT is determined from the saturation temperature obtained from the detection result of the suction pressure sensor 52 and the outside air temperature acquired from the detection result of the outside air temperature sensor 54. Moreover, since the heat exchange performance of the evaporator 14 greatly depends on the performance on the air side (fin side), the heat transfer coefficient K may be estimated from the heat exchange performance of the fins. Since the heat exchange performance of the fin is proportional to the amount of air blown from the fan, the relationship between the amount of air blown from the fan and the heat transfer characteristics is acquired in advance, and the heat transfer coefficient K is estimated using the relationship. Good. The amount of air blown from the fan can be converted from the rotational speed of the fan.

  Next, the control unit 50 estimates the quality (dryness) of the refrigerant at the outlet of the evaporator 14. The quality (dryness) can be estimated from the refrigerant pressure on the suction side of the compressor 11 and the refrigerant enthalpy at the outlet of the evaporator 14. The refrigerant enthalpy h3 at the outlet of the evaporator 14 can be estimated from the refrigerant enthalpy h1 at the outlet of the internal heat exchanger 30, the exchange heat quantity Qb of the evaporator 14, and the refrigerant circulation amount Gra of the refrigerant circuit 10. It is represented by the following formula (9).

[Equation 9]
h3 = h1 + Qb / Gra (9)

  Next, the control unit 50 estimates the amount of refrigerant in the evaporator 14. The refrigerant amount of the evaporator 14 can be estimated from the ratio of the liquid refrigerant amount and the gas refrigerant amount in the evaporator 14. The ratio between the liquid refrigerant amount and the gas refrigerant amount in the evaporator 14 can be estimated from the refrigerant pressure on the suction side of the compressor 11 and the quality (dryness) of the refrigerant at the outlet of the evaporator 14. The relationship between the refrigerant pressure on the suction side of the compressor 11, the refrigerant quality (dryness) at the outlet of the evaporator 14, and the refrigerant amount of the evaporator 14 is acquired in advance, and the refrigerant amount of the evaporator 14 is It is good to estimate using the relationship.

  Next, the control unit 50 estimates the amount of refrigerant in the accumulator 15. The amount of refrigerant in the accumulator 15 can be estimated by subtracting the amount of refrigerant in the condenser 12 and the amount of refrigerant in the evaporator 14 from the amount of refrigerant enclosed in the refrigeration cycle 1. That is, the refrigerant amount in the accumulator 15 can be estimated based on the refrigerant amount distribution in the refrigeration cycle 1.

<Operation of air conditioner>
In the air conditioner 100, the control unit 50 controls the refrigerant enthalpy h <b> 2 at the outlet of the condenser 12, the refrigerant enthalpy h <b> 0 on the discharge side of the compressor 11, the exchange heat quantity Qc of the condenser 12, and the refrigerant circulation circuit 10. It is estimated from the refrigerant circulation amount Gra. Therefore, the control unit 50 determines the refrigerant enthalpy h2 at the outlet of the condenser 12, the refrigerant enthalpy h1 at the outlet of the internal heat exchanger 30, the exchange heat quantity Qa of the internal heat exchanger 30, and the refrigerant of the refrigerant circulation circuit 10. Compared to the case of estimating from the circulation amount Gra, the estimation of the refrigerant amount of the condenser 12 is improved, and the certainty of reducing the amount of liquid refrigerant returning to the compressor 11 is improved. This further improves the reliability of the compressor 11.

Embodiment 3 FIG.
Below, the air conditioning apparatus which concerns on Embodiment 3 is demonstrated.
In the following description, descriptions that overlap or are similar to those in Embodiments 1 and 2 are simplified or omitted as appropriate. Moreover, although the case where the air conditioning apparatus which concerns on Embodiment 3 is the same as the air conditioning apparatus which concerns on Embodiment 1 below is demonstrated, it is the same as the air conditioning apparatus which concerns on Embodiment 2. It may be.
<Configuration of air conditioner>
FIG. 6 is a diagram for explaining the configuration of the air-conditioning apparatus according to Embodiment 3.
As shown in FIG. 6, the downstream side of the bypass flow path 20 is connected to a compressor of the compressor 11 that compresses the refrigerant.

<Operation of air conditioner>
In the air conditioner 100, the downstream side of the bypass channel 20 is connected to the compression unit of the compressor 11, and the refrigerant in the bypass channel 20 flows directly into the compression unit of the compressor 11. Compared to the case where the downstream side is connected to the portion between the accumulator 15 and the compressor 11 of the refrigerant circulation circuit 10 and the refrigerant in the bypass flow path 20 flows into the compressor 11 from the suction port of the compressor 11. The amount of liquid refrigerant that accumulates at the shell bottom of the compressor 11 is reduced. Therefore, it is suppressed that the lubricating oil collected on the shell bottom of the compressor 11 is diluted with the liquid refrigerant, and the reliability of the compressor 11 is further improved. In addition, the quality (dryness) of the refrigerant in the bypass channel 20 can be lowered.

Embodiment 4 FIG.
The air conditioner according to Embodiment 4 will be described below.
In the following description, descriptions that overlap or are similar to those of the first to third embodiments are appropriately simplified or omitted.
<Configuration of air conditioner>
The structure of the air conditioning apparatus 100 is the same as the structure of the air conditioning apparatus 100 shown in the first to third embodiments. As the refrigerant of the refrigeration cycle 1, HFO1234yf or HFO1234ze is used.

<Operation of air conditioner>
FIG. 7 is a Mollier diagram in the case where the refrigerant is HFO1234yf or HFO1234ze.
As shown in FIG. 7, when the refrigerant is HFO1234yf or HFO1234ze, the refrigerant temperature on the discharge side of the compressor 11 is lower than that when the refrigerant is R410A or the like, and excessively flows into the compressor 11. When the liquid refrigerant returns, the refrigerant on the discharge side of the compressor 11 is in a gas-liquid two-phase state in addition to the refrigerant on the suction side of the compressor 11 (that is, the gas-liquid two-phase state is set over the entire compression stroke). And an excessive load is easily applied to the compressor 11. Therefore, compared with the case where a refrigerant | coolant is R410A etc., the importance of performing the operation | movement shown by Embodiment 1-Embodiment 3 by the air conditioning apparatus 100 becomes high, and the reliability of the compressor 11 is increased. The effect of improving is remarkable.

  As mentioned above, although Embodiment 1-Embodiment 4 were demonstrated, this invention is not limited to description of each embodiment. For example, it is possible to combine all or some of the embodiments.

  DESCRIPTION OF SYMBOLS 1 Refrigeration cycle, 10 Refrigerant circulation circuit, 11 Compressor, 12 Condenser, 13 1st expansion device, 14 Evaporator, 15 Accumulator, 20 Bypass flow path, 21 2nd expansion device, 30 Internal heat exchanger, 40 Water circuit , 41 Pump, 50 control unit, 51 Discharge pressure sensor, 52 Suction pressure sensor, 53 Internal heat exchanger outlet temperature sensor, 54 Outside air temperature sensor, 55 Discharge temperature sensor, 56 Inlet water temperature sensor, 57 Hot water temperature sensor, 100 Air conditioning apparatus.

Claims (10)

A refrigerant circulation circuit in which a compressor, a condenser, a first expansion device, an evaporator, and an accumulator are connected in an annular shape;
A bypass passage that is connected to a second throttle device in the middle and bypasses the refrigerant that flows through a portion of the refrigerant circuit between the condenser and the first throttle device to the compressor;
An internal heat exchanger for exchanging heat between the refrigerant flowing through the portion of the refrigerant circulation circuit between the condenser and the first expansion device and the refrigerant that has passed through the second expansion device of the bypass flow path;
The refrigerant quantity in the accumulator estimated by the amount of refrigerant which is sealed in the refrigerant circuit in catching the refrigerant amount of the evaporator and the refrigerant amount of the condenser, the estimated amount of refrigerant in the accumulator Control means for controlling the opening degree of the second expansion device according to the flow rate and changing the amount of liquid refrigerant flowing into the compressor via the bypass flow path,
The control means lowers the frequency of the compressor when the amount of refrigerant in the accumulator is large compared to when the amount of refrigerant in the accumulator is small.
Refrigeration cycle equipment.   2. The refrigeration cycle according to claim 1, wherein when the amount of refrigerant in the accumulator is large, the control means narrows the opening of the second expansion device as compared with a case where the amount of refrigerant in the accumulator is small. apparatus.   The refrigeration cycle apparatus according to claim 1 or 2, wherein the control means changes the amount of liquid refrigerant flowing into the accumulator according to the amount of refrigerant in the accumulator.   The refrigeration cycle apparatus according to any one of claims 1 to 3, wherein the control unit estimates a refrigerant amount in the accumulator based on at least a result of estimating a refrigerant amount of the condenser and the evaporator. The condenser causes the refrigerant in the refrigerant circuit to exchange heat with water,
The control means estimates the amount of refrigerant in the condenser based on the temperature of refrigerant discharged from the compressor, the temperature of water flowing into the condenser, and the temperature of water flowing out of the condenser. The refrigeration cycle apparatus according to claim 4.   The refrigeration cycle apparatus according to any one of claims 1 to 5, wherein a downstream side of the bypass passage is connected to a portion of the refrigerant circulation circuit between the accumulator and the compressor.   The refrigeration cycle apparatus according to any one of claims 1 to 5, wherein a downstream side of the bypass flow path is connected to a compression unit of the compressor.   The refrigeration cycle apparatus according to any one of claims 1 to 7, wherein HFO1234yf or HFO1234ze is used as the refrigerant.   The air conditioning apparatus which is a refrigeration cycle apparatus as described in any one of Claims 1-8. A refrigerant circulation circuit in which a compressor, a condenser, a first expansion device, an evaporator, and an accumulator are annularly connected, and a second expansion device is connected in the middle, and the condensation of the refrigerant circulation circuit A bypass flow path for bypassing the refrigerant flowing through the portion between the condenser and the first throttling device to the compressor, and the refrigerant flowing through the portion between the condenser and the first throttling device of the refrigerant circulation circuit; An internal heat exchanger for exchanging heat between the refrigerant that has passed through the second expansion device of the bypass flow path, and a control method for a refrigeration cycle apparatus comprising:
The refrigerant quantity in the accumulator estimated by the amount of refrigerant which is sealed in the refrigerant circuit in catching the refrigerant amount of the evaporator and the refrigerant amount of the condenser, the estimated amount of refrigerant in the accumulator When the amount of refrigerant in the accumulator is small, the frequency of the compressor is lowered, and the opening of the second expansion device is controlled according to the amount of refrigerant in the accumulator, A control method for a refrigeration cycle apparatus, wherein the amount of liquid refrigerant flowing into the compressor via a bypass flow path is changed.

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