JP2000320916A - Refrigerating cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an operating efficiency of a refrigerating cycle by providing an opening communicating with a gas refrigerant of an upper portion of a liquid receiver through an upper portion of an introducing/discharging tube connected to a user side heat exchanger in the receiver and providing a circuit for by-passing the gas refrigerant from the upper portion of the receiver to the tube of the receiver. SOLUTION: A two-phase state refrigerant decompressed by an electronic expansion valve 4 flows from an introducing tube 5-1 to a liquid receiver 5, and flows out from a discharging tube 5-2. In this case, the two-phase refrigerant flowing from the tube 5-1 to the receiver 5 is gas-liquid separated in the receiver, a gas refrigerant flows out from an opening 5-3 provided at an upper portion of the tube 5-2 to the receiver 5, and a liquid side connecting tube 9 becomes the two-phase state. The gas refrigerant of the upper portion of the receiver is taken out by a bypass pipe 6, and hence a refrigerant dryness of an outlet of the receiver becomes large, that is, a gas refrigerant ratio of the refrigerant flowing out from the receiver 5 becomes large. Thus, the liquid refrigerant is forcibly stored in the receiver 5 due to a balance between inflowing liquid refrigerant to and outflowing liquid refrigerant from the receiver 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration cycle for air conditioning, and more particularly to a refrigeration cycle configuration suitable for protecting the global environment such as power saving and alternative refrigerant.

[0002]

2. Description of the Related Art In order to improve the workability and reliability of a refrigeration cycle for air conditioning, a refrigeration cycle system in which a refrigerant corresponding to a maximum pipe length of a connection pipe is filled in advance has been widely used. In such a refrigeration cycle, reducing the required amount of refrigerant is an issue, and as another important issue,
There is excess refrigerant storage that occurs when used below the maximum pipe length.

[0003] Such a prior art is disclosed in Japanese Patent Application Laid-Open No. 62-1589.
As shown in No. 59, the pressure is reduced by the capillary tube provided in the outdoor unit during the cooling operation, and the pressure is reduced by the capillary tube provided in the indoor unit during the heating operation. The refrigerant flow state is set to a gas-liquid two-phase flow state, so that the excess refrigerant stores the accumulator parameters such as the diameter of the inlet / outlet pipe in the accumulator, which is a low-pressure vessel, and the diameter of the oil return hole provided in the inlet / outlet pipe. Refrigeration cycles are known.

As disclosed in Japanese Patent Application Laid-Open No. Hei 6-137690, there is a refrigeration cycle in which an electronic expansion valve is provided in an indoor unit in order to expand the operating range of the indoor unit and share it with other models. . In this refrigeration cycle, the pressure is reduced by the two stages of the capillary tube of the outdoor unit and the electronic expansion valve of the indoor unit during the cooling operation, and reduced by the electronic expansion valve of the indoor unit during the heating operation. It is configured to store excess refrigerant in the accumulator.

According to the heat pump system using a non-azeotropic mixed refrigerant disclosed in JP-A-1-58964, a gas-liquid separator is provided between a heat source side heat exchanger and a use side heat exchanger. A refrigerant tank provided in a heat exchange relationship with the suction gas pipe is connected to the upper part of the gas-liquid separator by a first connection pipe, and the refrigerant tank is connected to the gas-liquid separator by a second connection pipe provided with an on-off valve in the middle. It is connected to the lower part, and is configured such that the high-boiling refrigerant is circulated in the refrigeration cycle by storing the low-boiling refrigerant extracted from the upper part of the gas-liquid separator during cooling operation as a liquid refrigerant in a refrigerant tank.

[0006]

The above prior art has the following problems.

First, in a refrigeration cycle configured to store refrigerant in an accumulator, the suction state of the compressor during operation always contains a small amount of liquid refrigerant, and the upper limit of the enthalpy in the suction state is saturated vapor enthalpy. is there. When the flow rate of the refrigerating machine oil discharged together with the refrigerant from the compressor is large, it is necessary to increase the diameter of the oil return hole in the accumulator in order to properly return the oil to the compressor. In this case, the liquid refrigerant is also sucked into the compressor at the same time, and the amount of the liquid refrigerant mixed into the suction refrigerant increases, so that the suction enthalpy is considerably smaller than the saturated vapor enthalpy. For this reason, it is necessary to reduce the refrigerant enthalpy at the evaporator to increase the refrigerant enthalpy change amount at the evaporator in order to secure the capacity, and to set the refrigerant supercooling degree at the condenser to be large.

[0008] Increasing the degree of subcooling by using a condenser having a certain size stores a liquid refrigerant having poor heat transfer performance in a part of the condenser. There has been a problem that the high-pressure side pressure of the cycle becomes a high operating point, the compressor input increases, and the operating efficiency of the refrigeration cycle decreases.

Further, as described in “Characteristics of Packaged Air Conditioner Using Alternative Refrigerant R407C” (Papers Collection of the Japanese Refrigeration Society Academic Lecture 1995, p.13 to p.16),
Non-azeotropic refrigerants such as R407C (HFC
(32/125 / 134a: 23/25 / 53wt%), the composition of the enclosed refrigerant and the refrigerant that circulates in the refrigeration cycle in a configuration where the excess refrigerant is stored in a state of high dryness like an accumulator There is a problem that the difference increases. In other words, the ratio of low-pressure refrigerant (high-boiling refrigerant) such as HFC134a in the stored refrigerant increases, and the composition of refrigerant circulating in the refrigeration cycle increases in the ratio of high-pressure refrigerant (low-boiling refrigerant) in HFC32,125. . As a result, compared to the case of R22, there is a problem that the high pressure of the refrigeration cycle becomes higher, the compressor input increases, and the operation efficiency of the refrigeration cycle decreases.

Further, in the conventional example using the non-azeotropic refrigerant mixture, the number of required refrigerant containers increases, and the cost increases. Further, since the refrigerant is dispersed and stored in two containers, the refrigeration cycle is stabilized. There is a problem with gender. In the cooling operation, the high-boiling-point refrigerant mainly circulates in the refrigeration cycle, but in the heating operation, the low-pressure refrigerant gasified in the refrigerant tank also circulates, so that there is a problem that the refrigerant composition greatly changes depending on the operation mode.

[0011]

In order to solve the above-mentioned problems, in the present invention, a liquid receiver having a smaller degree of refrigerant stiffness as compared with an accumulator is constituted as an excess refrigerant storage container, In the upper part of the inlet / outlet pipe connected to the use side heat exchanger in the inside, an opening communicating with the gas refrigerant at the upper part of the receiver is provided, and the gas refrigerant is bypassed from the upper part of the receiver to the inlet / outlet pipe of the receiver. A refrigeration cycle that controls the dryness of the refrigerant at the outlet of the liquid receiver by providing a circuit that performs a wide range of operation with a simplified configuration is provided. The operation range is expanded by the variable resistance electronic expansion valve provided in the outdoor unit and the opening and the bypass pipe provided in the inlet / outlet pipe in the liquid receiver.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment will be described below with reference to FIGS.

FIG. 1 shows a first embodiment. In FIG. 1, A is an outdoor unit, B is an indoor unit, 1 is a compressor, 2 is a four-way valve for switching the flow direction of the refrigerant in accordance with the cooling and heating operation, 3 is a heat source side heat exchanger, 4 is an electronic expansion valve, 5 Is a receiver, 5-
1,5-2 is an inlet / outlet pipe in the receiver, 5-3 is an inlet / outlet pipe 5
The opening provided in the upper part of -2, 5-4 is a gas refrigerant outlet from the upper part of the receiver, 6 is a bypass pipe, 7 is an on-off valve provided in the bypass pipe, and 8 is introduction of the receiver. A path connection port provided in the outlet pipe, 9 is a liquid side connection pipe connecting the outdoor unit A and the indoor unit B, 10 is a use side heat exchanger, and 11 is a gas connecting the outdoor unit A and the indoor unit B. 3 shows a side connection pipe.

During the cooling operation, the refrigerant is supplied to the compressor 1, the four-way valve 2, the heat source side heat exchanger 3, the electronic expansion valve 4, the liquid receiver 5, the liquid side connection pipe 9, and the use side heat exchanger as shown by the solid line. 10,
The gas circulates in the order of the gas connection pipe 11, the four-way valve 2, and the compressor 1. As for the refrigerant, the two-phase refrigerant whose pressure has been reduced by the electronic expansion valve 4 flows into the receiver from the inlet pipe 5-1 and flows out from the outlet pipe 5-2. At this time, the two-phase refrigerant flowing from the introduction pipe 5-1 into the receiver is separated into gas and liquid in the receiver, and the liquid refrigerant is discharged into the outlet pipe 5-2.
And the gas refrigerant flows out of the receiver 5 through the opening 5-3 provided in the upper part of the outlet pipe 5-2, and the liquid-side connection pipe 9 is in a two-phase state.

The refrigerant is previously sealed in the refrigeration cycle in consideration of the maximum pipe length. If the refrigerant is shorter than the maximum pipe length, the surplus refrigerant is stored in the receiver as a pipe with a low degree of dryness in the middle of the pipe. Is done. In addition, when performing the cooling operation under the overload operation condition in which both the outdoor air temperature and the indoor air temperature are high, the high pressure may increase excessively. In such a case, the on-off valve 7 is opened to open the upper port 5-4 of the receiver.
, The gas refrigerant in the upper part of the receiver is guided to the bypass connection port 8 between the receiver 5 and the liquid-side connection pipe 9 by the bypass pipe 6.

By taking out the gaseous refrigerant at the upper part of the receiver by the bypass pipe 6, the degree of cryogen at the outlet of the receiver, that is, the ratio of gas refrigerant flowing out of the receiver is set to be large. In other words, the liquid refrigerant is forcibly stored in the liquid receiver based on the balance of the flow of the liquid refrigerant into and out of the liquid receiver, and the amount of effective refrigerant in the refrigeration cycle is reduced. A wide range of operating conditions can be handled by controlling the degree of opening of the electronic expansion valve 4 with the degree of superheating of the refrigerant of the use side heat exchanger or the degree of superheating of the refrigerant discharged from the compressor being controlled in addition to the control by the bypass pipe 6 described above. I can do it.

The liquid receiver 4 retains the excess refrigerant in the middle of the pipe with a small dryness. Therefore, even when the non-azeotropic mixed refrigerant R407C, which is known as an alternative refrigerant to R22, is used, the circulating refrigerant composition and the sealed refrigerant are included. The composition is almost the same, and the high pressure does not rise abnormally. Further, since the refrigerant in the two-phase state flows through the liquid side connection pipe 9, the amount of refrigerant held in the pipe is reduced, and the required refrigerant amount can be reduced. Also, the refrigerant enthalpy at the inlet (evaporator outlet) of the compressor can be made larger than in a refrigeration cycle in which the excess refrigerant is retained in the accumulator, so that the heat source side heat exchanger 3 does not need to have a large degree of refrigerant subcooling. Therefore, the high pressure can be reduced, the compressor input can be reduced, and the coefficient of performance (COP) of the refrigeration cycle improves.
Further, since the degree of subcooling of the refrigerant at the outlet of the heat source side heat exchanger 3 may be small, the amount of refrigerant retained in the use side heat exchanger 3 can be reduced,
Further, there is an effect that the required refrigerant amount can be reduced.

During the heating operation, the refrigerant is supplied to the compressor 1, the four-way valve 2, the gas side connection pipe 11, the use side heat exchanger 10, the liquid side connection pipe 9, the liquid receiver 5, the electronic expansion valve 4, The heat source-side heat exchanger 3, the four-way valve 2, and the compressor 1 circulate in this order. The liquid connection pipe 9 is filled with a liquid refrigerant. Usually, the heat source side heat exchanger 3 which is about twice as large as the use side heat exchanger 10
The excess refrigerant is retained in the liquid-side connection pipe 9 during the heating operation as compared with the cooling operation in which the refrigerant becomes a condenser. For this reason, the capacity of the liquid receiver can be reduced, and there is an effect that the liquid receiver can be made compact. Correspondence to various operation states is performed by controlling the opening degree of the electronic expansion valve 4 as in the cooling operation.

In the heating operation, as described in the description of the cooling operation, the refrigerant enthalpy at the compressor inlet (evaporator outlet) can be larger than that in the refrigeration cycle in which the refrigerant is stored in the accumulator. The degree of subcooling of the refrigerant in the heat exchanger 10 can be reduced, and the high pressure of the refrigeration cycle is reduced, and the coefficient of performance (COP) of the refrigeration cycle is improved.

FIG. 2 shows a second embodiment. The meanings of the symbols 1 to 11 are the same as in the first embodiment. FIG. 2 differs from the embodiment of FIG. 1 in that a second pressure reducing mechanism 12 is provided in the middle of the bypass connection port 8 provided in the liquid-side connection pipe 9 and the inlet / outlet pipe of the receiver 5. . The flow of the refrigerant during the cooling operation is shown by a solid line in the figure. The refrigerant flowing out of the heat source side heat exchanger 3 is depressurized by the electronic expansion valve 4, enters the liquid receiver 5 in a two-phase state, flows out of the liquid receiver in the two-phase state, and is discharged by the second pressure reducing mechanism 12. It is squeezed and returns to the compressor 1 through the liquid side connection pipe 9 and the use side heat exchanger 10. The throttle 12 only affects the opening of the electronic expansion valve during the cooling operation, and there is no difference between the first embodiment and the operating point. The effect when the on-off valve 7 is opened is the same as in the first embodiment.

During the heating operation, the flow of the refrigerant flows through the use-side heat exchange 10, the liquid-side connection pipe 9, the second pressure reducing mechanism, the liquid receiver 5, and the electronic expansion valve 4 in the order indicated by the broken line. At this time, in this embodiment, the degree of subcooling of the refrigerant at the outlet of the use side heat exchanger 10 is larger than that of the first embodiment due to the effect of the restriction of the second pressure reducing mechanism 12, and the heating capacity is increased. Has the effect of doing

FIG. 3 shows a third embodiment. The meanings of the symbols 1 to 12 are the same as in the second embodiment. FIG. 3 differs from the embodiment of FIG. 2 in that the second pressure reducing mechanism 12 is provided in the indoor unit B between the use side heat exchanger 10 and the liquid side connection pipe 9. In this embodiment, as in the second embodiment, the degree of supercooling of the refrigerant is larger than in the first embodiment, and there is an effect that the heating capacity is increased.

FIG. 4 shows a fourth embodiment. The meanings of the symbols 1 to 12 are the same as in the third embodiment. In FIG. 4, the second pressure reducing mechanism 12 includes the bypass connection port 8 and the introduction pipe 5 of the liquid receiver 5.
-2 is different from the second embodiment. In this embodiment, when the bypass is performed during the cooling operation in which the flow of the refrigerant is indicated by the solid line, the bypass connection port 8 is connected to the second port.
Since the pressure difference before and after the bypass is large, the amount of gas to be bypassed is large because the pressure difference before and after the bypass is large, so that the amount of the liquid refrigerant held in the receiver 5 increases. It is more effective in reducing the high pressure under the overload condition than in the case of 1-3.

The fifth embodiment has a configuration in which the on-off valve 7 is replaced with a variable resistance valve 13 in the first to fourth embodiments. FIG. 5 shows an example in which the on-off valve 7 of the first embodiment shown in FIG. The resistance variable valve 13 may be a valve whose resistance changes continuously or a valve whose resistance changes stepwise. In this embodiment, the pressure during the cooling operation can be controlled more finely than in the embodiment described above, and the operation can be stabilized.

In the first to fifth embodiments, the type of the refrigerant is not mentioned, but as described in the section of the prior art, the surplus refrigerant is stored in the receiver having a small degree of refrigerant dryness. Therefore, even when a non-azeotropic refrigerant mixture is used, the filling composition and the circulation composition are substantially the same, and the operation of the refrigeration cycle can be stabilized.

[0026]

According to the present invention, in a refrigeration cycle configuration having an electronic expansion valve in an outdoor unit, an excess refrigerant in the refrigeration cycle is held in a receiver in a state in which the refrigerant dryness is small, With the structure that can control the amount of refrigerant that can be held in the refrigerator, the high pressure can be controlled to an appropriate range over a wide operating range even when a non-azeotropic refrigerant mixture is used as the refrigerant, and the effect of improving the operating efficiency of the refrigeration cycle is improved. There is. In addition, the degree of supercooling in the condenser can be reduced, and the refrigerant state in the liquid side connection pipe during the cooling operation can be made into a two-phase flow, so that the required refrigerant amount can be greatly reduced. In addition, since the inside of the liquid connection pipe during heating is filled with the liquid refrigerant, the difference in surplus refrigerant between the cooling operation and the heating operation is reduced, and the liquid receiver can be downsized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a third embodiment of the present invention.

FIG. 4 is a diagram showing a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a fifth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Four-way valve, 3 ... Heat source side heat exchanger, 4 ... Electronic expansion valve, 5 ... Liquid receiver, 5-1 ... Inlet / outlet pipe in liquid receiver,
5-2: Inlet / outlet in the receiver 5-3: Inlet / outlet 5-2
5-4: gas refrigerant outlet from the upper part of the receiver, 6: bypass pipe, 7: open / close valve provided on the bypass pipe, 8: inlet / outlet pipe of the receiver , A liquid side connection pipe connecting the outdoor unit A and the indoor unit B, 10 a use side heat exchanger, 11 a gas side connection connecting the outdoor unit A and the indoor unit B Pipe, 12: second pressure reducing mechanism, 13: variable resistance valve.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuki Urata 390 Muramatsu, Shimizu-shi, Shizuoka Prefecture Inside Hitachi Air Conditioning System Co., Ltd. (72) Inventor Hiroshi Takenaka 390 Muramatsu, Shimizu-shi Shizuoka Prefecture Inside Hitachi Air Conditioning System Co., Ltd. (72 ) Inventor Masahiro Ito 390 Muramatsu, Shimizu-shi, Shizuoka Prefecture Inside Hitachi Air Conditioning System (72) Inventor Keiji Tanaka 390 Muramatsu, Shimizu-shi Shizuoka Prefecture Inside Hitachi Air Conditioning System F-term (Reference) 3L092 AA02 BA05

Claims (6)

[Claims] 1. A compressor housed in an outdoor unit, a four-way valve, a heat source side heat exchanger, a (first) variable resistance pressure reducing mechanism, a liquid receiver,
In a refrigeration cycle in which a use-side heat exchanger housed in an indoor unit and a connection pipe connecting the outdoor unit and the indoor unit are sequentially connected, a liquid-side connection pipe and a use side provided in a liquid receiver are provided. At the top of the inlet / outlet connected to the heat exchanger, an opening is provided to communicate with the gas refrigerant in the receiver,
A refrigeration cycle, wherein a bypass passage is provided from an upper outlet of a receiver to a bypass connection port between the liquid-side connection pipe and the receiver. 2. The refrigeration cycle according to claim 1, wherein a second pressure reducing mechanism is provided between the bypass connection port and the liquid-side connection pipe. 3. The refrigeration cycle according to claim 1, wherein the second pressure reducing mechanism is provided between the liquid side pipe and the use side heat exchanger. 4. The refrigeration cycle according to claim 2, wherein a second pressure reducing mechanism is provided between the bypass connection port and the receiver. 5. The refrigeration cycle according to claim 1, wherein the on-off valve in the middle of the bypass passage from the receiver to the bypass connection port is a variable resistance valve. . 6. The refrigeration cycle according to claim 1, wherein the refrigerant in the refrigeration cycle is a single refrigerant or two or more refrigerants having different boiling points. .