JP2002303456A - Refrigeration air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that the amount of refrigerating machine oil which is circulated in a compressor is rendered to be lowered to cause mal- lubrication or that the oil is rendered to flow into a heat exchanger to invite bad efficiency, when the operational conditions or loading conditions are varied in a refrigerating cycle employing the refrigerating machine oil having no or a very little mutual solubility to refrigerant. SOLUTION: The refrigerating cycle employing the refrigerating machine oil which has a very little mutual solubility to refrigerant, comprises a refrigerating circuit for circulating refrigerant, in which the compressor, a heat sauce side heat exchanger, a depressurizer, and a user side heat exchanger are sequentially connected. The content of the oil that circulated in the cycle is controlled so as to be equal to or less than the dissolution rate of liquid refrigerant at the lowest temperature of the cycle, by providing an oil separator, or raising the supercooling rate of the refrigerant at the exit of the heat source side heat exchanger.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating and air-conditioning system using a refrigerating machine oil which has no mutual solubility or a very small refrigerating machine oil, in which a refrigerating machine oil discharged from a compressor into a refrigerant circuit is compressed. The present invention relates to a refrigeration and air-conditioning system for returning to a machine.

[0002]

2. Description of the Related Art FIG.
FIG. 9 is a refrigerant circuit diagram showing a refrigerator as a conventional refrigeration and air-conditioning apparatus disclosed in Japanese Patent Application Publication No. 9-1990, in which 1 is a compressor, 2 is a heat source side heat exchanger, 3 is a refrigerant pressure reducing device which is a capillary tube,
Is a use side heat exchanger, which is connected in series by piping to form a refrigeration cycle. Reference numeral 5 denotes a heat exchanger that exchanges heat between the pressure reducing device 3 and the suction pipe of the compressor 1.

[0003] Further, in this refrigerator, for example, HFC134a is used as a refrigerant, and as a refrigerating machine oil,
For example, an alkylbenzene oil that has no or very small solubility in HFC134a is used.

Next, the operation will be described with reference to a pressure-enthalpy diagram shown in FIG. In the refrigerator configured as described above, the high-temperature and high-pressure refrigerant vapor (point A in the figure) compressed by the compressor 1 is condensed by the heat-source-side heat exchanger 2,
The gas-liquid two-phase refrigerant becomes a gas-liquid two-phase refrigerant having a dryness, which is the ratio of the liquid refrigerant in the gas-liquid two-phase refrigerant, of about 0.1 (point B in the figure). It flows into the use side heat exchanger 4 as a phase refrigerant (point C in the figure). Further, the refrigerant evaporates in the use side heat exchanger 4, returns to the compressor 1 through the heat exchanger 5, and is compressed again. The refrigerating machine oil discharged together with the refrigerant from the compressor 1 circulates in the refrigerant circuit together with the vapor refrigerant and the liquid refrigerant, and returns to the compressor 1.

[0005] In such a refrigerating air conditioner, although the refrigerating machine oil has no mutual solubility with the refrigerant or is very small, it has excellent lubricity and abrasion resistance to sliding parts in the compressor 1. Since the alkylbenzene oil is used, a reliable refrigeration air conditioner can be obtained by reliably returning the refrigeration oil to the compressor.

As described above, in the conventional refrigeration and air-conditioning system, when the operating conditions and the load conditions are substantially constant and the flow rate of the refrigerant circulating in the refrigerant circuit is sufficiently ensured, the refrigeration oil circulates together with the refrigerant, The refrigeration oil flows back to the compressor without excessive stagnation in the piping and capillaries in the circuit. Further, in the conventional refrigeration air conditioner, the state of the outlet refrigerant of the heat source side heat exchanger 2 is a gas-liquid two-phase refrigerant, there is no liquid pipe through which only the liquid refrigerant flows, and the refrigeration oil stays in the liquid pipe. , Did not have to consider.

[0007]

Since the conventional refrigeration and air-conditioning system is configured as described above, the operating conditions and load conditions change greatly, and the flow rate of the refrigerant decreases or the refrigerant discharged from the compressor 1 is discharged. When the amount of refrigerating machine oil increases, the amount of oil staying in the refrigerant circuit increases, and the compressor 1
There is a problem that the amount of oil circulated to the compressor decreases, and lubrication failure occurs due to lack of refrigerating machine oil in the compressor 1 and the life is greatly shortened.

Further, if a large amount of refrigerating machine oil stays in the heat transfer tubes of the heat source side heat exchanger 2 and the use side heat exchanger 4, the heat transfer performance is reduced and the pressure loss is increased, and the energy efficiency of the refrigerating air conditioner is reduced. There were problems such as lowering.

Further, if a refrigerating air-conditioning apparatus having a long liquid pipe such as an outlet of the heat source side heat exchanger 2 through which only the liquid refrigerant flows has no mutual solubility with the refrigerant or uses a very small refrigerating machine oil, There is a problem that the amount of refrigeration oil retained in the liquid pipe increases, the amount of oil circulating to the compressor 1 decreases, and insufficient lubrication occurs in the compressor 1 due to lack of refrigeration oil.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. Therefore, even if the operating conditions and load conditions change, and even if there is a liquid pipe through which only the liquid refrigerant flows, the compressor can be used. It is an object of the present invention to obtain a refrigeration / air-conditioning apparatus that can reliably recirculate a discharged refrigerating machine oil to a compressor and sufficiently increase energy efficiency.

[0011]

According to a first aspect of the present invention, there is provided a refrigeration / air-conditioning apparatus for circulating a refrigerant in which a compressor, a heat source side heat exchanger, a pressure reducing device, and a use side heat exchanger are sequentially connected. In a refrigerating cycle using a refrigerating machine oil having extremely low mutual solubility with respect to the refrigerant, the content of the refrigerating machine oil circulating in the refrigerating cycle is set to be equal to or less than the dissolution rate of the liquid refrigerant at the lowest temperature of the refrigerating cycle. .

A refrigeration / air-conditioning apparatus according to a second aspect of the present invention returns refrigeration oil separated from refrigerant by an oil separator installed in the middle of a compressor discharge pipe to a compressor.

A refrigeration / air-conditioning apparatus according to a third aspect of the present invention includes an oil separator in a pipe connecting the outlet of the heat source side heat exchanger to the inlet of the pressure reducing device, and returns the refrigerating machine oil separated from the refrigerant to the compressor. A refrigeration cycle is provided.

A refrigeration / air-conditioning apparatus according to a fourth aspect of the present invention prevents refrigerant in the oil separator from flowing toward the compressor in the middle of an oil return pipe for returning refrigeration oil from the oil separator to the compressor. A switch is provided.

In the refrigeration / air-conditioning apparatus according to a fifth aspect of the present invention, the degree of supercooling of the refrigerant flowing out of the heat source side heat exchanger is increased to lower the temperature of the liquid refrigerant in the oil separator.

A refrigeration / air-conditioning apparatus according to a sixth aspect of the present invention, wherein the dissolution rate of alkylbenzene-based oil, which is a refrigerating machine oil, circulating in a refrigeration cycle in hydrofluorocarbon, which is a liquid refrigerant, is 0.8% or less. It is.

In a refrigeration / air-conditioning apparatus according to a seventh aspect of the present invention, the temperature of the liquid refrigerant in the oil separator is reduced by cooling with a heat exchanger provided in the oil separator or upstream of the oil separator. It is.

In the refrigeration / air-conditioning apparatus according to the eighth aspect of the present invention, the flow rate of the liquid refrigerant containing the hydrofluorocarbon refrigerant and the refrigeration oil which is an alkylbenzene oil flowing through the oil separator is 0.08 m / s. It is provided with an oil separator having the following main body container diameter.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a refrigerant circuit diagram showing an example of an embodiment of the present invention, and the same parts as those of the conventional device are denoted by the same reference numerals. In the figure, reference numeral 20 denotes an outdoor unit, which is a compressor 1, a four-way valve 6 for switching a flow during heating and cooling, a heat source side heat exchanger 2 operating as a condenser during heating and a condenser during cooling, and an electronic device as a pressure reducing device 3. It consists of an expansion valve. Reference numeral 21 denotes an indoor unit, which is constituted by the use side heat exchanger 4 which operates as a condenser during heating and as an evaporator during cooling. The outdoor unit 20 and the indoor unit 21 are connected by two pipes 15 and 16 to form a refrigeration cycle.
The indoor unit 21 is usually installed at a position higher than the outdoor unit 20.

In the refrigeration / air-conditioning apparatus, difluoromethane (referred to as HFC32) and pentafluoroethane (HFC32), which are hydrofluorocarbons, are used as refrigerants.
125 (hereinafter referred to as R410A), and as a refrigerating machine oil, for example, the mutual solubility with R410A is very small, and the specific gravity of the liquid refrigerant is less than that of liquid refrigerant. Alkylbenzene oils smaller than the specific gravity are used.

Next, the operation will be described with reference to the pressure-enthalpy diagram shown in FIG. First, when heating,
As shown by a solid line arrow, the high-temperature and high-pressure refrigerant vapor (corresponding to the point A in FIG. 2) compressed by the compressor 1 passes through the pipe 16 and is condensed by the use-side heat exchanger 4 operating as a condenser. Liquefaction (corresponding to point B in FIG. 2). This liquid refrigerant is decompressed by the refrigerant decompression device 3 which is an electronic expansion valve through a pipe 15, turns into a low-temperature low-pressure gas-liquid two-phase refrigerant, and flows into the heat source side heat exchanger 2 operating as an evaporator. (Corresponding to point C in FIG. 2). Further, this refrigerant evaporates in the heat source side heat source side heat exchanger 2, passes through the four-way valve 6, returns to the compressor 1, and is compressed again.

On the other hand, during cooling, as shown by the dashed arrow in FIG. 1, high-temperature and high-pressure refrigerant vapor compressed by the compressor 1 (FIG. 2).
(Corresponding to point A) is condensed and liquefied in the heat source side heat exchanger 2 operating as a condenser (corresponding to point B in FIG. 2). This liquid refrigerant is decompressed by the refrigerant decompression device 3 which is an electronic expansion valve to become a low-temperature low-pressure gas-liquid two-phase refrigerant.
It flows into the use side heat exchanger 4 operating as an evaporator (corresponding to the point C in FIG. 2). Further, this refrigerant evaporates in the use side heat source side heat exchanger 4, passes through the pipe 16 and the four-way valve 6,
It returns to the compressor 1 and is compressed again.

The alkylbenzene oil used as the refrigerating machine oil in the refrigerating air conditioner has very low mutual solubility with the refrigerant R410A, and the specific gravity of the alkylbenzene oil is smaller than the specific gravity of the liquid refrigerant of R410A. In the piping, even if it separates from the liquid refrigerant, it flows smoothly in the same direction as the liquid refrigerant, but in the descending liquid piping, if the liquid refrigerant flow rate is small, the refrigerating machine oil separated from the liquid refrigerant rises due to buoyancy. Therefore, there is a possibility that the refrigerant flows in the opposite direction to the refrigerant.

Therefore, in this embodiment, the pipe 15 between the use side heat exchanger 4 during heating and the pressure reducing device 3 for the refrigerant and the pipe 15 between the heat source side heat exchanger 2 during cooling and the pressure reducing device 3 for the refrigerant are used. The pipes are liquid pipes through which only the liquid refrigerant flows, and of these pipes, the downcomers through which the liquid refrigerant flows from above to below are:
The inner diameter of the pipe is set to be larger than the flow velocity at which the refrigerating machine oil floating as oil droplets in the liquid refrigerant descends when the liquid refrigerant descends.

FIG. 3 shows the result of an experimental study of the flow of the refrigerating machine oil flowing separately from the descending liquid pipe.
FIG. 3 is a visualization of the flow state of the refrigerating machine oil in the descending liquid pipe. In some cases, the refrigerating machine oil forms an oil film and flows along the inner wall of the pipe. It turned out that it flows in a liquid refrigerant. The diameter of the oil droplets (indicated by d in the figure) is of various sizes,
It was found that the descent speed of small oil droplets was relatively fast, but that of large oil droplets was relatively low. When the flow rate of the descending liquid refrigerant was gradually decreased, it was found that there were oil droplets stopped in the liquid refrigerant and oil droplets rising in the opposite direction to the flow direction of the liquid refrigerant.

FIG. 4 shows the flow in the descending liquid pipe recorded by a high-speed video, and the diameter of the oil droplet which is stationary when the descending liquid refrigerant flow rate is changed is read from the video. The relationship between the diameters of the oil droplets that were stationary at that time is shown. The horizontal axis in FIG. 4 is the oil droplet diameter, and the vertical axis is the average flow rate of the liquid refrigerant when the oil droplet is stationary (refrigerant volume flow rate /
Pipe cross-sectional area). That is, the refrigerant flow velocity on the vertical axis indicates the flow velocity of the refrigerant when oil droplets of various diameters are stationary, and indicates the flow velocity at which the oil droplets flow down with the liquid refrigerant if the refrigerant flow velocity is equal to or higher than this refrigerant flow velocity. (Less than,
Flow limit speed).

As can be seen from FIG. 4, the oil droplet having a small diameter has a small buoyancy, so that the flow limit speed is relatively small, and the oil droplet smoothly descends with the liquid refrigerant even if the refrigerant liquid flow velocity is small. As the increases, the buoyancy increases and the flow limit velocity also increases. (The black circle in the figure) Also, when the oil droplet diameter becomes about 2 mm or more, the flow limit speed starts to decrease, but this is because the oil droplet transitions from a sphere to a flat body and the fluid force received from the descending liquid refrigerant increases Probably because. (Black square mark in the figure) From this result, the flow limit velocity of the oil droplet generated in the liquid pipe changes depending on the oil droplet diameter, but when a liquid refrigerant flow velocity of 0.08 m / s or more is secured,
It can be seen that no matter what diameter oil droplets are generated, they flow smoothly.

Therefore, in this embodiment, the pipe 1 between the use side heat exchanger 4 during heating and the pressure reducing device 3 for refrigerant is used.
5 and a descending liquid pipe such as a pipe between the heat source side heat exchanger 2 and the pressure reducing device 3 for cooling at the time of cooling.
s or more, the refrigerating machine oil floating in the liquid refrigerant as oil droplets smoothly descends with the liquid refrigerant, and can flow back to the compressor 1 without causing stagnation in the liquid pipe. A highly reliable refrigeration and air-conditioning apparatus can be obtained without causing an oil quantity shortage in 1.

Embodiment 2 FIG. 5 is a refrigerant circuit diagram of a refrigeration / air-conditioning apparatus showing another example of the embodiment of the present invention. The compressor 1 is configured so that the number of revolutions can be varied by an inverter 7. The number of revolutions of the compressor 1 is controlled, and the flow rate of the refrigerant is increased or decreased so that the capacity corresponding to the load can be exhibited. The same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will not be repeated.

When the load decreases, the rotation speed of the compressor 1 is reduced by the inverter 7, the flow rate of the refrigerant circulating in the refrigerant circuit is reduced, and the heating capacity or the cooling capacity is reduced. In this embodiment, the minimum value of the number of revolutions of the compressor 1 is determined by determining the piping 15 between the use side heat exchanger 4 during heating and the pressure reducing device 3 of the refrigerant and the heat source side heat exchanger 2 during cooling and the refrigerant. The flow rate of the refrigerant in the descending liquid pipe such as the pipe between the pressure reducing devices 3 is set to be equal to or higher than the flow limit speed at which the refrigerating machine oil floating in the liquid refrigerant flows smoothly, that is, the liquid refrigerant flow rate is equal to or higher than 0.08 m / s. Is set to a high speed.

Therefore, even if the rotation speed of the compressor 1 is reduced and the flow rate of the refrigerant is reduced, the flow velocity of the refrigerant in the descending liquid pipe is higher than the flow limit velocity at which the refrigerating machine oil floating in the liquid refrigerant flows smoothly. Therefore, the refrigerating machine oil can be recirculated to the compressor 1 without causing stagnation in the liquid pipe, and a reliable refrigeration air-conditioning apparatus can be obtained without causing an oil shortage in the compressor 1. it can.

Embodiment 3 FIG. FIG. 6 is a cross-sectional view of a descending liquid pipe showing another example of the embodiment of the present invention. Numeral 8 denotes an oil droplet miniaturizing element installed in the liquid pipe. The oil droplet miniaturization element 8 is formed of a disk having a plurality of small holes (diameter d in the figure). In the liquid pipe on the upstream side of the oil droplet refinement element 8, oil droplets of various diameters are present. These oil droplets are refined when passing through the oil droplet refinement element 8, and the oil droplet diameter is reduced. In addition to passing only oil droplets having a diameter equal to or smaller than the diameter of the hole of the miniaturized element indicated by d, oil droplets larger than the diameter of the hole of the micronized element break down into small oil droplets and flow.

As described above, by providing the oil droplet miniaturization element 8 in the descending liquid pipe, the diameter of the oil droplet flowing in the liquid pipe becomes small, and the refrigerating machine oil easily flows in the same direction together with the liquid refrigerant. Therefore, the refrigerating machine oil can be recirculated to the compressor 1 without causing stagnation in the liquid piping, and a highly reliable refrigerating and air-conditioning apparatus can be obtained without causing an oil shortage in the compressor 1.

In the above-described embodiment, an example has been described in which the oil droplet miniaturization element 8 is constituted by a disk having a plurality of small holes having a diameter d, but the invention is not limited to this. It may be formed of a mesh or sintered metal.

Further, by providing a plurality of the oil droplet miniaturizing elements 8 at predetermined intervals in the descending liquid pipe, the effect is further exhibited.

Embodiment 4 FIG. Hereinafter, another example of the embodiment of the present invention will be described with reference to a refrigerant circuit diagram of a refrigerating air conditioner shown in FIG. In this embodiment, the amount of oil discharged from the compressor 1 to the refrigerant circuit is set to be equal to or less than the dissolution rate of the refrigerating machine oil in the liquid refrigerant. The compressor 1 that can always ensure the performance is used.

When alkylbenzene oil is added to the liquid refrigerant of R410A, the amount ratio (=
The result of measuring the dissolution rate of (mass of alkylbenzene oil / (mass of alkylbenzene oil + mass of refrigerant)) is shown in FIG. The vertical axis in the figure is the liquid refrigerant temperature, and the horizontal axis is R410A.
3 shows the dissolution rate of an alkylbenzene oil in the oil. As can be seen from this figure, the alkylbenzene oil is slightly dissolved in the liquid refrigerant of R410A, and the dissolution rate decreases as the liquid refrigerant temperature decreases. When the amount of oil discharged from the compressor to the refrigerant circuit is equal to or less than this dissolution rate, all of the alkylbenzene oil is dissolved in the liquid refrigerant in the liquid pipe. Therefore, the refrigerating machine oil does not stay in the liquid pipe and the compressor 1
There is no shortage of oil inside.

In a room air conditioner, the minimum value of the refrigerant temperature of the liquid pipe is about 30 ° C. Under this condition, as shown in FIG. 7, the alkylbenzene oil contains 0.8% of the R410A liquid refrigerant.
It turns out that it melt | dissolves above. Therefore, by setting the oil circulation rate (= oil mass flow rate / (oil mass flow rate + refrigerant mass flow rate)) discharged from the compressor 1 into the refrigerant circuit to be 0.8% or less, the alkylbenzene oil in the liquid pipe is All of them are dissolved in the liquid refrigerant and the refrigerating machine oil does not stay, so that there is no shortage of oil in the compressor 1.

Embodiment 5 FIG. 8 is a refrigerant circuit diagram of a refrigeration / air-conditioning apparatus showing another embodiment of the present invention, in which an oil separator 9 is provided in the middle of a discharge pipe of a compressor 1, and a lower portion of the oil separator 9 is a capillary. The compressor is connected to a suction pipe of the compressor 1 via a refrigerating machine oil decompression device 10, and the refrigerating machine oil separated by the oil separator 9 is returned to the compressor 1. In this embodiment, even if the amount of oil discharged from the compressor 1 becomes equal to or higher than the dissolution rate of the refrigerating machine oil in the liquid refrigerant, that is, 0.8% or more, the oil flows into the refrigerant circuit by the action of the oil separator. The oil amount is configured to be 0.8% or less.

Therefore, the amount of oil flowing out to the refrigerant circuit is
Since the refrigerating machine oil always dissolves in the liquid refrigerant or less, the refrigerating machine oil is completely dissolved in the liquid refrigerant in the liquid piping, and the refrigerating machine oil does not stay. Does not occur.

As a method for improving the oil separation efficiency in the oil separator 9, the diameter of the main body of the oil separator 9 is increased so that the flow rate of the vapor refrigerant in the oil separator 9 is reduced. 9 can improve the oil separation efficiency.

Embodiment 6 FIG. FIG. 9 is a refrigerant circuit diagram of a refrigerating air conditioner showing another embodiment. An oil separator 9 is provided in a pipe between a heat source side heat exchanger 2 and a refrigerant pressure reducing device 3 which is an electric expansion valve. I have. An upper part of the oil separator 9 is provided with a switch 11 which is an electromagnetic valve and a pressure reducing device 1 for refrigeration oil which is a capillary.
The compressor oil is connected to the suction pipe of the compressor 1 through the oil separator 9 so as to return the refrigerating machine oil stored in the upper part of the oil separator 9 to the compressor 1.

Next, the operation will be described. First, at the time of cooling, the high-temperature and high-pressure refrigerant vapor compressed by the compressor 1 is condensed and liquefied by the heat source side heat exchanger 2 operating as a condenser,
It flows into the oil separator 9. If the amount of oil flowing from the compressor 1 to the refrigerant circuit is equal to or higher than the dissolution rate of the alkylbenzene oil in the liquid refrigerant shown in FIG. 7, the refrigerating machine oil separates from the liquid refrigerant in the oil separator 9 and The refrigerating machine oil, which is an alkylbenzene oil having a specific gravity smaller than the specific gravity, stays in the upper portion of the oil separator 9. Since the switch 11 is opened at the time of cooling, the refrigerating machine oil staying in the upper portion of the oil separator 9 returns to the compressor 1 via the switch 11 and the refrigerating machine oil pressure reducing device 10. Further, since the amount of oil contained in the liquid refrigerant discharged from the oil separator 9 can be reduced, the oil flowing into the use-side heat exchanger 4 operating as an evaporator and staying in the heat transfer tube 15 causes a problem. This can also prevent the heat transfer performance from deteriorating.

As shown in FIG. 7, the dissolution rate of the alkylbenzene oil in the liquid refrigerant decreases as the temperature of the liquid refrigerant decreases. The amount of oil separated in the vessel 9 can be increased. That is, by lowering the degree of opening of the decompression device or increasing the degree of supercooling by increasing the amount of refrigerant charged,
By increasing the degree of supercooling indicated by the difference between the outlet temperature of the heat source side heat exchanger 2 of the refrigerant and the condensing temperature to decrease the temperature of the liquid refrigerant in the oil separator 9, oil separation in the oil separator 9 is performed. Efficiency can be improved.

On the other hand, at the time of heating, the high-temperature and high-pressure refrigerant vapor compressed by the compressor 1 passes through the pipe 16 and is condensed and liquefied by the use-side heat exchanger 4 operating as a condenser. This liquid refrigerant passes through a pipe 15 which is a downcomer, and is decompressed by a refrigerant pressure reducing device 3 which is an electronic expansion valve to become a low-temperature low-pressure gas-liquid two-phase refrigerant and flows into the oil separator 9. During heating, the gas-liquid two-phase refrigerant flows into the oil separator 9, so that the refrigerating machine oil cannot be separated. Therefore, the switch 11 is closed, and the refrigerant flows out of the oil separator 9 to the compressor 1. To prevent the energy efficiency from lowering or to break the compressor 1 by liquid compression.

Therefore, in this embodiment, during cooling, the refrigerating machine oil is separated from the liquid refrigerant at the outlet of the heat source side heat exchanger 2, which is a condenser, and returned to the compressor 1, so that the oil stays in the evaporator. Thus, a refrigeration / air-conditioning apparatus with high energy efficiency can be obtained. During heating, the oil separator 9
Since the refrigerant is prevented from flowing out of the compressor to the compressor, a decrease in energy efficiency can be prevented, and a refrigeration / air-conditioning apparatus that does not destroy the compressor 1 by liquid compression by liquid compression can be obtained.

Embodiment 7 FIG. FIG. 10 is a refrigerant circuit diagram of a refrigeration / air-conditioning apparatus showing another embodiment, in which an oil separator 9 provided between a heat source side heat exchanger 2 and a refrigerant pressure reducing device 3 which is an electric expansion valve is provided. Further, on the upper part of the oil separator, a switch 11 which is an electromagnetic valve and a pressure reducing device 1 for refrigeration oil which is a capillary.
The compressor oil is connected to the suction pipe of the compressor 1 through the oil separator 9 so as to return the refrigerating machine oil stored in the upper part of the oil separator 9 to the compressor 1. In contrast to the sixth embodiment, the pipe between the heat source side heat exchanger 2 and the oil separator 9 is provided with a heat exchanger 22 for lowering the temperature of the liquid refrigerant entering the oil separator during cooling. Put features.

Next, the operation will be described. First, during cooling, refrigerant vapor containing high-temperature and high-pressure refrigerating machine oil compressed by the compressor 1 is condensed and liquefied by the heat source side heat exchanger 2 operating as a condenser, and flows into the oil separator 9. . When the amount of oil flowing out from the compressor 1 to the refrigerant circuit is equal to or higher than the dissolution rate of the alkylbenzene oil in the liquid refrigerant shown in FIG.
The refrigerating machine oil is separated from the liquid refrigerant in the oil separator 9, and the refrigerating machine oil, which is an alkylbenzene oil having a smaller specific gravity than the liquid refrigerant, stays in the upper part of the oil separator 9. Since the switch 11 is opened at the time of cooling, the refrigerating machine oil staying in the upper part of the oil separator 9 returns to the compressor 1 via the switch 11 and the refrigerating machine oil pressure reducing device 10.

Further, since the switch 11 'is opened, a part of the liquid refrigerant at the lower portion of the oil separator 9 is vaporized through the pressure reducing device 10' which is a capillary, and a low temperature state is obtained to exchange heat. It returns to the compressor 1 via the compressor 22. At this time,
The temperature of the liquid refrigerant condensed and liquefied in the heat source side heat exchanger 2 is lowered by the heat exchanger 22 and flows into the oil separator 9 to promote the separation of the refrigerating machine oil and to leave the oil separator 9. Since the content of the refrigerating machine oil in the refrigerant can be reduced, the amount of the refrigerating machine oil separated from the liquid refrigerant before reaching the use-side heat exchanger 4 that operates as an evaporator can be significantly reduced. it can. Further, if the temperature is adjusted so as not to be lower than the temperature of the liquid refrigerant in the oil separator 9, the refrigerating machine oil contained in the liquid refrigerant flowing out of the oil separator 9 is transferred from the oil separator 9 to the use side heat exchange. It is also possible to eliminate the separation between the vessels 4.

Here, the heat exchanger 22 provided on the pipe between the heat source side heat exchanger 2 and the oil separator 9 may be provided with a double pipe or the like. , Pipes through which the low-temperature refrigerant passes through the heat exchanger itself,
A similar effect can be obtained by inserting the coil inside the coil.

On the other hand, at the time of heating, high-temperature and high-pressure refrigerant vapor compressed by the compressor 1 passes through the pipe 16 and is condensed and liquefied by the use-side heat exchanger 4 operating as a condenser. This liquid refrigerant passes through a pipe 15 which is a downcomer, and is decompressed by a refrigerant pressure reducing device 3 which is an electronic expansion valve to become a low-temperature low-pressure gas-liquid two-phase refrigerant and flows into the oil separator 9. At the time of heating, since the gas-liquid two-phase refrigerant flows into the oil separator 9, the refrigerating machine oil cannot be separated, so that the switches 11, 11 'are closed.
This prevents the refrigerant from flowing out of the oil separator into the compressor 1 to lower the energy efficiency and prevent the compressor 1 from being broken by liquid compression.

Therefore, in this embodiment, the sixth embodiment will be described. In comparison to the above, during cooling, the refrigerating machine oil is separated from the liquid refrigerant at the outlet of the heat source side heat exchanger 2 as a condenser and returned to the compressor 1, and the use side heat exchanger 4 operating as an evaporator
Since the amount of refrigerating machine oil flowing into the inside can be greatly reduced, a decrease in heat transfer performance caused by oil staying in the heat transfer tube 15 can be prevented, and a refrigerating air conditioner with high energy efficiency can be obtained. In addition, at the time of heating, the sixth embodiment. Similarly to the above, since the refrigerant is prevented from flowing out of the oil separator 9 to the compressor, a decrease in energy efficiency can be prevented, and a refrigeration / air-conditioning apparatus that does not destroy the compressor 1 by liquid compression by liquid compression can be obtained.

In the above embodiment, the case where the present invention is used for an air conditioner such as a room air conditioner which can arbitrarily adjust the indoor temperature is shown, but the present invention is not limited to this. It may be used for refrigerators and household refrigerators, and in this case, the same effect is obtained.

[0054]

As described above, the refrigeration / air-conditioning apparatus according to the first invention comprises a compressor, a heat source side heat exchanger, a pressure reducing device,
In a refrigeration cycle that uses refrigerating machine oil with extremely low mutual solubility in the refrigerant circuit that circulates the refrigerant that is connected sequentially to the use-side heat exchangers, the content of refrigerating machine oil circulating in the refrigerating cycle is refrigerated. Since the dissolution rate of the liquid refrigerant at the cycle minimum temperature is not more than the refrigerating machine oil does not become oil droplets in the liquid pipe, the refrigerating machine oil does not separate and stay in the pipe, and the oil to the compressor Return is better.

In the refrigeration / air-conditioning apparatus according to the second aspect of the present invention, the refrigerating machine oil separated from the refrigerant by the oil separator provided in the middle of the compressor discharge pipe is returned to the compressor. In addition, lubrication and abrasion resistance to sliding parts in the compressor are not reduced.

Further, the refrigeration / air-conditioning apparatus according to the third aspect of the present invention includes the oil separator installed in the pipe connecting the outlet of the heat source side heat exchanger to the inlet of the pressure reducing device, so that the refrigeration oil separated from the refrigerant is compressed. A refrigeration cycle for returning to the heat exchanger is provided, so that the refrigerating machine oil can be prevented from flowing into the use side heat exchanger during cooling, so that the efficiency of the heat exchanger does not decrease,
In addition, since the return of oil to the compressor is improved, wear of the drive unit can be prevented.

The refrigeration / air-conditioning apparatus according to the fourth aspect of the present invention is an opening / closing device for preventing refrigerant in the oil separator from flowing toward the compressor in the middle of an oil return pipe for returning refrigeration oil from the oil separator to the compressor. Since the heat exchanger is provided, it is possible to prevent the refrigerant from flowing into the compressor by short-circuiting during heating, and does not impair the energy efficiency.

In the refrigeration / air-conditioning apparatus according to the fifth aspect of the present invention, the supercooling degree of the refrigerant flowing out of the heat source side heat exchanger is increased to lower the temperature of the liquid refrigerant in the oil separator. Refrigeration oil is separated in the refrigeration cycle and oil droplets are less likely to be generated.

In the refrigeration / air-conditioning apparatus according to the sixth aspect of the present invention, the dissolution rate of the alkylbenzene-based oil, which is a refrigerating machine oil, circulating in the refrigeration cycle in hydrofluorocarbon, which is a liquid refrigerant, is set to 0.8% or less. The refrigerating machine oil does not separate in the refrigerating cycle to generate oil droplets, and the loss of energy efficiency due to the refrigerating machine oil remaining in the piping does not occur.

In the refrigeration / air-conditioning apparatus according to the seventh aspect, the temperature of the liquid refrigerant in the oil separator is reduced by cooling by the heat exchanger provided in the oil separator or upstream of the oil separator. During cooling, the refrigerating machine oil is separated from the liquid refrigerant at the outlet of the heat source side heat exchanger, which is a condenser, and returned to the compressor, and the amount of refrigerating machine oil flowing into the use side heat exchanger that operates as an evaporator is significantly increased. Therefore, a decrease in heat transfer performance caused by oil staying in the heat transfer tubes can be prevented, and a refrigeration / air-conditioning apparatus with high energy efficiency can be obtained.

In the refrigeration / air-conditioning apparatus according to the eighth invention, the flow rate of the liquid refrigerant containing the hydrofluorocarbon refrigerant and the refrigeration oil which is the alkylbenzene oil flowing through the oil separator is 0.08 m / s or less. The oil separator, which has the diameter of the main body container, eliminates the separation of oil in the refrigeration cycle to form oil droplets, resulting in loss of energy efficiency due to stagnation of refrigeration oil in the piping. Not.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram of a refrigeration / air-conditioning apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a pressure-enthalpy diagram showing the operation of the refrigeration / air-conditioning apparatus of FIG.

FIG. 3 is a conceptual diagram showing a flow state of refrigerating machine oil in a liquid pipe of the refrigerating air conditioner of FIG.

FIG. 4 is a relation diagram showing a relation between an oil droplet diameter and a flow limit velocity.

FIG. 5 is a refrigerant circuit diagram of a refrigeration / air-conditioning apparatus according to Embodiment 2 of the present invention.

FIG. 6 is a sectional view of a liquid pipe according to a third embodiment of the present invention.

FIG. 7 is a relationship diagram showing a dissolution rate of an alkylbenzene oil in a liquid refrigerant.

FIG. 8 is a refrigerant circuit diagram of a refrigeration / air-conditioning apparatus according to Embodiment 5 of the present invention.

FIG. 9 is a refrigerant circuit diagram of a refrigeration / air-conditioning apparatus showing Embodiment 6 of the present invention.

FIG. 10 is a refrigerant circuit diagram of a refrigeration / air-conditioning apparatus according to Embodiment 7 of the present invention.

FIG. 11 is a refrigerant circuit diagram of a conventional refrigeration / air-conditioning apparatus.

FIG. 12 is a pressure and enthalpy diagram showing the operation of the refrigeration / air-conditioning apparatus of FIG.

[Explanation of symbols]

Reference Signs List 1 compressor, 2 heat source side heat exchanger, 3 refrigerant decompression device, 4 use side heat exchanger, 8 miniaturization element, 9 oil separator, 11 switch.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C10N 40:30 C10N 40:30 (72) Inventor Satoshi Suzuki 2-3-2 Marunouchi, Chiyoda-ku, Tokyo No. Mitsubishi Electric Co., Ltd. Rishi Electric Co., Ltd. F-term (reference) 4H104 BA04A PA20

Claims (8)

[Claims] 1. A refrigerating machine oil having extremely low mutual solubility with respect to the refrigerant is used in a refrigerant circuit which circulates a refrigerant in which a compressor, a heat source side heat exchanger, a pressure reducing device, and a use side heat exchanger are sequentially connected. A refrigerating cycle, wherein the content of refrigerating machine oil circulating in the refrigerating cycle is equal to or less than a dissolution rate of a liquid refrigerant at a refrigerating cycle minimum temperature. 2. The refrigeration and air conditioning system according to claim 1, wherein the refrigerant circuit includes a circuit for returning the refrigerating machine oil separated from the refrigerant to the compressor by an oil separator installed in the middle of the compressor discharge pipe. apparatus. 3. The refrigerant circuit includes an oil separator in a pipe connecting the outlet of the heat source side heat exchanger to the inlet of the pressure reducing device, and a circuit for returning the refrigerating machine oil separated from the refrigerant to the compressor. The refrigeration / air-conditioning apparatus according to claim 1. 4. The refrigerant circuit further comprises a switch for preventing the refrigerant in the oil separator from flowing toward the compressor in the middle of an oil return pipe for returning the refrigerating machine oil from the oil separator to the compressor. The refrigeration / air-conditioning apparatus according to claim 2 or 3, wherein 5. The rate of dissolution of the refrigerating machine oil in the liquid refrigerant circulating in the refrigeration cycle depends on the temperature of the liquid refrigerant in the oil separator into which the refrigerant discharged from the heat source side heat exchanger has been introduced. 3. The method according to claim 2, wherein the degree of supercooling of the refrigerant at the outlet of the heat source side heat exchanger is increased so as to be lower than the temperature of the liquid refrigerant passing through the downcomer in the refrigerant circuit, so as to be within the melting range. Or the refrigeration / air-conditioning apparatus according to claim 3. 6. The method according to claim 1, wherein the content of the refrigerating machine oil circulating in the refrigerating cycle is 0.8% or less in the hydrofluorocarbon as the refrigerant and the alkylbenzene-based oil as the refrigerating machine oil. Item 6. A refrigeration / air-conditioning apparatus according to any one of Items 5. 7. The refrigeration and air conditioning system according to claim 5, wherein the temperature of the liquid refrigerant in the oil separator is reduced by cooling with a heat exchanger provided in the oil separator or upstream of the oil separator. apparatus. 8. An oil separator having a main body diameter such that a flow rate of a liquid refrigerant containing a refrigerant, which is a hydrofluorocarbon flowing therein, and a refrigerating machine oil, which is an alkylbenzene-based oil, is 0.08 m / s or less. The refrigeration / air-conditioning apparatus according to any one of claims 1 to 6, further comprising: