JPS6143630B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device for returning oil mixed in refrigerant in a low pressure section to the compressor in a refrigeration system using a positive displacement or centrifugal compressor. be.

[Prior art]

Conventionally, in a compressor that actively supplies oil to a working space, such as an oil injection screw compressor, oil injected into a rotor is discharged from the compressor together with refrigerant gas and enters an oil separator. Oil is separated in an oil separator, cooled in an oil cooler, and supplied to a compressor for recycling. However, it is impossible to separate 100% of the oil that enters the oil separator, and a small portion of the oil is not separated, but is dissolved in the refrigerant and passes through the condenser, where the refrigerant liquid is stored in the low-pressure section of the refrigeration system. The refrigerant flows into the refrigerant liquid storage section (generally a flooded evaporator, low-pressure receiver) and is stored there. That is, the refrigerant liquid mixed with oil is stored in the evaporator when the evaporator is a full liquid type, and is stored in the low pressure receiver after passing through the evaporator when the evaporator is a coil type.

Generally, an eliminator or the like is provided in the evaporator to prevent droplets from being entrained into the suction pipe, thereby preventing oil from entering the suction pipe along with the refrigerant vapor. Also, normally within a low pressure receiver, refrigerant vapor does not reach high enough speeds to entrain oil. Therefore, the oil that has entered these refrigerant liquid reservoirs is not discharged but remains and accumulates.

If such oil does not return to the compressor and accumulates, the compressor will run out of oil and will also adversely affect heat transfer in the heat exchanger. Therefore, the oil that has accumulated in the low pressure section of the refrigeration system must be returned to the compressor.

In addition, even in positive displacement compressors that do not use oil injection and dry type compressors, or centrifugal compressors, oil used for bearing lubrication gets mixed into the refrigerant promotion system, resulting in oil shortage and heat exchanger transfer. Since this causes thermal inhibition, the oil must be extracted and returned to the refrigeration system.

Conventionally, as a means of returning oil, a refrigerant liquid containing a large amount of oil (herein referred to as oil refrigerant liquid) out of the stored refrigerant liquid is guided to another heat exchanger, and then the refrigerant liquid containing a large amount of oil (referred to as oil refrigerant liquid in this specification) is introduced into another heat exchanger, and then the refrigerant liquid containing a large amount of oil (herein referred to as oil refrigerant liquid) is introduced into another heat exchanger, and then the refrigerant liquid containing a large amount of oil is introduced into another heat exchanger. Alternatively, the oil separated by the oil separator mentioned above is guided and heated, and the oil is transferred along with the flow of the evaporated refrigerant gas to be guided to the suction pipe of the compressor. It was getting worse.

[Problem that the invention seeks to solve]

However, in such conventional systems, among the gas compressed in the compressor, the refrigerant gas that evaporates in the evaporator contributes to the refrigeration effect;
The refrigerant gas that evaporates in the separate heat exchanger does not contribute to the refrigeration effect at all. Therefore, in the compressor, even the refrigerant gas that does not contribute to the refrigeration action is needlessly compressed and circulated, resulting in a problem in that the efficiency of the refrigeration system is reduced.

The present invention solves the above problems and allows oil return without impairing the efficiency of the refrigeration system.

The purpose of the present invention is to provide an oil return device for a refrigeration system.

[Means for solving problems]

In order to achieve this objective, the inventors conducted repeated research and developed a refrigeration system using an economizer.
The present invention was developed by focusing on the use of the economizer refrigerant.

As a means to solve the above problems, the present invention forms a refrigeration cycle by a compressor, a condenser, an evaporator, and a refrigerant path connecting these, and the refrigerant path runs from the outlet of the condenser to the inlet of the evaporator. In an oil return device for a refrigeration system, an economizer is provided in the middle of the refrigeration system, and a gas phase part of the economizer is connected to an intermediate pressure stage of the compressor. A heat exchanger is installed at a position lower than the liquid level of the oil refrigerant liquid storage section.
The oil refrigerant liquid containing a large amount of oil among the liquids stored in the oil refrigerant liquid storage section is led to the heated side of the heat exchanger, and is exchanged with the refrigerant liquid led from the economizer to exchange heat with the evaporated refrigerant vapor. The present invention provides an oil return device for a refrigeration system, characterized in that the oil is guided to a refrigerant path on the suction side of the compressor.

[Effect]

Since the present invention is configured as described above, the loss due to wasteful compression of gas in the compressor is the same as in the conventional case, but since the refrigerant liquid exiting the economizer is supercooled in the heat exchanger, this Supercooling increases the refrigeration effect, which can compensate for the above-mentioned losses and thus prevent a decrease in efficiency.

〔Example〕

The present invention will be explained with reference to the drawings based on examples.

Figure 1 shows a system using an open economizer as the economizer 46, with a compressor 1, a condenser 1
5, an economizer 46, and an evaporator 17. In the evaporator 17, the refrigerant liquid is stored at the bottom of the evaporator 17, forming an oil refrigerant liquid storage section. A heat exchanger 47 is provided at a position lower than the liquid level of this evaporator 17.

The main oil recovery mechanism includes an oil separator 11 between the discharge pipes 31 and 32, and the oil passes through the oil pipe 35, oil pump 12, oil cooler 13, oil pipe 34,
The oil is returned to the compressor and used for bearing oil supply or for oil injection into the working space in the case of an oil injection type compressor. 3
3 is an outlet pipe connected to an economizer 46 via an expansion valve 16. The gas phase part of the economizer 46 is connected by an intermediate suction pipe 48 to the intermediate pressure stage of the compressor 1 where the highest cycle efficiency can be obtained.

The liquid phase part of the economizer 46 is connected to the heating side of the heat exchanger 47 through a pipe 43, and further connected to the heating side of the heat exchanger 47 through a pipe 44,
It is connected to the evaporator 17 via a float valve 49 and piping 50. The gas phase portion of the evaporator 17 is connected to the suction port of the compressor 1 through a suction pipe 30.

The heat exchanger 47 is connected to the vicinity of the oil-rich portion of the liquid phase portion of the evaporator 17 through an oil return pipe 51, and the oil-rich refrigerant liquid is guided to the heated side. . The oil refrigerant liquid guided to the heat exchanger 47 is heated and the refrigerant evaporates, and the oil contained in the refrigerant is also carried along with the evaporated refrigerant gas to the oil return pipe 37.
is guided to the suction pipe 30 and returned to the compressor 1.

This evaporated gas is sucked in from the suction port of the compressor 1, but at this time, the refrigerant liquid in the pipe 43 is supercooled, so that it does not reduce the refrigerating capacity of the refrigerator. A Mollier diagram of this example is shown in FIG. Since the heat exchanger 47 is disposed downstream of the economizer 46, the oil can be returned to the compressor 1 in the heat exchanger 47 without impairing the increase in refrigeration effect due to the economizer cycle. Moreover, since the value of the refrigeration effect hh is increased by the supercooling effect of →, even if there is a loss in the compressor 1 that evaporates in the heat exchanger 47 and wastefully compresses the refrigerant gas that does not contribute to the refrigeration effect. This loss can be compensated for by the above-mentioned effect of increasing the refrigeration effect due to supercooling, and a decrease in the efficiency of the entire refrigeration system can be prevented.

FIG. 2 shows another embodiment, in which the economizer 46
This uses a closed economizer. The refrigerant liquid led from the condenser 15 to the outlet pipe 33 is branched, one side enters the pipe 52, and the high-pressure refrigerant liquid flows through the heating side of the economizer 46, the pipe 43, the heating side of the heat exchanger 47, and the pipe 44. Then, it passes through the expansion valve 53, becomes a low-pressure refrigerant, and reaches the evaporator 17 via the pipe 50. The other branched refrigerant liquid reaches the expansion valve 16 via the pipe 54, is depressurized, enters the economizer 46, is heated and becomes refrigerant vapor, and flows into the intermediate suction pipe 4.
8, the intermediate pressure stage of the compressor 1 is reached where the highest cycle efficiency can be obtained. A Mollier diagram of this example is shown in FIG. It has the same effect as the one in FIG.

FIG. 3 shows another embodiment, in which the evaporator 17 of FIG. 1 is of a liquid circulation coil type, and is equipped with a low-pressure receiver 18 and a refrigerant pump 19.

The liquid phase part of the economizer 46 is connected to the pipe 43 by
Connected to the heating side of the heat exchanger 47, and further connected to the piping 4
4. Connected to the low pressure receiver 18 via the float valve 49 and piping 50. The gas phase portion of the low pressure receiver 18 is connected to the suction port of the compressor 1 through a suction pipe 30.

The liquid phase portion of the low pressure receiver 18 is connected to the low pressure receiver 18 again via a pipe 55, a refrigerant pump 19, a pipe 56, an evaporator 17, and a pipe 57. In the low-pressure receiver 18, the refrigerant liquid is stored at the bottom, forming a refrigerant liquid storage section. heat exchanger 4
7 is connected to the vicinity of a portion containing a large amount of oil in the liquid phase portion of the low-pressure receiver 18 through an oil return pipe 51, so that the oil refrigerant liquid is guided to the heated side.

It has the same effect as the one in FIG.

Note that as the economizer 46, a closed economizer may be used as in FIG.

As the oil refrigerant liquid storage section in the low pressure section, the evaporator 1
7. Other locations in the low-pressure receiver 18 can also be selected as low-pressure portions and in which oil refrigerant liquid is stored.

As the compressor, in addition to rotary displacement types such as rotary vane type, rotary piston type, screw type, and Roots type, systems such as reciprocating displacement type and centrifugal type are also used. Further, an oil injection type or a dry type may be used.

〔Effect of the invention〕

According to the present invention, the increase in the refrigeration effect due to supercooling can be achieved without impairing the increase in the refrigeration effect in the economizer cycle, while compensating for the loss due to refrigerant gas generation in places other than the evaporator, and preventing a decrease in the efficiency of the refrigeration system. Therefore, it is possible to provide an oil return device for a refrigeration system that can return oil flowing into a low pressure section to a compressor, which is extremely effective in practice.

[Brief explanation of the drawing]

1, 2, and 3 show different embodiments of the present invention, and FIG. 4 shows the different embodiments of the present invention.
Mollier diagram of the example in the figure, Figure 5 is the second
FIG. 3 shows a Mollier diagram of the embodiment in the figure. 1... Compressor, 3... Oil supply hole, 11... Oil separator, 12... Oil pump, 13... Oil cooler, 15
... Condenser, 16 ... Expansion valve, 17 ... Evaporator,
18...Low pressure receiver, 19...Refrigerant pump, 3
0... Suction pipe, 31, 32... Discharge pipe, 33...
Outlet pipe, 34, 35... Oil pipe, 37... Oil return pipe, 43, 44... Piping, 46... Economizer, 47... Heat exchanger, 48... Intermediate suction pipe, 4
9...Float valve, 50...Piping, 51...Oil return pipe, 52...Piping, 53...Expansion valve, 54...
Piping, 55, 56, 57... Piping.

Claims (1)

[Claims] 1. A refrigeration cycle is formed by a compressor, a condenser, an evaporator, and a refrigerant path connecting these, and an economizer is provided in the middle of the refrigerant path from the outlet of the condenser to the inlet of the evaporator. , in an oil return device for a refrigeration system in which a gas phase portion of the economizer is connected to an intermediate pressure stage of the compressor, an oil refrigerant liquid storage section in a low pressure section of the refrigeration system where an oil refrigerant liquid is stored; A heat exchanger is provided at a position lower than the liquid level, and an oil refrigerant liquid containing a large amount of oil among the liquids stored in the oil refrigerant liquid storage part is guided to the heated side of the heat exchanger, and the oil refrigerant liquid containing a large amount of oil is guided from the economizer. An oil return device for a refrigeration system, characterized in that it is configured to exchange heat with a refrigerant liquid and guide evaporated refrigerant vapor and oil to a refrigerant path on the suction side of the compressor. 2. The device according to claim 1, wherein the economizer is a closed economizer. 3. The apparatus of claim 1, wherein the economizer is an open economizer. 4. The device according to claim 1, wherein the storage section is an evaporator. 5. The device of claim 1, wherein the reservoir is a low pressure receiver.