CN115823761A

CN115823761A - Two-stage refrigeration system

Info

Publication number: CN115823761A
Application number: CN202310101212.8A
Authority: CN
Inventors: 周康; 董岩; 何雨果; 熊小文
Original assignee: Cnispgroup Technology Co ltd
Current assignee: Cnispgroup Technology Co ltd
Priority date: 2023-01-31
Filing date: 2023-01-31
Publication date: 2023-03-21
Anticipated expiration: 2043-01-31
Also published as: CN115823761B

Abstract

The invention discloses a secondary refrigeration system, comprising: the refrigeration system comprises a compressor, a condenser, an ejector, a flash evaporation container, a first evaporator and a second evaporator, wherein in a first working mode, the first evaporator participates in refrigeration, and in a second working mode, the second evaporator participates in refrigeration in cooperation with the first evaporator. This second grade refrigerating system utilizes the compressor as the quantity of the refrigerant of power increase flow through the second evaporator and combines to utilize the heat transfer pipeline to absorb heat to increase the super-cooled rate of refrigerant in the second mode of operation to can show the refrigerating output that improves the second evaporator, compare in the mode that utilizes the ejector to drive the refrigerant flow through the second evaporator, this system is showing the refrigerating system who is superior to among the prior art to the promotion of the refrigerating output of second evaporator in the second mode of operation.

Description

Two-stage refrigeration system

Technical Field

The invention relates to the technical field of refrigeration, in particular to a secondary refrigeration system.

Background

As is known, a conventional refrigeration system generally comprises a compressor, an evaporator, a condenser, an expansion device, a storage container (for storing refrigerant), valve means and associated piping (refrigeration piping) for connecting the above-mentioned components, the compressor providing power to cause refrigerant to flow from an outlet side of the compressor and to pass through the condenser, the storage container, the expansion device, the evaporator in turn, and then to enter the compressor through an inlet side of the compressor, thereby forming a continuous cycle refrigeration circuit. The refrigerant is expanded by the expansion valve and then converted into a gaseous state or a gas-liquid two-phase mixed state, and the refrigerant in the state absorbs the heat of the gas in the ambient environment (indoor environment) outside the evaporator in the process of passing through the evaporator, so that the ambient environment is refrigerated.

For the working condition with the requirement of the secondary refrigeration temperature range, the single number or type of evaporators are difficult to meet the requirement of the secondary refrigeration temperature range, for example, if the refrigeration system is required to selectively maintain the indoor environment in the temperature range of-5 ℃ to 10 ℃ and the temperature range of-35 ℃ to-5 ℃, the single evaporator is difficult to realize. To enable the two temperature ranges of the indoor environment to be adjusted, two evaporators and expansion elements corresponding to the two evaporators are provided in the refrigeration circuit, wherein the first evaporator is used for maintaining the indoor environment at a higher temperature range (e.g., a temperature range of-5 ℃ to 10 ℃), and the second evaporator is used for maintaining the indoor temperature at a lower temperature range (e.g., a temperature range of-35 ℃ to-5 ℃) alone or in combination with the first evaporator.

The refrigerant in the above-mentioned conventional refrigeration system (including the two-stage refrigeration system) flows out from the evaporator and then directly enters into the compressor through the inlet side of the compressor, and since the corresponding expansion part has a large throttle pressure, it is easy to cause a large pressure difference between the outlet side and the inlet side of the compressor, and the large pressure difference may cause the refrigerant to generate a large compression ratio, which may reduce the efficiency of the compressor, so that the noise of the compressor is increased, and the large compression ratio causes the temperature of the refrigerant at the outlet side to be too high, thereby affecting the refrigeration efficiency.

In order to solve the above problems, a refrigeration system is provided in the prior art, in which a flash evaporation container is selected as a storage container, and the flash evaporation container is used for gas-liquid separation of refrigerant flowing into the flash evaporation container by means of gravity; optionally configuring the compressor to have two inlet sides and one outlet side, the two inlet sides including a bottom inlet side (the inlet side being a low pressure inlet side) and an intermediate inlet side (the inlet side being a medium pressure inlet side); an ejector is additionally arranged between the flash evaporation container and the condenser, and the ejector is provided with a high-pressure inlet end, a low-pressure inlet end and an outlet end; the outlet of the condenser is connected with the high-pressure inlet end of the ejector through a pipeline, so that the liquid refrigerant flowing out of the outlet of the condenser flows into the ejector through the high-pressure inlet end and flows out of the outlet end; an outlet leading-out pipeline of the self-evaporator is connected to a low-pressure inlet end of the ejector so that the gaseous or gas-liquid two-phase refrigerant flowing out of the evaporator is injected (or attracted) by the refrigerant entering the ejector through a high-pressure inlet end, and the two refrigerants are mixed in the ejector and finally flow out of an outlet end of the ejector; the pipeline is led out from the outlet end of the ejector and extends into the liquid refrigerant of the flash evaporation container above the liquid level, so that the refrigerant mixed by the ejector is guided to the flash evaporation container, and the liquid phase part of the refrigerant entering the flash evaporation container falls down by means of gravity.

In the above system, a line leads from the flash vessel, which line is connected to the intermediate inlet side of the compressor, which allows the vapor portion of the refrigerant in the flash vessel to enter the compressor through the line, the intermediate inlet side, for replenishing the compressor with refrigerant, and thus, the line becomes a make-up gas line. The pipeline is used for supplying air to the compressor, so that the compression ratio of the refrigerant passing through the compressor can be reduced, and the efficiency of the compressor can be improved to a certain degree.

However, in the actual operation of the above refrigeration system, the applicant found the following problems:

1. when the indoor temperature is maintained in a higher temperature range by using the refrigeration system (the working mode in which the refrigeration system is located is not called as a first working mode), namely, when the refrigeration system participates in heat exchange refrigeration only through the first evaporator, the first evaporator can generate relatively higher refrigerating capacity by adopting the refrigeration loop, so that the refrigeration efficiency in the temperature range is improved, and the noise of the compressor is lower.

2. However, when the indoor temperature is maintained in a lower temperature range by using the refrigeration system (the operation mode in which the refrigeration system is located is not referred to as the second operation mode), that is, when the second evaporator or both evaporators participate in heat exchange refrigeration, the above-mentioned refrigeration circuit cannot produce ideal refrigeration efficiency in the temperature range, the relative cooling capacity of the second evaporator is not high, and the refrigeration system cannot rapidly reduce the indoor temperature to the lower temperature range. The applicant has found, by analysis, that the cause of this problem is: 1. on one hand, the refrigerant flowing out of the evaporator can only participate in the refrigeration cycle after passing through the ejector, and the ejector has limited ejection effect on the refrigerant as a power source, so that sufficient refrigerant cannot be maintained to pass through the second evaporator; on the other hand, since all the refrigerant flowing out of the evaporator needs to pass through the ejector and enter the flash evaporation container, the refrigerant is used for supplementing gas for the compressor through gas-liquid separation of the flash evaporation container, excessive gaseous refrigerant supplement for the compressor can cause the compression ratio of the refrigerant to be too small, and the too small compression ratio can cause the compressor to run under the too small load state, which not only can cause the pressure of the liquid refrigerant flowing to the high-pressure inlet side after passing through the condenser to be insufficient, but also can cause the insufficient ejection power of the refrigerant from the evaporator, and can increase the load of the condenser.

3. When the refrigeration system is operating in the second mode of operation, operating the compressor at too little load may also reduce the efficiency of the compressor.

Disclosure of Invention

In view of the above technical problems in the prior art, embodiments of the present invention provide a two-stage refrigeration system.

In order to solve the technical problem, the embodiment of the invention adopts the following technical scheme:

a two-stage refrigeration system comprising:

a compressor having a low pressure inlet side, a medium pressure inlet side, and an outlet side;

a condenser having an inlet connected to an outlet side of the compressor such that the refrigerant compressed by the compressor flows toward the condenser;

the high-pressure inlet end of the ejector is connected with the outlet of the condenser, so that the refrigerant flowing out of the outlet of the condenser flows to the ejector;

the top of the flash evaporation container is connected with the outlet end of the ejector; a gas supplement pipeline is led out from the top of the flash evaporation container and connected to the medium pressure inlet side of the compressor, a supply pipeline is led out from the bottom of the flash evaporation container, and a first refrigeration pipeline and a second refrigeration pipeline are led out from the far end of the supply pipeline;

an evaporator comprising a first evaporator for maintaining a first temperature range and a second evaporator for maintaining a second temperature range, the second temperature range being lower than the first temperature range; the first evaporator and the second evaporator are respectively arranged on the first refrigeration pipeline and the second refrigeration pipeline in parallel, and a first expansion valve and a second expansion valve are correspondingly arranged at the upstream of the first evaporator and the upstream of the second evaporator; wherein:

a first ejector pipeline is led out from the outlet of the first evaporator and is connected to the low-pressure inlet end of the ejector;

a first return line is led out from the outlet of the second evaporator and connected to the low-pressure inlet side of the compressor;

and a first heat exchanger is arranged on a second refrigeration pipeline at the upstream of the second expansion valve, a first heat exchange pipeline is led out from a pipeline at the upstream of the evaporator, so that the first heat exchange pipeline passes through the first heat exchanger, a third expansion valve is arranged on the first heat exchange pipeline, and the first heat exchange pipeline passing through the first heat exchanger is used as a second injection pipeline and is connected to the low-pressure inlet end of the injector.

Preferably, the first and second liquid crystal display panels are,

a second heat exchanger is arranged on the first refrigeration pipeline at the upstream of the first expansion valve; a first refrigeration pipeline at the upstream of the second heat exchanger is provided with a first branch pipeline and a second branch pipeline which are arranged in parallel, the first branch pipeline is provided with a first electric control switch valve, and the second branch pipeline is provided with a throttle valve;

a second heat exchange pipeline is led out from a first refrigeration pipeline at the downstream of the second heat exchanger, so that the second heat exchange pipeline passes through the second heat exchanger, a fourth expansion valve is arranged on the second heat exchange pipeline, and the second heat exchange pipeline passing through the second heat exchanger is used as a third injection pipeline to be connected to the low-pressure inlet end of the injector; wherein:

the first heat exchange line leads from the first refrigeration line downstream of the second heat exchanger.

Preferably, the first and second electrodes are formed of a metal,

a second return pipeline is led out from the outlet of the first evaporator and connected to the low-pressure inlet side of the compressor;

and a first flow valve is arranged on the first injection pipeline, and a second flow valve is arranged on the second return pipeline.

Preferably, a third heat exchanger is arranged on a pipeline between the ejector and the condenser, and a third heat exchange pipeline is led out from a pipeline at the downstream of the third heat exchanger, so that the third heat exchange pipeline passes through the third heat exchanger, a fifth expansion valve is arranged on the third heat exchange pipeline, and the third heat exchange pipeline passing through the third heat exchanger is connected to the top of the flash evaporation container.

Preferably, the ejector comprises a first ejector and a second ejector; the first ejector pipeline is connected to the low-pressure inlet end of the first ejector, and the second ejector pipeline and the third ejector pipeline are connected to the low-pressure inlet end of the second ejector.

Preferably, a third flow valve is arranged on the air supply pipeline.

Preferably, a second electrically-controlled switch valve is arranged on the first heat exchange pipeline.

Preferably, a third electrically-controlled switch valve is arranged at the upstream of the high-pressure inlet end of the second ejector; and a fourth electric control switch valve is arranged at the upper stream of the low-pressure inlet end of the second ejector.

Preferably, a pressure sensor is disposed on the air supply pipeline, downstream of the outlet side of the compressor, upstream of the low pressure inlet side of the compressor, and the like.

Preferably, a fifth electrically controlled switching valve is disposed downstream of the outlet side of the compressor, and a sixth electrically controlled switching valve is disposed upstream of the low pressure inlet side of the compressor.

Compared with the prior art, the secondary refrigeration system disclosed by the invention has the beneficial effects that:

this refrigerating system utilizes the compressor as the volume of the refrigerant of power increase flow through the second evaporator and combines to utilize heat transfer pipeline heat absorption to increase the super-cooled rate of refrigerant in the second mode of operation to can show the refrigerating output that improves the second evaporator, compare in the mode that utilizes ejector drive refrigerant flow through the second evaporator, this system is showing better than the refrigerating system among the prior art to the promotion of the refrigerating output of second evaporator in the second mode of operation.

The summary of various implementations or examples of the technology described in this disclosure is not a comprehensive disclosure of the full scope or all features of the disclosed technology.

Drawings

In the drawings, which are not necessarily drawn to scale, like reference numerals may describe similar components in different views. Like reference numerals having letter suffixes or different letter suffixes may represent different instances of similar components. The drawings illustrate various embodiments, by way of example and not by way of limitation, and together with the description and claims, serve to explain the inventive embodiments. The same reference numbers will be used throughout the drawings to refer to the same or like parts, where appropriate. Such embodiments are illustrative, and are not intended to be exhaustive or exclusive embodiments of the present apparatus or method.

Fig. 1 is a refrigerant flow diagram of a two-stage refrigeration system according to an embodiment of the present invention during a first mode of operation.

Fig. 2 is a flow diagram of refrigerant in a two-stage refrigeration system according to an embodiment of the present invention during a second mode of operation.

Reference numerals:

11-a compressor; 12-a condenser; 131-a first ejector; 1311-high pressure inlet port; 1312-low pressure inlet port; 1313-an outlet end; 132-a second eductor; 1321-high pressure inlet port; 1322-a low pressure inlet end; 1323-an outlet port; 14-a flash vessel; 151-first evaporator; 1511-first expansion valve; 152-a second evaporator; 1521-a second expansion valve; 21-a first heat exchanger; 22-a second heat exchanger; 23-a third heat exchanger; 31-supply line; 321-a first refrigeration circuit; 3211-a first branch line; 3212-a second branch line; 322-a second refrigeration circuit; 331-a first return line; 332-a second return line; 34-total return line; 41-a first heat exchange line; 411 — third expansion valve; 42-a second heat exchange circuit; 421-a fourth expansion valve; 43-a third heat exchange circuit; 431-a fifth expansion valve; 51-a first injection line; 52-second bleed line; 53-third injection line; 54-auxiliary injection pipeline; 61-a first flow valve; 62-a second flow valve; 63-a third flow valve; 71-a first pressure sensor; 72-a second pressure sensor; 73-a third pressure sensor; 81-a first circulation line; 82-a second circulation line; 83-third recycle line; 84-a gas supplement pipeline; 85-a compensation pipeline; 91-a first electrically controlled on-off valve; 92-a second electrically controlled on-off valve; 93-a third electrically controlled on-off valve; 94-a fourth electrically controlled on-off valve; 95-fifth electric control switch valve; 96-a sixth electrically controlled on-off valve; 97-seventh electrically controlled on-off valve; 98-eighth electrically controlled on-off valve; 99-throttle valve.

Detailed Description

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

To maintain the following description of the embodiments of the present invention clear and concise, a detailed description of known functions and known components of the invention have been omitted.

Embodiments of the present invention disclose a two-stage refrigeration system having two operating modes (a first operating mode and a second operating mode) in terms of temperature control, the refrigeration system being dedicated to provide two temperature ranges (a first temperature range and a second temperature range) for an indoor environment by operating in the two operating modes, i.e., in the first operating mode, the refrigeration system is dedicated to maintain the indoor environment within the first temperature range; in a second mode of operation, the refrigeration system is dedicated to maintaining the indoor environment within a second temperature range. The second temperature range is lower than the first temperature range, e.g., the first temperature range is approximately a temperature range of-5 ℃ to 10 ℃ in which items in the indoor environment may be refrigerated, and thus the first temperature range may be considered a refrigeration temperature and, correspondingly, the first mode of operation may be considered a refrigeration mode; the second temperature range is approximately a temperature range of-35 c to-5 c that allows items in the indoor environment to be frozen, and thus, the second temperature range may be considered a freezing temperature and, correspondingly, the second mode of operation may be considered a freezing mode.

As shown in fig. 1 and 2, the main body part of the refrigerating system includes: the system comprises a compressor 11, a condenser 12, a flash tank, an ejector, an evaporator, a heat exchanger, relevant pipelines, an expansion valve, a switch valve and a pressure sensor.

A compressor 11 having two inlet sides and one outlet side is selected as the compressor 11 of the present refrigeration system, i.e. the compressor 11 has a low pressure inlet side, a medium pressure inlet side and an outlet side. Both the low pressure inlet side and the medium pressure inlet side allow refrigerant (in a gaseous state) to enter the compressor 11, however, both the low pressure inlet side and the medium pressure inlet side define a pressure range for allowing refrigerant to enter the compressor 11, the pressure range being set at least one purpose of avoiding an excessive pressure difference between refrigerant entering the compressor 11 through the low pressure inlet side and compressed and refrigerant entering the compressor 11 through the medium pressure inlet side. To be able to monitor to avoid that the pressure on each side of the compressor 11 exceeds a defined pressure range, a first pressure sensor 71 is provided on the line downstream of the outlet side of the compressor 11, a second pressure sensor 72 is provided on the line upstream of the low pressure inlet side, and a third pressure sensor 73 is provided on the line upstream of the medium pressure inlet side.

The condenser 12 is located downstream of an outlet side of the compressor 11, the condenser 12 is installed outdoors when installed, the condenser 12 has an inlet and an outlet, the outlet side of the compressor 11 is connected to the inlet of the condenser 12 through a first circulation line 81, which allows high-pressure gaseous refrigerant compressed by the compressor 11 to enter the condenser 12 through the first circulation line 81 and to flow out of the outlet of the condenser 12, and the refrigerant is reduced in temperature by the condenser 12 to be converted into liquid refrigerant while passing through the condenser 12.

The ejector comprises a first ejector 131 and a second ejector 132; the first and

second ejectors

131, 132 each have a high

pressure inlet end

1311, 1321, a low

pressure inlet end

1312, 1322 and an

outlet end

1313, 1323. The first ejector 131 and the second ejector 132 are arranged in parallel, the outlet of the condenser 12 is connected to the high-

pressure inlet ports

1311, 1321 of the first ejector 131 and the second ejector 132 through the second circulation line 82, and an electrically controlled on-off valve (a third electrically controlled on-off valve 93) is provided upstream of the high-pressure inlet port 1321 of the second ejector 132. Refrigerant exiting the condenser 12 enters the first eductor 131 and optionally the second eductor 132 via the second recirculation line 82 and exits the outlet end 1313 of the first eductor 131 and the outlet end 1323 of the second eductor 132.

The flash tank 14 is for storing the refrigerant, and the flash tank 14 is for gas-liquid separating the refrigerant; the flash vessel 14 has an inlet connection at the top which is connected to the outlet ends 1313, 1323 of the first and

second ejectors

131, 132 by a third recycle line 83, which allows refrigerant flowing from the outlet ends 1313, 1323 of the first and

second ejectors

131, 132 to enter the flash vessel 14, an outlet connection at the top of the flash vessel 14 which is also connected by other lines to other components for the flash vessel 14 to receive refrigerant otherwise.

The outlet connection at the top of the flash vessel 14 is connected to the medium pressure inlet side of the compressor 11 by a fourth circulation line, which allows gaseous refrigerant in the flash vessel 14 to enter the compressor 11 through the fourth circulation line, and since the gaseous refrigerant in this respect enters the compressor 11 for the purpose of replenishing the compressor 11, the fourth circulation line is not referred to as a make-up gas line 84. The gas supply line 84 is provided with an electrically controlled flow rate control valve (third flow rate valve 63) for controlling the flow rate of the refrigerant entering the compressor 11 through the medium pressure inlet side.

The evaporator includes a first evaporator 151 and a second evaporator 152, the first evaporator 151 contributing to maintain the indoor environment within a first temperature range, the second evaporator 152 contributing to maintain the indoor environment within a second temperature range in combination with the first evaporator 151, and since the second temperature range is lower than the first temperature range, the heat exchange (heat absorption) capacity of the second evaporator 152 is required to be higher than that of the first evaporator 151.

A feed line 31 leads from an outlet connection at the bottom of the flash vessel 14, the distal end of the feed line 31 being split into two paths, a first refrigeration line 321 and a second refrigeration line 322. First evaporator 151 is provided in first refrigeration line 321, second evaporator 152 is provided in second refrigeration line 322, and first expansion valve 1511 is provided in first refrigeration line 321 upstream of first evaporator 151, and second expansion valve 1521 is provided in second refrigeration line 322 upstream of second evaporator 152. Since the compressor 11 makes the refrigerant enter the flash tank 14 at a certain pressure, the liquid refrigerant in the flash tank 14 can enter the first refrigeration line 321 and the second refrigeration line 322 through the supply line 31 respectively to pass through the first expansion valve 1511 and the second expansion valve 1521, and the expansion valves are used for expanding the liquid refrigerant to form a gas-liquid mixed refrigerant, and the refrigerant absorbs heat when passing through the corresponding evaporators, thereby achieving the purpose of refrigeration.

A second return line 332 leads from the outlet of the first evaporator 151 and a first return line 331 leads from the outlet of the second evaporator 152, the first return line 331 and the second return line 332 being connected at distal ends to form a total return line 34, the total return line 34 being connected to the low pressure inlet side of the compressor 11. From the outlet of the first evaporator 151 a first bleed line 51 leads, which first bleed line 51 is connected to the low pressure inlet end 1312 of the first ejector 131. In this way, in fact, the outlet of the first evaporator 151 is divided into two lines, and the outlet of the second evaporator 152 is divided into only one line, so that the refrigerant flowing out of the outlet of the first evaporator 151 can be selectively introduced into the compressor 11 and/or the first ejector 131, and the refrigerant flowing out of the outlet of the second evaporator 152 is only used for being introduced into the compressor 11.

An electric control flow control valve (a second flow valve 62) is arranged on the second return pipeline 332, an electric control flow control valve (a first flow valve 61) is also arranged on the first injection pipeline 51, and the two electric control flow control valves have the adjusting capacity from closing to the maximum opening degree, so that the two electric control flow control valves are matched to adjust the distribution ratio of the refrigerant flowing through the second return pipeline 332 and the first injection pipeline 51 and can close any one of the two pipelines.

One heat exchanger is provided in second refrigeration line 322 upstream of second expansion valve 1521, and this heat exchanger is not referred to as first heat exchanger 21, and one heat exchanger is provided in first refrigeration line 321 upstream of first expansion valve 1511, and this heat exchanger is not referred to as second heat exchanger 22. The first heat exchanger 21 is configured to have a larger heat exchange capacity than the second heat exchanger 22. The first refrigeration line 321 upstream of the second heat exchanger 22 is formed with two branches, i.e., a first branch line 3211 and a second branch line 3212, an electrically controlled on-off valve (a first electrically controlled on-off valve 91) is provided on the first branch line 3211, and a throttle valve 99 is provided on the second branch line 3212, the throttle valve 99 being used to reduce the flow rate of refrigerant passing through the second branch line 3212. An electrically controlled on-off valve (an eighth electrically controlled on-off valve 98) is provided on the second refrigeration line 322 upstream of the first heat exchanger 21, and is used to control the refrigerant to enter the second refrigeration line 322.

A first heat exchange pipeline 41 is led out from the first refrigeration pipeline 321 downstream of the second heat exchanger 22, so that the first heat exchange pipeline 41 passes through the first heat exchanger 21, a third expansion valve 411 is arranged on the first heat exchange pipeline 41, an electrically controlled switch valve (a second electrically controlled switch valve 92) is arranged on the first heat exchange pipeline 41 upstream of the third expansion valve 411, and the first heat exchange pipeline 41 passing through the first heat exchanger 21 is connected to the low-pressure inlet end 1322 of the second ejector 132 as a second ejector pipeline 52. The first heat exchange line 41 leads a part of the refrigerant in the first refrigeration line 321 out, the refrigerant is expanded by the third expansion valve 411 to form a gas-liquid mixed refrigerant, and the refrigerant absorbs heat of the refrigerant in the second refrigeration line 322 after passing through the first heat exchanger 21.

A second heat exchange pipeline 42 is led out from the first refrigeration pipeline 321 downstream of the second heat exchanger 22, so that the second heat exchange pipeline 42 passes through the second heat exchanger 22, a fourth expansion valve 421 is arranged on the second heat exchange pipeline 42, the second heat exchange pipeline 42 passing through the second heat exchanger 22 is collected with the second injection pipeline 52 as a third injection pipeline 53 to form a secondary injection pipeline 54, and is connected to the low-pressure inlet end 1322 of the second injector 132, and an electrically controlled switch valve (a fourth electrically controlled switch valve 94) is arranged on the secondary injection pipeline 54. The second heat exchange line 42 leads a part of the refrigerant in the first refrigeration line 321 out, the refrigerant is expanded by the fourth expansion valve 421 to form a gas-liquid mixed refrigerant, and the refrigerant absorbs heat of the refrigerant in the second refrigeration line 322 after passing through the second heat exchanger 22.

The third heat exchanger 23 is installed on the second circulation pipeline 82, the third heat exchange pipeline 43 is led out from the second circulation pipeline 82 at the downstream of the third heat exchanger 23, so that the third heat exchange pipeline 43 passes through the third heat exchanger 23, the fifth expansion valve 431 is installed on the third heat exchange pipeline 43, an electric control switch valve (a seventh electric control switch valve 97) is installed on the third heat exchange pipeline 43 at the upstream of the fifth expansion valve 431, the electric control switch valve is used for controlling the on-off of the third heat exchange pipeline 43, and the third heat exchange pipeline 43 passing through the third heat exchanger 23 is connected to an inlet joint of the flash evaporation container 14 as a compensation pipeline 85. The third heat exchange line 43 serves to draw a portion of the refrigerant in the first circulation line 81 expanded by the fifth expansion valve 431 to form a gas-liquid mixture refrigerant, which serves to absorb heat of the refrigerant in the second circulation line 82.

An electrically controlled switching valve (a fifth electrically controlled switching valve 95) is installed downstream of the outlet side of the compressor 11, and an electrically controlled switching valve (a sixth electrically controlled switching valve 96) is installed upstream of the low pressure inlet side of the compressor 11, so that both the electrically controlled switching valves are opened when the refrigeration system is operated, and so that both the electrically controlled switching valves are closed when the compressor 11 is repaired or refrigerant is injected into the system.

The operation of the refrigeration system described above in the first and second modes of operation is described below.

First mode of operation

As shown in fig. 1, when the ambient temperature needs to be adjusted and maintained within the first temperature range, the compressor 11 is operated to make the refrigerant enter the condenser 12 through the first circulation line 81, the condenser 12 is used for cooling the refrigerant to convert the gaseous refrigerant into the liquid refrigerant, the refrigerant flowing out of the condenser 12 enters the first ejector 131 through the high-pressure inlet end 1311 of the first ejector 131, the refrigerant performs an ejector effect on the refrigerant from the low-pressure inlet end 1312 while passing through the first ejector 131, the refrigerant sucked from the low-pressure inlet end 1312 also enters the first ejector 131, the two refrigerants are mixed in the first ejector 131 and then enter the flash container 14 through a pipeline, the flash container 14 performs gas-liquid separation on the part of the refrigerant, the gaseous refrigerant enters the compressor 11 from the medium-pressure inlet side through the gas supplement line 84 to participate in the circulation, and the liquid refrigerant falls down by gravity.

The eighth electrically controlled on-off valve 98 is controlled to be closed, the first electrically controlled on-off valve 91 is controlled to be opened, the second electrically controlled on-off valve 92 is controlled to be closed, the liquid refrigerant enters the first refrigeration pipeline 321 via the supply pipeline 31 without entering the second refrigeration pipeline 322, the refrigerant entering the first refrigeration pipeline 321 can simultaneously pass through the first branch pipeline 3211 and the second branch pipeline 3212, and then passes through the first expansion valve 1511, after passing through the first expansion valve 1511, the liquid refrigerant is converted into a gas-liquid mixed refrigerant, and after passing through the first evaporator 151, the refrigerant in this state causes the first evaporator 151 to absorb heat to the indoor environment so as to control the indoor environment within the first temperature range.

The refrigerant flowing through the first evaporator 151 flows out of the outlet of the first evaporator 151 and is then split into two paths, one path directly entering the compressor 11 from the low pressure inlet side through the second return line 332 and the other path entering the first ejector 131 from the low pressure inlet port 1312 through the first ejector line 51 and then flowing to the flash tank 14 by mixing with the refrigerant from the condenser 12.

The operation of the refrigeration system is adapted to general conditions, and the general conditions refer to: the outdoor temperature is not high, and the required cooling speed is not high.

In the first working mode, the refrigeration system provided by the invention can also adapt to special working conditions, wherein the special working conditions refer to the working conditions that the outdoor temperature is high and rapid cooling is required:

when the outdoor temperature is higher, on the premise that the pressure of the refrigerant on the low-pressure inlet side of the compressor 11 can meet the requirement of the pressure range, the opening degree of the first flow valve 61 and the opening degree of the second flow valve 62 are adjusted, so that more refrigerant passing through the first evaporator 151 enters the flash evaporation container 14 through the first injection pipeline 51 and the first injector 131, the injection effect of the injector is more obvious in the improvement of the refrigeration effect of the medium-temperature evaporator (the first evaporator 151), and the refrigeration capacity of the first evaporator 151 can be further improved.

If the indoor environment cooling speed is still not fast under the working condition of high outdoor temperature in the manner, the fourth electronic control switch valve 94 on the secondary injection pipeline 54 is opened, the second electronic control switch valve 92 is closed, at the moment, the second heat exchange pipeline 42 and the third injection pipeline 53 are conducted, a part of refrigerant in the first refrigeration pipeline 321 flows through the second heat exchanger 22 after being expanded by the fourth expansion valve 421, and absorbs the heat of the refrigerant in the first refrigeration pipeline 321 when passing through the second heat exchanger 22, so that the supercooling degree of the refrigerant in the first refrigeration pipeline 321 is increased, the refrigerating capacity of the first evaporator 151 is increased, and the cooling speed of the indoor environment is increased. The heat-absorbed refrigerant passes through the secondary ejector line 54 through the second ejector 132 and into the flash vessel 14.

In the first mode, the refrigeration system provided by the invention can ensure that the refrigeration system operates stably.

On the premise that the pressure of the refrigerant at the low pressure inlet side of the compressor 11 is ensured to be within the pressure range, if the pressure of the refrigerant at the medium pressure inlet side of the compressor 11 is high, the pressure at the medium pressure inlet side can be reduced to a reasonable range by controlling the third flow valve 63 to reduce the flow rate of the refrigerant passing through the gas supplementing pipeline 84, which is beneficial to the smooth operation of the compressor 11 protected by the compressor 11 and reduces the noise of the compressor 11.

On the premise that it is ensured that the pressure of the refrigerant at the low-pressure inlet side of the compressor 11 is within the pressure range, if the pressure of the refrigerant at the medium-pressure inlet side of the compressor 11 is insufficient and the pressure of the refrigerant is still insufficient while the third flow valve 63 is adjusted to the maximum, the seventh electrically controlled on-off valve 97 may be opened. After the first switching valve is opened, a part of the refrigerant in the second circulation line 82 enters the third heat exchange line 43, so that the part of the refrigerant passes through the third heat exchanger 23 after being expanded by the fifth expansion valve 431 to absorb heat of the refrigerant in the second circulation line 82, and most of the heat-absorbed refrigerant is in a gaseous state, and the part of the refrigerant enters the flash tank 14 through the compensating line 85 to increase the pressure of the gaseous refrigerant, thereby effectively increasing the pressure of the refrigerant at the medium pressure inlet side of the compressor 11.

In the operation process of the system, if the pressure on the outlet side of the compressor 11 is too high, the third electrically controlled switch valve 93 can be opened, so that the refrigerant flowing out of the condenser 12 can also flow into the flash evaporation container 14 through the second ejector 132, which is not only beneficial to reducing the pressure on the outlet side of the compressor 11, but also can increase the ejection effect on the direction from the secondary ejection pipeline 54, thereby not only ensuring the stable operation of the compressor 11, but also increasing the refrigerating capacity of the first evaporator 151.

Second mode of operation

As shown in fig. 2, when it is required to adjust and maintain the ambient temperature within the second temperature range, the compressor 11 is operated to make the refrigerant enter the condenser 12 through the first circulation line 81, the condenser 12 is used to cool the refrigerant and convert the gaseous refrigerant into the liquid refrigerant, the refrigerant flowing out of the condenser 12 enters the first ejector 131 and the second ejector 132 through the high pressure inlet ends 1311, 1321 of the first ejector 131 and the second ejector 132, the refrigerant performs an ejector action on the refrigerant from the low pressure inlet ends 1312, 1322 during passing through the first ejector 131 and the second ejector 132, and then draws the refrigerant from the low

pressure inlet end

1312, 1322 into the first ejector 131 and the second ejector 132, the two refrigerant components are mixed in the first ejector 131 and the second ejector 132 and then enter the flash tank 14 through the injection line, the flash tank 14 separates the refrigerant, the gaseous refrigerant enters the compressor 11 from the medium pressure inlet end through the make-up gas line 84 to participate in the circulation, and the liquid refrigerant falls by means of gravity.

The first electrically controlled switch valve 91 is controlled to be closed, the second electrically controlled switch valve 92 and the eighth electrically controlled switch valve 98 are controlled to be opened, the liquid refrigerant is divided into two paths and respectively enters the first refrigeration pipeline 321 and the second refrigeration pipeline 322, and the refrigerant entering the first refrigeration pipeline 321 can only pass through the second branch pipeline 3212 and is limited by the throttle valve 99, so that the refrigerant passing through the second refrigeration pipeline 322 is more than the refrigerant passing through the first refrigeration pipeline 321.

Refrigerant flowing through the first refrigeration line 321: a first portion, which is expanded by the first expansion valve 1511 and flows through the first evaporator 151, and then enters the first ejector 131 through the first ejector line 51, is used to cool the first evaporator 151 by operating it; a second portion enters the first heat exchange line 41 and absorbs heat through the third expansion valve 411 in the refrigerant in the second refrigeration line 322 passing through the first heat exchanger 21 to increase the subcooling of the refrigerant in the second refrigeration line 322; the third portion enters the second heat exchange line 42 and absorbs heat of the refrigerant flowing through the first refrigeration line 321 in the second heat exchanger 22 through the fourth expansion valve 421 to increase the supercooling degree of the refrigerant in the first refrigeration line 321, thereby increasing the cooling capacity of the first evaporator 151. The first and second

heat exchange lines

41 and 42, after passing through the respective heat exchangers, are drawn by the second eductor 132 as second and

third bleed lines

52 and 53, respectively, and ultimately returned to the flash vessel 14.

The refrigerant flowing through the second refrigeration line 322 passes through the first heat exchanger 21, is absorbed by the refrigerant from the first refrigeration line 321, and is increased in supercooling degree, the refrigerant increased in supercooling degree passes through the second expansion valve 1521, is expanded, and passes through the second evaporator 152, so that the second evaporator 152 absorbs heat, and cools the indoor environment, and the refrigerant flowing out of the second evaporator 152 passes through the first return line 331 and the main return line 34, and then enters the compressor 11 on the low-pressure inlet side.

From the above, it can be seen that:

on the one hand, the refrigerant flowing out of the second evaporator 152 is entirely returned to the low pressure inlet side of the compressor 11 directly, which allows the power of the refrigerant flowing through the second expansion valve 1521 and the second evaporator 152 to be provided directly by the compressor 11, not by the ejector, and thus, the power for driving the refrigerant through the second evaporator 152 is sufficient, enabling the amount of the refrigerant passing through the second evaporator 152 to be increased significantly; on the other hand, the refrigerant in the second refrigeration line 322 absorbs heat from the refrigerant in the first refrigeration line 321 before passing through the second expansion valve 1521, so as to increase the degree of subcooling thereof, and thus the cooling capacity (or refrigeration efficiency) of the second evaporator 152 can be greatly increased.

Therefore, in the second operation mode of the refrigeration system, the amount of the refrigerant flowing through the second evaporator 152 is increased by using the compressor 11 as power, and the supercooling degree of the refrigerant is increased by using the heat absorption of the heat exchange pipeline, so that the cooling capacity of the second evaporator 152 can be significantly increased.

In addition, the degree of vaporization of the refrigerant passing through the second evaporator 152 can be greatly increased by increasing the supercooling degree of the refrigerant passing through the second evaporator 152, so that the amount of the liquid refrigerant entering the compressor 11 is greatly reduced, which is beneficial to improving the operation of the compressor 11 and prolonging the service life of the compressor 11.

Further, in the second operation mode, a portion of the refrigerant (the refrigerant flowing through the second evaporator 152) is circulated between the outlet side and the low pressure inlet side of the compressor 11 without passing through the ejector, so that the load of the compressor 11 is appropriately increased, and the load of the condenser 12 is reduced, which is advantageous for increasing the efficiency of the compressor 11.

In the second mode of operation, refrigerant in the first refrigeration line 321 passes only through the second branch line 3212 and is restricted by the throttling valve 99, which allows a substantial portion of the liquid refrigerant exiting the flash vessel 14 to flow into the second refrigeration line 322, thereby ensuring an adequate supply of refrigerant to the second evaporator 152.

In the second mode of operation, the first evaporator 151 is used to assist the second evaporator 152 in cooling the indoor environment, and almost all of the refrigerant entering the first refrigeration line 321 is returned to the flash tank 14 via the ejector, primarily for make-up air to the medium pressure inlet side of the compressor 11 via the make-up air line 84.

If the pressure requirement on the low pressure inlet side of the compressor 11 can be met by only relying on the refrigerant in the first return line 331, the second flow valve 62 is closed and the first flow valve 61 is fully opened so that the refrigerant flowing out of the first evaporator 151 flows entirely to the flash vessel 14 for replenishing the medium pressure inlet side of the compressor 11.

If the pressure of the refrigerant on the medium pressure inlet side of the compressor 11 is excessively high, the third flow valve 63 is controlled to reduce the supply of the refrigerant on the medium pressure inlet side; if the pressure at the medium pressure inlet side is insufficient, the seventh electrically controlled switch is turned on, so that the third heat exchange pipeline 43 is opened, and further, air is supplemented to the flash evaporation container 14 through the compensation pipeline 85, so as to increase the supply of the refrigerant at the medium pressure inlet side.

Moreover, although exemplary embodiments have been described herein, the scope of the present invention includes any and all embodiments based on the present invention with equivalent elements, modifications, omissions, combinations (e.g., of various embodiments across), adaptations or alterations. The elements of the claims are to be interpreted broadly based on the language employed in the claims and not limited to examples described in the present specification or during the prosecution of the application, which examples are to be construed as non-exclusive. It is intended, therefore, that the specification and examples be considered as exemplary only, with a true scope and spirit being indicated by the following claims and their full scope of equivalents.

The above description is intended to be illustrative and not restrictive. For example, the above-described examples (or one or more versions thereof) may be used in combination with each other. For example, other embodiments may be used by those of ordinary skill in the art upon reading the above description. In addition, in the above-described embodiments, various features may be grouped together to streamline the disclosure. This should not be interpreted as an intention that a disclosed feature not claimed is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the detailed description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that these embodiments may be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

The above embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and the scope of the present invention is defined by the claims. Various modifications and equivalents may be made by those skilled in the art within the spirit and scope of the present invention, and such modifications and equivalents should also be considered as falling within the scope of the present invention.

Claims

1. A two-stage refrigeration system, comprising:

a first ejector pipeline is led out from an outlet of the first evaporator and connected to a low-pressure inlet end of the ejector;

a first return line is led out from an outlet of the second evaporator and connected to a low-pressure inlet side of the compressor;

2. The secondary refrigeration system of claim 1,

3. The secondary refrigeration system of claim 2,

4. The secondary refrigeration system of claim 1, wherein a third heat exchanger is disposed on the pipeline between the ejector and the condenser, and a third heat exchange pipeline is led out from a pipeline downstream of the third heat exchanger, so that the third heat exchange pipeline passes through the third heat exchanger, and a fifth expansion valve is disposed on the third heat exchange pipeline, and the third heat exchange pipeline after passing through the third heat exchanger is connected to the top of the flash evaporation container.

5. The two-stage refrigeration system according to claim 2, wherein the ejector comprises a first ejector and a second ejector; the first ejector pipeline is connected to the low-pressure inlet end of the first ejector, and the second ejector pipeline and the third ejector pipeline are connected to the low-pressure inlet end of the second ejector.

6. The two-stage refrigeration system of claim 2, wherein a third flow valve is disposed on the air supply line.

7. The two-stage refrigeration system as recited in claim 2 wherein a second electrically controlled on-off valve is disposed on the first heat exchange line.

8. The two-stage refrigeration system according to claim 5, wherein a third electrically controlled on-off valve is disposed upstream of the high pressure inlet end of the second ejector; and a fourth electric control switch valve is arranged at the upper stream of the low-pressure inlet end of the second ejector.

9. The two-stage refrigeration system of claim 1, wherein a pressure sensor is disposed downstream of an outlet side of the compressor, upstream of a low pressure inlet side of the compressor, and on the supply line.

10. The two-stage refrigeration system according to claim 1, wherein a fifth electrically controlled switching valve is disposed downstream of an outlet side of the compressor, and a sixth electrically controlled switching valve is disposed upstream of a low pressure inlet side of the compressor.