CN109612145B

CN109612145B - CO intensified by multiple jet set2Dual temperature refrigeration system

Info

Publication number: CN109612145B
Application number: CN201811484601.9A
Authority: CN
Inventors: 高晨晨; 赵红霞; 陈威; 宋明刚; 马训刚
Original assignee: SHANDONG SHENZHOU REFRIGERATION EQUIPMENT CO LTD
Current assignee: SHANDONG SHENZHOU REFRIGERATION EQUIPMENT CO LTD
Priority date: 2018-12-06
Filing date: 2018-12-06
Publication date: 2020-11-27
Anticipated expiration: 2038-12-06
Also published as: CN109612145A

Abstract

The invention relates to a CO intensified by a plurality of injector groups₂The outlet of the high-temperature compressor of the transcritical double-temperature refrigerating system is connected with the inlet of the gas cooler; the outlet of the gas cooler is divided into two paths, one path is connected with the first inlet of the gas-liquid ejector group, and the other path is connected with the first inlet of the gas-liquid ejector group; the second inlet of the gas-gas ejector group is connected with the saturated gas outlet of the gas-liquid separator; the second inlet of the gas-liquid ejector group is connected with the saturated liquid outlet of the gas-liquid separator; the outlets of the two groups of ejectors are connected with the inlet of the liquid storage device; the outlet of the liquid storage device is divided into two paths, one path is that saturated gas is connected with the inlet of the high-temperature compressor, and the other path is that saturated liquid is respectively connected with the inlets of the first throttling valve and the second throttling valve; the outlet of the first throttle valve is connected with the inlet of the medium-temperature evaporator; the outlet of the medium temperature evaporator is connected with the inlet of the gas-liquid separator; the outlet of the second throttling valve is connected with the inlet of the low-temperature evaporator; the outlet of the low-temperature evaporator is connected with the inlet of the low-temperature compressor; the outlet of the low-temperature compressor is connected with the inlet of the gas-liquid separator; two outlets of the gas-liquid separator are respectively connected with second inlets of the gas-gas ejector group and the gas-liquid ejector group. In CO₂The ejector set and the flooded intermediate-temperature evaporator are added in the dual-temperature refrigeration system, so that the performance of the refrigeration system is improved to a great extent, and the dual-temperature refrigeration system can better adapt to the national conditions of high-temperature climate in China.

Description

CO intensified by multiple jet set2Dual temperature refrigeration system

Technical Field

The invention relates to the technical field of refrigeration, in particular to CO intensified by a plurality of ejector groups₂A dual temperature refrigeration system, principles and applications thereof.

Background

197 countries from the world have agreed to reduce the emission of chemical refrigerants due to ozone depletion caused by chlorofluorocarbons (CFCs) and Hydrochlorofluorocarbons (HCFCs), and the impact of Hydrofluorocarbons (HFCs) on global warming. With the acceleration of the progress of the Montreal protocol and the achievement of the Basgali amendment, it is expected that the emissions of the greenhouse gas Hydrofluorocarbons (HFCs) will be reduced by 88% in the 21 st century. To reduce the environmental impact of chemical refrigerants, CO₂As a natural refrigerant (ODP is 0, GWP is negligible), the refrigerant is an important refrigerant substitute. In fact, CO₂The refrigerant is the most environment-friendly refrigerant in the field of commercial refrigeration, is a natural working medium which is non-toxic, non-flammable, cheap and easy to obtain, and has excellent thermophysical properties.

At present, the market supermarket in northern Europe uses CO in large quantity₂As a refrigerant, the emission of a large amount of greenhouse gases is indirectly reduced. At present, the market supermarket in northern Europe uses CO in large quantity₂As a refrigerant, the emission of a large amount of greenhouse gases is indirectly reduced. CO2₂Refrigeration systems as refrigerants have been developed to the second generation, CO₂The schematic diagram of the auxiliary compression refrigeration system is shown in fig. 1. In the system, a high-temperature and high-pressure refrigerant at the outlet of a compressor enters a gas cooler (a condenser is called as a gas cooler in transcritical circulation), is cooled and depressurized by a throttle valve, and enters a gas-liquid separator to be separated into saturated liquid and saturated gas. The saturated gas is compressed by the auxiliary compressor and enters the gas cooler, and the saturated liquid respectively enters the medium-temperature evaporator and the low-temperature evaporator after passing through different throttling valves. The refrigerant at the outlet of the low-temperature evaporator is compressed by the low-temperature compressor, is mixed with the refrigerant at the outlet of the medium-temperature evaporator, is compressed by the medium-temperature compressor, and enters the gas cooler to complete the circulation.

However, since the critical temperature of carbon dioxide (about 31 ℃ C.) is low, CO₂The refrigeration system is very sensitive to changes in ambient temperature and the COP decreases significantly as the ambient temperature increases. Therefore, in countries with high ambient temperature, the system is energy inefficient and its application is greatly limited. In most areas of China, the ambient temperature is higher than that in summerCO₂Critical temperature, CO₂Refrigeration systems are inevitably operated in transcritical mode. The high temperature and high pressure gas from the gas cooler causes a large amount of throttling loss in the throttling process, so that the efficiency of the whole system is low. To recover part of the expansion work of the throttling process, an ejector set may be added to the system to increase the efficiency of the overall system. In CO₂In refrigeration systems, the addition of a pump circuit is required when the intermediate temperature evaporator is a flooded evaporator, which increases initial and operational costs, as well as increases the complexity of the system. The ejector for ejecting liquid can be added to replace a pump loop, so that the cost can be saved, the system stability can be improved, and the system efficiency can be improved.

The ejector has the advantages of simple structure, low manufacturing cost, no moving parts and the like. The main working principle is to increase the pressure of the secondary flow (low-pressure fluid) by the primary flow (high-pressure fluid), so that CO can be utilized₂The high-pressure side fluid of the refrigerating system injects the low-pressure fluid from the evaporator, and the suction pressure of the compressor is improved to reduce the power consumption of the compressor and improve the gas transmission capacity of the compressor. However, the use of the ejector is currently subject to major limitations: the ejection fluid is gas; can only adapt to a single working condition (especially refrigerating capacity).

Related patents such as "a transcritical CO2 dual stage compression and pressurization refrigeration system" (application No. 201711290797.3) address the problem of excessive throttling losses in transcritical CO2 refrigeration systems, suggest that the two-stage compression and expansion tanks reduce the discharge temperature of the compressed gas while reducing throttling losses, but do not address supermarket dual temperature refrigeration systems and do not use ejectors. The related patents such as "a mechanically-assisted subcooling CO2 transcritical refrigeration and heating integrated system" (application No. 201810093169.4) are directed to the refrigeration and heating integrated system and do not address the problem of reducing throttling losses.

Disclosure of Invention

In order to solve the defects and shortcomings in the prior art, two groups of ejectors (one group of supercritical gas for ejecting saturated gas, namely a gas-gas ejector group, and one group of supercritical gas for ejecting saturated liquid, namely a gas-liquid ejector group) are added in a conventional CO2 dual-temperature refrigeration system, and a medium-temperature evaporator is replaced by a flooded evaporator from a dry type, and a system diagram is shown in FIG. 2. The ejector group can be adjusted according to the working condition change of the medium-low temperature cold quantity, and has great flexibility in the actual engineering application. In a high-temperature environment, the gas-gas ejector group can eject saturated gas from a gas-liquid separator by using fluid at the outlet of a gas cooler so as to improve the suction pressure of the compressor, reduce the power consumption of the compressor and improve the gas transmission capacity of the compressor; the gas-liquid ejector group can eject liquid from a gas-liquid separator by using outlet fluid of the gas cooler, and the energy consumption of the system is reduced and the energy efficiency is improved by replacing a pump to do work. The medium temperature evaporator is changed into a flooded type, so that the heat exchange efficiency of the evaporator in the refrigeration house can be improved, and the return gas overheating of the medium temperature evaporator is reduced. The two groups of ejector groups and the flooded medium-temperature evaporator are added, so that the energy efficiency of the whole system can be effectively improved.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

CO (carbon monoxide) of multi-injector group₂The dual-temperature refrigeration system comprises a group of high-temperature compressors, wherein the outlets of the high-temperature compressors are connected with the inlets of the gas coolers; the outlet of the gas cooler is divided into two paths, one path is connected with the first inlet of the gas-liquid ejector group, and the other path is connected with the first inlet of the gas-liquid ejector group; the second inlet of the gas-gas ejector group is connected with the saturated gas outlet of the gas-liquid separator; the second inlet of the gas-liquid ejector group is connected with the saturated liquid outlet of the gas-liquid separator; the outlets of the two groups of ejectors are connected with the inlet of the liquid storage device; the outlet of the liquid storage device is divided into two paths, one path is that saturated gas is connected with the inlet of the high-temperature compressor, and the other path is that saturated liquid is respectively connected with the inlets of the first throttling valve and the second throttling valve; the outlet of the first throttle valve is connected with the inlet of the medium-temperature evaporator; the outlet of the medium temperature evaporator is connected with the inlet of the gas-liquid separator; the outlet of the second throttling valve is connected with the inlet of the low-temperature evaporator; the outlet of the low-temperature evaporator is connected with the inlet of the low-temperature compressor; the outlet of the low-temperature compressor is connected with the inlet of the gas-liquid separator; two outlets of the gas-liquid separator are respectively connected with second inlets of the gas-gas ejector group and the gas-liquid ejector groupAre connected.

The fluid pressure from the gas cooler outlet in the gas-gas ejector set is higher than the pressure of the saturated gas from the gas-liquid separator gas outlet; the pressure of the fluid from the gas cooler outlet in the set of gas-liquid ejectors is higher than the pressure of the saturated gas-liquid from the gas outlet of the gas-liquid separator.

Saturated gas refrigerant at the gas outlet of the gas-liquid separator is injected by high-pressure gas from a gas cooler in the gas-gas ejector group, mixed in the gas-gas ejector group and then pressurized to flow into the liquid storage device; and saturated liquid refrigerant at the liquid outlet of the gas-liquid separator is injected by high-pressure gas from the gas cooler in the gas-liquid ejector group, mixed in the gas-liquid ejector group and then pressurized to flow into the liquid storage device.

Each group of the gas-gas ejector groups consists of ejectors with different specifications, and the control logic of the gas-gas ejector groups is to start and stop a plurality of ejectors according to the pressure change of a gas-liquid separator caused by the change of refrigerating capacity; each group of the gas-liquid ejector groups consists of ejectors with different specifications, and the control logic of the gas-liquid ejector groups is to start and stop a plurality of ejectors according to the liquid level change of a gas-liquid separator caused by the change of refrigerating capacity.

Compared with the prior art, the invention has the advantages and positive effects that:

1. the invention is more suitable for temperate climates. The higher the ambient temperature, the higher the pressure of the gas cooler, the existing CO₂The greater the throttling losses of the refrigeration system, reducing the efficiency of the overall system. But multiple injector group intensified CO₂The double-temperature refrigerating system can inject saturated gas from the gas-liquid separator by using the refrigerant flowing out of the gas cooler as primary flow through the added gas-gas ejector set, and the suction pressure of the high-temperature compressor is lifted from the pressure of the gas-liquid separator to the pressure of the liquid accumulator, so that the aims of recovering partial throttling loss and reducing the power consumption of the compressor are fulfilled. Meanwhile, the gas transmission capacity of the compressor can be increased by improving the suction pressure, the gas transmission efficiency of the compressor is improved, and the number of the compressors used by the system is reduced.

2. The invention combines the gas-liquid ejector group with the flooded intermediate temperature evaporator, can use the flooded evaporator to improve the heat exchange efficiency of the refrigeration house, can also use the refrigerant flowing out of the gas cooler as a primary flow to eject the saturated liquid from the gas-liquid separator to replace a liquid pump to do work, and reduces the initial cost and energy consumption of the system.

3. The injectors used in the invention are set injectors, each set of gas-gas injector group consists of a plurality of injectors with different specifications, and each set of gas-liquid injector group consists of a plurality of injectors with different specifications. When the cold quantity of the middle-low temperature evaporator is changed, ejectors with different specifications can be combined to meet the operation requirement of the system.

5. The invention is suitable for the situation of China, can be efficiently operated in most areas of China, and can effectively relieve the current situation of energy shortage of China. The system is mainly applied to a double-temperature-zone supermarket refrigeration system and cold-chain logistics, and has a great significance and influence in the field of future commercial refrigeration.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.

FIG. 1 shows the present CO₂An auxiliary compression refrigeration system;

FIG. 2 is CO of a multi-injector group designed according to the present invention₂A dual temperature refrigeration system;

FIG. 3 is CO of a multi-injector group designed according to the present invention₂A pressure-enthalpy diagram for the dual temperature refrigeration system;

101, an auxiliary compressor; 102. a gas cooler; 103. a high pressure throttle valve; 104 a reservoir; 105. A first throttle valve; 106. a medium temperature evaporator; 107. a second throttle valve; 108. a low temperature evaporator; 109. A cryogenic compressor; 110. a medium temperature compressor; 201. a high temperature compressor; 202. a gas cooler; 203. A gas-gas injector group; 204. a gas-liquid ejector group; 205. a reservoir; 206. a first throttle valve; 207. A medium temperature evaporator; 208. a second throttle valve; 209. a low temperature evaporator; 210. a low temperature evaporator; 211 gas-liquid separator.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

As shown in FIG. 2, a multi-injector set enhanced CO of the present invention₂A dual temperature refrigeration system comprising:

the system comprises a high-temperature compressor, a gas cooler, a gas-gas ejector group, a gas-liquid separator, a first throttling valve, a medium-temperature evaporator, a second throttling valve, a low-temperature evaporator, a low-temperature compressor and a liquid storage device.

The high-temperature compressor is a CO2 transcritical compressor, and the outlet of the high-temperature compressor is connected with the inlet of the gas cooler; the outlet of the gas cooler is divided into two paths, one path is connected with the first inlet of the gas-liquid ejector group, and the other path is connected with the first inlet of the gas-liquid ejector group; the second inlet of the gas-gas ejector group is connected with the saturated gas outlet of the gas-liquid separator; the second inlet of the gas-liquid ejector group is connected with the saturated liquid outlet of the gas-liquid separator; the outlets of the two groups of ejectors are connected with the inlet of the liquid storage device; the outlet of the liquid storage device is divided into two paths, one path is that saturated gas is connected with the inlet of the high-temperature compressor, and the other path is that saturated liquid is respectively connected with the inlets of the first throttling valve and the second throttling valve; the outlet of the first throttle valve is connected with the inlet of the medium-temperature evaporator; the outlet of the medium temperature evaporator is connected with the inlet of the gas-liquid separator; the outlet of the second throttling valve is connected with the inlet of the low-temperature evaporator; the outlet of the low-temperature evaporator is connected with the inlet of the low-temperature compressor; the low-temperature compressor is a CO2 subcritical compressor, and the outlet of the low-temperature compressor is connected with the inlet of the gas-liquid separator; two outlets of the gas-liquid separator are respectively connected with inlets of the gas-gas ejector group and the gas-liquid ejector group.

Saturated gas refrigerant at the gas outlet of the gas-liquid separator is injected by high-pressure gas from a gas cooler in the gas-gas ejector group, mixed in the gas-gas ejector group and then pressurized to flow into the liquid storage device; and the liquid refrigerant at the liquid outlet of the gas-liquid separator is injected by high-pressure gas from the gas cooler in the gas-liquid ejector group, mixed in the gas-liquid ejector group and then pressurized to flow into the liquid storage device.

Each group of the gas-gas ejector groups consists of ejectors with different specifications, and the control logic of the gas-gas ejector groups is to start and stop a plurality of ejectors according to the pressure change of a gas-liquid separator caused by the change of refrigerating capacity; each group of the gas-liquid ejector groups consists of ejectors with different specifications, and the control logic of the gas-liquid ejector groups is to start and stop a plurality of ejectors according to the liquid level change of a gas-liquid separator caused by the change of refrigerating capacity. The expansion loss in the throttling process of the high-pressure valve can be effectively recovered by using the gas-gas ejector group, the suction pressure of the high-temperature compressor is improved, the power consumption is reduced, and the gas transmission capacity of the compressor is increased; the gas-liquid ejector set can replace a liquid pump to work, and the initial cost and the operation cost are reduced. Under the high-temperature environment, the performance of the whole system is effectively improved by combining and utilizing the two groups of ejector sets.

FIG. 3 shows a multi-injector set enhanced CO of the present invention₂The working flow of the operation of the dual-temperature refrigeration system is that saturated gas separated from an accumulator (state point 1 in figure 3) is compressed into high-temperature and high-pressure supercritical gas by a transcritical CO2 high-temperature compressor (state point 2 in figure 3). The high-temperature high-pressure supercritical gas is cooled by the gas cooler to become high-pressure low-temperature supercritical gas (state point 3 in fig. 3), and enters the nozzles of the gas-gas and gas-liquid ejector sets, and the high-pressure low-temperature supercritical gas is expanded by the nozzles to become low-pressure high-speed gas-liquid two-phase fluid (state point 3s in fig. 3). The fluid in the gas-gas ejector group ejects saturated gas from a gas-liquid separator (state point 10 in fig. 3), is mixed in a mixing chamber, is subjected to pressure rise through a diffusion tube to be changed into a two-phase flow state (state point 4 in fig. 3), and then enters a liquid storage device; the fluid in the gas-liquid ejector group ejects saturated liquid from the gas-liquid separator (state point 9 in fig. 3), and after mixing in the mixing chamber, the fluid is boosted by the diffusion tube to become a two-phase fluidState (state point 5 in fig. 3), and then into the reservoir. The saturated gas in the accumulator (state point 1 in fig. 3) is compressed by the compressor again to become supercritical gas with high temperature and high pressure, thus performing the cycle of the high pressure side. Saturated liquid (state point 6 in fig. 3) in the liquid storage device is throttled by the first throttling valve and enters the flooded medium-temperature evaporator, and the refrigerant is still in a two-phase flow state after absorbing heat in the flooded medium-temperature evaporator (state point 8 in fig. 3); the refrigerant enters the low-temperature evaporator by throttling of the second throttling valve, becomes saturated gas (state point 12 in figure 3) after absorbing heat in the low-temperature evaporator, becomes superheated gas (state point 13 in figure 3) after being overheated by a pipeline, and is compressed into a gas-liquid separator by the low-temperature compressor. Saturated gas in the gas-liquid separator is injected by the gas-gas injector group, and saturated liquid in the gas-liquid separator is injected by the gas-liquid injector group, so that circulation on the low-pressure side is completed. The above description completes the whole cycle process.

The whole system working process of the invention has three different working pressures, namely the pressure of a gas cooler, the suction pressure of a high-temperature compressor, the pressure of a gas-liquid separator and the suction pressure of a low-temperature compressor in turn. Wherein the gas cooler pressure is determined by the ambient temperature, since there is an optimum gas cooler pressure at each ambient temperature; the suction pressure of the high-temperature compressor is determined by the outlet pressure of the ejector, which is the optimal pressure designed according to the design working condition; the pressure of the gas-liquid separator is designed according to the design pressure of the medium temperature evaporator; the suction pressure of the cryogenic compressor is the design pressure of the cryogenic evaporator.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. CO intensified by multiple jet set₂Two temperature refrigerating system, its characterized in that: comprises a high-temperature compressor, a gas cooler and a gas-gas jetThe device comprises an injector group, a gas-liquid separator, a first throttling valve, a medium-temperature evaporator, a second throttling valve, a low-temperature evaporator, a low-temperature compressor and a liquid storage device, wherein the outlet of the high-temperature compressor is connected with the inlet of a gas cooler; the outlet of the gas cooler is divided into two paths, one path is connected with the first inlet of the gas-liquid ejector group, and the other path is connected with the first inlet of the gas-liquid ejector group; the second inlet of the gas-gas ejector group is connected with the saturated gas outlet of the gas-liquid separator; the second inlet of the gas-liquid ejector group is connected with the saturated liquid outlet of the gas-liquid separator; the outlets of the two groups of ejectors are connected with the inlet of the liquid storage device; the outlet of the liquid storage device is divided into two paths, one path is that saturated gas is connected with the inlet of the high-temperature compressor, and the other path is that saturated liquid is respectively connected with the inlets of the first throttling valve and the second throttling valve; the outlet of the first throttle valve is connected with the inlet of the medium-temperature evaporator; the outlet of the medium temperature evaporator is connected with the inlet of the gas-liquid separator; the medium temperature evaporator is a flooded evaporator, and the outlet of the medium temperature evaporator is connected with the inlet of the gas-liquid separator; the outlet of the second throttling valve is connected with the inlet of the low-temperature evaporator; the outlet of the low-temperature evaporator is connected with the inlet of the low-temperature compressor; the outlet of the low-temperature compressor is connected with the inlet of the gas-liquid separator; two outlets of the gas-liquid separator are respectively connected with second inlets of the gas-gas ejector group and the gas-liquid ejector group.

2. A multi-injector set enhanced CO as claimed in claim 1₂The working method of the double-temperature refrigerating system is characterized in that: the fluid pressure from the gas cooler outlet in the gas-gas ejector set is higher than the pressure of the saturated gas from the gas-liquid separator gas outlet; the fluid pressure from the gas cooler outlet in the set of gas-liquid ejectors is higher than the pressure of the saturated liquid from the gas outlet of the gas-liquid separator.

3. A multi-injector set enhanced CO as claimed in claim 1₂The working method of the double-temperature refrigerating system is characterized in that: the saturated gas refrigerant at the gas outlet of the gas-liquid separator is from the gas in the gas-gas ejector groupHigh-pressure gas of the cooler is injected, mixed in the gas-gas injector group and then pressurized to flow into the liquid storage device; and the liquid refrigerant at the liquid outlet of the gas-liquid separator is injected by high-pressure gas from the gas cooler in the gas-liquid ejector group, mixed in the gas-liquid ejector group and then pressurized to flow into the liquid storage device.

4. A multi-injector set enhanced CO as claimed in claim 1₂The working method of the double-temperature refrigerating system is characterized in that: each group of the gas-gas ejector groups consists of ejectors with different specifications, and the control logic of the gas-gas ejector groups is to start and stop a plurality of ejectors according to the pressure change of a gas-liquid separator caused by the change of refrigerating capacity; each group of the gas-liquid ejector groups consists of ejectors with different specifications, and the control logic of the gas-liquid ejector groups is to start and stop a plurality of ejectors according to the liquid level change of a gas-liquid separator caused by the change of refrigerating capacity.