Transcritical CO2 refrigerating system integrating vortex tube and ejector and working method of transcritical CO2 refrigerating system

Abstract

The invention relates to the technical field of refrigeration and low-temperature engineering, and discloses a transcritical CO2 refrigeration system integrating a vortex tube and an ejector and a working method of the transcritical CO2 refrigeration system. According to the system, supercritical CO2 is separated into two sub-critical two-phase flows with different pressures through the vortex tube, after high-pressure two-phase flows at a hot end flow through the gas-liquid separator to separate out liquid and are throttled, the high-pressure two-phase flows and low-pressure two-phase flows at a cold end outlet are converged and enter the evaporator, and energy loss in the throttling process in a traditional system is reduced. The ejector and the high-low pressure compressor work cooperatively, the pressure energy of high-pressure gas is recycled, the system circulation efficiency is improved, the load of the compressor unit is reduced, and the system working efficiency is remarkably improved especially in the high-temperature environment. A closed circulation loop formed by the system ensures full utilization of CO2 refrigerants, the economical efficiency and environmental protection performance of the system are enhanced, and the problems that a traditional transcritical CO2 refrigerating system is large in throttling loss and low in working efficiency in the high-temperature environment are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of refrigeration and cryogenic engineering, and particularly relates to a transcritical CO 2 refrigeration system integrating a vortex tube and an ejector and its working method. Background Art

[0002] Global energy and environmental issues have promoted the technological innovation of environmentally friendly refrigerants in the refrigeration industry. Traditional halogenated hydrocarbon refrigerants have been gradually replaced due to the ozone depletion potential (ODP) problem, but the global warming potential (GWP) of existing refrigerants still has a significant impact on the environment. Currently, the technological development in the industry mainly focuses on two major directions: one is to reduce the GWP value of refrigerants through chemical structure optimization, and the other is to develop new green and environmentally friendly refrigerants to replace high-GWP substances. For example, although hydrofluorocarbons (HFCs) have zero ODP characteristics, their high GWP values lead to prominent greenhouse effect problems, and it is urgent to achieve a balance between environmental friendliness and refrigeration performance through technological improvement.

[0003] CO 2 As a natural substance, with ODP = 0 and GWP = 1, it has no destructive effect on the environment, and has the advantages of being safe, non-toxic, having good thermal stability, low viscosity, and good heat transfer characteristics, and has been gradually applied in refrigeration systems. Figure 1 is the flow chart of a traditional transcritical CO 2 refrigeration system. In this system, due to the relatively low critical temperature of CO 2 (about 31.2 °C), after the gas at the outlet of the evaporator 5 is boosted by the compressor 9, the heat rejection process (process II-III) of the system mainly occurs in the supercritical region above the critical point. At this time, CO 2 cannot be condensed into a liquid during the cooling process, so that the condenser in the traditional refrigeration system is replaced by the gas cooler 1. However, at present, the transcritical CO 2 refrigeration system still has the development bottlenecks of a relatively large pressure difference between the high-pressure and low-pressure parts inside the system, resulting in more energy loss during the throttling process and lower working efficiency of the system under high-temperature environmental conditions. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above problems and provide a transcritical CO 2 refrigeration system integrating a vortex tube and an ejector and its working method, aiming to solve the problems of large throttling loss and low working efficiency under high-temperature environment in the existing traditional transcritical CO 2 refrigeration system.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a transcritical CO 2The refrigeration system includes a gas cooler, a vortex tube, a gas-liquid separator, a throttle valve, an evaporator, an ejector, a low-pressure compressor, and a high-pressure compressor; The outlet of the gas cooler is connected to the inlet of the vortex tube, the hot-end outlet of the vortex tube is connected to the inlet of the gas-liquid separator, and the liquid outlet of the gas-liquid separator is merged with the cold-end outlet of the vortex tube after passing through the throttle valve and then connected to the inlet of the evaporator; The gas outlet of the gas-liquid separator is connected to the working fluid inlet of the ejector. The outlet of the evaporator is divided into two paths. The first path is connected to the entrained fluid inlet of the ejector, and the second path is connected to the inlet of the low-pressure compressor; The outlet of the low-pressure compressor is merged with the outlet of the ejector and then connected to the inlet of the high-pressure compressor. The outlet of the high-pressure compressor is connected to the inlet of the gas cooler, forming a closed circulation loop.

[0006] A further improvement of the present invention is that the pressure at the cold-end outlet of the vortex tube is lower than the pressure at the hot-end outlet, and the temperature at the cold-end outlet is lower than the temperature at the hot-end outlet.

[0007] A further improvement of the present invention is that the gas-liquid separator is of a vertical structure, with its liquid outlet at the bottom and its gas outlet at the top.

[0008] A further improvement of the present invention is that the mixed fluid outlet of the ejector and the outlet of the low-pressure compressor are merged through a pipeline and then connected to the inlet of the high-pressure compressor.

[0009] A further improvement of the present invention is that the pressure at the working fluid inlet of the ejector is higher than the pressure at the entrained fluid inlet, and the pressure at the ejector outlet is equal to the pressure at the outlet of the low-pressure compressor and the pressure at the inlet of the high-pressure compressor.

[0010] A further improvement of the present invention is that the low-pressure compressor and the high-pressure compressor form a two-stage compression structure.

[0011] A further improvement of the present invention is that the pressure at the gas outlet of the gas-liquid separator is greater than the pressure at the outlet of the evaporator.

[0012] In a second aspect, the present invention also provides a working method for an integrated vortex tube and ejector transcritical CO 2 refrigeration system, including the following steps: S1, The supercritical CO 2 working medium completes heat rejection in the gas cooler and then enters the vortex tube for energy separation. The hot-end outlet of the vortex tube outputs a high-pressure two-phase fluid to the gas-liquid separator, and the cold-end outlet outputs a low-pressure two-phase fluid; S2, The gas-liquid separator separates the high-pressure two-phase fluid into top gas and bottom liquid. The bottom liquid is depressurized by the throttle valve and then mixed with the fluid at the cold-end outlet of the vortex tube and enters the evaporator to absorb heat and evaporate; S3. The gas at the top of the gas-liquid separator serves as the working fluid of the ejector, entraining a part of the low-temperature gas at the outlet of the evaporator. S4. The remaining gas at the outlet of the evaporator is boosted in pressure by a low-pressure compressor and then mixed with the gas at the outlet of the ejector. The mixed gas is compressed to the supercritical state by a high-pressure compressor and then returns to the gas cooler to complete the cycle.

[0013] A further improvement of the present invention lies in that, in S1, the pressure of the hot-end high-pressure two-phase fluid is 2 - 4 MPa higher than that of the cold-end low-pressure two-phase fluid.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a transcritical CO₂ refrigeration system integrating a vortex tube and an ejector. This system utilizes the energy separation effect of the vortex tube to first convert supercritical CO₂ into two subcritical two-phase flows at different pressures. Subsequently, the high-pressure two-phase flow at the hot-end outlet enters the gas-liquid separator to separate the liquid, and after throttling, it converges with the low-pressure two-phase flow at the cold-end outlet and enters the evaporator. This design reduces the energy loss during the throttling process of directly throttling supercritical CO₂ in the traditional CO₂ refrigeration system. 2 At the same time, the coordinated operation of the ejector with the low-pressure compressor and the high-pressure compressor not only efficiently utilizes the pressure energy of the high-pressure gas separated by the gas-liquid separator, enhances the cycle efficiency of the system, but also effectively reduces the working load of the entire compressor unit. Especially in a high-temperature environment, the overall working efficiency is significantly improved. In addition, the closed circulation loop formed by the system ensures the full utilization of the CO₂ refrigerant, further enhancing the economy and environmental protection of the system, thereby effectively overcoming the problems of large throttling losses and low working efficiency in a high-temperature environment in the traditional transcritical CO₂ refrigeration system. 2 2 2 2 2

[0015] The present invention also provides a working method for a transcritical CO₂ refrigeration system integrating a vortex tube and an ejector. Through the vortex tube, energy separation is achieved, the thermal energy and pressure energy of the supercritical CO₂ working medium are optimized and utilized, the throttling loss is reduced, and the heat exchange efficiency of the evaporator is improved; by using the ejector entrainment technology, the pressure energy of the high-pressure gas separated by the gas-liquid separator is efficiently utilized, and the system energy consumption is reduced; in combination with the coordinated operation of the low-pressure compressor and the high-pressure compressor, the compressor load is balanced, the system stability and energy efficiency ratio are enhanced, a closed circulation loop is formed, ensuring the full utilization of the refrigerant, and realizing the dual benefits of economy and environmental protection. 2 2 BRIEF DESCRIPTION OF THE DRAWINGS

[0016] ​​​​​​​The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the disclosure of the present invention in any way. Additionally, the shapes and proportional dimensions of the components in the figures are only schematic and are used to assist in understanding the present invention, rather than specifically defining the shapes and proportional dimensions of the components of the present invention.

[0017] Figure 1 For the traditional transcritical CO in the prior art 2 Flow chart of the refrigeration system; Figure 2 A transcritical CO integrating a vortex tube and an ejector according to the present invention 2 Schematic flow diagram of the refrigeration system.

[0018] Wherein: 1. Gas cooler; 2. Vortex tube; 3. Gas-liquid separator; 4. Throttle valve; 5. Evaporator; 6. Ejector; 7. Low-pressure compressor; 8. High-pressure compressor; 9. Compressor. Detailed implementation manners

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Generally, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0021] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0022] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships in which the inventive product is customarily placed during use, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Additionally, terms such as "first", "second", etc. are only used for descriptive distinction and cannot be construed as indicating or implying relative importance.

[0023] In addition, when the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and it does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0024] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, when terms such as "arranged", "installed", "connected", and "coupled" appear, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] The present invention will be further described in detail below with reference to the accompanying drawings: Traditional transcritical CO 2 refrigeration systems have the disadvantages of large throttling losses and low working efficiency in high-temperature environments. The present invention proposes to use a simple thermal device - a vortex tube to replace the throttle valve in the traditional transcritical CO 2 refrigeration system, and cleverly utilize the ability of the vortex tube to separate fluids with different pressures and temperatures, effectively alleviating the problem of large throttling losses in the traditional system. At the same time, an ejector is added to the system, and the ejector uses high-pressure gas to entrain low-pressure gas, reducing the power consumption of the system and improving the working efficiency of the entire system in high-temperature environments.

[0026] As Figure 2 shown, the present invention provides a transcritical CO 2 refrigeration system integrating a vortex tube and an ejector, including a gas cooler 1, a vortex tube 2, a gas-liquid separator 3, a throttle valve 4, an evaporator 5, an ejector 6, a low-pressure compressor 7, and a high-pressure compressor 8; wherein the outlet of the gas cooler 1 is connected to the inlet of the vortex tube 2, the hot-end outlet of the vortex tube 2 is connected to the inlet of the gas-liquid separator 3, the liquid outlet of the gas-liquid separator 3 is joined with the cold-end outlet of the vortex tube 2 through the throttle valve 4 and then connected to the inlet of the evaporator 5; the gas outlet of the gas-liquid separator 3 is connected to the working fluid inlet of the ejector 6, the outlet of the evaporator 5 is divided into two paths, the first path is connected to the entrained fluid inlet of the ejector 6, and the second path is connected to the inlet of the low-pressure compressor 7; the outlet of the low-pressure compressor 7 and the outlet of the ejector 6 are joined and then connected to the inlet of the high-pressure compressor 8, and the outlet of the high-pressure compressor 8 is connected to the inlet of the gas cooler 1 to form a closed loop.

[0027] The outlet pressure of the cold end of the vortex tube 2 is lower than the outlet pressure of the hot end, and the outlet temperature of the cold end is lower than the outlet temperature of the hot end. By utilizing the centrifugal force and energy separation characteristics of the high-speed rotating fluid inside the vortex tube 2, the supercritical CO 2 The fluid is separated into two streams, low temperature and low pressure (cold end) and high temperature and high pressure (hot end), to replace the one-way pressure reduction of the traditional throttling valve and reduce the thermodynamic irreversible loss of the throttling process. At the same time, the low temperature fluid at the cold end directly participates in evaporative refrigeration, and the high temperature fluid at the hot end recovers gas phase energy through the gas-liquid separator 3, realizing the cascade effect of cold and hot fluids and improving the energy efficiency of the system.

[0028] The gas-liquid separator 3 is a vertical structure with a liquid outlet at the bottom and a gas outlet at the top. The vertical layout uses gravity to accelerate the liquid phase CO 2 Sinking and gas phase CO 2 rise, avoiding gas-liquid entrainment, and ensuring that pure liquid CO enters throttle valve 4 2 , reducing flash evaporation losses. In addition, the top gas phase outlet and the bottom liquid phase outlet are separated, which reduces the residual rate of droplets in the gas phase and ensures the stability of the working fluid of the ejector 6.

[0029] The gas outlet pressure of the gas-liquid separator 3 is greater than the outlet pressure of the evaporator 5. Through the ejector 6 and the high-pressure gas-liquid separator 3 outlet gas, the pressure of the gas at the outlet of the evaporator 5 can be increased, reducing the power consumption of the compressors 7 and 8. The mixed fluid outlet of the ejector 6 and the outlet of the low-pressure compressor 7 are connected to the inlet of the high-pressure compressor 8 after merging through a pipeline; the working fluid inlet pressure of the ejector 6 is higher than the inlet pressure of the ejector fluid, and the ejector 6 outlet pressure is equal to the outlet pressure of the low-pressure compressor 7 and the inlet pressure of the high-pressure compressor 8.

[0030] The low-pressure compressor 7 and the high-pressure compressor 8 form a two-stage compression structure to ensure CO 2 The working medium reaches a supercritical state before entering the gas cooler 1 .

[0031] It should be noted that the low-pressure compressor 7 and the high-pressure compressor 8 can be scroll compressors or piston compressors, etc., as long as they can compress CO 2 That's it.

[0032] The present invention also provides a transcritical CO2-integrated vortex tube and injector. 2 The working method of the refrigeration system comprises the following steps: Step S1, supercritical CO 2 After the working medium has completed heat removal in the gas cooler 1, it enters the vortex tube 2 for energy separation. The hot end outlet of the vortex tube 2 outputs a high-pressure two-phase fluid to the gas-liquid separator 3, and the cold end outlet outputs a low-pressure two-phase fluid; Step S2: The gas-liquid separator 3 separates the high-pressure two-phase fluid into top gas and bottom liquid. The bottom liquid is depressurized by the throttle valve 4 and then mixed with the two-phase fluid at the cold-end outlet of the vortex tube 2, and then enters the evaporator 5 to absorb heat and evaporate to produce a refrigeration effect. Step S3: The top gas of the gas-liquid separator 3 serves as the working fluid of the ejector 6, which entrains a part of the low-temperature gas at the outlet of the evaporator 5 to generate a medium-pressure gas. Step S4: The remaining gas at the outlet of the evaporator 5 is boosted in pressure by the low-pressure compressor 7 and then mixed with the gas at the outlet of the ejector 6. Subsequently, the mixed gas enters the high-pressure compressor 8 to continue to be boosted in pressure and temperature to the supercritical state, and then returns to the gas cooler 1 to release heat and cool to the supercritical state with a temperature higher than the critical temperature, thus completing a cycle.

[0033] It should be noted that the pressure of the high-pressure two-phase fluid at the hot end of the vortex tube 2 is 2 - 4 MPa higher than that of the low-pressure two-phase fluid at the cold end.

[0034] Working principle The present invention uses a vortex tube to replace the throttle valve in the traditional transcritical CO 2 refrigeration system, and at the same time introduces an ejector, which effectively alleviates the problem of large throttling losses in the traditional system and improves the overall energy efficiency of the transcritical CO 2 refrigeration system. In this system, the supercritical CO 2 at the outlet of the gas cooler can be separated into two-phase CO with different pressures and temperatures through the vortex tube 2 . The higher-pressure CO 2 two-phase fluid at the hot-end outlet of the vortex tube is further separated into gas and liquid by the gas-liquid separator. The liquid is depressurized by the throttle valve and then mixed with the lower-pressure CO 2 two-phase fluid at the cold-end outlet of the vortex tube, and then enters the evaporator to absorb heat and generate refrigerating capacity. The gas serves as the working fluid and enters the ejector to entrain a part of the gas at the outlet of the evaporator. The remaining gas at the outlet of the evaporator is boosted in pressure by the low-pressure compressor and then mixed with the gas at the outlet of the ejector. Then, it is further increased in pressure and temperature by the high-pressure compressor, and finally cooled by the gas cooler to complete a cycle. The present invention is an innovative improvement of the existing transcritical CO 2 refrigeration system, which will play a certain role in promoting the popularization and application of the environmental-friendly refrigerant refrigeration system.

[0035] Upon reading the above description, many embodiments and many applications beyond the provided examples will be apparent to those skilled in the art. Accordingly, the scope of this teaching should not be determined with reference to the above description, but rather should be determined with reference to the full scope of the foregoing claims and the equivalents thereof. For the sake of completeness, all articles and references including the disclosures of patent applications and patents are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein from the foregoing claims is not intended to abandon such subject matter, nor should it be considered that the applicant has not considered such subject matter to be a part of the disclosed inventive subject matter.

[0036] The above is a further detailed description of the present invention. It cannot be determined that the specific embodiments of the present invention are limited thereto. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the scope of protection determined by the claims submitted for the present invention.

Claims

1. A transcritical CO2 refrigeration system integrating a vortex tube and an ejector, characterized in that: It comprises a gas cooler (1), a vortex tube (2), a gas-liquid separator (3), a throttle valve (4), an evaporator (5), an ejector (6), a low-pressure compressor (7) and a high-pressure compressor (8); The outlet of the gas cooler (1) is connected to the inlet of the vortex tube (2), the hot end outlet of the vortex tube (2) is connected to the inlet of the gas-liquid separator (3), and the liquid outlet of the gas-liquid separator (3) is connected to the inlet of the evaporator (5) after merging with the cold end outlet of the vortex tube (2) through a throttle valve (4); The gas outlet of the gas-liquid separator (3) is connected to the working fluid inlet of the ejector (6), and the outlet of the evaporator (5) is divided into two paths, the first path is connected to the ejector fluid inlet of the ejector (6), and the second path is connected to the inlet of the low-pressure compressor (7); The outlet of the low-pressure compressor (7) merges with the outlet of the ejector (6) and is then connected to the inlet of the high-pressure compressor (8). The outlet of the high-pressure compressor (8) is connected to the inlet of the gas cooler (1), forming a closed circulation loop.

2. A transcritical CO2 refrigeration system integrating a vortex tube and an ejector according to claim 1, characterized in that: The cold end outlet pressure of the vortex tube (2) is lower than the hot end outlet pressure, and the cold end outlet temperature is lower than the hot end outlet temperature.

3. A transcritical CO2 refrigeration system integrating a vortex tube and an ejector according to claim 1, characterized in that: The gas-liquid separator (3) is a vertical structure, with a liquid outlet located at the bottom and a gas outlet located at the top.

4. A transcritical CO2 refrigeration system integrating a vortex tube and an ejector according to claim 1, characterized in that: The mixed fluid outlet of the ejector (6) is connected to the inlet of the high-pressure compressor (8) after merging with the outlet of the low-pressure compressor (7) through a pipeline.

5. A transcritical CO2 refrigeration system integrating a vortex tube and an ejector according to claim 1, characterized in that: The working fluid inlet pressure of the ejector (6) is higher than the ejection fluid inlet pressure, and the ejector (6) outlet pressure is equal to the low-pressure compressor (7) outlet pressure and the high-pressure compressor (8) inlet pressure.

6. A transcritical CO2 refrigeration system integrating a vortex tube and an ejector according to claim 1, characterized in that: The low-pressure compressor (7) and the high-pressure compressor (8) form a two-stage compression structure.

7. A transcritical CO2 refrigeration system integrating a vortex tube and an ejector according to claim 1, characterized in that: The gas outlet pressure of the gas-liquid separator (3) is greater than the outlet pressure of the evaporator (5).

8. A method for operating a transcritical CO2 refrigeration system integrating a vortex tube and an ejector, characterized in that: The following steps are involved: S1, after the supercritical CO2 working medium has completed heat removal in the gas cooler (1), it enters the vortex tube (2) for energy separation, the hot end outlet of the vortex tube (2) outputs a high-pressure two-phase fluid to the gas-liquid separator (3), and the cold end outlet outputs a low-pressure two-phase fluid; S2, the gas-liquid separator (3) separates the high-pressure two-phase fluid into top gas and bottom liquid. The bottom liquid is depressurized by the throttle valve (4) and mixed with the fluid at the cold end outlet of the vortex tube (2), and enters the evaporator (5) to absorb heat and evaporate; S3, the gas at the top of the gas-liquid separator (3) is used as the working fluid of the ejector (6) to eject part of the low-temperature gas at the outlet of the evaporator (5); S4, the residual gas at the outlet of the evaporator (5) is pressurized by the low-pressure compressor (7) and mixed with the gas at the outlet of the ejector (6). The mixed gas is compressed to a supercritical state by the high-pressure compressor (8) and then returns to the gas cooler (1) to complete the cycle.

9. The operating method of a transcritical CO2 refrigeration system integrating a vortex tube and an ejector according to claim 8, characterized in that: In S1, the pressure of the high-pressure two-phase fluid at the hot end is 2-4 MPa higher than the pressure of the low-pressure two-phase fluid at the cold end.

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