Carbon dioxide refrigeration system

Abstract

The utility model relates to a carbon dioxide refrigerating system. The carbon dioxide refrigerating system comprises a first compressor, an air cooler, a liquid reservoir and a first evaporator, an outlet of the first compressor is connected with an inlet of the air cooler, the carbon dioxide refrigerating system further comprises an economizer and an ejector, and an outlet main flow path of the air cooler is connected with a main side inlet of the economizer; an outlet auxiliary flow path of the air cooler is connected with an auxiliary side inlet of the economizer, a main side outlet of the economizer is connected with an active flow inlet of the ejector, and an auxiliary side outlet of the economizer is connected with a medium-pressure cavity of the first compressor; an ejection flow inlet of the ejector is connected with an outlet of the first evaporator, an outlet of the ejector is connected with an inlet of the liquid reservoir, a liquid outlet of the liquid reservoir is connected with an inlet of the first evaporator, and a gas outlet of the liquid reservoir is connected with an air suction port of the first compressor. According to the carbon dioxide refrigerating system, pressure loss caused by large pressure difference can be reduced, and the refrigerating capacity of the system can be further improved.

Description

Technical Field

[0001] The utility model relates to the technical field of refrigeration, and in particular to a carbon dioxide refrigeration system. Background Art

[0002] This section provides background information related to the present invention which does not necessarily constitute prior art.

[0003] Because carbon dioxide has the advantages of high heat transfer efficiency, low viscosity, no ozone depletion potential, non-toxicity, non-flammability and low price, with the advancement of the energy revolution and the dual carbon strategy, the application of refrigeration systems using carbon dioxide as a refrigerant is becoming more and more widespread.

[0004] However, since the critical temperature of carbon dioxide is lower than that of conventional refrigerants, traditional carbon dioxide refrigeration systems require a higher exhaust pressure to meet the heat exchange temperature difference, resulting in a large pressure difference between the high and low pressures of the refrigeration system, serious throttling losses, and low system energy efficiency. Utility Model Content

[0005] The purpose of the present invention is to solve or alleviate at least one of the above problems.

[0006] In particular, an object of the present invention is to provide a carbon dioxide refrigeration system, in which the evaporation-side refrigerant of the system increases the suction-side pressure of the first compressor by injection, and the injection fluid dryness is reduced and the injection fluid flow rate is increased by setting an economizer, that is, through the synergistic effect and specific combination of the economizer and the ejector, the pressure loss caused by the large pressure difference of the carbon dioxide refrigeration system can be effectively reduced and the compression power consumption can be effectively reduced accordingly, and at the same time, the system refrigeration capacity can be further improved and the high-pressure safety can be improved without increasing energy consumption and system size.

[0007] According to the present utility model, a carbon dioxide refrigeration system is provided, which includes a first compressor, an air cooler, a liquid reservoir and a first evaporator, the outlet of the first compressor is connected to the inlet of the air cooler, and the carbon dioxide refrigeration system also includes an economizer and an ejector, the outlet main flow path of the air cooler is connected to the main side inlet of the economizer, the outlet auxiliary flow path of the air cooler is connected to the auxiliary side inlet of the economizer, the main side outlet of the economizer is connected to the active flow inlet of the ejector, the auxiliary side outlet of the economizer is connected to the medium-pressure chamber of the first compressor, the ejector inlet is connected to the outlet of the first evaporator, the outlet of the ejector is connected to the inlet of the liquid reservoir, the liquid outlet of the liquid reservoir is connected to the inlet of the first evaporator, and the gas outlet of the liquid reservoir is connected to the suction port of the first compressor.

[0008] In the above carbon dioxide refrigeration system, a regulating valve is provided in the outlet auxiliary flow path of the air cooler, and the regulating valve is an injection enthalpy increase regulating valve.

[0009] In the above carbon dioxide refrigeration system, a second throttle valve is provided between the liquid outlet of the liquid receiver and the inlet of the first evaporator.

[0010] In the above carbon dioxide refrigeration system, the carbon dioxide refrigeration system further includes a heat exchanger, and the heat exchanger is located between the economizer and the ejector.

[0011] In the above carbon dioxide refrigeration system, the primary side outlet of the economizer is connected to the active inlet of the ejector via the heat exchanger, and the gas outlet of the liquid receiver is connected to the suction port of the first compressor via the heat exchanger.

[0012] In the above carbon dioxide refrigeration system, the heat exchanger is a plate heat exchanger.

[0013] In the above-mentioned carbon dioxide refrigeration system, the carbon dioxide refrigeration system also includes a second evaporator and a second compressor, the inlet of the second evaporator is connected to the liquid outlet of the liquid receiver, the outlet of the second evaporator is connected to the suction port of the second compressor, and the outlet of the second compressor is connected to the suction port of the first compressor.

[0014] In the above carbon dioxide refrigeration system, a third throttle valve is provided between the inlet of the second evaporator and the liquid outlet of the liquid receiver.

[0015] In the above carbon dioxide refrigeration system, a gas bypass valve is provided between the gas outlet of the liquid receiver and the air intake of the first compressor.

[0016] In the above carbon dioxide refrigeration system, a heat recovery device is provided at the outlet of the second compressor.

[0017] According to the carbon dioxide refrigeration system of the present invention, by providing an economizer and an ejector with synergistic and specific combination, the pressure loss caused by the large pressure difference of the carbon dioxide refrigeration system is effectively reduced and the compression power consumption is correspondingly effectively reduced. At the same time, the system refrigeration capacity is further enhanced and the high-pressure safety is improved without increasing energy consumption and system size.

[0018] Furthermore, the CO2 refrigeration system of the present invention organically combines jet enthalpy increase technology with expansion work recovery technology. An economizer is used to cool the CO2 main flow path fluid at the air cooler outlet, reducing the system's optimal exhaust pressure. The flow rate of the auxiliary flow path is regulated by a jet enthalpy increase control valve to adapt to different operating conditions to a certain extent. Simultaneously, the reduction in air cooler outlet temperature brought about by the economizer significantly reduces the refrigerant dryness at the ejector outlet, increasing the mass flow rate on the evaporation side and thereby improving the system's cooling capacity. Furthermore, the CO2 refrigeration system of the present invention utilizes an ejector to replace the traditional CO2 high-pressure throttle valve to recover expansion work, thereby reducing system throttling losses and improving overall system performance. Furthermore, the CO2 refrigeration system of the present invention utilizes a heat exchanger between the economizer and the ejector, allowing the saturated gaseous refrigerant in the liquid reservoir to exchange heat with the cooled refrigerant in the air cooler before entering the first compressor intake port, thereby ensuring the necessary superheat and improving the reliability of the first compressor's operation. Simultaneously, the refrigerant in the main flow path can also be slightly subcooled, further reducing the dryness and increasing the refrigerant circulation capacity of the first evaporator. In addition, by providing a second compressor and a second evaporator, the liquid refrigerant in the liquid receiver can pass through the two evaporators respectively, thereby meeting medium-temperature and low-temperature refrigeration applications at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings only illustrate some embodiments of the related art and the present invention by way of example, but the present invention is not limited to the embodiments shown in the accompanying drawings.

[0020] Figure 1 It is a flow chart of a carbon dioxide refrigeration system in related technology.

[0021] Figure 2 It is a flow chart of a carbon dioxide refrigeration system according to the first embodiment of the present utility model.

[0022] Figure 3 3 is a pressure-enthalpy comparison diagram of the carbon dioxide refrigeration system according to the first embodiment of the present invention and the carbon dioxide refrigeration system in the related art.

[0023] Figure 4 It is a schematic flow chart of a carbon dioxide refrigeration system according to the second embodiment of the present invention.

[0024] Figure 5 It is a schematic flow chart of a carbon dioxide refrigeration system according to the third embodiment of the present invention.

[0025] Figure 6 4 is a pressure-enthalpy diagram of a carbon dioxide refrigeration system according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present disclosure will be described in detail below by way of exemplary embodiments with reference to the accompanying drawings. In several figures, similar reference numerals represent similar parts and assemblies. The following detailed description of the present disclosure is for illustrative purposes only and is by no means a limitation of the present disclosure and its applications or uses. The embodiments described in this specification are not exhaustive and are merely some of a plurality of possible embodiments. The exemplary embodiments can be implemented in many different forms and should not be construed as limiting the scope of the present disclosure. In some exemplary embodiments, well-known processes, well-known device structures, and well-known technologies may not be described in detail.

[0027] Below, we will refer to the attached Figure 1 The carbon dioxide refrigeration system in the related art is described and reference will be made to Figures 2 to 6 The carbon dioxide refrigeration system according to the present invention is described. In the accompanying drawings, like reference numerals represent like parts and / or components.

[0028] like Figure 1 As shown, in the related art, a carbon dioxide refrigeration system includes a first compressor 1, an air cooler 2, a liquid receiver 3, and a first evaporator 4. The outlet of the first compressor 1 is connected to the inlet of the air cooler 2, which is in turn connected to the inlet of the liquid receiver 3 via a first throttle valve 11. The liquid outlet of the liquid receiver 3 is connected to the inlet of the first evaporator 4 via a second throttle valve 12, and the gas outlet of the liquid receiver 3 is connected to the suction port of the first compressor 1 via a gas bypass valve 13. The outlet of the first evaporator 4 is also connected to the suction port of the first compressor 1.

[0029] When the carbon dioxide refrigeration system is operating, the carbon dioxide refrigerant is compressed by the first compressor 1 and then enters the air cooler 2 for cooling. The first throttle valve 11 adjusts the high-pressure pressure according to the outlet temperature of the air cooler 2, and expands the high-pressure carbon dioxide refrigerant to a gas-liquid mixed state before entering the liquid reservoir 3. The gaseous refrigerant in the liquid reservoir 3 returns to the intake port of the first compressor 1 through the gas outlet of the liquid reservoir 3. The gas bypass valve 13 is used to control the pressure of the liquid reservoir 3. The saturated liquid refrigerant in the liquid reservoir 3 passes through the second throttle valve 12, undergoes phase change heat in the first evaporator 4, and finally returns to the intake port of the first compressor 1. After mixing with the bypass refrigerant from the gas outlet of the liquid reservoir 3, it enters the first compressor 1 to begin the next cycle.

[0030] Due to the low critical temperature of carbon dioxide, related technologies require a high exhaust pressure in first compressor 1 to meet the required heat exchange temperature difference. Furthermore, the low evaporation pressure of first evaporator 4 results in a large pressure difference between the inlet and outlet of first compressor 1. This high pressure ratio results in high power consumption during the compression process of first compressor 1, resulting in low system energy efficiency.

[0031] In order to overcome the above-mentioned problems or similar problems in the related art, the present invention provides the following carbon dioxide refrigeration system.

[0032] Figure 2 A first embodiment of the present invention is schematically shown.

[0033] like Figure 2 As shown, the carbon dioxide refrigeration system of the present invention includes a first compressor 1, an air cooler 2, a liquid receiver 3, an economizer 5, an ejector 6 and a first evaporator 4. The economizer 5 includes a primary side and an auxiliary side. The main flow path fluid enters the economizer 5 from the primary side inlet, exchanges heat with the auxiliary flow path fluid and then exits from the primary side outlet ( Figure 2 The ejector 6 includes an active inlet ( Figure 2 The point connected to point d in the middle), the jet inlet ( Figure 2 The point connected to point h) and the exit ( Figure 2 The fluid entering the active inlet of the ejector 6 can eject the fluid connected to the ejection inlet of the ejector 6, and the two fluids are mixed in the ejector 6 and then leave the ejector 6 from the outlet of the ejector 6.

[0034] In this embodiment, the outlet of the air cooler 2 is connected to the primary inlet of the economizer 5, which is connected to the active flow inlet of the ejector 6, the ejector flow inlet of the ejector 6 is connected to the outlet of the first evaporator 4, and the outlet of the ejector 6 is connected to the inlet of the liquid reservoir 3. The liquid outlet of the liquid reservoir 3 is connected to the inlet of the first evaporator 4 via the second throttle valve 12, and the gas outlet of the liquid reservoir 3 is connected to the suction port of the first compressor 1.

[0035] In this embodiment, the carbon dioxide refrigerant is compressed by the first compressor 1 and enters the air cooler 2. After being cooled by the air cooler 2, a portion of the fluid (the main flow path fluid) enters the primary side of the economizer 5. After absorbing heat from the auxiliary flow path fluid on the secondary side of the economizer 5, it leaves the economizer 5 through the primary side outlet. Another portion of the fluid (the auxiliary flow path fluid) cooled by the air cooler 2 enters the secondary side of the economizer 5 after being throttled by the regulating valve 7. The auxiliary flow path fluid absorbs heat from the refrigerant on the primary side, evaporating and returning to the intermediate pressure chamber of the first compressor 1 to participate in compression.

[0036] After leaving the economizer 5, the main flow path fluid enters the active inlet of the ejector 6, ejecting the refrigerant at the outlet of the first evaporator 4. The main flow path fluid and the refrigerant at the outlet of the first evaporator 4 mix within the ejector 6 before entering the liquid receiver 3 from the ejector 6 outlet. The saturated liquid refrigerant in the liquid receiver 3 passes through the second throttle valve 12 and enters the first evaporator 4 for heat exchange before returning to the ejector 6. The saturated gaseous refrigerant then returns from the gas outlet of the liquid receiver 3 to the intake port of the first compressor 1, beginning the next cycle.

[0037] Furthermore, the regulating valve 7 of this embodiment is an injection enthalpy increase regulating valve, which is used to adjust the amount of the auxiliary flow path (EVI loop) fluid that exchanges heat with the main flow path fluid in the economizer 5.

[0038] The carbon dioxide refrigeration system of this embodiment effectively reduces the pressure loss caused by the large pressure difference of the carbon dioxide refrigeration system and correspondingly effectively reduces the compression power consumption by providing an economizer 5 and an ejector 6 that work synergistically and in a specific combination. At the same time, it further improves the system refrigeration capacity and improves high-pressure safety without increasing energy consumption and system size.

[0039] Furthermore, the CO2 refrigeration system of the present invention organically combines jet enthalpy increase technology with expansion work recovery technology. Economizer 5 is used to cool the CO2 main flow path fluid at the outlet of air cooler 2, thereby reducing the system's optimal exhaust pressure. Adjusting the flow rate of the auxiliary flow path via the jet enthalpy increase control valve can, to a certain extent, adapt to different operating conditions. Simultaneously, the reduction in air cooler 2 outlet temperature brought about by economizer 5 can significantly reduce the refrigerant dryness at the outlet of ejector 6, increase the mass flow rate on the evaporation side, and thereby improve the system's cooling capacity. Furthermore, the CO2 refrigeration system of the present invention utilizes ejector 6 in place of the traditional CO2 high-pressure throttle valve to recover expansion work, thereby reducing the system's throttling losses and improving the system's overall performance.

[0040] Figure 3 Schematic diagram showing the comparison of pressure and enthalpy between the carbon dioxide refrigeration system of this embodiment and the carbon dioxide refrigeration system of the related art. Figure 3 In the figure, the horizontal axis is the enthalpy value of the carbon dioxide refrigerant (unit is KJ / Kg), and the vertical axis is the pressure value of the carbon dioxide refrigerant (unit is bar). The curve in the figure is the saturation curve, the dotted line is the pressure-enthalpy diagram of the carbon dioxide refrigerant in the carbon dioxide refrigeration system in the related art, and the solid line is the pressure-enthalpy diagram of the carbon dioxide refrigerant in the carbon dioxide refrigeration system of this embodiment. Among them, a, b, c, d... in the figure are the same as Figure 1 and Figure 2 a, b, c, d... in the table correspond to each other.

[0041] like Figure 3 As shown, since the evaporation side refrigerant is lifted by the injection of the first compressor 1 suction side ( Figure 3 The pressure at point a in the figure can save the pressure loss caused by the large pressure difference of the carbon dioxide refrigeration system and effectively reduce power consumption. In addition, in order to consider the pressure on the evaporation side, the traditional carbon dioxide refrigeration cycle will design a medium-pressure liquid storage tank, and the pressure is controlled by intermittent gas bypass back to the suction port of the first compressor 1, which makes it difficult to ensure the continuity of system operation. The liquid storage tank 3 of the carbon dioxide refrigeration system in this embodiment is set on the low-pressure side, and the saturated gas refrigerant returns directly from the liquid storage tank 3 to the first compressor 1, avoiding the pressure drop loss caused by secondary throttling, and can significantly reduce the power consumption of the system (first compressor 1).

[0042] Figure 4 A second embodiment of the present invention is shown.

[0043] like Figure 4 As shown, the carbon dioxide refrigeration system of this embodiment adds a heat exchanger 8 on the basis of the first embodiment. Specifically, the heat exchanger 8 is located between the main side outlet of the economizer 5 and the active inlet of the ejector 6. The main flow path fluid of the main side outlet of the economizer 5 enters the active inlet of the ejector 6 through the heat exchanger 8, and the saturated gaseous refrigerant in the liquid storage tank 3 exchanges heat with the main flow path fluid of the main side outlet of the economizer 5 through the heat exchanger 8 to ensure the necessary superheat of the gaseous refrigerant and improve the reliability of the operation of the first compressor 1. The superheated steam after heat exchange returns to the suction port of the first compressor 1 for compression. At the same time, the refrigerant in the main flow path can also obtain a small amount of subcooling, thereby reducing the dryness ( Figure 3 Point e in the figure) increases the refrigerant circulation amount of the first evaporator 4.

[0044] Furthermore, the heat exchanger 8 is a plate heat exchanger, which has a high heat transfer coefficient and ensures effective heat exchange between the two fluids.

[0045] Figure 5 A third embodiment of the present invention is shown.

[0046] On the basis of the first embodiment or the second embodiment, the carbon dioxide refrigeration system of the third embodiment further includes a second evaporator 101 and a second compressor 102 . Figure 5 An embodiment is shown in which a second evaporator 101 and a second compressor 102 are added on the basis of the second embodiment.

[0047] like Figure 5 As shown, the inlet of the second evaporator 101 is connected to the liquid outlet of the liquid reservoir 3 through the third throttle valve 14, the outlet of the second evaporator 101 is connected to the suction port of the second compressor 102, and the outlet of the second compressor 102 is connected to the suction port of the first compressor 1.

[0048] In this embodiment, a portion of the saturated liquid refrigerant in the liquid receiver 3 is throttled by the second throttle valve 12 and then enters the first evaporator 4 for heat exchange. The heat-exchanged refrigerant is then ejected back into the ejector 6. Another portion of the saturated liquid refrigerant is throttled by the third throttle valve 14 and then enters the second evaporator 101 for heat exchange. The heat-exchanged refrigerant then enters the intake port of the second compressor 102. This portion of refrigerant is compressed in the second compressor 102, mixed with the saturated gaseous refrigerant at the gas outlet of the liquid receiver 3, and then enters the intake port of the first compressor to begin the next cycle. A gas bypass valve 13 is provided between the gas outlet of the liquid receiver 3 and the intake port of the first compressor 1 to regulate the flow rate or control the pressure of the liquid receiver 3.

[0049] Figure 6 Schematic diagram of pressure and enthalpy of the carbon dioxide refrigeration system of this embodiment. Figure 6 In the figure, the horizontal axis is the enthalpy value of the carbon dioxide refrigerant (unit is KJ / Kg), and the vertical axis is the pressure value of the carbon dioxide refrigerant (unit is bar). The curve in the figure is the saturation curve, and the solid line is the pressure-enthalpy diagram of the carbon dioxide refrigerant in the carbon dioxide refrigeration system of this embodiment. Among them, a, b, c, d... in the figure are the same as Figure 5 a, b, c, d... in the table correspond to each other.

[0050] In this embodiment, if Figure 6 As shown, after being throttled by the third throttle valve 14, the pressure of the refrigerant entering the second evaporator 101 ( Figure 6 The pressure of the refrigerant entering the first evaporator 4 after being throttled by the second throttle valve 12 ( Figure 6 g point in the figure), so that the refrigeration system of this embodiment can meet the needs of medium-temperature and low-temperature refrigeration applications at the same time.

[0051] Furthermore, in this embodiment, a heat recovery device (not shown in the figure) is provided at the outlet of the second compressor 102.

[0052] In addition, it should be noted that in this document, the terms "first" and "second" are used only to better distinguish the relevant components and are not intended to have a specific limiting effect. For example, the use of "first" does not necessarily mean that there is a "second", and vice versa.

[0053] Although the present invention has been described with reference to exemplary embodiments, it should be understood that the present invention is not limited to the embodiments described and illustrated in detail herein, and that those skilled in the art may make various changes to the exemplary embodiments without departing from the scope defined by the claims.

Claims

1. A carbon dioxide refrigeration system, comprising a first compressor, an air cooler, a liquid receiver, and a first evaporator, wherein the outlet of the first compressor is connected to the inlet of the air cooler. It is characterized by: The carbon dioxide refrigeration system also includes an economizer and an ejector. The outlet main flow path of the air cooler is connected to the main side inlet of the economizer, the outlet auxiliary flow path of the air cooler is connected to the auxiliary side inlet of the economizer, the main side outlet of the economizer is connected to the active flow inlet of the ejector, the auxiliary side outlet of the economizer is connected to the intermediate pressure chamber of the first compressor, the ejector inlet is connected to the outlet of the first evaporator, the outlet of the ejector is connected to the inlet of the liquid reservoir, the liquid outlet of the liquid reservoir is connected to the inlet of the first evaporator, and the gas outlet of the liquid reservoir is connected to the suction port of the first compressor.

2. The carbon dioxide refrigeration system according to claim 1, characterized in that: A regulating valve is provided in the outlet auxiliary flow path of the air cooler, and the regulating valve is an injection enthalpy increasing regulating valve.

3. The carbon dioxide refrigeration system according to claim 1, characterized in that: A second throttle valve is provided between the liquid outlet of the liquid receiver and the inlet of the first evaporator.

4. The carbon dioxide refrigeration system according to claim 1, characterized in that: The carbon dioxide refrigeration system further includes a heat exchanger located between the economizer and the ejector.

5. The carbon dioxide refrigeration system according to claim 4, characterized in that: The primary side outlet of the economizer is connected to the active inlet of the ejector via the heat exchanger, and the gas outlet of the liquid receiver is connected to the suction port of the first compressor via the heat exchanger.

6. The carbon dioxide refrigeration system according to claim 4 or 5, characterized in that: The heat exchanger is a plate heat exchanger.

7. The carbon dioxide refrigeration system according to any one of claims 1 to 5, characterized in that: The carbon dioxide refrigeration system also includes a second evaporator and a second compressor, the inlet of the second evaporator is connected to the liquid outlet of the liquid receiver, the outlet of the second evaporator is connected to the suction port of the second compressor, and the outlet of the second compressor is connected to the suction port of the first compressor.

8. The carbon dioxide refrigeration system according to claim 7, characterized in that: A third throttle valve is provided between the inlet of the second evaporator and the liquid outlet of the liquid receiver.

9. The carbon dioxide refrigeration system according to claim 7, characterized in that: A gas bypass valve is provided between the gas outlet of the liquid receiver and the air intake of the first compressor.

10. The carbon dioxide refrigeration system according to claim 7, characterized in that: A heat recovery device is provided at the outlet of the second compressor.

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