A two-stage condensation evaporation heat exchange system used in a cascade refrigeration system / phase change heat transfer cooling system

Abstract

The present invention provides a two-stage condensation evaporation heat exchange system applied in a cascade refrigeration system / phase change heat transfer system, specifically relating to the field of refrigeration technology, wherein the condensation evaporation heat exchange system is provided with a first heat exchanger, a second heat exchanger, and a throttling expansion component, and when applied in a cascade refrigeration system or a phase change heat transfer system, the refrigerant in the condensed state in the high-temperature refrigeration system is supercooled inside the second heat exchanger, and enters the first heat exchanger for evaporation refrigeration after throttling expansion by the throttling expansion component, and exchanges heat with the opposite low-temperature refrigeration system or the phase change heat transfer system, and the return air containing the unevaporated refrigerant enters the second heat exchanger, and enters the high-temperature refrigeration cycle after obtaining a certain degree of superheat in the second heat exchanger. The system reduces the heat exchange temperature difference at the condensation end and simplifies the high-temperature refrigeration system, while solving the technical problem of large and unstable heat exchange temperature difference caused by the required superheat at the end of the heat exchanger.

Description

Technical Field

[0001] The present invention relates to a two-stage condensation evaporation heat exchange system used in a cascade refrigeration system / phase change heat transfer system, and in particular to a condensation evaporation heat exchange system in a high-temperature refrigeration system, belonging to the technical field of refrigeration. Background Art

[0002] In recent years, environmentally friendly natural refrigerant carbon dioxide has received more and more attention in the field of commercial refrigeration. In view of the relatively high pressure of carbon dioxide refrigeration system, for the sake of system safety and energy saving, carbon dioxide subcritical refrigeration system is generally used in freezing and refrigeration system. The system is usually implemented in cascade form or cold load form.

[0003] In a carbon dioxide subcritical refrigeration system, carbon dioxide refrigerant or coolant is used as the low-temperature stage, and ammonia or other refrigerants such as Freon are commonly used as the high-temperature stage. Gravity and pump supply are mostly used for liquid supply. This liquid supply method makes the high-temperature stage refrigeration system complex and requires a large amount of refrigerant. The advantage is that the heat exchange temperature difference of the condenser evaporator can be controlled to be very small. When the high-temperature stage refrigeration system adopts a direct expansion liquid supply system, the high-temperature stage refrigeration system can be simple and the refrigerant injection amount is small, but the disadvantage is that the superheat causes a large heat exchange temperature difference of the condenser evaporator, and it is often difficult to ensure that the refrigerant of the high-temperature stage refrigeration system is in a two-phase flow state, which affects the heat exchange temperature difference.

[0004] In order to reduce the heat exchange temperature difference at the condensing end, avoid the direct expansion liquid supply system from completely evaporating in the condensing evaporator, avoid the unstable heat exchange temperature difference caused by superheat at the end of the heat exchanger, reduce the refrigerant charge in the high-temperature refrigeration system, and simplify the high-temperature refrigeration system, refrigeration R&D personnel urgently need to develop a two-stage condensation evaporation heat exchange system for use in cascade refrigeration systems / phase change heat transfer systems. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] The purpose of the present invention is to provide a two-stage condensation evaporation heat exchange system used in a cascade refrigeration system / phase change heat transfer system. On the one hand, it reduces the heat exchange temperature difference at the condensation end, avoids the technical problem of unstable heat exchange temperature difference caused by the direct expansion liquid supply system completely evaporating in the condenser evaporator and the overheating at the end of the heat exchanger; on the other hand, it solves the technical problem of complex structure of high-temperature refrigeration system. Of course, it also solves the technical problem of large refrigerant charge and many uncontrollable factors in high-temperature refrigeration system.

[0007] (II) Technical solution

[0008] In order to solve the above technical problems, the present invention provides a two-stage condensation evaporation heat exchange system applied in a cascade refrigeration system / phase change heat transfer cooling system, comprising: a second heat exchanger, a throttling expansion component, and a first heat exchanger, wherein the second heat exchanger is located on one side of the high-temperature refrigeration system, and is used for subcooling the evaporator supply liquid on the high-temperature and high-pressure side and superheating the evaporator return gas containing unevaporated refrigerant on the low-temperature and low-pressure side; the throttling expansion component is located on one side of the high-temperature refrigeration system, and throttling and expanding the high-temperature and high-pressure side refrigerant after being supercooled by the second heat exchanger; the first heat exchanger is located between the high-temperature refrigeration system and the low-temperature refrigeration system, and is used for heat exchange between evaporation of the high-temperature refrigeration system and condensation of the low-temperature refrigeration system, the high-temperature and high-pressure side refrigerant of the high-temperature refrigeration system is throttled and expanded by the throttling expansion component, enters the first heat exchanger for evaporation, and then exchanges heat with the condensation end of the opposite low-temperature refrigeration system, and by adjusting the refrigerant flow rate flowing into the first heat exchanger, the return gas after the refrigerant evaporates in the first heat exchanger contains unevaporated refrigerant and does not overheat, thereby reducing the heat exchange temperature difference between the condensation and evaporation sides in the first heat exchanger.

[0009] The throttling expansion component is an important automatic control component in the refrigeration system. By receiving the change of the refrigerant superheat at the outlet of the first heat exchanger, the opening degree of the valve is changed, and the refrigerant flow rate flowing into the first heat exchanger is adjusted, so that the refrigerant flow rate always matches the load of the first heat exchanger, reducing the possibility of compressor liquid hammer. The first heat exchanger is a key heat exchanger in the cascade refrigeration system or the phase change heat transfer system, specifically a condenser evaporator, which is used for heat exchange between the evaporation of the high-temperature refrigeration system and the condensation of the low-temperature refrigeration system (or the phase change heat transfer system). The cold capacity of the high-temperature refrigeration system is used to condense the gas discharged from the compressor of the low-temperature refrigeration system. It is both the evaporator of the high-temperature refrigeration system and the condenser of the low-temperature refrigeration system. The second heat exchanger is specifically a regenerator, which uses the refrigerant vapor discharged from the high-temperature side of the first heat exchanger to supercool the high-pressure refrigerant liquid that is about to enter the first heat exchanger through the throttling expansion component, so that the steam entering the compressor is effectively superheated, preventing the compressor from sucking liquid, and also supercooling the refrigerant liquid on the high-pressure side, reducing throttling losses.

[0010] The low temperature refrigeration system in the cascade refrigeration system or the phase change heat transfer cooling system operates under subcritical conditions of carbon dioxide. The second heat exchanger can be used to superheat the evaporator return air containing unevaporated refrigerant on the low temperature and low pressure side, and the specific data of the certain proportion of the unevaporated refrigerant is determined according to the actual cooling load used.

[0011] Preferably, the first heat exchanger adopts one of a plate heat exchanger, a shell and tube heat exchanger, and a shell and plate heat exchanger. In the carbon dioxide subcritical refrigeration system, the prior art mostly uses a shell and tube heat exchanger, which makes the refrigeration system mainly supply liquid by gravity, and there are technical problems such as large heat exchange temperature difference, large refrigerant filling amount, low refrigeration efficiency, and high energy consumption. When the first heat exchanger adopts a plate heat exchanger, the refrigeration system mainly uses a pump to supply liquid, which solves the technical problems of complex system, large refrigerant filling amount, and many uncontrollable factors.

[0012] Preferably, the refrigerant of the high-temperature refrigeration system enters the second heat exchanger through the first liquid inlet pipe for supercooling, and enters the first heat exchanger through the second liquid inlet pipe for evaporative refrigeration after throttling expansion by the throttling expansion component.

[0013] Preferably, the return gas of the refrigerant of the high-temperature refrigeration system after evaporation and refrigeration in the first heat exchanger contains unevaporated refrigerant liquid, without overheating, and enters the second heat exchanger through the first return air pipe, exchanges heat with the refrigerant liquid of the high-temperature refrigeration system on the other side, and completely evaporates into superheated refrigerant vapor, and then returns to the suction end of the compressor through the second return air pipe to complete the refrigeration cycle.

[0014] Preferably, the throttling expansion component is an external balanced thermal expansion valve, which is connected to a balancing pipe and a temperature-sensing package, wherein the balancing pipe is connected to the first return air pipe section or the second return air pipe section, and the temperature-sensing package collects the temperature inside the first return air pipe or the second return air pipe, and controls the flow of the external balanced thermal expansion valve according to the temperature-sensing package signal, so that the high-temperature refrigerant in the first heat exchanger always maintains a two-phase flow heat exchange state. The external balanced thermal expansion valve is provided with an external balancing pipe, which directly introduces the pressure at the outlet of the first heat exchanger into the valve, fully considering the resistance loss of the first heat exchanger, and is suitable for systems with large changes in refrigerant flow and large resistance on the first heat exchanger side.

[0015] Preferably, the throttling expansion component is an internal balanced thermal expansion valve, which is connected to a temperature sensing package, which collects the temperature inside the first return air pipe or the second return air pipe, and controls the flow of the internal balanced thermal expansion valve according to the temperature sensing package signal, so that the high-temperature refrigerant in the first heat exchanger always maintains a two-phase flow heat exchange state. The internal balanced thermal expansion valve directly uses the pressure of the throttled refrigerant as the evaporation pressure, has a simple structure and is suitable for systems with relatively small resistance of the first heat exchanger.

[0016] Preferably, the throttling expansion component is an electronic expansion valve, and the electronic expansion valve is connected to a sensor, and the sensor collects the temperature and / or pressure inside the first return air pipe or the second return air pipe, and controls the flow of the electronic expansion valve according to the signal, so that the high-temperature refrigerant in the first heat exchanger always maintains a two-phase flow heat exchange state. The electronic expansion valve uses the temperature sensor or the pressure sensor to sense the change in the superheat of the refrigerant at the outlet of the first heat exchanger, and generates an electrical signal to control the opening degree of the valve, adjust the refrigerant flow into the first heat exchanger, so that the refrigerant flow always matches the load of the first heat exchanger, and reduce the possibility of compressor liquid hammer.

[0017] (III) Beneficial effects

[0018] According to the present invention, a two-stage condensation evaporation heat exchange system is provided for use in a cascade refrigeration system / phase change heat transfer system. The system adopts a direct expansion liquid supply system, which makes the high-temperature refrigeration system simple and reduces the refrigerant injection amount. The system reduces the heat exchange temperature difference at the condensation end, avoiding the technical problem of unstable heat exchange temperature difference caused by complete evaporation of the direct expansion liquid supply system in the condenser evaporator and superheat at the end of the heat exchanger.

[0019] In a preferred embodiment, the throttling expansion component adopts various forms, such as: an external balanced thermal expansion valve, an internal balanced thermal expansion valve, an electronic expansion valve, etc., which generates a signal to control the flow of the valve according to the change of the superheat of the refrigerant at the outlet of the first heat exchanger, and adjusts the refrigerant flow into the first heat exchanger, so that the refrigerant flow always matches the load of the first heat exchanger, reducing the possibility of compressor liquid hammer. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram showing the working principle of a two-stage condensation-evaporation heat exchange system applied in a cascade refrigeration system / phase-change heat transfer cooling system according to the first embodiment of the present invention;

[0021] Figure 2 Schematic diagram showing the working principle of a two-stage condensation evaporation heat exchange system applied in a cascade refrigeration system / phase change heat transfer cooling system according to the second embodiment of the present invention Figure 1 ;

[0022] Figure 3 Schematic diagram showing the working principle of a two-stage condensation evaporation heat exchange system applied in a cascade refrigeration system / phase change heat transfer cooling system according to the second embodiment of the present invention Figure 2 ;

[0023] Figure 4 Schematic diagram showing the working principle of a two-stage condensation evaporation heat exchange system applied in a cascade refrigeration system / phase change heat transfer cooling system according to the second embodiment of the present invention Figure 3 ;

[0024] Figure 5 Schematic diagram showing the working principle of a two-stage condensation evaporation heat exchange system applied in a cascade refrigeration system / phase change heat transfer cooling system according to the second embodiment of the present invention Figure 4 ;

[0025] Figure 6 Schematic diagram showing the working principle of a two-stage condensation evaporation heat exchange system applied in a cascade refrigeration system / phase change heat transfer cooling system according to the second embodiment of the present invention Figure 5 ;

[0026] Figure 7 A schematic diagram showing the working principle of a two-stage condensation-evaporation heat exchange system applied in a cascade refrigeration system / phase-change heat transfer cooling system according to a third embodiment of the present invention;

[0027] Description of labels:

[0028] 1. First heat exchanger; 11. Plate heat exchanger; 21. Second heat exchanger; 22. Low-temperature heat exchanger; 3. Throttling expansion component; 30. Temperature sensing package; 31. External balanced thermal expansion valve; 311. Balance pipe; 32. Internal balanced thermal expansion valve; 33. Electronic expansion valve; 330. Sensor; 34. Low-temperature electronic expansion valve; 41. First return air pipe; 42. Second liquid inlet pipe; 51. Second return air pipe; 52. First liquid inlet pipe; 6. Condenser; 71. High-temperature compressor; 72. Low-temperature compressor; 73. Pump; 81. High-temperature oil separator; 82. Low-temperature oil separator; 91. High-temperature liquid storage tank; 92. Low-temperature liquid storage tank; 93. Low-pressure circulation barrel; 10. Low-temperature evaporator. DETAILED DESCRIPTION

[0029] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0030] The most critical concept of the present invention is that the high-temperature refrigeration system adopts direct expansion liquid supply, and the liquid supply is not completely evaporated in the first heat exchanger, so there is no influence of superheat on the heat exchange temperature difference, and the superheat required by the direct expansion liquid supply system is obtained in the second heat exchanger.

[0031] Embodiment 1:

[0032] Figure 1 A schematic diagram showing the working principle of a two-stage condensation evaporation heat exchange system applied in a cascade refrigeration system / phase change heat transfer cooling system according to the first embodiment of the present invention.

[0033] The present invention provides a two-stage condensation evaporation heat exchange system applied in a cascade refrigeration system / phase change heat transfer system. When applied in a carbon dioxide subcritical cascade refrigeration system, it specifically includes: a high-temperature refrigeration system and a low-temperature refrigeration system, wherein the high-temperature refrigeration system uses a Freon refrigerant, and the low-temperature refrigeration system uses a carbon dioxide refrigerant. A two-stage condensation evaporation heat exchange system is also provided on the high-temperature refrigeration system, and the system includes: a second heat exchanger 21, a throttling expansion component 3, and a first heat exchanger 1, wherein the second heat exchanger 21 and the throttling expansion component 3 are located on one side of the high-temperature refrigeration system, and the first heat exchanger 1 is located between the high-temperature refrigeration system and the low-temperature refrigeration system, and is responsible for connecting the high-temperature refrigeration system and the low-temperature refrigeration system, and is specifically a condensation evaporator, and uses the cold capacity of the high-temperature refrigeration system to condense the gas discharged from the compressor of the low-temperature refrigeration system. Therefore, the first heat exchanger 1 is both an evaporator of the high-temperature refrigeration system and a condenser of the low-temperature refrigeration system. The throttling expansion component 3 is an important automatic control component in the refrigeration system. By receiving the change of the refrigerant superheat at the outlet of the first heat exchanger 1, the valve opening degree is changed, and the refrigerant flow rate flowing into the first heat exchanger 1 is adjusted, so that the refrigerant flow rate always matches the load of the first heat exchanger 1, reducing the possibility of compressor liquid hammer. The second heat exchanger 21 is used for supercooling the high-temperature and high-pressure refrigerant in the high-temperature refrigeration system. Specifically, it is a regenerator, which uses the refrigerant vapor coming out of the Freon side of the first heat exchanger 1 to supercool the high-pressure refrigerant liquid that is about to enter the first heat exchanger 1 through the throttling expansion component 3, so that the steam entering the compressor is effectively superheated, preventing the compressor from sucking liquid, and also supercooling the refrigerant liquid on the high-pressure side, reducing throttling losses.

[0034] The high-temperature and high-pressure refrigerant in the high-temperature refrigeration system enters the first heat exchanger 1 for evaporation and refrigeration after throttling expansion, and exchanges heat with the low-temperature refrigeration system on the opposite side to ensure a constant heat exchange temperature difference. The refrigerant of the high-temperature refrigeration system enters the second heat exchanger 21 through the first liquid inlet pipe 52 for supercooling, and enters the first heat exchanger 1 through the second liquid inlet pipe 42 for evaporation and refrigeration after throttling expansion by the throttling expansion component 3. After evaporation and refrigeration in the first heat exchanger 1, the refrigerant of the high-temperature refrigeration system enters the second heat exchanger 21 through the first return pipe 41, and completely changes into superheated refrigerant vapor after heat exchange with the refrigerant liquid of the high-temperature refrigeration system, and then returns to the suction end of the compressor through the second return pipe 51 to complete the refrigeration cycle. The first heat exchanger 1 adopts a shell and tube heat exchanger, and the first heat exchanger 1 adopts a shell and tube heat exchanger, and its heat exchange temperature difference is generally above 5°C.

[0035] Embodiment 2:

[0036] Figure 2 Schematic diagram showing the working principle of a two-stage condensation evaporation heat exchange system applied in a cascade refrigeration system / phase change heat transfer cooling system according to the second embodiment of the present invention Figure 1 ; Figure 3 Schematic diagram showing the working principle of a two-stage condensation evaporation heat exchange system applied in a cascade refrigeration system / phase change heat transfer cooling system according to the second embodiment of the present invention Figure 2 .

[0037] Combination Figure 2 and Figure 3 As shown, the present invention provides another two-stage condensation evaporation heat exchange system used in a cascade refrigeration system / phase change heat transfer system. When used in a carbon dioxide subcritical cascade refrigeration system, it specifically includes: a high-temperature refrigeration system and a low-temperature refrigeration system. The high-temperature refrigeration system uses Freon refrigerant, and the low-temperature refrigeration system uses carbon dioxide refrigerant. The high-temperature refrigeration system is provided with a two-stage condensation evaporation heat exchange system, which includes: a second heat exchanger 21, a throttling expansion component 3, and a first heat exchanger 1, wherein the second heat exchanger 21 and the throttling expansion component 3 are located on one side of the high-temperature refrigeration system, and the first heat exchanger 1 is located between the high-temperature refrigeration system and the low-temperature refrigeration system, and is responsible for connecting the high-temperature refrigeration system and the low-temperature refrigeration system, and is specifically a condenser evaporator, which uses the cold capacity of the high-temperature refrigeration system to condense the gas discharged from the compressor of the low-temperature refrigeration system, and is both an evaporator of the high-temperature refrigeration system and a condenser of the low-temperature refrigeration system. The throttling expansion component 3 is specifically an external balanced thermal expansion valve, which receives the change of the refrigerant superheat at the outlet of the first heat exchanger 1, changes the valve opening, and adjusts the refrigerant flow rate flowing into the first heat exchanger 1, so that the refrigerant flow rate always matches the load of the first heat exchanger 1, reducing the possibility of compressor liquid hammer. The second heat exchanger 21 is specifically a regenerator, which uses the refrigerant vapor coming out of the Freon side of the first heat exchanger 1 to supercool the high-pressure refrigerant liquid that is to enter the first heat exchanger 1 through the throttling expansion component 3, so that the vapor entering the compressor is effectively superheated.

[0038] The high-temperature and high-pressure refrigerant in the high-temperature refrigeration system enters the first heat exchanger 1 for evaporative refrigeration after throttling expansion, and exchanges heat with the low-temperature refrigeration system on the opposite side to ensure a constant heat exchange temperature difference. The Freon refrigerant in the high-temperature refrigeration system enters the second heat exchanger 21 through the first liquid inlet pipe 52 for supercooling, and enters the first heat exchanger 1 for evaporative refrigeration through the second liquid inlet pipe 42 after throttling expansion by the throttling expansion component 3. After evaporative refrigeration in the first heat exchanger 1, the refrigerant in the high-temperature refrigeration system enters the second heat exchanger 21 through the first return air pipe 41, and completely changes into superheated refrigerant vapor after heat exchange with the refrigerant liquid of the high-temperature refrigeration system, and then returns to the suction end of the compressor through the second return air pipe 51 to complete the refrigeration cycle. The first heat exchanger 1 adopts a plate heat exchanger 11. The high temperature and high pressure refrigerant liquid enters the second heat exchanger 21, and the low temperature and low pressure two-phase return gas enters the second heat exchanger 21 from the other side. The heat of the high temperature and high pressure refrigerant liquid is absorbed by the low temperature and low pressure refrigerant liquid, the high temperature and high pressure supply liquid is supercooled, and the low temperature and low pressure refrigerant liquid evaporates, ensuring that the return gas end of the compressor is superheated refrigerant vapor.

[0039] The first heat exchanger 1 uses a plate heat exchanger 11 or a plate and shell heat exchanger, and the heat exchange temperature difference can reach 3°C. In order to ensure the stability of the condensation temperature on the carbon dioxide side, the refrigerant on the Freon side is required to maintain a two-phase flow state throughout the heat exchanger. Conventional Freon direct expansion refrigeration systems are difficult to ensure that the refrigerant in the first heat exchanger 1 is in a two-phase flow state. This system sets a second Freon heat exchanger 21 and adjusts the position of the temperature sensor or temperature sensor and pressure sensor of the throttling expansion component 3, so that the Freon flowing out of the first heat exchanger 1 is still in a two-phase flow state. At the same time, the two-phase flow is completely evaporated into Freon gas through heat exchange in the second heat exchanger 21, so that the refrigerant returning to the Freon compressor is superheated Freon gas. Due to the unique structure of the plate heat exchanger 11 or the plate and shell heat exchanger, the amount of Freon charged is much smaller than that of the shell and tube heat exchanger.

[0040] like Figure 2 As shown, the throttling expansion component 3 can be an external balanced thermal expansion valve 31, which is connected to a balancing pipe 311 and a temperature sensing bag 30. The balancing pipe 311 is connected to the second return air pipe 51 section. The temperature sensing bag 30 collects the temperature inside the second return air pipe 51. The external balanced thermal expansion valve 31 determines the valve opening degree according to the temperature collected by the temperature sensing bag 30.

[0041] like Figure 3As shown, the throttling expansion component 3 is an external balanced thermal expansion valve 31, the external balanced thermal expansion valve 31 is connected with a balance pipe 311 and a temperature sensing package 30, the balance pipe 311 is connected to the pipe section of the first return air pipe 41, the temperature sensing package 30 collects the temperature inside the first return air pipe 41, and the external balanced thermal expansion valve 31 determines the valve opening degree according to the temperature collected by the temperature sensing package 30. The balance pipe 311 of the external balanced thermal expansion valve 31 directly introduces the pressure at the outlet of the first heat exchanger 1 into the valve, fully considering the resistance loss of the first heat exchanger 1, and is suitable for systems with large refrigerant flow changes and large resistance on the first heat exchanger 1 side.

[0042] Figure 4 Schematic diagram showing the working principle of a two-stage condensation evaporation heat exchange system applied in a cascade refrigeration system / phase change heat transfer cooling system according to the second embodiment of the present invention Figure 3 The throttling expansion component 3 may also be an internal balanced thermal expansion valve 32, which is connected to a temperature sensing package 30, which collects the temperature inside the first return air pipe 41 or the second return air pipe 51, and the internal balanced thermal expansion valve 32 determines the valve opening degree according to the temperature collected by the temperature sensing package 30. The internal balanced thermal expansion valve 32 directly uses the pressure of the refrigerant after throttling as the evaporation pressure, has a simple structure and is suitable for systems with relatively small resistance of the first heat exchanger 1.

[0043] Figure 5 Schematic diagram showing the working principle of a two-stage condensation evaporation heat exchange system applied in a cascade refrigeration system / phase change heat transfer cooling system according to the second embodiment of the present invention Figure 4 . The throttling expansion component 3 can also be an electronic expansion valve 33, and the electronic expansion valve 33 is connected to a sensor 330. The sensor 330 collects the temperature and / or pressure inside the second return air pipe 51, and controls the opening degree of the electronic expansion valve 33 according to the temperature signal and / or pressure signal, so that the refrigerant in the first heat exchanger 1 always maintains a two-phase flow. Of course, the sensor 330 can also be located in the first return air pipe 41, collects the temperature and / or pressure inside the first return air pipe 41, and controls the opening degree of the electronic expansion valve 33 according to the temperature signal and / or pressure signal, so that the refrigerant in the first heat exchanger 1 always maintains a two-phase flow. The electronic expansion valve 33 uses the sensor 330 to sense the change in the superheat of the refrigerant at the outlet of the first heat exchanger 1, generates an electrical signal to control the opening degree of the valve, and adjusts the refrigerant flow rate flowing into the first heat exchanger 1, so that the refrigerant flow rate always matches the load of the first heat exchanger 1, reducing the possibility of compressor liquid hammer.

[0044] Figure 6 Schematic diagram showing the working principle of a two-stage condensation evaporation heat exchange system applied in a cascade refrigeration system / phase change heat transfer cooling system according to the second embodiment of the present invention Figure 5The cascade refrigeration system can be understood as two independent refrigeration systems, and the first heat exchanger 1 combines the two independent refrigeration systems to form a cascade system. The first heat exchanger 1 is both an evaporator of the high-temperature refrigeration system on the Freon side and a condenser of the low-temperature refrigeration system on the carbon dioxide side. For the high-temperature refrigeration system on the Freon side, the high-temperature compressor 71 inhales low-temperature and low-pressure Freon refrigerant gas, compresses it by driving the compression component through the operation of the motor, and then discharges high-temperature and high-pressure refrigerant superheated gas. The refrigerant superheated gas passes through the high-temperature oil separator 81 to separate the lubricating oil in the superheated gas, and then enters the condenser 6. The high-temperature and high-pressure superheated gas releases heat to the outside through the condenser 6, thereby condensing into a saturated high-pressure liquid. The high-pressure liquid flows to the high-temperature liquid storage tank 91, is temporarily stored in the high-temperature liquid storage tank 91, and then is supercooled through the second heat exchanger 21 to become a supercooled high-pressure liquid. After throttling through the external balanced thermal expansion valve 31, it enters the low-temperature side of the first heat exchanger 1, absorbs the heat of the high-temperature and high-pressure superheated carbon dioxide on the plate side, and becomes a low-temperature and low-pressure Freon vapor. After being superheated through the second heat exchanger 21, the Freon vapor enters the suction chamber of the high-temperature compressor 71 to complete a cycle.

[0045] For the low-temperature refrigeration system on the carbon dioxide side, the low-temperature compressor 72 inhales low-temperature and low-pressure carbon dioxide refrigerant gas, compresses it by driving the compression component through the operation of the motor, and then discharges high-temperature and high-pressure refrigerant superheated gas. The refrigerant superheated gas passes through the low-temperature oil separator 82 to separate the lubricating oil in the superheated gas, and then enters the high-temperature side of the first heat exchanger 1. The high-temperature and high-pressure superheated gas releases heat to the low-temperature side through the first heat exchanger 1, thereby condensing into a saturated high-pressure liquid. The high-pressure liquid flows to the low-temperature liquid storage tank 92, is temporarily stored in the low-temperature liquid storage tank 92, and then is supercooled by the low-temperature heat exchanger 22 to become a supercooled high-pressure liquid. After throttling by the low-temperature electronic expansion valve 34, it enters the low-temperature evaporator 10, absorbs heat from the air or other media, and becomes low-temperature and low-pressure carbon dioxide vapor. After being superheated by the low-temperature heat exchanger 22, the carbon dioxide vapor enters the suction chamber of the low-temperature compressor 72 to complete a cycle.

[0046] For the entire cascade refrigeration system, the low-temperature electronic expansion valve 34 on the carbon dioxide side generates an electrical signal through the temperature sensor and the pressure sensor according to the change of the load of the low-temperature evaporator 10 of the carbon dioxide. After the superheat controller analyzes the electrical signal, it issues an instruction to control the opening degree of the low-temperature electronic expansion valve 34 on the carbon dioxide side. After throttling, the carbon dioxide liquid becomes a gas-liquid two-phase mixture and enters the low-temperature evaporator 10 of the carbon dioxide, and then absorbs heat and vaporizes for refrigeration. The vaporized carbon dioxide vapor is superheated through the low-temperature evaporator 10, enters the suction chamber of the low-temperature compressor 72, and is then compressed to become a high-temperature and high-pressure superheated gas. After the superheated gas passes through the low-temperature oil separator 82, it enters the high-temperature side of the first heat exchanger 1 to release heat and condense. After condensing into liquid, it enters the carbon dioxide low-temperature liquid storage tank 92 for temporary storage, and then passes through the low-temperature heat exchanger 22 for supercooling, and then supplies liquid to the low-temperature electronic expansion valve 34. After the first heat exchanger 1 releases heat through carbon dioxide, it transfers heat to the Freon refrigerant on the low-temperature side through the high-temperature side. The Freon refrigerant on the high-temperature side absorbs heat, evaporates, and cools to become a gas. Due to the change in superheat, the external balanced thermal expansion valve 31 on the Freon side controls the valve opening degree to supply low-temperature liquid to the first heat exchanger 1. After the Freon gas is overheated by the second heat exchanger 21, it enters the suction chamber of the high-temperature compressor 71, and then is compressed to become a high-temperature and high-pressure superheated gas. After passing through the high-temperature oil separator 81, the superheated gas enters the condenser 6 to release heat and condenses into liquid. The liquid enters the high-temperature liquid storage tank 91 for temporary storage, and is supercooled by the second heat exchanger 21 to supply liquid to the throttling expansion component 3.

[0047] The first heat exchanger 1 ensures the heat exchange temperature difference through superheat control, pressure control, and start-stop coordination control. The low-temperature side of the first heat exchanger 1 ensures that there is an appropriate amount of refrigerant on the low-temperature side of the first heat exchanger 1 for heat absorption and evaporation through superheat control, and maintains the evaporation pressure on the low-temperature side through the start-stop or energy level adjustment of the Freon compressor, thereby ensuring the evaporation temperature on the Freon side. The high-temperature side of the first heat exchanger 1 coordinates the energy level adjustment or start-stop of the low-temperature compressor 72 on the carbon dioxide side through pressure control to ensure the condensation pressure on the plate side, thereby ensuring the condensation temperature on the carbon dioxide side. Since carbon dioxide is highly sensitive to pressure, in order to maintain the stability of the system, when the low-temperature compressor 72 on the carbon dioxide side reaches the start-up conditions, it needs to be opened for a long time to ensure that it can be opened only after the high-temperature compressor 71 on the Freon side is opened first. By ensuring the evaporation temperature on the Freon side and the condensation temperature on the carbon dioxide side, the heat exchange temperature difference of the first heat exchanger 1 is guaranteed.

[0048] Embodiment 3:

[0049] Figure 7The schematic diagram of the working principle of the two-stage condensation evaporation heat exchange system applied in the cascade refrigeration system / phase change heat transfer cooling system of the third embodiment of the present invention is shown. The present invention provides another two-stage condensation evaporation heat exchange system applied in the cascade refrigeration system / phase change heat transfer cooling system. When applied in the phase change heat transfer cooling system, it is specifically a carbon dioxide cooling system, which is composed of a complete Freon refrigeration system and a carbon dioxide refrigeration system powered by a pump without a compressor. The first heat exchanger 1 combines the two systems together to form a carbon dioxide cooling system. The first heat exchanger 1 is specifically a condensation evaporator, which is both an evaporator of the Freon side system and a condenser of the carbon dioxide side. The two-stage condensation evaporation heat exchange system also includes: a second heat exchanger 21 and a throttling expansion component 3, wherein the second heat exchanger 21 and the throttling expansion component 3 are located on the side of the Freon side system, and the throttling expansion component 3 is specifically an external balanced thermal expansion valve 31, which receives the change of the refrigerant superheat at the outlet of the first heat exchanger 1 through the temperature sensing package 30, changes the valve opening, and adjusts the refrigerant flow rate flowing into the first heat exchanger 1, so that the refrigerant flow rate always matches the load of the first heat exchanger 1, reducing the possibility of compressor liquid hammer. The second heat exchanger 21 is specifically a regenerator, which uses the refrigerant vapor coming out of the Freon side of the first heat exchanger 1 to supercool the high-pressure refrigerant liquid that will enter the first heat exchanger 1 through the throttling expansion component 3, so that the steam entering the compressor is effectively superheated. The high-temperature and high-pressure refrigerant in the Freon side refrigeration system enters the first heat exchanger 1 after throttling expansion for evaporative refrigeration, and exchanges heat with the low-temperature refrigeration system on the opposite side to ensure a constant heat exchange temperature difference.

[0050] For the Freon side refrigeration system, the high temperature stage compressor 71 sucks in low temperature and low pressure refrigerant gas, compresses it by driving the compression component through the operation of the motor, and then discharges high temperature and high pressure refrigerant superheated gas. The refrigerant superheated gas enters the high temperature stage oil separator 81, separates the lubricating oil in the superheated gas, and then enters the condenser 6. The high temperature and high pressure superheated gas releases heat to the outside through the condenser 6, thereby condensing into a saturated high pressure liquid. The high pressure liquid flows to the high temperature stage liquid receiver 91, and in the high temperature stage liquid receiver 91, It is temporarily stored inside, and then enters the second heat exchanger 21 through the first liquid inlet pipe 52 for supercooling, becoming a supercooled high-pressure liquid. After throttling by the balanced thermal expansion valve 31 outside the throttling expansion component 3, it enters the plate side of the plate heat exchanger 11 of the first heat exchanger 1 through the second liquid inlet pipe 42, absorbs the heat of the carbon dioxide on the plate side, and becomes low-temperature and low-pressure Freon steam. The Freon steam enters the second heat exchanger 21 through the first return air pipe 41, is superheated, and then returns to the suction chamber of the high-temperature stage compressor 71 through the second return air pipe 51 to complete a cycle.

[0051] For the carbon dioxide side refrigeration system, the pump 73 sucks low-temperature and low-pressure liquid refrigerant from the low-pressure circulation barrel 93, drives the impeller to do work through the motor, and transports the refrigerant to the low-temperature evaporator 10. The low-temperature and low-pressure liquid refrigerant absorbs heat in the low-temperature evaporator 10 and becomes carbon dioxide wet vapor. The carbon dioxide wet vapor returns to the low-pressure circulation barrel 93 through the return pipe. The unevaporated liquid in the carbon dioxide wet vapor remains in the low-pressure circulation barrel 93, and the gas enters the low-temperature stage side of the heat exchanger 11 of the first heat exchanger 1, releases heat and is condensed into liquid, and flows back to the low-pressure circulation barrel 93 by gravity to complete a cycle.

[0052] For the entire carbon dioxide cooling system, according to the change of the load of the first heat exchanger 1, the automatic control system sends a command to start the carbon dioxide pump 73, and the pump 73 transports the low-temperature and low-pressure carbon dioxide liquid to the first heat exchanger 1. The liquid in the first heat exchanger 1 absorbs heat and cools to become wet steam. The wet steam returns to the low-pressure circulation barrel 93 through the return pipe. The unevaporated liquid in the wet steam remains in the low-pressure circulation barrel 93, and the gas enters the low-temperature side of the first heat exchanger 1 to release heat. After being condensed into liquid, it flows into the low-pressure circulation barrel 93 by gravity. After the first heat exchanger 1 releases heat through carbon dioxide, it transfers heat to the Freon refrigerant through the first heat exchanger 1. The Freon refrigerant absorbs heat, evaporates, and refrigerates to become gas. Due to the change in superheat, the external balanced thermal expansion valve 31 on the Freon side controls the valve opening to supply liquid to the high-temperature side of the first heat exchanger 1. After the Freon gas is overheated by the second heat exchanger 21, it enters the suction chamber of the high-temperature compressor 71, and then is compressed to become high-temperature and high-pressure superheated gas. After the superheated gas passes through the high-temperature oil separator 81, it enters the condenser 6 to release heat and condenses into liquid. The liquid enters the high-temperature liquid storage tank 91 for temporary storage, and is supercooled by the second heat exchanger 21 to supply liquid to the external balanced thermal expansion valve 31. The first heat exchanger 1 ensures the heat exchange temperature difference through superheat control, pressure control, and start-stop coordinated control.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A two-stage condensation evaporation heat exchange system used in a cascade refrigeration system / phase change heat transfer system, comprising: A second heat exchanger (21), the second heat exchanger (21) being located on one side of the high-temperature stage refrigeration system and being used for subcooling the evaporator supply liquid on the high-temperature and high-pressure side and for superheating the evaporator return air containing unevaporated refrigerant on the low-temperature and low-pressure side; A throttling expansion component (3), the throttling expansion component (3) being located on one side of the high-temperature stage refrigeration system and throttling and expanding the high-temperature and high-pressure side refrigerant after being overcooled in the second heat exchanger (21); A first heat exchanger (1), wherein the first heat exchanger (1) is located between a high-temperature refrigeration system and a low-temperature refrigeration system and is used for heat exchange between evaporation of the high-temperature refrigeration system and condensation of the low-temperature refrigeration system. The high-temperature and high-pressure side refrigerant of the high-temperature refrigeration system is throttled and expanded by a throttling expansion component (3), enters the first heat exchanger (1) for evaporation, and then exchanges heat with the condensation end of the opposite low-temperature refrigeration system. By adjusting the refrigerant flow rate flowing into the first heat exchanger (1), the return air after the refrigerant evaporates in the first heat exchanger (1) contains unevaporated refrigerant and does not overheat, thereby reducing the heat exchange temperature difference between the condensation and evaporation sides in the first heat exchanger (1).

2. The two-stage condensation-evaporation heat exchange system used in the cascade refrigeration system / phase-change heat transfer cooling system according to claim 1, characterized in that: The first heat exchanger (1) is one of a plate heat exchanger (11), a shell and tube heat exchanger, and a shell and plate heat exchanger.

3. The two-stage condensation-evaporation heat exchange system used in the cascade refrigeration system / phase-change heat transfer cooling system according to claim 1, characterized in that: The refrigerant of the high-temperature refrigeration system enters the second heat exchanger (21) through the first liquid inlet pipe (52) for subcooling, and after throttling expansion by the throttling expansion component (3), enters the first heat exchanger (1) through the second liquid inlet pipe (42) for evaporative refrigeration.

4. The two-stage condensation-evaporation heat exchange system used in the cascade refrigeration system / phase-change heat transfer cooling system according to claim 1, characterized in that: The return gas of the refrigerant of the high-temperature refrigeration system after evaporation and refrigeration in the first heat exchanger (1) contains unevaporated refrigerant and is not overheated. The return gas enters the second heat exchanger (21) through the first return gas pipe (41), exchanges heat with the refrigerant liquid of the high-temperature refrigeration system on the other side, and completely evaporates into refrigerant vapor in a superheated state. The refrigerant vapor then returns to the suction end of the compressor through the second return gas pipe (51) to complete the refrigeration cycle.

5. The two-stage condensation-evaporation heat exchange system used in a cascade refrigeration system / phase-change heat transfer cooling system according to claim 1 or 4, characterized in that: The throttling expansion component (3) is an external balanced thermal expansion valve (31). The external balanced thermal expansion valve (31) is connected to a balancing pipe (311) and a temperature sensing package (30). The balancing pipe (311) is connected to a first return air pipe (41) section or a second return air pipe (51) section. The temperature sensing package (30) collects the temperature inside the first return air pipe (41) or the second return air pipe (51), and controls the flow rate of the external balanced thermal expansion valve (31) according to a signal from the temperature sensing package (30), so that the high-temperature refrigerant in the first heat exchanger (1) always maintains a two-phase flow heat exchange state.

6. The two-stage condensation-evaporation heat exchange system used in a cascade refrigeration system / phase-change heat transfer cooling system according to claim 1 or 4, characterized in that: The throttling expansion component (3) is an internally balanced thermal expansion valve (32). The internally balanced thermal expansion valve (32) is connected to a temperature sensing package (30). The temperature sensing package (30) collects the temperature inside the first return air pipe (41) or the second return air pipe (51), and controls the flow rate of the internally balanced thermal expansion valve (32) according to a signal from the temperature sensing package (30), so that the high-temperature refrigerant in the first heat exchanger (1) always maintains a two-phase flow heat exchange state.

7. The two-stage condensation-evaporation heat exchange system used in a cascade refrigeration system / phase-change heat transfer cooling system according to claim 1 or 4, characterized in that: The throttling expansion component (3) is an electronic expansion valve (33), and the electronic expansion valve (33) is connected to a sensor (330). The sensor (330) collects the temperature and / or pressure inside the first return air pipe (41) or the second return air pipe (51), and controls the flow rate of the electronic expansion valve (33) according to the signal, so that the high-temperature refrigerant in the first heat exchanger (1) always maintains a two-phase flow heat exchange state.

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