CN211876409U - A two-stage condensing evaporation heat exchange system applied in cascade refrigeration system/phase change heat carrier refrigeration system - Google Patents

Abstract

The utility model provides a two-stage condensation-evaporation heat-exchange system applied in a cascade refrigeration system/phase-change heat-carrying cooling system, in particular to the technical field of refrigeration, wherein the condensation-evaporation heat exchange system is provided with a first heat exchanger , the second heat exchanger, the throttling expansion component, when applied in the cascade refrigeration system or the phase change heat carrier cooling system, the refrigerant in the condensed state in the high temperature stage refrigeration system is subcooled inside the second heat exchanger, After being throttled and expanded by the throttling expansion component, it enters the first heat exchanger for evaporative cooling, and exchanges heat with the opposite low-temperature stage refrigeration system or the phase-change heat-carrying cooling system, and the return gas containing the unevaporated refrigerant enters the second heat exchanger , after the second heat exchanger obtains a certain degree of superheat and then enters the high-temperature refrigeration cycle. The system reduces the heat exchange temperature difference at the condensing end and simplifies the high-temperature stage refrigeration system, and at the same time solves the technical problem of large and unstable heat exchange temperature difference caused by the necessary superheat at the end of the heat exchanger.

Description

A two-stage refrigeration system used in cascade refrigeration system/phase change heat carrier refrigeration system Condensation-evaporation heat exchange system

technical field

The utility model relates to a two-stage condensation-evaporation heat exchange system applied in a cascade refrigeration system/phase-change heat-carrying refrigeration system, in particular to a condensation-evaporation heat exchange system in a high-temperature stage refrigeration system, belonging to the technical field of refrigeration.

Background technique

In recent years, the environment-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 the carbon dioxide refrigeration system and the consideration of system safety and energy saving, the subcritical carbon dioxide is generally used in the refrigeration system. Refrigeration system, which is usually realized in cascade form or cooling form.

In the carbon dioxide subcritical refrigeration system, it is more common to use carbon dioxide refrigerant or carrier refrigerant for the low temperature stage, and other refrigerants such as ammonia or freon for the high temperature stage. The secondary refrigeration system is complex and the amount of refrigerant injected is large. However, the disadvantage is that the heat exchange temperature difference of the condensing evaporator is large due to the degree of superheat, 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.

In order to reduce the heat exchange temperature difference at the condensing end, avoid the direct expansion liquid supply system being completely evaporated in the condensing evaporator, the heat exchange temperature difference caused by the superheat at the end of the heat exchanger is unstable, and reducing the refrigerant charge in the high temperature stage refrigeration system, To simplify the high-temperature refrigeration system, refrigeration R&D personnel urgently need to develop a two-stage condensing-evaporation heat exchange system applied in the cascade refrigeration system/phase change heat carrier refrigeration system.

SUMMARY OF THE INVENTION

(1) Technical problems solved

The purpose of this utility model is to provide a two-stage condensation-evaporation heat-exchange system applied in a cascade refrigeration system/phase-change heat-carrying cooling system. On the one hand, the heat exchange temperature difference at the condensing end is reduced, and the direct expansion liquid supply system is avoided. Complete evaporation in the condensing evaporator, and the technical problem of unstable heat exchange temperature difference caused by superheat at the end of the heat exchanger; on the other hand, it solves the technical problem of the complex structure of the high-temperature stage refrigeration system. Of course, at the same time, the technical problems of large refrigerant charge and many uncontrollable factors in the high-temperature refrigeration system are solved.

(2) Technical solutions

In order to solve the above technical problems, the utility model provides a two-stage condensation-evaporation heat exchange system applied in a cascade refrigeration system/phase-change heat-carrying cooling system, comprising: a second heat exchanger, a throttling expansion part, a first heat exchanger, the second heat exchanger is located on one side of the high temperature stage refrigeration system, and is used for subcooling of the liquid supply to the evaporator on the high temperature and high pressure side and superheating of the return gas of the evaporator containing the unevaporated refrigerant on the low temperature and low pressure side; The throttling and expansion component is located on one side of the high-temperature stage refrigeration system, and throttles and expands the refrigerant on the high-temperature and high-pressure side after subcooling of the second heat exchanger; the first heat exchanger is located in the high-temperature stage refrigeration system and the low-temperature stage refrigeration system. It is used for heat exchange between the evaporation of the high temperature stage refrigeration system and the condensation of the low temperature stage refrigeration system. The high temperature and high pressure side refrigerant of the high temperature stage refrigeration system is throttled and expanded by the throttling expansion component, and enters the first heat exchanger for evaporation. Then, it exchanges heat with the condensing end of the opposite low-temperature stage refrigeration system. By adjusting the flow of refrigerant flowing into the first heat exchanger, the return air after the refrigerant is evaporated in the first heat exchanger contains unevaporated refrigerant and does not occur. Overheating, thereby reducing the heat exchange temperature difference between the condensing and evaporating sides in the first heat exchanger.

The throttling expansion component is an important automatic control component in the refrigeration system. By receiving the change of the superheat degree of the refrigerant at the outlet of the first heat exchanger, the opening degree of the valve is changed, and the flow of the refrigerant flowing into the first heat exchanger is adjusted, so that the flow rate of the refrigerant flowing into the first heat exchanger is adjusted. The refrigerant flow always matches the load of the first heat exchanger, reducing the possibility of compressor liquid slamming. The first heat exchanger is a key heat exchanger in a cascade refrigeration system or a phase change heat carrier cooling system, specifically a condensing evaporator, which is used for the evaporation of a high temperature stage refrigeration system and a low temperature stage refrigeration system (or phase change). The heat exchange between the condensation of the heat exchange and cooling system) uses the cooling capacity of the high temperature stage refrigeration system to condense the gas discharged from the compressor of the low temperature stage refrigeration system, which is not only the evaporator of the high temperature stage refrigeration system, but also the low temperature stage refrigeration system. condenser. 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 will enter the first heat exchanger through the throttling expansion part, so that the The compressor vapor is effectively superheated to prevent the compressor suction from carrying liquid, which also makes the high-pressure side refrigerant liquid supercool, reducing throttling loss.

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

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, shell-and-tube heat exchangers are often used in the prior art, so that the refrigeration system is mainly supplied by gravity, which has large heat exchange temperature difference, large refrigerant charge, low refrigeration efficiency, and high energy consumption. technical problem. When the first heat exchanger adopts the plate heat exchanger, the refrigeration system mainly adopts the pump liquid supply, which solves the technical problems of complex system, large refrigerant charge and many uncontrollable factors.

Preferably, the refrigerant of the high-temperature stage refrigeration system enters the second heat exchanger through the first liquid inlet pipe for subcooling, and then enters the first heat exchanger through the second liquid inlet pipe after being throttled and expanded by the throttle expansion component. Evaporative cooling.

Preferably, the return gas of the refrigerant of the high-temperature stage refrigeration system after evaporating and refrigerating in the first heat exchanger contains unevaporated refrigerant liquid without overheating, and enters the second heat exchanger through the first return gas pipe, and is connected with another The refrigerant liquid in the high-temperature stage refrigeration system on one side is completely evaporated into superheated refrigerant vapor after heat exchange, and then returns to the suction end of the compressor through the second air return pipe to complete the refrigeration cycle.

Preferably, the throttling expansion component is an external balance type thermal expansion valve, the external balance type thermal expansion valve is connected with a balance pipe and a temperature sensing package, and the balance pipe is connected to the first air return pipe section or the second air return pipe In the pipe section, the temperature sensor collects the temperature inside the first air return pipe or the second air return pipe, and controls the flow rate of the external balance thermal expansion valve according to the signal of the temperature sensor, so that the high temperature refrigerant in the first heat exchanger is always maintained at two levels. Phase flow heat transfer state. The external balance type thermal expansion valve is provided with an external balance 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 large changes in the refrigerant flow and the first heat exchanger. A system with high resistance on the heat exchanger side.

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

Preferably, the throttling expansion component is an electronic expansion valve, the electronic expansion valve is connected with a sensor, the sensor collects the temperature and/or pressure inside the first air return pipe or the second air return pipe, and controls the electronic expansion valve according to the signal flow, 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 of the superheat degree of the refrigerant at the outlet of the first heat exchanger, and generates an electrical signal to control the opening degree of the valve, and adjust the flow of the refrigerant flowing into the first heat exchanger, so that the Refrigerant flow is always matched to the load of the first heat exchanger, reducing the possibility of compressor liquid hammer.

(3) Beneficial effects

According to the utility model, there is provided a two-stage condensation-evaporation heat-exchange system applied in a cascade refrigeration system/phase-change heat-carrying refrigeration system. Less perfusion; the system reduces the heat exchange temperature difference at the condensing end, avoiding the complete evaporation of the direct expansion liquid supply system in the condensing evaporator, and the technical problem of unstable heat exchange temperature difference caused by superheat at the end of the heat exchanger.

In a preferred embodiment, the throttling expansion component adopts various forms, such as: external balance type thermal expansion valve, internal balance type thermal expansion valve, electronic expansion valve, etc., according to the degree of superheat of the refrigerant at the outlet of the first heat exchanger The change of , generates a signal to control the flow of the valve, and adjusts the flow of refrigerant flowing into the first heat exchanger, so that the flow of refrigerant always matches the load of the first heat exchanger, reducing the possibility of compressor liquid hammer.

Description of drawings

1 shows a schematic diagram of the working principle of a two-stage condensation-evaporation heat-exchange system applied in a cascade refrigeration system/phase-change heat-carrying cooling system according to the first embodiment of the present invention;

2 shows a schematic diagram 1 of the working principle of a two-stage condensation-evaporation heat exchange system applied in a cascade refrigeration system/phase-change heat-carrying cooling system according to the second embodiment of the present invention;

3 shows a schematic diagram 2 of the working principle of a two-stage condensation-evaporation heat exchange system applied in a cascade refrigeration system/phase-change heat-carrying cooling system according to the second embodiment of the present invention;

Fig. 4 shows the schematic diagram 3 of the working principle of the two-stage condensation-evaporation heat exchange system applied in the cascade refrigeration system/phase-change heat carrier cooling system according to the second embodiment of the present invention;

5 shows a schematic diagram 4 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 according to the second embodiment of the present invention;

6 shows the schematic diagram 5 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 according to the second embodiment of the present invention;

7 shows a 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 according to the third embodiment of the present invention;

Label description:

1. The first heat exchanger; 11. The plate heat exchanger; 21. The second heat exchanger; 22. The low temperature heat exchanger; 3. The throttle expansion part; Expansion valve; 311. Balance pipe; 32. Internal balance type thermal expansion valve; 33. Electronic expansion valve; 330. Sensor; 34. Low temperature electronic expansion valve; 41. First return pipe; 42. Second liquid inlet pipe; 51. Second air return pipe; 52. First liquid inlet pipe; 6. Condenser; 71. High temperature stage compressor; 72. Low temperature stage compressor; 73. Pump; 81. High temperature stage oil separator; 82. Low temperature stage Oil separator; 91. High temperature grade accumulator; 92. Low temperature grade accumulator; 93. Low pressure circulating barrel; 10. Low temperature grade evaporator.

Detailed ways

The specific embodiments of the present utility model will be described in further detail below with reference to the accompanying drawings and embodiments. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

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

Example 1:

FIG. 1 shows a schematic diagram of the working principle of the two-stage condensation-evaporation heat exchange system applied in the cascade refrigeration system/phase-change heat carrier refrigeration system according to the first embodiment of the present invention.

The utility model provides a two-stage condensation-evaporation heat exchange system applied in a cascade refrigeration system/phase-change heat-carrying refrigeration system. When applied in a carbon dioxide subcritical cascade refrigeration system, it specifically includes: a high-temperature stage refrigeration system and a A low temperature stage refrigeration system, the high temperature stage refrigeration system adopts Freon refrigerant, the low temperature stage refrigeration system adopts carbon dioxide refrigerant, and a two-stage condensation-evaporation heat exchange system is also provided on the high temperature stage refrigeration system, and the system includes: The second heat exchanger 21, the throttling and expansion part 3, and the first heat exchanger 1, wherein the second heat exchanger 21 and the throttling and expansion part 3 are located on one side of the high temperature stage refrigeration system, and the first heat exchanger 1 is located at the high temperature Between the high-temperature stage refrigeration system and the low-temperature stage refrigeration system, it is responsible for connecting the high-temperature stage refrigeration system and the low-temperature stage refrigeration system, specifically a condensing evaporator, which uses the cooling capacity of the high-temperature stage refrigeration system to condense the gas discharged from the low-temperature stage refrigeration system compressor. Therefore, the first heat exchanger 1 is not only the evaporator of the high temperature stage refrigeration system, but also the condenser of the low temperature stage refrigeration system. The throttling and expansion part 3 is an important automatic control part in the refrigeration system. By receiving the change of the superheat degree of the refrigerant at the outlet of the first heat exchanger 1, the opening degree of the valve is changed, and the refrigerant flowing into the first heat exchanger 1 is adjusted. The flow rate of the refrigerant is always matched with the load of the first heat exchanger 1, thereby reducing the possibility of liquid hammer of the compressor. The second heat exchanger 21 is used for the subcooling of the high temperature and high pressure refrigerant in the high temperature stage refrigeration system, and is specifically a regenerator, which uses the refrigerant vapor coming out of the Freon side of the first heat exchanger 1 to supercool the refrigerant through the section. The high-pressure refrigerant liquid flowing into the first heat exchanger 1 from the expansion part 3, thus effectively superheating the steam entering the compressor, preventing the suction of the compressor from carrying liquid, and also supercooling the refrigerant liquid on the high-pressure side, reducing the throttling loss. .

The high temperature and high pressure refrigerant in the high temperature stage refrigeration system is throttled and expanded and then enters the first heat exchanger 1 for evaporative cooling, and exchanges heat with the opposite low temperature stage refrigeration system to ensure a constant heat exchange temperature difference. The refrigerant of the high temperature stage refrigeration system enters the second heat exchanger 21 through the first liquid inlet pipe 52 for subcooling, and then enters the first heat exchange through the second liquid inlet pipe 42 after being throttled and expanded by the throttling expansion part 3. 1 evaporative cooling. After the refrigerant of the high-temperature stage refrigeration system is evaporated and cooled in the first heat exchanger 1, it enters the second heat exchanger 21 through the first air return pipe 41, and is completely phase-changed with the refrigerant liquid of the high-temperature stage refrigeration system after heat exchange. The superheated refrigerant vapor is returned to the suction end of the compressor through the second gas 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 whose heat exchange temperature difference is generally above 5°C.

Example 2:

Fig. 2 shows the schematic diagram 1 of the working principle of the two-stage condensation-evaporation heat exchange system applied in the cascade refrigeration system/phase change heat carrier cooling system according to the second embodiment of the present utility model; Fig. 3 shows the second embodiment of the present utility model. Embodiment Schematic diagram 2 of the working principle of a two-stage condensation-evaporation heat exchange system applied in a cascade refrigeration system/phase-change heat carrier refrigeration system.

2 and 3, the present utility model provides another two-stage condensation-evaporation heat exchange system applied in a cascade refrigeration system/phase change heat carrier refrigeration system, which is applied in a carbon dioxide subcritical cascade refrigeration system. In particular, it includes: a high temperature stage refrigeration system and a low temperature stage refrigeration system, the high temperature stage refrigeration system adopts Freon refrigerant, the low temperature stage refrigeration system adopts carbon dioxide refrigerant, and the high temperature stage refrigeration system is provided with a two-stage condensing system An evaporative heat exchange system, the system includes: a second heat exchanger 21, a throttling and expansion part 3, and a first heat exchanger 1, wherein the second heat exchanger 21 and the throttling and expansion part 3 are located on one side of the high-temperature stage refrigeration system, The first heat exchanger 1 is located between the high temperature stage refrigeration system and the low temperature stage refrigeration system, and is responsible for connecting the high temperature stage refrigeration system and the low temperature stage refrigeration system, specifically a condensing evaporator, which utilizes the cooling capacity of the high temperature stage refrigeration system to condense the low temperature stage. The gas discharged from the compressor of the secondary refrigeration system is both the evaporator of the high temperature refrigeration system and the condenser of the low temperature refrigeration system. The throttling expansion component 3 is specifically an externally balanced thermal expansion valve, which changes the opening degree of the valve by receiving the change of the superheat degree of the refrigerant at the outlet of the first heat exchanger 1 to adjust the flow of the refrigerant flowing into the first heat exchanger 1 . , so that the refrigerant flow always matches the load of the first heat exchanger 1 and reduces 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 that will enter the first heat exchanger 1 through the throttling expansion part 3 . liquid, which effectively superheats the steam entering the compressor.

The high temperature and high pressure refrigerant in the high temperature stage refrigeration system is throttled and expanded and then enters the first heat exchanger 1 for evaporative cooling, and exchanges heat with the opposite low temperature stage refrigeration system to ensure a constant heat exchange temperature difference. The freon refrigerant of the high temperature stage refrigeration system enters the second heat exchanger 21 through the first liquid inlet pipe 52 for subcooling, and then enters the first heat exchanger through the second liquid inlet pipe 42 after being throttled and expanded by the throttling expansion part 3. Heater 1 evaporative cooling. After the refrigerant of the high-temperature stage refrigeration system is evaporated and cooled in the first heat exchanger 1, it enters the second heat exchanger 21 through the first air return pipe 41, and is completely phase-changed with the refrigerant liquid of the high-temperature stage refrigeration system after heat exchange. The superheated refrigerant vapor is returned to the suction end of the compressor through the second gas return 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, the low temperature and low pressure two-phase flow return gas enters the second heat exchanger 21 from the other side, and the heat of the high temperature and high pressure refrigerant liquid is absorbed by the low temperature and low pressure refrigerant liquid, and the high temperature and high pressure The supply liquid is supercooled, and the low-temperature and low-pressure refrigerant liquid is evaporated to ensure that the return end of the compressor is superheated refrigerant vapor.

The first heat exchanger 1 adopts the plate heat exchanger 11 or the plate and shell heat exchanger. 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. During the whole process of the heat exchanger, it is difficult for the conventional Freon direct expansion refrigeration system to ensure that the refrigerant in the first heat exchanger 1 is in a two-phase flow state. 3, the position of the temperature sensor or the pressure sensor, so that the freon flowing out of the first heat exchanger 1 is still in a two-phase flow state, and at the same time, the two-phase flow is completely evaporated into freon through the heat exchange of the second heat exchanger 21 gas, 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 charging amount of Freon is much smaller than that of the shell and tube heat exchanger.

As shown in FIG. 2 , the throttling expansion component 3 may be an external balance type thermal expansion valve 31 , and the external balance type thermal expansion valve 31 is connected with a balance tube 311 and a temperature sensing package 30 , and the balance tube 311 is connected to the In the second air return pipe 51, the temperature sensor package 30 collects the temperature inside the second air return line 51, and the externally balanced thermal expansion valve 31 determines the valve opening degree according to the temperature collected by the temperature sensor package 30.

As shown in FIG. 3 , the throttling expansion component 3 is an external balance type thermal expansion valve 31 , the external balance type thermal expansion valve 31 is connected with a balance pipe 311 and a temperature sensing package 30 , and the balance pipe 311 is connected to the first For a section of the return gas pipe 41 , the temperature sensing package 30 collects the temperature inside the first return gas pipe 41 , and the externally 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 balance type 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 large changes in refrigerant flow and the first heat exchanger. A system with large resistance on the 1 side of the heat exchanger.

FIG. 4 shows a schematic diagram 3 of the working principle of the two-stage condensation-evaporation heat exchange system applied in the cascade refrigeration system/phase-change heat carrier refrigeration system according to the second embodiment of the present invention. The throttling expansion component 3 can also be an internal balance type thermal expansion valve 32, the internal balance type thermal expansion valve 32 is connected with a temperature sensing package 30, and the temperature sensing package 30 collects the first return gas pipe 41 or the second return gas pipe 41. For the temperature inside the gas pipe 51 , the internal balance type thermal expansion valve 32 determines the valve opening degree according to the temperature collected by the temperature sensing package 30 . The internal balance type thermal expansion valve 32 directly uses the pressure of the throttled refrigerant as the evaporation pressure, and has a simple structure and is suitable for a system with relatively small resistance of the first heat exchanger 1 .

FIG. 5 shows a schematic diagram 4 of the working principle of the two-stage condensation-evaporation heat exchange system applied in the cascade refrigeration system/phase-change heat carrier refrigeration system according to the second embodiment of the present invention. The throttling expansion component 3 can also be an electronic expansion valve 33, and the electronic expansion valve 33 is connected with a sensor 330, and the sensor 330 collects the temperature and/or pressure inside the second air return pipe 51, according to the temperature signal and/or The pressure signal controls the opening degree of the electronic expansion valve 33, 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 air return pipe 41, collect the temperature and/or pressure inside the first air return pipe 41, and control the opening of the electronic expansion valve 33 according to the temperature signal and/or the pressure signal, so that the first heat exchange The refrigerant in device 1 is always in two-phase flow. The electronic expansion valve 33 uses the sensor 330 to sense the change of the superheat degree of the refrigerant at the outlet of the first heat exchanger 1, and generates an electrical signal to control the opening degree of the valve, so as to adjust the flow of the refrigerant flowing into the first heat exchanger 1, so as to make refrigeration The agent flow always matches the load of the first heat exchanger 1, reducing the possibility of compressor liquid slamming.

FIG. 6 shows a schematic diagram 5 of the working principle of the two-stage condensation-evaporation heat exchange system applied in the cascade refrigeration system/phase-change heat carrier refrigeration system according to the second embodiment of the present invention. The cascade refrigeration system can be understood as a combination of 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 not only the evaporator of the high temperature stage refrigeration system on the freon side, but also the condenser of the low temperature stage refrigeration system on the carbon dioxide side. For the high temperature stage refrigeration system on the freon side, the high temperature stage compressor 71 inhales the low temperature and low pressure freon refrigerant gas, drives the compression components to compress it through the motor operation, and then discharges the high temperature and high pressure refrigerant superheated gas, and the refrigerant superheated gas passes through the high temperature stage The 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, and the high-pressure liquid flows to the high-temperature liquid storage. The heat exchanger 91 is temporarily stored in the high temperature liquid accumulator 91, and then it is supercooled by the second heat exchanger 21 and becomes a supercooled high-pressure liquid. After being throttled by the external balance type thermal expansion valve 31, it enters the first heat exchanger. The low temperature side of the heat exchanger 1 absorbs the heat of the high temperature and high pressure superheated carbon dioxide on the plate side, and turns into low temperature and low pressure Freon vapor. cycle.

For the low temperature stage refrigeration system on the carbon dioxide side, the low temperature stage compressor 72 inhales the low temperature and low pressure carbon dioxide refrigerant gas, drives the compression components to compress it through the motor operation, and then discharges the high temperature and high pressure refrigerant superheated gas, and the refrigerant superheated gas passes through the low temperature stage. The oil separator 82 separates 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 passes through the first heat exchanger 1 to release heat to the low temperature side, thereby condensing into a saturated high pressure The liquid, the high pressure liquid flows to the low temperature level accumulator 92, is temporarily stored in the low temperature level accumulator 92, and then is supercooled by the low temperature level heat exchanger 22, and becomes a supercooled high pressure liquid, and passes through the low temperature level electronic expansion valve 34. After throttling, it enters the low-temperature stage evaporator 10, absorbs the heat of air or other media, and becomes low-temperature and low-pressure carbon dioxide vapor. one cycle.

For the entire cascade refrigeration system, the low temperature stage electronic expansion valve 34 on the carbon dioxide side generates an electrical signal through a temperature sensor and a pressure sensor according to the load change of the carbon dioxide low temperature stage evaporator 10, and after the superheat controller analyzes the electrical signal, it issues an instruction to control The opening degree of the low-temperature stage electronic expansion valve 34 on the carbon dioxide side, the carbon dioxide liquid becomes a gas-liquid two-phase mixture after being throttled and enters the carbon dioxide low-temperature stage evaporator 10, and then absorbs heat for gasification and refrigeration, and the gasified carbon dioxide vapor passes through the low-temperature stage. The evaporator 10 is overheated and enters the suction chamber of the low-temperature stage compressor 72, and then is compressed to become a high-temperature and high-pressure superheated gas. After passing through the low-temperature stage oil separator 82, the superheated gas enters the high-temperature side of the first heat exchanger 1 to release heat and condense, After being condensed into liquid, it enters into the low temperature carbon dioxide liquid storage tank 92 for temporary storage, passes through the low temperature heat exchanger 22 for subcooling, and then supplies liquid to the low temperature electronic expansion valve 34 . After the first heat exchanger 1 releases heat from carbon dioxide, it transfers heat to the freon refrigerant on the low temperature side through the high temperature side, and the freon refrigerant on the high temperature side absorbs heat and evaporates and cools, and turns into a gas. Due to the change of superheat, the freon side balances outside The type thermal expansion valve 31 controls the valve opening to supply liquid to the first heat exchanger 1 at low temperature. After the freon gas is superheated by the second heat exchanger 21, it enters the suction chamber of the high temperature stage compressor 71, and then is compressed to become high temperature and high pressure superheating. After passing through the high temperature oil separator 81, the superheated gas enters the condenser 6 to release heat, condenses into a liquid, and the liquid enters the high temperature liquid accumulator 91 for temporary storage, and passes through the second heat exchanger 21 to be supercooled to supply the throttling expansion component. 3 liquid supply.

The first heat exchanger 1 ensures the heat exchange temperature difference through superheat control, pressure control, and coordinated control of on-off and off. The low temperature side of the first heat exchanger 1 is controlled by the degree of superheat to ensure that there is an appropriate amount of refrigerant on the low temperature side of the first heat exchanger 1 for heat absorption and evaporation, and the evaporating pressure on the low temperature side is maintained by the start-stop or energy level adjustment of the Freon compressor. , thus ensuring the freon side evaporation temperature. The high temperature side of the first heat exchanger 1 is controlled by pressure to coordinate the energy level adjustment or start and stop of the low temperature stage compressor 72 on the carbon dioxide side to ensure the condensing pressure on the plate side, thereby ensuring the condensation temperature on the carbon dioxide side. Due to the high sensitivity of carbon dioxide to pressure, in order to maintain the stability of the system, when the low-temperature stage compressor 72 on the carbon dioxide side reaches the start-up condition, it is necessary to extend the opening to ensure that the high-temperature stage compressor 71 on the freon side is preferentially turned on. on. By ensuring the evaporation temperature of the freon side and the condensation temperature of the carbon dioxide side, the heat exchange temperature difference of the first heat exchanger 1 is further ensured.

Example 3:

FIG. 7 shows a schematic diagram of the working principle of the two-stage condensation-evaporation heat exchange system applied in the cascade refrigeration system/phase-change heat carrier refrigeration system according to the third embodiment of the present invention. The utility model provides another two-stage condensation-evaporation heat exchange system applied in a cascade refrigeration system/phase-change heat-carrying and cooling system. A complete Freon refrigeration system is combined with a carbon dioxide refrigeration system powered by a pump without a compressor. The first heat exchanger 1 combines the two systems to form a carbon dioxide cooling system. The first heat exchanger 1 is specifically a condensing evaporator, and the condensing evaporator is both the evaporator of the Freon side system and the condenser of the carbon dioxide side. The two-stage condensation-evaporation heat exchange system further includes: a second heat exchanger 21 and a throttling expansion part 3, wherein the second heat exchanger 21 and the throttling expansion part 3 are located on the side of the Freon side system, and the throttling and expansion part 3 The expansion component 3 is specifically an externally balanced thermal expansion valve 31 , which receives the change of the superheat degree of the refrigerant at the outlet of the first heat exchanger 1 through the temperature sensing package 30 , changes the opening degree of the valve, and adjusts the refrigerant flowing into the first heat exchanger 1 . The flow rate of the refrigerant is always matched with the load of the first heat exchanger 1, thereby reducing the possibility of liquid hammer of the compressor. 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 that will enter the first heat exchanger 1 through the throttling expansion part 3 . liquid, which effectively superheats the steam entering the compressor. The high-temperature and high-pressure refrigerant in the freon side refrigeration system is throttled and expanded and then enters the first heat exchanger 1 for evaporative refrigeration, and exchanges heat with the opposite-side low-temperature stage refrigeration system to ensure a constant heat exchange temperature difference.

For the Freon side refrigeration system, the high temperature stage compressor 71 inhales the low temperature and low pressure refrigerant gas, drives the compression components to compress it through the motor operation, and then discharges the high temperature and high pressure refrigerant superheated gas, which enters the high temperature stage oil separator 81, the lubricating oil in the superheated gas is separated, and then enters the condenser 6, and 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, and the high-pressure liquid flows to the high-temperature stage liquid reservoir 91, It is temporarily stored in the high-temperature liquid accumulator 91, and then enters the second heat exchanger 21 through the first liquid inlet pipe 52 to be supercooled, and becomes a supercooled high-pressure liquid, which passes through the throttling expansion part 3 and the external balance thermal expansion valve. After 31 throttling, the second liquid inlet pipe 42 enters the plate side of the plate heat exchanger 11 of the first heat exchanger 1, absorbs the heat of carbon dioxide on the plate side, and becomes low-temperature and low-pressure Freon steam, and the Freon steam passes through the first return pipe. 41 enters the second heat exchanger 21 and is overheated, and then returns to the suction chamber of the high temperature stage compressor 71 through the second air return pipe 51 to complete a cycle.

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, where the low-temperature and low-pressure liquid refrigerant is stored in the low-temperature evaporator 10. The endothermic becomes carbon dioxide wet steam, the carbon dioxide wet steam returns to the low-pressure circulation barrel 93 through the return pipe, the unevaporated liquid in the carbon dioxide wet steam remains in the low-pressure circulation barrel 93, and the gas enters the heat exchanger of the first heat exchanger 1 11. On the low-temperature stage side, the exothermic heat is condensed into liquid, which is returned to the low-pressure circulation barrel 93 by gravity to complete a cycle.

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 an instruction to turn on 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, and the first heat exchanger 1. The liquid absorbs heat and refrigerates into wet steam, and the wet steam returns to the low-pressure circulation barrel 93 through the return gas pipe. The unevaporated liquid in the wet steam remains in the low-pressure circulation barrel 93, and the gas enters the first heat exchanger 1. The low-temperature stage side is released The heat, after being condensed into a liquid, flows into the low-pressure circulation barrel 93 by gravity. After the first heat exchanger 1 releases heat from carbon dioxide, it transfers heat to the freon refrigerant through the first heat exchanger 1, and the freon refrigerant absorbs heat and evaporates and cools, and turns into gas. Due to the change of superheat, the freon side external balance heat The expansion valve 31 controls the valve opening to supply liquid to the high temperature stage 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 stage compressor 71, and then is compressed to become high temperature and high pressure. The superheated gas, after passing through the high temperature oil separator 81, enters the condenser 6 to release heat, condenses into liquid, and the liquid enters the high temperature liquid accumulator 91 for temporary storage, passes through the second heat exchanger 21 to be supercooled, and is fed to the external balance type The thermal expansion valve 31 supplies liquid. The first heat exchanger 1 ensures the heat exchange temperature difference through superheat control, pressure control, and coordinated control of on-off and off.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the within the protection scope of the present invention.

Claims (7)

1. The utility model provides an use two segmentation condensation evaporation heat transfer systems in cascade refrigerating system/phase transition heat transfer cold carrier system, includes:

the second heat exchanger (21) is positioned at one side of the high-temperature stage refrigeration system and is used for supercooling liquid supplied by the high-temperature high-pressure side evaporator and superheating return air of the evaporator with the low-temperature low-pressure side containing unevaporated refrigerant;

the throttling expansion part (3) is positioned on one side of the high-temperature-level refrigeration system, and throttles and expands the high-temperature high-pressure-side refrigerant after the second heat exchanger (21) is supercooled;

the first heat exchanger (1), first heat exchanger (1) is located between high temperature level refrigerating system and the low temperature level refrigerating system, be used for the heat transfer between the evaporation of high temperature level refrigerating system and the condensation of low temperature level refrigerating system, the high temperature high pressure side refrigerant of high temperature level refrigerating system throttles the expansion through throttle expansion part (3), get into first heat exchanger (1) and evaporate back and the condensation end heat transfer of offside low temperature level refrigerating system, through adjusting the refrigerant flow who flows into first heat exchanger (1), make the return air of refrigerant after the evaporation in first heat exchanger (1) contain the refrigerant that does not evaporate, do not take place overheated, thereby reduce the heat transfer difference in temperature of condensation and evaporation both sides in first heat exchanger (1).

2. The two-stage condensation evaporation heat exchange system applied to the cascade refrigeration system/phase-change heat exchange hot carrier refrigeration system according to claim 1, wherein 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 applied to the cascade refrigeration system/phase-change heat exchange hot carrier refrigeration system according to claim 1, wherein the refrigerant of the high-temperature stage 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 evaporation refrigeration through the second liquid inlet pipe (42) after being throttled and expanded by the throttling expansion component (3).

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

5. The two-stage condensation evaporation heat exchange system applied to the cascade refrigeration system/phase-change heat exchange hot and cold system according to claim 1 or 4, wherein the throttling expansion part (3) is an external balance type thermal expansion valve (31), the external balance type thermal expansion valve (31) is connected with a balance pipe (311) and a temperature sensing package (30), the balance pipe (311) is connected with a first air return pipe (41) section or a second air return pipe (51) section, the temperature sensing package (30) collects the temperature inside the first air return pipe (41) or the second air return pipe (51), and the flow of the external balance type thermal expansion valve (31) is controlled according to a signal of the temperature sensing package (30), so that the high-temperature-level refrigerant in the first heat exchanger (1) is always kept in a two-phase flow heat exchange state.

6. The two-stage condensation evaporation heat exchange system applied to the cascade refrigeration system/phase-change heat exchange hot and cold system according to claim 1 or 4, wherein the throttling expansion part (3) is an internal balance type thermostatic expansion valve (32), the internal balance type thermostatic expansion valve (32) is connected with a temperature sensing bulb (30), the temperature sensing bulb (30) collects the temperature inside the first air return pipe (41) or the second air return pipe (51), and the flow of the internal balance type thermostatic expansion valve (32) is controlled according to a signal of the temperature sensing bulb (30), so that the high-temperature-level refrigerant in the first heat exchanger (1) is always kept in a two-phase flow heat exchange state.

7. The two-stage condensation evaporation heat exchange system applied to the cascade refrigeration system/phase-change heat exchange hot carrier cold system according to claim 1 or 4, wherein the throttling expansion part (3) is an electronic expansion valve (33), the electronic expansion valve (33) is connected with a sensor (330), the sensor (330) collects the temperature and/or pressure inside the first air return pipe (41) or the second air return pipe (51), and the flow of the electronic expansion valve (33) is controlled according to a signal, so that the high-temperature-level refrigerant in the first heat exchanger (1) is always kept in a two-phase flow heat exchange state.

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