A heat dissipation structure of explosion-proof electrical box

Abstract

The present invention relates to the technical field of explosion-proof electrical equipment. The present invention discloses a heat dissipation structure for an explosion-proof electrical box, which includes a box body and a heating element. A plate-type evaporator is provided inside the box body, a U-shaped evaporator is suspended outside the plate-type evaporator, the heating element is connected to the U-shaped evaporator, a back plate is provided on the back of the box body, a first condenser is provided outside the back plate, and a plurality of first fins are provided on the first condenser. Compared with the prior art, the advantages of the present invention are: relying on passive heat dissipation to avoid the risk of electric sparks, having no mechanical moving parts, and a low failure rate, a nested design of the plate-type evaporator and the U-shaped evaporator, saving space inside the box body, realizing step-by-step heat transfer through two-way working fluid phase change circulation heat transfer, effectively dissipating the heat load, the chimney effect of the first fin + the air guide cover, the capillary wick working fluid circulation, high heat dissipation efficiency, utilizing the working fluid phase change latent heat and natural convection to dissipate heat, and extremely low energy consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of explosion-proof electrical equipment, in particular to a heat dissipation structure of an explosion-proof electrical box. Background Art

[0002] The heat dissipation design of explosion-proof electrical enclosures is crucial for ensuring safe operation in flammable and explosive environments. Because explosion-proof equipment requires a tight seal to prevent internal explosions or sparks while also effectively controlling internal temperature rise, its heat dissipation structure must balance explosion-proof performance with thermal management efficiency.

[0003] The heat dissipation structure of explosion-proof electrical boxes can be divided into natural heat dissipation, heat exchange heat dissipation and forced heat dissipation.

[0004] Natural heat dissipation usually involves adding metal cooling fins to the surface of the box (usually the top or sides) to increase the heat dissipation area and transfer heat to the outside air. However, this method cannot effectively transfer the heat from the heating components inside the electrical box to the cooling fins, resulting in limited overall heat dissipation capacity of the cooling device and inability to cope with high temperature and high load scenarios.

[0005] Heat exchange and heat dissipation usually choose a water cooling / oil cooling system, which uses circulating coolant (water or oil) to remove heat. This method requires an explosion-proof pump and sealed pipelines. As a mechanical moving part, the circulating pump requires regular maintenance and has a certain usage cost.

[0006] Forced heat dissipation requires explosion-proof fans or air pumps. Explosion-proof air conditioners or semiconductor refrigeration can also be used. However, explosion-proof fans and explosion-proof air conditioners also require regular maintenance to avoid failures. The initial equipment cost of explosion-proof air conditioners or semiconductor refrigeration is relatively high, and they can only be used in some precision instruments or high-temperature environments. Summary of the Invention

[0007] The technical problem to be solved by the present invention is that the existing heat dissipation structure of the explosion-proof electrical box has many limitations, and a heat dissipation structure of the explosion-proof electrical box is provided.

[0008] To solve the above technical problems, the present invention provides a technical solution: a heat dissipation structure of an explosion-proof electrical box, comprising a box body and a heating element, a box door being provided on the front of the box body, a plate-type evaporator being provided inside the box body, a U-shaped evaporator being suspended outside the plate-type evaporator, the heating element being connected to the U-shaped evaporator, a back plate being provided on the back of the box body, a first condenser being provided outside the back plate, and a plurality of first fins being provided on the first condenser;

[0009] A second condenser is provided in the plate-type evaporator. A liquid main is provided at one end of the second condenser, and a gas main is provided at the other end. The liquid main and the gas main extend to the outside of the plate-type evaporator. A liquid branch is provided on one side of the U-shaped evaporator to connect with the liquid main, and a gas branch is provided on the other side to connect with the gas main.

[0010] Furthermore, the first fins extend in a vertical direction, and a vertically penetrating air guide is provided on the outside of the back plate, and the air guide is wrapped around the outside of the first fins.

[0011] Furthermore, a siphon chamber extending vertically is provided on one side of the plate-type evaporator, and an air guide chamber extending vertically is provided on the other side. A reflux channel is provided at the bottom of the plate-type evaporator to connect the air guide chamber and the siphon chamber.

[0012] Furthermore, a steam interface is provided at the top of the first condenser, a liquid interface is provided at the bottom, a reflux interface is provided at the bottom of the siphon cavity to connect with the liquid interface, and an exhaust interface is provided at the top of the air guide cavity to connect with the steam interface.

[0013] Furthermore, multiple evaporation channels are arranged inside the plate-type evaporator and F-type capillary wicks are nested, wherein the evaporation channel connects the siphon chamber with the air guide chamber, the vertical part of the F-type capillary wick is nested in the siphon chamber, the straight part is nested in the evaporation channel, and the second condenser is nested in the straight part of the F-type capillary wick.

[0014] Furthermore, the second condenser is arranged at an angle, wherein the end close to the siphon chamber is lower than the other end, the straight part of the F-type capillary core is also inclined at the same angle as the evaporation channel, and a plurality of first steam grooves are arranged on the inner wall of the evaporation channel along its inclined direction, and the end of the first steam groove extends into the air guide cavity.

[0015] Furthermore, a bent cover plate is provided on the top of the U-shaped evaporator, a liquid storage chamber is provided on one side of the interior, and an evaporation chamber is provided on the other side. A liquid supply channel is provided at the bottom of the U-shaped evaporator to connect the liquid storage chamber with the evaporation chamber, and a heat conduction plate is provided in the evaporation chamber to fit the heating element.

[0016] Furthermore, a plurality of second fins extending vertically are provided on one side of the heat conducting plate close to the evaporation chamber, plate-type capillary wicks are nested between the second fins, and a plurality of second steam grooves extending vertically are provided on the sidewalls of the second fins.

[0017] Furthermore, the liquid branch pipe is communicated with the top of the liquid storage chamber, and the gas branch pipe is communicated with the top of the evaporation chamber.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. The present invention completely relies on passive heat dissipation, which can avoid the risk of electric sparks.

[0020] 2. The present invention has no mechanical moving parts and has a low failure rate.

[0021] 3. The plate-type evaporator and the U-type evaporator are nested in the present invention, which saves the internal space of the box.

[0022] 4. The present invention realizes step-by-step heat transfer through two-way working medium phase change circulation heat transfer, effectively disperses the heat load, and the chimney effect of the first fin + guide cover and the capillary core working medium circulation synergistically improve the heat dissipation efficiency.

[0023] 5. The present invention utilizes the latent heat of phase change of the working fluid and natural convection to dissipate heat, with extremely low energy consumption, which is in line with the trend of green manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the present invention.

[0025] Figure 2 It is a structural schematic diagram of the back side of the present invention.

[0026] Figure 3 It is a structural schematic diagram of the present invention when the door is opened.

[0027] Figure 4 It is a structural schematic diagram of the first fin of the present invention.

[0028] Figure 5 It is a schematic diagram of the explosion structure of the front side of the box body of the present invention.

[0029] Figure 6 It is a schematic diagram of the explosion structure of the back side of the box body of the present invention.

[0030] Figure 7 It is a schematic diagram of the structural explosion of the plate type evaporator of the present invention.

[0031] Figure 8 It is a structural schematic diagram of the U-shaped evaporator of the present invention.

[0032] Figure 9 It is a schematic diagram of the explosion structure of the U-shaped evaporator of the present invention.

[0033] Figure 10 It is a schematic diagram of the internal structure of the U-shaped evaporator of the present invention.

[0034] As shown in the figure: 1. Box body, 2. Box door, 3. Air guide cover, 4. Heating element, 5. U-shaped evaporator, 6. Plate-type evaporator, 7. Liquid main pipe, 8. Gas main pipe, 9. Back plate, 10. First condenser, 11. First fin, 12. Steam interface, 13. Liquid interface, 14. Exhaust interface, 15. Reflux interface, 16. Siphon chamber, 17. Gas guide chamber, 18. Evaporation channel, 19. First steam groove, 20. Reflux channel, 21. F-type capillary wick, 22. Second condenser, 23. Bent cover, 24. Heat conduction plate, 25. Liquid branch pipe, 26. Gas branch pipe, 27. Liquid storage chamber, 28. Liquid supply channel, 29. Evaporation chamber, 30. Second fin, 31. Second steam groove, 32. Plate-type capillary wick. DETAILED DESCRIPTION

[0035] The present invention will be described in further detail below with reference to the accompanying drawings.

[0036] Combined with attachment Figure 1 , Attachment Figure 2 , Attachment Figure 3 and attached Figure 4 A heat dissipation structure of an explosion-proof electrical box includes a box body 1 and a heating element 4. A box door 2 is provided on the front of the box body 1, a plate-type evaporator 6 is provided inside, a U-shaped evaporator 5 is suspended outside the plate-type evaporator 6, and the heating element 4 is connected to the U-shaped evaporator 5. A back plate 9 is provided on the back of the box body 1, a first condenser 10 is provided outside the back plate 9, and a plurality of first fins 11 are provided on the first condenser 10. The back plate 9 is welded to the back side of the box body 1 to form an explosion-proof sealed isolation.

[0037] Combined with attachment Figure 8 , Attachment Figure 9 and attached Figure 10 A bent cover plate 23 is provided on the top of the U-shaped evaporator 5, a liquid storage chamber 27 is provided on one side of the interior, and an evaporation chamber 29 is provided on the other side. A liquid supply channel 28 is provided at the bottom of the U-shaped evaporator 5 to connect the liquid storage chamber 27 with the evaporation chamber 29, and a heat conducting plate 24 is provided in the evaporation chamber 29 to fit the heating element 4.

[0038] Combined with attachment Figure 9 and attached Figure 10 A plurality of second fins 30 extending vertically are provided on one side of the heat conducting plate 24 close to the evaporation chamber 29 , a plate-type capillary wick 32 is nested between the second fins 30 , and a plurality of second steam grooves 31 extending vertically are provided on the sidewalls of the second fins 30 .

[0039] Combined with attachment Figure 7 A second condenser 22 is provided in the plate-type evaporator 6, a liquid main pipe 7 is provided at one end of the second condenser 22, and a gas main pipe 8 is provided at the other end. The liquid main pipe 7 and the gas main pipe 8 extend to the outside of the plate-type evaporator 6, and a liquid storage chamber 27 of the U-shaped evaporator 5 is provided with a liquid branch pipe 25 connected to the liquid main pipe 7, and a gas branch pipe 26 is provided in the evaporation chamber 29 to connect to the gas main pipe 8.

[0040] In the above structure, the U-shaped evaporator 5 absorbs the heat generated by the heating element 4 and transfers it to the second condenser 22 in the plate-type evaporator 6 as the first heat transfer structure. All connections on the pipe connection path involved in the first heat transfer structure are welded to ensure airtightness, so that the first heat transfer structure forms a constant volume environment.

[0041] Since the heating element 4 in a common electrical box, such as the IGBT module, is a composite fully controlled voltage-driven power semiconductor device, which is usually used to achieve efficient power conversion and control in high-voltage and high-current scenarios, it is the main heating element in most electrical boxes. Its existing radiator target temperature is usually set at 80°C, so the working fluid in the first heat transfer structure uses an electronic fluoride liquid with a boiling point below 80°C, such as 3M Novec 7200 with a boiling point of 76°C.

[0042] The U-shaped evaporator 5, due to its own contour, can store a certain amount of liquid working medium in the liquid storage chamber 27, the liquid supply channel 28, and the bottom of the evaporation chamber 29. At the same time, the plate-shaped capillary wick 32 in the evaporation chamber 29 continuously absorbs the liquid working medium through the capillary effect. When the heating element 4 is working, the heat it generates is first transferred to the heat conducting plate 24, causing the temperature of the second fin 30 and its nested plate-shaped capillary wick 32 to rise. When the temperature reaches the boiling point of the liquid working medium, the liquid working medium in the plate-shaped capillary wick 32 near the second fin 30 begins to vaporize. Guided by the second steam groove 31, it continues to rise to the top of the evaporation chamber 29, enters the gas branch 26, and then merges into the gas main pipe 8. Finally, the gaseous working medium enters the second condenser 22. When the second condenser 22 is cooled and its internal temperature reaches the liquefaction temperature of the gaseous working medium, the gaseous working medium is converted back into liquid in the second condenser 22. The condensed liquid working medium enters the liquid main pipe 7 and is diverted to the liquid branch 25, and finally returns to the liquid storage chamber 27 to complete the cycle.

[0043] In order to ensure that the liquid working medium in the second condenser 22 cannot enter the gas main pipe 8 and the gaseous working medium cannot enter the liquid main pipe 7, the second condenser 22 is arranged at an angle, wherein the height of the end connected to the liquid main pipe 7 is lower than the other end. In addition, in order to ensure that the condensed liquid working medium can smoothly flow back to the liquid storage chamber 27, the installation height of the U-shaped evaporator 5 needs to ensure that the height of the connection between the liquid storage chamber 27 and the liquid branch pipe 25 is lower than the lowest point of the inclined second condenser 22.

[0044] Combined with attachment Figure 3 and attached Figure 6 The first fin 11 extends in the vertical direction, and a vertically penetrating air guide 3 is provided on the outside of the back plate 9 , and the air guide 3 is wrapped around the outside of the first fin 11 .

[0045] In order to meet the explosion-proof requirements of the electrical box, the present invention does not use power components to transfer the second condenser 22 to the air outside the box 1 for cooling, but uses a vertical first fin 11 to cooperate with the air deflector 3 to form a vertical air circulation channel, transfer the heat of the second condenser 22 to the first fin 11 and heat the air around it. The density of the heated air decreases and continues to rise and is finally discharged from the top of the air deflector 3. Since the air around the first fin 11 is heated and discharged to form a local low pressure, fresh air is continuously inhaled through the air deflector 3 and heated by the first fin 11 again to be discharged to achieve the circulation of cooling air in the form of a chimney effect.

[0046] If the second condenser tube 22 is directly welded to the first fin 11 to form a fin heat exchanger structure, the second condenser tube 22 is short in length and cannot form a sufficient heat exchange area with the first fin 11, resulting in limited heat transfer effect. If the second condenser tube 22 uses a bend tube with a longer tube path to ensure that a sufficient heat exchange area is formed with the first fin 11, it will cause the height difference between the liquid main pipe 7 and the gas main pipe 8 to be too large, and the U-shaped evaporator 5 will be difficult to install normally. Therefore, a plate-type evaporator 6 is used to absorb heat from the second condenser tube 22 and transfer it to the first condenser tube 10. The first condenser tube 10 uses a bend tube to be welded to the first fin 11.

[0047] Combined with attachment Figure 5 , Attachment Figure 6 and attached Figure 7 A siphon chamber 16 extending vertically is provided on one side of the plate-type evaporator 6, and an air guide chamber 17 extending vertically is provided on the other side. A reflux channel 20 is provided at the bottom of the plate-type evaporator 6 to connect the air guide chamber 17 with the siphon chamber 16. A steam interface 12 is provided at the top of the first condenser 10, and a liquid interface 13 is provided at the bottom. A reflux interface 15 is provided at the bottom of the siphon chamber 16 to connect with the liquid interface 13, and an exhaust interface 14 is provided at the top of the air guide chamber 17 to connect with the steam interface 12.

[0048] The plate-type evaporator 6 absorbs the heat brought by the second condenser tube 22 and transfers it to the first condenser tube 10, and the first fin 11 transfers the heat to the external air as the second heat transfer structure. In order to ensure that the temperature of the second condenser tube 22 is sufficient to evaporate the working fluid in the plate-type evaporator 6, the boiling point of the working fluid in the second heat transfer structure needs to be lower than the electronic fluoride liquid in the first heat transfer structure. Therefore, the working fluid of the second heat transfer structure uses methanol with a boiling point of 64.7°C.

[0049] The temperature of the gaseous electronic fluoride liquid entering the second condenser 22 is greater than or equal to its own boiling point, so the temperature of the second condenser 22 is greater than the boiling point of the methanol in the plate-type evaporator 6. The liquid methanol absorbs heat and forms gaseous methanol after contacting the second condenser 22, so that the heat of the gaseous electronic fluoride liquid in the second condenser 22 is reduced and then converted into liquid. The gaseous methanol in the plate-type evaporator 6 continuously converges upward and enters the first condenser 10 through the exhaust interface 14, transfers heat to the external air through the first fin 11 and is converted back into liquid, and returns to the plate-type evaporator 6 through the reflux interface 15.

[0050] The siphon chamber 16 can keep the liquid level of the liquid methanol inside it consistent with the liquid level in the first condenser 10 through the siphon effect, but since the second condenser 22 is arranged flat at a slight inclination in the plate-type evaporator 6, the liquid level of the liquid methanol needs to be higher to fully contact the second condenser 22.

[0051] In summary, combined with the Figure 7 A plurality of evaporation channels 18 are arranged inside the plate-type evaporator 6 and an F-type capillary wick 21 is nested, wherein the evaporation channel 18 connects the siphon chamber 16 with the air guide chamber 17, the vertical part of the F-type capillary wick 21 is nested in the siphon chamber 16, the straight part is nested in the evaporation channel 18, and the second condenser 22 is nested in the straight part of the F-type capillary wick 21.

[0052] In conjunction with the accompanying drawings, the second condenser 22 is arranged at an angle, and the straight part of the F-type capillary core 21 is also inclined at the same angle as the evaporation channel 18. A plurality of first steam grooves 19 are arranged on the inner wall of the evaporation channel 18 along its inclined direction, and the end of the first steam groove 19 extends into the air guide cavity 17.

[0053] The F-type capillary core 21 can continuously absorb liquid methanol through the capillary effect. The liquid methanol can continuously flow in the porous capillary structure inside the F-type capillary core 21 until the F-type capillary core 21 is completely filled and soaked. The second condenser 22 continuously heats the F-type capillary core 21 around it to vaporize the liquid methanol there. The gaseous methanol moves through the first steam tank 19 in the evaporation channel 18 and finally gathers in the gas guide cavity 17 and enters the exhaust interface 14.

[0054] Since the first condenser 10 needs to rely on the first fin 11 to form a chimney effect to achieve convective heat exchange, the first fin 11 needs to have a certain height. Figure 4The vertical height of the first fin 11 is roughly equivalent to the height of the box body 1. The steam interface 12 of the first condenser 10 needs to be close to the top of the first fin 11, and the liquid interface 13 needs to be close to the bottom of the first fin 11. The steam interface 12 and the liquid interface 13 have a certain height difference. Therefore, the vertical part in the F-type capillary core 21 needs to use capillary force to resist the gravity of the liquid working medium to raise the methanol liquid level to the height of the evaporation channel 18.

[0055] Assuming that the height difference between the evaporation channel 18 and the reflux interface 15 is h meters and the methanol density is ρ, the capillary pressure P required to raise the methanol liquid level satisfies the following relationship:

[0056]

[0057] The density of methanol at 60°C is about 800 kg / m 3 , g is taken as 9.8N / kg;

[0058] but ;

[0059] Therefore, for every 1 m height difference between the evaporation channel 18 and the reflux interface 15 , a pressure of about 7840 Pa needs to be provided for capillary suction.

[0060] Capillary pressure that the capillary wick can provide The following relationship is satisfied:

[0061]

[0062] Where σ is the surface tension of the working fluid, θ is the contact angle between the working fluid and the capillary material, and r is the equivalent pore size of the capillary structure.

[0063] The surface tension of methanol is inversely proportional to its temperature. Existing experiments have tested the relationship between the surface tension of methanol and its temperature at 20°C to 60°C: Wu Meng, Measurement and Analysis of Surface Tension of Alcohols in Gas Purification Absorbents, "Shandong Industrial Technology", Issue 21, 2014, Pages 78-79. Since the temperature of liquid methanol in this device is lower than the boiling point, the surface tension of methanol is temporarily taken as 0.0216N / m corresponding to 60°C.

[0064] Currently, the equivalent pore size of common ceramic microporous capillary cores is between 0.5μm and 5μm. Through plasma treatment or structural design, a wetting angle lower than 10° can be achieved, so cosθ=0.98 is temporarily taken.

[0065] In summary, when the F-type capillary core 21 needs to lift methanol by h meters, the required equivalent capillary pore diameter is , referring to the height of the conventional explosion-proof electrical box, h<2 meters, it is obvious that the conventional ceramic microporous capillary core can meet the pressure required for the reflux of liquid methanol in the plate-type evaporator 6. At the same time, the siphon effect of the siphon cavity 16 makes the methanol liquid level inside it consistent with the liquid level in the first condenser 10. The actual suction pressure required for the reflux of liquid methanol will be smaller.

[0066] In summary, the internal structure of the plate-type evaporator 6 can realize the counter-gravity reflux of the liquid working medium without external power.

[0067] The above description of the present invention and its embodiments is non-limiting, and the actual structure is not limited thereto. In short, if a person skilled in the art is inspired by the above, and does not deviate from the purpose of the invention, without creatively designing a structure and embodiment similar to the technical solution, they shall fall within the scope of protection of the present invention.

Claims

1. An explosion-proof electrical box heat dissipation structure, comprising a box body (1) and a heating element (4), wherein a box door (2) is provided on the front of the box body (1), and characterized in that: A plate-type evaporator (6) is provided inside the box (1), a U-shaped evaporator (5) is suspended outside the plate-type evaporator (6), a heating element (4) is connected to the U-shaped evaporator (5), a back plate (9) is provided on the back of the box (1), a first condensing tube (10) is provided outside the back plate (9), and a plurality of first fins (11) are provided on the first condensing tube (10); A second condenser (22) is provided in the plate-type evaporator (6), a liquid main pipe (7) is provided at one end of the second condenser (22), and a gas main pipe (8) is provided at the other end, the liquid main pipe (7) and the gas main pipe (8) extend to the outside of the plate-type evaporator (6), a liquid branch pipe (25) is provided on one side of the U-shaped evaporator (5) and is connected to the liquid main pipe (7), and a gas branch pipe (26) is provided on the other side of the U-shaped evaporator (5) and is connected to the gas main pipe (8); A siphon chamber (16) extending vertically is provided on one side of the plate-type evaporator (6), and an air guide chamber (17) extending vertically is provided on the other side. A reflux channel (20) is provided at the bottom of the plate-type evaporator (6) to connect the air guide chamber (17) with the siphon chamber (16). A plurality of evaporation channels (18) are provided inside the plate-type evaporator (6) and an F-type capillary wick (21) is nested therein, wherein the evaporation channel (18) connects the siphon chamber (16) with the air guide chamber (17). The vertical portion of the F-type capillary wick (21) is nested in the siphon chamber (16), and the straight portion is nested in the evaporation channel (18). The second condenser (22) is nested in the straight portion of the F-type capillary wick (21).

2. The heat dissipation structure of the explosion-proof electrical box according to claim 1, characterized in that: The first fin (11) extends in a vertical direction, and a vertically penetrating air guide (3) is provided on the outside of the back plate (9), and the air guide (3) is wrapped around the outside of the first fin (11).

3. The heat dissipation structure of the explosion-proof electrical box according to claim 1, characterized in that: The first condenser (10) is provided with a steam interface (12) at the top and a liquid interface (13) at the bottom. A reflux interface (15) is provided at the bottom of the siphon cavity (16) and is connected to the liquid interface (13). An exhaust interface (14) is provided at the top of the air guide cavity (17) and is connected to the steam interface (12).

4. The heat dissipation structure of the explosion-proof electrical box according to claim 1, characterized in that: The second condenser (22) is arranged at an angle, wherein one end close to the siphon chamber (16) is lower than the other end, and the straight portion of the F-type capillary core (21) is also inclined at the same angle as the evaporation channel (18). A plurality of first steam grooves (19) are arranged on the inner wall of the evaporation channel (18) along its inclined direction, and the ends of the first steam grooves (19) extend into the air guide chamber (17).

5. The heat dissipation structure of the explosion-proof electrical box according to claim 1, characterized in that: A bent cover plate (23) is provided on the top of the U-shaped evaporator (5), a liquid storage chamber (27) is provided on one side of the interior, and an evaporation chamber (29) is provided on the other side. A liquid supply channel (28) is provided on the bottom of the U-shaped evaporator (5) to connect the liquid storage chamber (27) and the evaporation chamber (29), and a heat conduction plate (24) is provided in the evaporation chamber (29) to fit the heating element (4).

6. The heat dissipation structure of the explosion-proof electrical box according to claim 5, characterized in that: A plurality of second fins (30) extending in a vertical direction are provided on one side of the heat conducting plate (24) close to the evaporation chamber (29), plate-shaped capillary wicks (32) are nested between the second fins (30), and a plurality of second steam grooves (31) extending in a vertical direction are provided on the side walls of the second fins (30).

7. The heat dissipation structure of the explosion-proof electrical box according to claim 5, characterized in that: The liquid branch pipe (25) is in communication with the top of the liquid storage chamber (27), and the gas branch pipe (26) is in communication with the top of the evaporation chamber (29).

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