Microchannel circulation thin liquid film preheating device and method

Abstract

The invention relates to the technical field of two-phase flow heat transfer and semiconductor material preparation, and discloses a micro-channel circulation thin liquid film preheating device and method.The device comprises a gas-liquid mixing and heating assembly, the gas-liquid mixing and heating assembly comprises a shell and a base plate, a micro-channel, an air inlet pipe and an outlet pipe are arranged in the base plate, and the top end of the shell communicates with a liquid inlet pipe; the air inlet pipe, the liquid inlet pipe and the outlet pipe are respectively communicated with the micro-channel; the working medium preheating assembly comprises a gas preheating part and a liquid preheating part, an external gas working medium is preheated through the gas preheating part and then conveyed into the micro-channel through a gas inlet pipe, and an external liquid working medium is preheated through the liquid preheating part and then conveyed into the micro-channel through a liquid inlet pipe; and the preheated liquid working medium is sheared by the preheated gas working medium when entering the micro-channel to form a circulation thin liquid film form, and flows out through the outlet pipe after exchanging heat with the substrate. According to the invention, the inlet mixing mode is improved, the stable control of the outlet temperature is realized, and the heat-sensitive material is ensured to have a more stable flowing form and more uniform temperature distribution.

Description

Technical Field

[0001] The present invention relates to the technical fields of two-phase flow heat transfer and semiconductor material preparation, and particularly relates to a microchannel circulating thin liquid film preheating device and method. Background Art

[0002] In the manufacturing process of semiconductor chips, thin film deposition is a key step affecting chip performance. There are mainly two deposition methods, namely physical vapor deposition (PVD) and chemical vapor deposition (CVD). Physical vapor deposition uses physical methods (such as evaporation, sputtering, etc.) to vaporize the coating material and deposit it into a film on the substrate surface; chemical vapor deposition is to make a gaseous compound containing thin film elements undergo a chemical reaction on the substrate surface to generate a thin film. Therefore, gasification pretreatment of the material to be deposited is an essential step.

[0003] However, the physical properties of the raw materials used in the thin film deposition step are relatively complex, with viscosity and thermal sensitivity. Their viscosity is generally high, and their flow and heat transfer capabilities are poor. At the same time, they are sensitive to temperature changes and are extremely prone to local overheating during the gasification process, resulting in denaturation or fouling. Conventional vaporizers have a large floor area and are prone to temperature runaway. Their research and development and improvement are mainly aimed at the vaporization requirements of bulk chemicals and their production raw materials, and it is difficult to achieve precise control of the flow state and temperature of the material to be deposited in small batches and continuous operation, and it is impossible to solve the problem of uneven internal heating of the fluid caused by low laminar flow heat transfer efficiency.

[0004] Therefore, there is an urgent need for a microchannel circulating thin liquid film preheating device and method to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a microchannel circulating thin liquid film preheating device and method to solve the problems existing in the above prior art.

[0006] To achieve the above purpose, the present invention provides the following solution: The present invention provides a microchannel circulating thin liquid film preheating device, including:

[0007] A gas-liquid mixing heating assembly, including a housing and a substrate. The substrate is located inside the housing. A microchannel is provided inside the substrate. One side of the substrate is connected to an intake pipe, and the other side of the substrate is connected to an outlet pipe. The top of the housing is connected to a liquid inlet pipe. The intake pipe and the liquid inlet pipe are respectively connected to one end of the microchannel, and the outlet pipe is connected to the other end of the microchannel;

[0008] The working medium preheating assembly includes a gas preheater and a liquid preheater. The external gas working medium is preheated by the gas preheater and then transported to the microchannel through the intake pipe. The external liquid working medium is preheated by the liquid preheater and then transported to the microchannel through the liquid inlet pipe. When the preheated liquid working medium enters the microchannel, it is sheared by the preheated gas working medium to form a circulating thin liquid film shape, exchanges heat with the substrate, and then flows out through the outlet pipe.

[0009] A microchannel circulating thin liquid film preheating device according to the present invention, the substrate includes a metal base plate and a metal base cover. Microchannel grooves are provided on the opposite sides of the metal base plate and the metal base cover. The two microchannel grooves are spliced to form the microchannel. Intake pipe welding grooves are provided on both the metal base plate and the metal base cover. The intake pipe is fixedly connected in the intake pipe welding groove. An inlet liquid hole is provided at the top of the metal base cover. The inlet liquid hole is communicated with the liquid inlet pipe. An intake channel and a liquid inlet channel are provided at the inlet end of the microchannel. The intake channel and the liquid inlet channel are respectively communicated with the intake pipe and the inlet liquid hole.

[0010] A microchannel circulating thin liquid film preheating device according to the present invention, the gas preheater includes a gas heater. The external gas working medium is transported into the gas heater for preheating. One end of a ventilation hose is connected to the output end of the gas heater. The other end of the ventilation hose is connected to the intake pipe. A branch is connected to the ventilation hose through a tee joint. A micro regulating valve is installed on the branch.

[0011] A microchannel circulating thin liquid film preheating device according to the present invention, the liquid preheater includes a liquid heater. A threaded coiled pipe is provided on the liquid heater. The external liquid working medium is transported into the threaded coiled pipe and preheated by the liquid heater and then transported into the liquid inlet pipe.

[0012] A microchannel circulating thin liquid film preheating device according to the present invention, the housing includes an engineering base plate and an engineering cover. The substrate is located between the engineering base plate and the engineering cover. Intake pipe placement grooves are provided on both the engineering base plate and the engineering cover. The intake pipe is located in the intake pipe placement groove. A liquid inlet pipe placement groove is provided on the engineering cover. The liquid inlet pipe is located in the liquid inlet pipe placement groove.

[0013] A microchannel circulating thin liquid film preheating device according to the present invention, heating sheet placement grooves are provided on both sides of the top of the engineering base plate. Heating sheets are fixedly connected in the heating sheet placement grooves. The heating sheets are in contact with the metal base plate.

[0014] A microchannel circulating thin liquid film preheating device provided by the present invention, wherein a thermocouple hole is formed on the substrate.

[0015] According to the present invention, the microchannel is a spiral microchannel, and the cross-section of the microchannel is rectangular.

[0016] According to the present invention, the cross-sectional area of the microchannel is 0.5 - 2.25 mm 2 , the aspect ratio is 0.5 - 2, the effective flow length is 200 - 2000 mm, the spiral pitch is 5 - 2.5 mm, and the number of spirals is 1 - 10.

[0017] A microchannel circulating thin liquid film preheating method includes the following steps:

[0018] The external gas working medium is preheated by the gas preheating part, and the preheated gas working medium is transported into the microchannel through the intake pipe;

[0019] The external liquid working medium is preheated by the liquid preheating part, and the preheated liquid working medium is transported into the microchannel through the liquid inlet pipe;

[0020] The liquid working medium flows in the microchannel in the form of a thin liquid film under the high-speed shear of the gas working medium, and exchanges heat with the substrate during the flow, and then flows out from the other end of the microchannel after heat exchange.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects:

[0022] A microchannel circulating thin liquid film preheating device and method provided by the present invention, wherein the external gas working medium is preheated by the gas preheating part and then transported into the microchannel through the intake pipe, and the external liquid working medium is preheated by the liquid preheating part and then transported into the microchannel through the liquid inlet pipe. When the preheated liquid working medium enters the microchannel, it is sheared by the preheated gas working medium to form a circulating thin liquid film shape, and flows in the microchannel. After heat exchange with the substrate during the flow, it flows out through the outlet pipe. This application improves the inlet mixing method. By optimizing the inlet structure and regulating the gas-liquid phase flow rate, the gas-liquid phase operation range for forming circulation is broadened, the flow length required for forming circulation is shortened, and the stable control of the outlet temperature is achieved by adjusting the competition mechanism between the gas-liquid phase convective heat transfer and the liquid-wall heat conduction in terms of heat transfer contribution. The heat-sensitive material preheated by the present invention has a more stable flow pattern and a more uniform temperature distribution. Description of the Drawings

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings:

[0024] Figure 1 Schematic diagram of the overall structure of the gas-liquid mixing heating component of the present invention;

[0025] Figure 2 Schematic diagram of the internal structure of the substrate of the present invention;

[0026] Figure 3 Schematic diagram of the top surface structure of the substrate of the present invention;

[0027] Figure 4 Schematic diagram of the structure of the gas preheating part of the present invention;

[0028] Figure 5 Schematic diagram of the structure of the liquid preheating part of the present invention;

[0029] Figure 6 Schematic diagram of the structure at the mixing place of the gas working medium and the liquid working medium of the present invention;

[0030] Figure 7 For the present invention Figure 6 Schematic diagram of the A-A cross-section in;

[0031] Figure 8 Schematic diagram of the change of the temperature of tetraethyl orthosilicate after preheating with the gas phase flow rate under different heating powers and different flow rates of the present invention;

[0032] Among them, 1. Metal-based bottom plate; 2. Metal-based cover plate; 3. Inlet gas pipe; 4. Inlet liquid pipe; 5. Outlet pipe; 6. Welding groove for the inlet gas pipe; 7. Groove for the inlet gas channel; 8. Groove for the inlet liquid channel; 9. Micro-channel groove; 10. Thermocouple hole; 11. Inlet liquid hole; 12. Engineering bottom plate; 13. Groove for placing the heating sheet; 14. Groove for placing the inlet gas pipe; 15. Engineering cover plate; 16. Groove for placing the inlet liquid pipe; 17. Gas heater; 18. Ventilation hose; 19. Three-way joint; 20. Micro flow regulating valve; 21. Liquid heater; 22. Spiral coil. Detailed implementation manners

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0034] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] Referring to Figures 1-8 , the present invention provides a microchannel circulating thin liquid film preheating device, including:

[0036] A gas-liquid mixing heating component, including a housing and a substrate. The substrate is located inside the housing. A microchannel is provided inside the substrate. One side of the substrate is connected to an intake pipe 3, and the other side of the substrate is connected to an outlet pipe 5. The top of the housing is connected to a liquid inlet pipe 4. The intake pipe 3 and the liquid inlet pipe 4 are respectively connected to one end of the microchannel, and the outlet pipe 5 is connected to the other end of the microchannel;

[0037] A working fluid preheating component, including a gas preheating part and a liquid preheating part. The external gas working fluid is preheated by the gas preheating part and then transported into the microchannel through the intake pipe 3. The external liquid working fluid is preheated by the liquid preheating part and then transported into the microchannel through the liquid inlet pipe 4. When the preheated liquid working fluid enters the microchannel, it is sheared by the preheated gas working fluid to form a thin liquid film shape, and after exchanging heat with the substrate, it flows out through the outlet pipe 5.

[0038] In an embodiment of the present invention, the external gas working fluid is preheated by the gas preheating part and then transported into the microchannel through the intake pipe 3. The external liquid working fluid is preheated by the liquid preheating part and then transported into the microchannel through the liquid inlet pipe 4. When the preheated liquid working fluid enters the microchannel, it is sheared by the preheated gas working fluid to form a circulating thin liquid film shape and flows in the microchannel. During the flowing process, it exchanges heat with the substrate and then flows out through the outlet pipe 5.

[0039] As an optional implementation manner, the substrate includes a metal base plate 1 and a metal base cover 2. Microchannel grooves 9 are provided on the opposite sides of the metal base plate 1 and the metal base cover 2. The two microchannel grooves 9 are spliced into a microchannel. Intake pipe welding grooves 6 are provided on both the metal base plate 1 and the metal base cover 2. The intake pipe 3 is fixedly connected in the intake pipe welding groove 6. A liquid inlet hole 11 is provided at the top of the metal base cover 2. The liquid inlet hole 11 is connected to the liquid inlet pipe 4. An intake channel 7 and a liquid inlet channel 8 are provided at the inlet end of the microchannel. The intake channel 7 and the liquid inlet channel 8 are respectively connected to the intake pipe 3 and the liquid inlet hole 11.

[0040] In an embodiment of the present invention, the metal plate material is ensured to have excellent heat transfer performance and good thermal uniformity, and the metal plates are combined by the method of high-temperature vacuum sintering.

[0041] As an alternative embodiment, the gas preheating member includes a gas heater 17. The external gas working medium is transported into the gas heater 17 for preheating. One end of a ventilation hose 18 is connected to the output end of the gas heater 17, and the other end of the ventilation hose 18 is connected to the intake pipe 3. A branch is connected to the ventilation hose 18 through a tee joint 19, and a micro regulating valve 20 is installed on the branch.

[0042] In an embodiment of the present invention, the flow rate distribution ratio of the gas between the main path and the branch is adjusted by the provided tee joint 19 and micro regulating valve 20 to ensure that the temperature of the carrier gas is controllable within a large range.

[0043] As an alternative embodiment, the liquid preheating member includes a liquid heater 21. A threaded coil pipe 22 is provided on the liquid heater 21. The external liquid working medium is transported into the threaded coil pipe 22 and is preheated by the liquid heater 21 and then transported into the liquid inlet pipe 4.

[0044] In an embodiment of the present invention, the liquid heater 21 is a water bath heater. The liquid flows through the threaded coil pipe 22 by an injection pump, and the flow length is 100 - 5000 mm to ensure that the liquid is fully heated in the water bath heater and the temperature is consistent with the preset temperature of the water bath heater.

[0045] As an alternative embodiment, the housing includes an engineering base plate 12 and an engineering cover plate 15. The substrate is located between the engineering base plate 12 and the engineering cover plate 15. Intake pipe placement grooves 14 are provided on both the engineering base plate 12 and the engineering cover plate 15. The intake pipe 3 is located in the intake pipe placement groove 14. A liquid inlet pipe placement groove 16 is provided on the engineering cover plate 15, and the liquid inlet pipe 4 is located in the liquid inlet pipe placement groove 16.

[0046] In an embodiment of the present invention, the sizes of the engineering base plate 12 and the engineering cover plate 15 are determined according to the size of the substrate. After assembly, the housing fits tightly with the substrate, playing a role in stabilizing the substrate and isolating air, and minimizing the influence of the ambient temperature on the accurate measurement of the outlet temperature.

[0047] As an alternative embodiment, heating sheet placement grooves 13 are provided on both sides at the top of the engineering base plate 12. Heating sheets are fixedly connected in the heating sheet placement grooves 13, and the heating sheets are in contact with the metal base plate 1.

[0048] In an embodiment of the present invention, the heating sheets are placed through the provided heating sheet placement grooves 13, and the substrate is heated by the provided heating sheets.

[0049] As an alternative embodiment, thermocouple holes 10 are provided on the substrate.

[0050] In an embodiment of the present invention, the provided thermocouple holes 10 are used to place thermocouples.

[0051] As an alternative embodiment, the microchannel is a spiral microchannel, and the cross-section of the microchannel is rectangular.

[0052] In one embodiment of the present invention, the microchannel is a spiral microchannel to ensure the heat exchange effect with the substrate.

[0053] As an alternative embodiment, the cross-sectional area of the microchannel is 0.5 - 2.25 mm 2 , the aspect ratio is 0.5 - 2, the effective flow length is 200 - 2000 mm, the spiral pitch is 5 - 2.5 mm, and the number of spirals is 1 - 10.

[0054] A method for preheating a thin liquid film in a microchannel circulation includes the following steps:

[0055] The external gas working medium is preheated through a gas preheating component, and the preheated gas working medium is transported into the microchannel through the inlet pipe 3;

[0056] The external liquid working medium is preheated through a liquid preheating component, and the preheated liquid working medium is transported into the microchannel through the liquid inlet pipe 4;

[0057] The liquid working medium flows in the microchannel in the form of a thin liquid film under the high-speed shear of the gas working medium, and exchanges heat with the substrate during the flow, and then flows out from the other end of the microchannel after heat exchange.

[0058] In one embodiment of the present invention, during use, the total volume flow rate of the gas working medium is controlled by a gas flow controller, and the flow rate range is 100 - 10000 mL / min. The external gas working medium enters the gas heater 17 for heating, and the heated gas working medium is branched through the three-way joint 19. The pressure drop of the branch is controlled by the micro-regulating valve 20, so as to adjust the flow rate distribution ratio of the gas in the main path and the branch component to vary between 1:10 and 10:1. The carrier gas temperature change range is 20 - 150 °C, and it is transported into the microchannel;

[0059] The volume flow rate of the external liquid working medium is controlled by an injection pump, and the flow rate range is 0.001 - 10 mL / min. It enters the spiral coil 22 and is fully heat-exchanged through the liquid heater 21. The heat-exchanged liquid working medium is transported into the microchannel through the liquid inlet pipe 4, and the initial material temperature change range is 20 - 80 °C;

[0060] The gas working medium is injected through a square narrow hole into the mixing transition zone. The low-flow material flowing in from the liquid inlet pipe 4 enters the transition zone along the long and narrow channel under the action of capillary force and external pressure, and flows in the form of a circulating thin liquid film after being sheared by the high-speed gas flow. During the flow, the liquid material mainly exchanges heat with the heated high-temperature metal wall surface to increase the temperature. After sufficient heat exchange, the two-phase flows out through the outlet pipe 5, and the final outlet temperature is 25 - 150 °C.

[0061] In one embodiment of the present invention, the cross-section of the microchannel is rectangular, with a width of 1.5 mm, a width-to-height ratio of 1, and a cross-sectional area of 2.25 mm 2 , the effective flow length in the microchannel is 380 mm, the spiral pitch is 1.5 mm, the number of spirals is 1, the intake channel is 7 mm long, and the cross-section is a square of 0.6×0.6 mm. The liquid inlet channel is 5 mm long, 0.4 mm wide, and 1.5 mm high.

[0062] In one embodiment of the present invention, nitrogen is used as the gas working medium. In the gas heating module, the gas heater 17 adopts a gas intelligent temperature controller, and the total gas volume flow rate is 2000 mL / min; after the gas flows through the ventilation hose 18 and enters the three-way joint 19, the gas flow rate in the main passage is respectively controlled at 300, 600, 900, 1200, 1500 mL / min through the micro regulating valve 20, and the outlet temperature of nitrogen is controlled at 23-26 °C.

[0063] In one embodiment of the present invention, tetraethyl orthosilicate is used as the liquid working medium. In the liquid preheating module, a constant temperature water bath is adopted. Under the conditions that the liquid volume flow rates are 0.5, 1, 1.5, 2 mL / min respectively, the liquid flows through the spiral coil to achieve sufficient heat exchange, and the temperature of the preheated liquid is controlled at 20 °C.

[0064] In one embodiment of the present invention, a gas-liquid two-phase circulating thin liquid film heat test platform is built. The gas phase is provided by a nitrogen cylinder, and the total gas phase flow rate is controlled by the pressure regulating valve of the gas cylinder. Nitrogen first enters a small gas heater with adjustable heating power and preheating temperature and is heated to 25 °C, and then is led out by a two-way joint with two branch passages, and the gas phase flow rate is preliminarily distributed by adjusting the opening of the branch valve; the carrier gas flow rate flowing into the test section is accurately controlled by using a micro regulating valve and a rotameter, and the connecting pipelines are all wrapped with heat preservation cotton to reduce the heat exchange between the carrier gas and the environment; the liquid phase is pumped in by an injection pump; a plurality of thermocouple holes are evenly distributed under the microchannel to monitor the temperature during the whole flow process and after preheating; by adjusting the voltage and current applied to the heating sheet, the power of the heating sheet is changed; a gas-liquid separator is installed at the outlet. A small amount of gas evaporated during the flow and heat transfer process is discharged from the outlet of the upper chamber. After a very small amount of gas mixed into the liquid fails to be discharged in time and enters the lower chamber, it is separated during the falling process and discharged from the outlet on the side wall. The unevaporated liquid phase is discharged from the lower chamber into a beaker, and the mass of the beaker is weighed by a precision electronic balance. When the outlet temperature is stable at a certain value and fluctuates within 0.2 °C, the reading of the balance is recorded once every 30 s under this operating condition and counted. The difference between the readings of the two times before and after is the weight of the unevaporated liquid phase. A total of 4 times are taken, and their average value is calculated, which is the amount of evaporated liquid under this operating condition.

[0065] Specifically, the main distribution range of the liquid phase outlet temperature is 20-60°C, and the local maximum temperature can reach 55.57°C. Thermocouple monitoring is used to ensure that the local temperature does not exceed the boiling point of the material to be heated. Studies have shown that at different powers, the liquid phase outlet temperature generally shows a downward trend with the increase of the gas phase flow rate, and with the increase of heating power, when the gas phase flow rate increases, the outlet temperature drops significantly. This is because the increase in gas phase flow rate increases the turbulence of the gas-liquid interface and strengthens the heat transfer at the gas-liquid interface. As the gas phase flow rate further increases, the convective heat transfer effect is weakened due to the decrease in the gas-liquid temperature difference. After sufficient heat exchange, the relative thermal equilibrium of the gas-liquid phase is finally reached. Therefore, at high gas phase flow rates, the final temperatures of different liquid phases tend to be However, under certain liquid phase flow conditions, the increase in gas phase flow also promotes the transformation of the gas-liquid two-phase flow pattern to a circulation that can form a thin liquid film, and the larger the gas phase flow, the stronger the shearing effect on the thin liquid film, the thinner the liquid film thickness, the thinner the heat transfer boundary layer, and the smaller the heat transfer resistance. Therefore, the heat exchange effect with the microchannel hot wall is stronger. For example, when the liquid phase flow rate is 1.5mL / min and the heating power is 1W, when the gas phase flow rate increases from 300mL / min to 600mL / min, the final outlet temperature of the liquid phase increases slightly. Through the comprehensive regulation of gas and liquid phase flow and heating power, the precise control of the temperature of tetraethyl orthosilicate between 20-60°C is achieved in this implementation case.

[0066] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0067] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A microchannel circulation thin liquid film preheating device, characterized in that, Comprising: A gas-liquid mixing and heating component, including a housing and a substrate. The substrate is located inside the housing. A microchannel is provided inside the substrate. An intake pipe (3) is connected to one side of the substrate, and an outlet pipe (5) is connected to the other side of the substrate. A liquid inlet pipe (4) is connected to the top of the housing. The intake pipe (3) and the liquid inlet pipe (4) are respectively connected to one end of the microchannel, and the outlet pipe (5) is connected to the other end of the microchannel. A working medium preheating component, including a gas preheating part and a liquid preheating part. The external gas working medium is preheated through the gas preheating part and then transported to the microchannel through the intake pipe (3). The external liquid working medium is preheated through the liquid preheating part and then transported to the microchannel through the liquid inlet pipe (4). When the preheated liquid working medium enters the microchannel, it is sheared by the preheated gas working medium to form a thin liquid film shape, exchanges heat with the substrate, and then flows out through the outlet pipe (5).

2. The preheating device for a microchannel circulating thin liquid film according to claim 1, wherein: The substrate includes a metal base plate (1) and a metal base cover plate (2). Microchannel grooves (9) are provided on the opposite sides of the metal base plate (1) and the metal base cover plate (2). The two microchannel grooves (9) are spliced to form the microchannel. Intake pipe welding grooves (6) are provided on both the metal base plate (1) and the metal base cover plate (2). The intake pipe (3) is fixedly connected in the intake pipe welding groove (6). An inlet liquid hole (11) is provided at the top of the metal base cover plate (2), and the inlet liquid hole (11) is communicated with the liquid inlet pipe (4). An intake channel (7) and a liquid inlet channel (8) are provided at the inlet end of the microchannel, and the intake channel (7) and the liquid inlet channel (8) are respectively communicated with the intake pipe (3) and the inlet liquid hole (11).

3. The preheating device for a microchannel circulating thin liquid film according to claim 1, characterized in that: The gas preheating part includes a gas heater (17). The external gas working medium is transported into the gas heater (17) for preheating. One end of a ventilation hose (18) is connected to the output end of the gas heater (17), and the other end of the ventilation hose (18) is connected to the intake pipe (3). A branch is connected to the ventilation hose (18) through a tee joint (19), and a micro flow regulating valve (20) is installed on the branch.

4. A microchannel circulating thin liquid film preheating device according to claim 1, characterized in that: The liquid preheating part includes a liquid heater (21). A threaded coil pipe (22) is provided on the liquid heater (21). The external liquid working medium is transported into the threaded coil pipe (22) and preheated by the liquid heater (21) and then transported into the liquid inlet pipe (4).

5. A microchannel circulating thin liquid film preheating device according to claim 2, characterized in that: The housing includes an engineering base plate (12) and an engineering cover plate (15). The substrate is located between the engineering base plate (12) and the engineering cover plate (15). Intake pipe placement grooves (14) are provided on both the engineering base plate (12) and the engineering cover plate (15). The intake pipe (3) is located in the intake pipe placement groove (14). A liquid inlet pipe placement groove (16) is provided on the engineering cover plate (15), and the liquid inlet pipe (4) is located in the liquid inlet pipe placement groove (16).

6. The preheating device for a microchannel circulating thin liquid film according to claim 5, wherein: Both sides of the top end of the engineering floor slab (12) are provided with heating sheet placement grooves (13), and heating sheets are fixedly connected in the heating sheet placement grooves (13), and the heating sheets are in contact with the metal base plate (1).

7. A microchannel circulation thin liquid film preheating device according to claim 1, characterized in that: Thermocouple holes (10) are provided in the substrate.

8. A microchannel circulating thin liquid film preheating device according to claim 1, characterized in that: The microchannel is a spiral microchannel, and the cross section of the microchannel is rectangular.

9. A microchannel circulation thin liquid film preheating device according to claim 8, characterized in that: The cross-sectional area of the microchannel is 0.5 - 2.25 mm 2 , the aspect ratio is 0.5 - 2, the effective flow length is 200 - 2000 mm, the spiral pitch is 1.5 - 2.5 mm, and the number of spirals is 1 - 10.

10. A method for preheating a thin liquid film with microchannel circulation, applicable to the microchannel circulation thin liquid film preheating device described in claim 1, characterized in that, It includes the following steps: The external gas working medium is preheated by the gas preheating member, and the preheated gas working medium is transported to the microchannel through the intake pipe (3); The external liquid working medium is preheated by the liquid preheating member, and the preheated liquid working medium is transported to the microchannel through the liquid inlet pipe (4); The liquid working medium flows in the microchannel in the form of a circulating thin liquid film under the high-speed shearing of the gas working medium, and exchanges heat with the substrate during the flow, and flows out from the other end of the microchannel after heat exchange.

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