Visual testing device for micro-channel flow boiling

Abstract

The invention discloses a visual testing device for micro-channel flow boiling, which can obtain stable flow. The pressing plate, the main body plate, the heat conductor and the heat insulation base are fixedly pressed and connected into a whole. A working medium flow channel of a micro channel is arranged in the main body plate, and the working medium flow channel is composed of an inlet channel, an inlet variable-diameter channel section, an inlet end stable flow channel section, a test flow channel section, an outlet end stable flow channel section, an outlet variable-diameter channel section and an outlet channel. The visual plate is located between the pressing plate and the main body plate, a first sealing ring is arranged between the visual plate and the main body plate, and a second sealing ring is arranged between the main body plate and the heat conductor. A data acquisition hole corresponding to the test flow channel is formed in the visual plate; the heat conductor is composed of a heat conductor upper block, a heat conductor fixing block and a heat conductor lower block, the top end of the heat conductor upper block is connected with a test piece through a welding layer, and a boiling heating piece is arranged between the heat conductor lower block and the heat insulation base; the heat conductor is provided with a plurality of groups of temperature measuring holes. The device can obtain stable flow and is suitable for testing high-pressure working media.

Description

Technical Field

[0001] The invention relates to the field of testing technology, and more particularly to a visualization testing device for micro-channel flow boiling. Background Art

[0002] As electronic devices continue to become smaller and more powerful, traditional air cooling and single-phase liquid cooling methods can no longer meet their heat dissipation needs. Microchannel flow boiling provides an efficient thermal management solution that can significantly improve thermal efficiency. In addition, with the development of surface modification technology, the development of various modified surfaces can effectively improve the performance of microchannel flow boiling. Therefore, the study of microchannel flow boiling with different modified surfaces is crucial, and the research content involves flow pattern, heat transfer coefficient and pressure drop. The study of microchannel flow boiling requires a test and visualization experimental section that can accurately observe the flow pattern, measure heat transfer performance and pressure drop.

[0003] The test and visualization sections proposed in the literatures such as "Experimental investigation of the effect of heat sink orientation on subcooled flow boiling performance in a rectangular microgap channel", "Experimental investigation into unstable two-phase flow phenomena during flow boiling in multi-microchannels", and "Static and dynamic flow instability of a parallel microchannel heat sink at high heat fluxes" cannot be tested for pressure drop, and the test and visualization sections do not have an inlet stable section. Therefore, the fluid directly enters the test surface after passing through the sudden change pipeline, and the obtained flow pattern and heat transfer coefficient cannot ensure accuracy. Although the flow boiling test and visualization experimental sections disclosed in the literatures such as "A comparative study of flow boiling performance in the interconnected microchannel net and rectangular microchannels", "Experimental study on pressure drop characteristics of flow boiling in parallel multi-microchannels", and "Experimental study on flow boiling characteristics of non-azeotropic binary mixture (R134a / R245fa) in rectangular microchannels" are equipped with pressure drop test ports, they are set at the expansion inlet and contraction outlet. Therefore, the measured pressure drop is not accurate. Although the researchers used empirical formulas to calculate the pressure drop at the expansion inlet and contraction outlet, and subtracted the calculated pressure drop from the measured pressure drop to obtain the pressure drop of the test section, they still could not accurately obtain the pressure drop of the test section. Moreover, the flow boiling test and visualization experiment section still does not have a flow stabilization section, and the accuracy of the flow pattern, heat transfer coefficient and pressure drop of the test section cannot be guaranteed. Moreover, the currently available literature cannot arbitrarily replace the modified surface, which will increase the research cost. Therefore, it is very necessary to design a high-pressure resistant micro-channel flow boiling test and visualization experiment section to test the micro-channel flow boiling heat transfer performance, pressure drop characteristics, and flow pattern distribution. Summary of the invention

[0004] The purpose of the present invention is to provide a visual testing device for flow boiling in a micro-channel in order to address the technical defects in the prior art. The device can obtain a stable flow and can be used for testing both ordinary working fluids and high-pressure working fluids.

[0005] The technical solution adopted to achieve the purpose of the present invention is: A visualization test device for boiling flow in a micro-channel, comprising a pressing plate, a visualization plate, a main plate, a test piece, a heat conductor, a boiling heating piece and a heat-insulating base; the pressing plate, the main plate, the heat conductor and the heat-insulating base are fixedly pressed and connected as a whole; a working fluid flow channel of a micro-channel is arranged in the main plate, and the working fluid flow channel is composed of an inlet channel, an inlet variable-diameter channel section, an inlet end stable channel section, a test channel section, an outlet end stable channel section, an outlet variable-diameter channel section and an outlet channel; the visualization plate is located between the pressing plate and the main plate, a first sealing ring is arranged between the visualization plate and the main plate, and a second sealing ring is arranged between the main plate and the heat conductor; the pressing plate and the test channel A visualization window is provided at a corresponding position for recording the flow type in the test flow channel through the visualization board; a data acquisition hole corresponding to the test flow channel is provided on the visualization board, and the center of the lower end of the data acquisition hole is just opposite to the center of the two ends of the test piece; the heat conductor is composed of a heat conductor upper block, a heat conductor fixing block and a heat conductor lower block, and the top of the heat conductor upper block is connected to the test piece for testing the working fluid in the flow channel through a welding layer, and the boiling heating plate for providing heat flux density is provided between the heat conductor lower block and the insulation base; a plurality of groups of temperature measuring holes are provided on the heat conductor, and the distances between the plurality of groups of temperature measuring holes and the heat conductor fixing block satisfy the linear temperature distribution.

[0006] The main body plate is provided with a heat conductor matching area for tight matching with the upper block of the heat conductor, and positions on the main body plate corresponding to the temperature measuring holes are respectively provided with temperature measuring device plug holes.

[0007] The heat conductor is made of copper, and the depth of the temperature measuring hole is half the width of the test piece; the inlet end stable flow channel section, the test flow channel section, and the outlet end stable flow channel section are located on the upper surface of the main body plate.

[0008] A temperature measuring device positioning column is installed at the temperature measuring device socket. The temperature measuring device positioning column is a cylinder concentric with the temperature measuring device socket and is used to fix the temperature measuring device. The connection between the temperature measuring device positioning column, the temperature measuring device and the main plate is coated with sealant for preventing leakage of the working fluid.

[0009] The thickness of the upper block of the heat conductor is consistent with the width of the test piece and is consistent with the width of the microchannel of the test flow channel section.

[0010] The pressure plate, the main plate, the heat conductor fixing block and the heat insulating base are fixedly pressed and connected into one by means of hexagon socket screws and nuts, so that the pressure plate, the visualization plate, the first sealing ring, the main plate, the heat conductor, the second sealing ring, the boiling heating plate and the heat insulating base are pressed in sequence from top to bottom to achieve a sealing effect; the heat conductor fixing block, the second sealing ring and the main plate are connected into one by means of heat insulating hexagon socket screws, so that the heat conductor, the second sealing ring and the main plate are pressed in sequence from bottom to top to achieve a sealing effect.

[0011] The boiling heating plate is a ceramic heating plate, and thermal conductive glue or thermal conductive silicone grease is applied between the boiling heating plate and the heat conductor.

[0012] The data acquisition hole is divided into an upper hole and a lower hole. The upper hole is a threaded hole, which is used to connect a differential pressure sensor and a pressure sensor to measure the pressure drop generated when the working fluid flows through the heat transfer surface of the test piece and the fluid pressure at the outlet of the test piece; the lower hole is a through hole smaller than the upper hole, and the center of the lower hole is exactly opposite to the center of the two ends of the test piece.

[0013] The material of the main body plate is polyetheretherketone or polyimide; the first sealing ring and the second sealing ring are O-rings, the material of which is silicone, nitrile or fluororubber, and the welding layer is solder with different melting points; the material of the visualization board is polycarbonate or acrylic; the material of the insulation base is polyetheretherketone or polyimide or bakelite.

[0014] The main body plate is provided with sealing ring grooves corresponding to the first sealing ring and the second sealing ring, respectively. The first sealing ring and the second sealing ring are placed in the corresponding sealing ring grooves to achieve sealing.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The visualization test device for flow boiling in a microchannel of the present invention is provided with a fluid flow stabilization section at both the inlet and outlet ends of the working fluid flow channel to ensure the accuracy of the flow pattern, pressure drop and heat transfer tests.

[0016] 2. The visualization test device for flow boiling in a microchannel of the present invention is sealed by structural design and sealing rings, and has the characteristics of high pressure resistance. It can be used to test normal pressure working fluids such as water, and can also be used to test high pressure working fluids such as refrigerants.

[0017] 3. The visualization test device for flow boiling in a micro-channel of the present invention can obtain the flow pattern of the working fluid flowing in the micro-channel, the heat transfer performance of the working fluid and the pressure drop characteristics through a combination of structural design.

[0018] 4. The visualization test device for micro-channel flow boiling of the present invention can melt the welding layer through the heating plate, so that the test plate can be easily replaced to test the heat transfer and pressure drop performance of different modified surfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Shown is a cross-sectional view of a visualization test device for micro-channel flow boiling of the present invention; Figure 2 Shown is an exploded view of a visualization test device for micro-channel flow boiling of the present invention; Figure 3 The three-dimensional diagram of the main plate in the top view is shown; Figure 4 The three-dimensional diagram of the main plate in the upward direction is shown; Figure 5 Shown is a cross-sectional view of the main body plate; Figure 6 Shown is a schematic diagram of the structure of the heat conductor; Figure 7 Shown is a three-dimensional view of the pressure plate; Figure 8 Shown is a schematic diagram of the visualization board. DETAILED DESCRIPTION

[0020] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] The schematic diagram of the visualization test device for microchannel flow boiling of the present invention is as follows Figure 1-Figure 8As shown, it includes a pressing plate 1, a visualization plate 2, a main plate 4, a test piece 5, a heat conductor 6, a boiling heating plate 10 and a heat-insulating base 7. The pressing plate 1, the main plate 4, the heat conductor 6 and the heat-insulating base 7 are fixedly pressed and connected as a whole. A working fluid flow channel with a micro-channel is arranged in the main plate 4, and the working fluid flow channel is composed of an inlet channel 4h, an inlet variable-diameter channel section 4g, an inlet end stable flow channel section 4f, a test flow channel section 4k, an outlet end stable flow channel section 4d, an outlet variable-diameter channel section 4c and an outlet channel 4b. The inlet end stable flow channel section 4f can ensure the accuracy of the flow pattern, heat transfer coefficient and pressure drop test, and the outlet end stable flow channel section 4d ensures that the outlet variable-diameter channel 4c has no effect on the pressure drop measurement point and the test section flow pattern. The visualization board 2 is located between the pressure plate 1 and the main body plate 4, a first sealing ring 3 is provided between the visualization board 2 and the main body plate 4, and a second sealing ring 9 is provided between the main body plate 4 and the heat conductor 6, so as to realize the overall sealing of the pressure plate 1, the visualization board 2, the main body plate 4 and the heat conductor 6, and can be used for testing ordinary working fluids as well as testing high-pressure working fluids. In this embodiment, the inlet end stable flow channel section 4f, the test flow channel section 4k, and the outlet end stable flow channel section 4d are preferably located on the upper surface of the main body plate 4, and a visualization window 1b is provided at a position corresponding to the pressure plate 1 and the test flow channel 4k, which is used to record the flow type in the test flow channel through the visualization board 2. The visualization board 2 is provided with a data acquisition hole corresponding to the test flow channel, and the lower end center of the data acquisition hole is directly opposite to the center of the two ends of the test piece 5, so as to accurately measure the data generated when the working fluid flows through the heat transfer surface of the test piece.

[0022] The heat conductor 6 is composed of a heat conductor upper block 6b, a heat conductor fixing block 6c and a heat conductor lower block 6e. The top of the heat conductor upper block 6b is connected to the test piece 5 for testing the working fluid in the working fluid flow channel through a welding layer 8, and the test piece 5 is arranged corresponding to the test flow channel section 4k. The boiling heating plate 10 for providing heat flux density is arranged between the heat conductor lower block 6e and the insulation base 7. The heat conductor 6 is provided with multiple groups of temperature measuring holes 6a, and the distances between the multiple groups of temperature measuring holes 6a and the heat conductor fixing block 6c meet the temperature linear distribution. The heat transfer coefficient is calculated according to the measured temperature using Fourier's law. The temperature measuring holes 6a can be arranged on the heat conductor upper block 6b and / or the heat conductor lower block 6e according to the use needs.

[0023] In this embodiment, a heat conductor matching area 4e is provided on the main plate 4 for tight matching with the heat conductor upper block 6b, and temperature measuring device plug holes 4a are respectively provided at positions on the main plate 4 corresponding to the temperature measuring holes 6a.

[0024] In this embodiment, the heat conductor 6 is made of copper, and the depth of the temperature measuring hole 6a is half the width of the test piece 5. The heat of the boiling heating piece 10 is transferred to the test piece 5 through the heat conductor 6.

[0025] In this embodiment, in order to facilitate the installation of the temperature measuring device, a temperature measuring device positioning column 14 is installed at the temperature measuring device socket 4a. The temperature measuring device positioning column 14 is a cylinder concentric with the temperature measuring device socket 4a and is used to fix the temperature measuring device. The connection between the temperature measuring device positioning column and the temperature measuring device and the main plate is coated with a sealant for preventing leakage of the working fluid. The sealant is preferably epoxy resin glue.

[0026] In this embodiment, the thickness of the upper block of the heat conductor is consistent with the width of the test piece and is consistent with the width of the microchannel of the test flow channel section.

[0027] In this embodiment, the pressing plate 1, the main plate 4, the heat conductor fixing block 6c and the heat insulation base 7 are fixed and pressed together by the hexagon socket screw 11 and the nut 12, so that the pressing plate 1, the visualization plate 2, the first sealing ring 3, the main plate 4, the heat conductor 6, the second sealing ring 9, the boiling heating plate 10 and the heat insulation base 7 are pressed from top to bottom in sequence to achieve a sealing effect. The heat conductor fixing block 6c, the second sealing ring 9 and the main plate 4 are connected together by the heat insulation hexagon socket screw 13, so that the heat conductor 6, the second sealing ring 9 and the main plate are pressed from bottom to top in sequence to achieve a sealing effect. The main plate 4 is provided with a first mounting hole 4j and a second mounting hole 4l, the first mounting hole 4j and the second mounting hole 4l are threaded holes, the first mounting hole 4j is used to cooperate with the hexagon socket screw 11 to achieve a fastening and sealing effect, and the second mounting hole 4l is used to cooperate with the heat insulation hexagon socket screw 13 to achieve a fastening and sealing effect. The connection holes of the inlet channel 4h and the outlet channel 4b are both threaded holes. The third mounting hole 6d of the heat conducting block 6 is a through hole for inserting the heat insulating hexagon socket screw 13. The fourth mounting hole 1a of the pressing plate 1 is a through hole for inserting the hexagon socket screw 11.

[0028] In this embodiment, the boiling heating plate 10 is a ceramic heating plate, and thermal conductive glue or thermal conductive silicone grease is applied between the boiling heating plate 10 and the heat conductor 6 .

[0029] The data acquisition hole is divided into an upper hole 2a and a lower hole 2b. The upper hole 2a is a threaded hole, which is used to connect the differential pressure sensor and the pressure sensor to measure the pressure drop generated when the working fluid flows through the heat transfer surface of the test piece and the fluid pressure at the outlet of the test piece. The lower hole 2b is a through hole smaller than the upper hole, with a diameter of 1mm. The center of the lower hole 2b is directly opposite to the center of the two ends of the test piece 5, so as to accurately measure the pressure drop generated when the working fluid flows through the heat transfer surface of the test piece and the fluid pressure at the outlet of the test piece.

[0030] In this embodiment, sealing ring grooves corresponding to the first sealing ring 3 and the second sealing ring 9 are respectively provided on the main body plate 4, and the first sealing ring 3 and the second sealing ring 9 are placed in the corresponding sealing ring grooves to achieve sealing.

[0031] In this embodiment, the material of the main plate 4 is polyetheretherketone or polyimide. The first sealing ring 3 and the second sealing ring 9 are O-rings, and the material is silicone, nitrile or fluorine rubber. The welding layer 8 can be solder with different melting points, and the test piece 5 is fixed on the thermal conductor 6. The pressing plate 1 is made of stainless steel or aluminum.

[0032] The material of the visualization board 2 is polycarbonate (PC) or acrylic with high light transmittance and low thermal conductivity, and the flow pattern of the test flow channel section 4k can be directly photographed by a high-speed camera.

[0033] The heat-insulating base 7 is made of polyetheretherketone (PEEK) or polyimide (PI) or bakelite. The fifth mounting hole of the heat-insulating base 7 is a threaded hole for connecting the hexagon socket screw 11.

[0034] The heat-insulating hexagon socket screw 13 is made of PEEK to prevent heat loss of the heat-conducting block 6 .

[0035] In this embodiment, the number of the temperature measuring holes 6a is 12, and the diameter is 1 mm. The diameter of the temperature measuring device plug hole is 1 mm, and the diameter of the inner hole of the temperature measuring device positioning column 14 is 1.1 mm.

[0036] When the test device of the present application is used for testing, the test fluid with a specific dryness, temperature and pressure enters the main plate 4 through the inlet channel 4h at a specific flow rate, and then enters the inlet end stable flow channel section 4f through the inlet variable diameter channel section 4g. The flow field and temperature field of the test fluid are fully developed in the insulated inlet end stable flow channel section 4f, and then flows into the test flow channel section 4k with a constant heat flux density. On the test flow channel section 4k, the test fluid flows and boils. Afterwards, the test fluid enters the outlet variable diameter channel section 4c through the outlet end stable flow channel section 4d, and then flows out of the main plate 4 through the outlet channel 4b.

[0037] During the flow boiling process of the test fluid, the flow pressure drop is measured by the pressure difference sensor installed on the visualization board 2, and the fluid inlet pressure of the test flow channel section 4k is measured by the pressure sensor. The outlet pressure of the test flow channel section 4k can be calculated by the inlet pressure and the pressure drop. The fluid temperature can be obtained according to the correspondence between the test fluid pressure and the temperature. According to the temperature measured by the temperature measuring device (the temperature measuring device is preferably a thermocouple) installed in the main board 4, the heat flux density and the wall temperature of the test flow channel section 4k can be calculated according to Fourier's law. The heat transfer coefficient can be calculated based on the wall temperature of the test flow channel section 4k and the fluid temperature. During the test, the flow pattern in the test flow channel section 4k can be observed through the video collector located at the top of the visualization window 1b.

[0038] The visualization test device for the flow boiling of a micro-channel of the present invention is provided with a fluid flow stabilization section at the inlet and outlet of the working fluid flow channel to ensure the accuracy of the flow pattern, pressure drop and heat transfer test. It is sealed by structural design and sealing ring, has the characteristics of high pressure resistance, and can be used to test normal pressure working fluids such as water, and can also be used to test high pressure working fluids such as refrigerants. The flow pattern of the working fluid flowing in the micro-channel, the heat transfer performance of the working fluid and the pressure drop characteristics can be obtained through the combination of structural design.

[0039] The above is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A visual testing device for micro-channel flow boiling, characterized in that: It includes a pressing plate, a visualization plate, a main body plate, a test piece, a heat conductor, a boiling heating plate and a heat insulating base; the pressing plate, the main body plate, the heat conductor and the heat insulating base are fixedly pressed and connected as a whole; a working fluid flow channel with a tiny channel is arranged in the main body plate, and the working fluid flow channel consists of an inlet groove, an inlet variable diameter groove section, an inlet end stable flow channel section, a test flow channel section, an outlet end stable flow channel section, an outlet variable diameter groove section and an outlet groove; the visualization plate is located between the pressing plate and the main body plate, a first sealing ring is arranged between the visualization plate and the main body plate, and a second sealing ring is arranged between the main body plate and the heat conductor; a visual A window is provided for recording the flow pattern in the test flow channel through the visualization board; a data acquisition hole corresponding to the test flow channel is arranged on the visualization board, and the center of the lower end of the data acquisition hole is just opposite to the center of the two ends of the test piece; the heat conductor is composed of a heat conductor upper block, a heat conductor fixing block and a heat conductor lower block, the top of the heat conductor upper block is connected to the test piece for working fluid testing in the working fluid flow channel through a welding layer, and the boiling heating plate for providing heat flux density is arranged between the heat conductor lower block and the insulation base; a plurality of groups of temperature measuring holes are arranged on the heat conductor, and the distances between the plurality of groups of temperature measuring holes and the heat conductor fixing block satisfy the linear temperature distribution.

2. The visualization test device for microchannel flow boiling according to claim 1, characterized in that: The main body plate is provided with a heat conductor matching area for tight matching with the upper block of the heat conductor, and positions on the main body plate corresponding to the temperature measuring holes are respectively provided with temperature measuring device plug holes.

3. The visualization test device for microchannel flow boiling according to claim 1 or 2, characterized in that: The heat conductor is made of copper, and the depth of the temperature measuring hole is half the width of the test piece; the inlet end stable flow channel section, the test flow channel section, and the outlet end stable flow channel section are located on the upper surface of the main body plate.

4. The visualization test device for microchannel flow boiling according to claim 2, characterized in that: A temperature measuring device positioning column is installed at the temperature measuring device socket. The temperature measuring device positioning column is a cylinder concentric with the temperature measuring device socket and is used to fix the temperature measuring device. The connection between the temperature measuring device positioning column, the temperature measuring device and the main plate is coated with sealant for preventing leakage of the working fluid.

5. The visualization test device for microchannel flow boiling according to claim 3, characterized in that: The thickness of the upper block of the heat conductor is consistent with the width of the test piece and is consistent with the width of the microchannel of the test flow channel section.

6. The visualization test device for microchannel flow boiling according to claim 3, characterized in that: The pressure plate, the main plate, the heat conductor fixing block and the heat insulating base are fixedly pressed and connected into one by means of hexagon socket screws and nuts, so that the pressure plate, the visualization plate, the first sealing ring, the main plate, the heat conductor, the second sealing ring, the boiling heating plate and the heat insulating base are pressed in sequence from top to bottom to achieve a sealing effect; the heat conductor fixing block, the second sealing ring and the main plate are connected into one by means of heat insulating hexagon socket screws, so that the heat conductor, the second sealing ring and the main plate are pressed in sequence from bottom to top to achieve a sealing effect.

7. The visualization test device for microchannel flow boiling according to claim 3, characterized in that: The boiling heating plate is a ceramic heating plate, and thermal conductive glue or thermal conductive silicone grease is applied between the boiling heating plate and the heat conductor.

8. The visualization test device for microchannel flow boiling according to claim 1, characterized in that: The data acquisition hole is divided into an upper hole and a lower hole. The upper hole is a threaded hole, which is used to connect a differential pressure sensor and a pressure sensor to measure the pressure drop generated when the working fluid flows through the heat transfer surface of the test piece and the fluid pressure at the outlet of the test piece; the lower hole is a through hole smaller than the upper hole, and the center of the lower hole is exactly opposite to the center of the two ends of the test piece.

9. The visualization test device for microchannel flow boiling according to claim 1, characterized in that: The material of the main body plate is polyetheretherketone or polyimide; the first sealing ring and the second sealing ring are O-rings, the material of which is silicone, nitrile or fluororubber, and the welding layer is solder with different melting points; the material of the visualization board is polycarbonate or acrylic; the material of the insulation base is polyetheretherketone or polyimide or bakelite.

10. The visualization test device for microchannel flow boiling according to claim 1, characterized in that: The main body plate is provided with sealing ring grooves corresponding to the first sealing ring and the second sealing ring, respectively. The first sealing ring and the second sealing ring are placed in the corresponding sealing ring grooves to achieve sealing.

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