1. The utility model provides a supercritical carbon dioxide microchannel heat transfer experimental system which characterized in that: the supercritical carbon dioxide micro-channel heat exchange experimental system comprises a carbon dioxide gas supply system for providing a supercritical carbon dioxide working medium and a carbon dioxide working medium circulation test system; the carbon dioxide working medium circulation test system comprises a main bypass, a vertical micro-channel heat exchange experimental section (7), a first bypass of the vertical micro-channel heat exchange experimental section (7), a horizontal micro-channel heat exchange experimental section (8) and a bypass of the horizontal micro-channel heat exchange experimental section (8), the inlet of the first bypass of the vertical micro-channel heat exchange experimental section (7) and the inlet of the first bypass of the vertical micro-channel heat exchange experimental section (7) are converged and then connected with the outlet of the carbon dioxide gas supply system, the outlets of the first bypasses of the vertical micro-channel heat exchange experimental section (7) and the vertical micro-channel heat exchange experimental section (7) are connected with the inlets of the bypasses of the horizontal micro-channel heat exchange experimental section (8) and the horizontal micro-channel heat exchange experimental section (8), the bypass outlet of the horizontal micro-channel heat exchange experiment section (8) and the bypass outlet of the horizontal micro-channel heat exchange experiment section (8) are converged and then connected with the outlet of the total bypass and the inlet of the carbon dioxide gas supply system.

Wherein, vertical microchannel heat transfer experiment section (7) and horizontal microchannel heat transfer experiment section (8) all include micro-pipeline (781), first adiabatic sleeve (782), second adiabatic sleeve (783), heating unit (785), heat insulation layer (784), micro-pipeline (781) both ends and experimental system's pipeline intercommunication, and closely suit in the middle of micro-pipeline (781) a plurality of heating unit (785), and all heating unit (785) are all closely wrapped up by heat insulation layer (784). The first heat-insulating sleeve (782) and the second heat-insulating sleeve (783) are respectively positioned at two sides of the heating unit (785) and tightly sleeved on the micro-pipeline (781).

2. The supercritical carbon dioxide micro-channel heat exchange experimental system according to claim 1, characterized in that: the carbon dioxide gas supply system comprises a carbon dioxide gas storage cylinder (1), a liquid storage tank (2), a high-pressure pump (3), a filter (4) and a cooler (9), wherein supercritical carbon dioxide working media are stored in the liquid storage tank (2), a connector above the liquid storage tank (2) is respectively communicated with the carbon dioxide gas storage cylinder (1) and the cooler (9), a stop valve (v1) and a check valve (v2) are arranged on a carbon dioxide gas cylinder gas outlet pipeline, and a stop valve (v19) is arranged on a pipeline between the liquid storage tank (2) and the cooler (9); an exhaust pipeline is arranged above the liquid storage tank (2); the outlet below the liquid storage tank (2) is connected with the high-pressure pump (3), and a stop valve (v3) is arranged on the pipeline; the outlet of the high-pressure pump (3) is communicated with the inlet end of the filter (4), the supercritical carbon dioxide working medium at the outlet of the filter (4) is sent into the carbon dioxide working medium circulation test system, the fluid flowing out of the carbon dioxide working medium circulation test system is sent into the cooler (9) for cooling circulation, and the front end of the inlet of the cooler (9) is provided with a back pressure valve.

3. The supercritical carbon dioxide micro-channel heat exchange experimental system according to claim 1, characterized in that: the carbon dioxide working medium circulation test system further comprises a flowmeter (5) and a preheater (6). The flowmeter (5) and the preheater (6) are arranged on a pipeline connected with an outlet of the carbon dioxide gas supply system and at an inlet of a first bypass of the vertical micro-channel heat exchange experiment section (7) and the vertical micro-channel heat exchange experiment section (7).

4. The supercritical carbon dioxide micro-channel heat exchange experimental system according to claim 3, characterized in that: the carbon dioxide working medium circulation test system further comprises a vertical micro-channel heat exchange experiment section (7) and a second bypass, wherein two ends of the second bypass of the vertical micro-channel heat exchange experiment section (7) are respectively connected with an outlet of the preheater (6) and an outlet of the vertical micro-channel heat exchange experiment section (7).

5. The supercritical carbon dioxide micro-channel heat exchange experimental system according to claim 1, characterized in that: the heating unit (785) is composed of a heat conduction block (7851), a heating piece (7853), a heat conduction clamping piece (7852) and a temperature thermocouple (7854), wherein the heat conduction block (7851), the heating piece (7853) and the heat conduction clamping piece (7852) are all disc-shaped, a convex shaft is arranged in the middle of the heat conduction block (7851), a first through hole is formed in the axis of the convex shaft and used for being sleeved on the micro-pipeline (781), a second through hole is formed in the middle of the heating piece (7853) and the heat conduction clamping piece (7852) and used for being sleeved on the convex shaft, the inner diameter of the second through hole of the heating piece (7853) is larger than the outer diameter of the convex shaft, and the inner diameter of the second through hole of the heat conduction clamping piece (7852) is equal to the outer diameter of the convex shaft. The heating power of the heating units (785) is provided by electrically controlled heating plates (7853), each heating unit (785) can be independently controlled, and the heating power is adjusted through an electric circuit. Different heating powers correspond to different heat flux densities input to the surface of the microcircuit (781).

6. The supercritical carbon dioxide micro-channel heat exchange experimental system according to claim 5, characterized in that: the wall surface of the heat insulation layer (784) is provided with a gap for connecting the heating sheet (7853) and the temperature thermocouple (7854).

7. The supercritical carbon dioxide micro-channel heat exchange experimental system according to claim 5, characterized in that: the heat conducting block (7851) and the heat conducting clamping piece (7852) are made of the same material with high heat conductivity, and the same material comprises copper, aluminum, copper alloy, aluminum alloy and the like.

8. The supercritical carbon dioxide micro-channel heat exchange experimental system according to claim 5, characterized in that: by adjusting the heating power of the heating unit (785), different heat flow density conditions of the surface of the micro pipeline (781) are realized. By adjusting the distribution of the heating units (785), the axial distribution among local heat flow input areas on the wall surface of the fluid in the micro pipeline (781) and the axial size of the local heat flow input areas are realized, so that different wall surface heat flow conditions are simulated.

9. The supercritical carbon dioxide micro-channel heat exchange experimental system according to claim 8, characterized in that: the wall surface heat flow conditions comprise uniform heat flow conditions, different heat flow density conditions, non-uniform heat flow distribution, periodic heat flow distribution and the like.

10. The supercritical carbon dioxide microchannel heat exchange experimental system according to claims 1-9, wherein: supercritical carbon dioxide may be substituted for the other fluid medium.

Background

Hypersonic aircraft experience intense aerodynamic heating during high-speed flight in the atmosphere. The temperature of these surfaces may locally exceed 1000 degrees celsius when the aircraft is flying at speeds greater than mach 3, and more particularly at hypersonic speeds greater than mach 5. In order to ensure that the aircraft fuselage and its internal environment operate normally within the permitted temperature range, effective structural thermal protection design is required. Typical hypersonic aircraft thermal protection systems can be divided into three categories: passive thermal protection, semi-passive thermal protection, and active thermal protection.

A heat convection mechanism utilizing a supercritical carbon dioxide pipeline belongs to an active thermal protection system. The supercritical carbon dioxide medium is transported by utilizing the micro-channel structure arranged in the thermal protection layer, and heat is taken away and the temperature is reduced through convection heat exchange. For this reason, the heat exchange performance of supercritical carbon dioxide in a microchannel structure needs to be experimentally studied. Meanwhile, aiming at the non-uniform characteristic of pneumatic heating, an experimental system is required to apply the wall boundary condition of non-uniform heat flow to the wall of the experimental section.

Disclosure of Invention

Aiming at the characteristic that the flowing heat transfer of the supercritical carbon dioxide is unevenly heated in the heat protection structure of the hypersonic aircraft and the application requirement, the invention designs a set of complete supercritical carbon dioxide micro-channel heat exchange experimental system which can select horizontal flow or vertical flow and can select different flow directions and simultaneously provide the conditions of the uneven heat flow wall surface.

The technical scheme of the invention is as follows:

a supercritical carbon dioxide micro-channel heat exchange experimental system comprises a carbon dioxide gas supply system and a carbon dioxide working medium circulation test system, wherein the carbon dioxide gas supply system is used for providing a supercritical carbon dioxide working medium; the carbon dioxide working medium circulation test system comprises a total bypass, a vertical micro-channel heat exchange experiment section, a first bypass of the vertical micro-channel heat exchange experiment section, a horizontal micro-channel heat exchange experiment section and a horizontal micro-channel heat exchange experiment section bypass, wherein the inlet of the first bypass of the vertical micro-channel heat exchange experiment section and the inlet of the first bypass of the vertical micro-channel heat exchange experiment section are converged and then connected with the outlet of a carbon dioxide gas supply system, the outlet of the first bypass of the vertical micro-channel heat exchange experiment section and the outlet of the first bypass of the vertical micro-channel heat exchange experiment section are connected with the inlet of the horizontal micro-channel heat exchange experiment section and the inlet of the horizontal micro-channel heat exchange experiment section bypass, and the outlet of the total bypass is connected with the inlet of the carbon dioxide gas supply system after the outlet of the horizontal micro-channel heat exchange experiment section is converged. Wherein, the entry and the export of vertical microchannel heat transfer experiment section, horizontal microchannel heat transfer experiment section all are equipped with the stop valve, are equipped with the stop valve on total bypass, the first bypass of vertical microchannel heat transfer experiment section and the horizontal microchannel heat transfer experiment section bypass for control switching and flow.

The heat exchange performance experiment of the carbon dioxide in the horizontal and/or vertical flowing state can be carried out by adjusting the opening, closing and flow of the total bypass, the vertical micro-channel heat exchange experiment section, the first bypass of the vertical micro-channel heat exchange experiment section, the horizontal micro-channel heat exchange experiment section and the bypass of the horizontal micro-channel heat exchange experiment section.

The vertical microchannel heat exchange experiment section and the horizontal microchannel heat exchange experiment section comprise a micro pipeline, a first heat insulation sleeve, a second heat insulation sleeve, heating units and a heat insulation layer, the two ends of the micro pipeline are communicated with the pipeline of the experiment system, the plurality of heating units are tightly sleeved in the middle of the micro pipeline, and all the heating units are tightly wrapped by the heat insulation layer. The first heat-insulating sleeve and the second heat-insulating sleeve are respectively positioned at two sides of the heating unit and tightly sleeved on the micro pipeline.

Further, the carbon dioxide gas supply system comprises a carbon dioxide gas storage cylinder, a liquid storage tank, a high-pressure pump, a filter and a cooler, wherein supercritical carbon dioxide working medium is stored in the liquid storage tank, a connector above the liquid storage tank is respectively communicated with the carbon dioxide gas storage cylinder and the cooler, a stop valve and a check valve are arranged on a gas outlet pipeline of the carbon dioxide gas cylinder, and a stop valve is arranged on a pipeline between the liquid storage tank and the cooler; an exhaust pipeline is arranged above the liquid storage tank; the outlet below the liquid storage tank is connected with the high-pressure pump, and a stop valve is arranged on the pipeline; the outlet of the high-pressure pump is communicated with the inlet end of the filter, the supercritical carbon dioxide working medium at the outlet of the filter is sent into the carbon dioxide working medium circulation test system, the fluid flowing out of the carbon dioxide working medium circulation test system is sent into the cooler for cooling circulation, and the front end of the inlet of the cooler is provided with a back pressure valve.

Further, the carbon dioxide working medium circulation test system also comprises a flowmeter and a preheater. The flowmeter and the preheater are arranged on a pipeline connected with the inlet of the first bypass of the vertical micro-channel heat exchange experimental section and the outlet of the carbon dioxide gas supply system.

Furthermore, the carbon dioxide working medium circulation test system further comprises a second bypass of the vertical micro-channel heat exchange experimental section, and two ends of the second bypass of the vertical micro-channel heat exchange experimental section are respectively connected with an outlet of the preheater and an outlet of the vertical micro-channel heat exchange experimental section. Through adjusting the opening and closing of the first bypass of the vertical microchannel heat exchange experiment section and the second bypass of the vertical microchannel heat exchange experiment section, the heat exchange performance experiment of carbon dioxide in different flow directions under a vertical flow state can be realized.

Furthermore, the heating unit is composed of a heat conduction block, a heating plate, a heat conduction clamping piece and a temperature thermocouple, wherein the heat conduction block, the heating plate and the heat conduction clamping piece are all disc-shaped, a convex shaft is arranged in the middle of the heat conduction block, the axis of the convex shaft is provided with a first through hole for being sleeved on a micro-pipeline, a second through hole is arranged in the middle of the heating plate and the heat conduction clamping piece for being sleeved on the convex shaft, the inner diameter of the second through hole of the heating plate is larger than the outer diameter of the convex shaft, and the inner diameter of the second through hole of the heat conduction clamping piece is equal to the outer diameter of the convex shaft. The heating power of the heating units is provided by electrically controlled heating plates, each heating unit can be independently controlled, and the heating power is adjusted through a circuit. Different heating powers correspond to different heat flux densities input to the surfaces of the microtubes.

Furthermore, the wall surface of the heat insulation layer is provided with a gap for connecting the heating plate and the temperature thermocouple.

Furthermore, the heat conducting block and the heat conducting clip are made of the same material with high heat conductivity, including copper, aluminum, copper alloy, aluminum alloy and the like.

Furthermore, different heat flux density conditions of the surfaces of the micro pipelines are realized by adjusting the heating power of the heating unit. By adjusting the distribution of the heating units, the axial distribution among the local heat flow input areas on the wall surface of the fluid in the micro-pipeline and the axial size of the local heat flow input areas are realized, so that different wall surface heat flow conditions are simulated.

Further, the wall surface heat flow conditions include uniform heat flow conditions, different heat flow density conditions, non-uniform heat flow distribution, periodic heat flow distribution, and the like.

Further, supercritical carbon dioxide may be substituted for other fluid media.

The invention has the beneficial effects that: the invention provides a supercritical carbon dioxide micro-channel heat exchange experiment system, which can select carbon dioxide working medium to flow horizontally or vertically through bypass adjustment and can select different flow directions to perform heat exchange experiments, and can simulate and provide non-uniform heat flow wall surface conditions through the arrangement of a heating unit, so that the heat exchange performance of the supercritical carbon dioxide in a micro-channel structure closer to the reality can be researched.

Drawings

FIG. 1 is a structural diagram of a supercritical carbon dioxide micro-channel heat exchange experimental system of the present invention;

in the figure, a carbon dioxide gas cylinder 1; a liquid storage tank 2; a high-pressure pump 3; a filter 4; a mass flow meter 5; a preheater 6; a vertical microchannel heat exchange experimental section 7; a horizontal micro-channel heat exchange experimental section 8; a cooler 9; a v1 stop valve; a v2 check valve; a v3 stop valve; v4 throttle valve; v 5-v 15 stop valves; v17 back pressure valve; v18, v19 and v20 stop valves; v21 safety valve; p 1-p 6 pressure transmitter; t 1-t 9 temperature transmitter.

FIG. 2 is an overall structure diagram of a horizontal and vertical microchannel heat exchange experimental section;

FIG. 3 is an exploded view of a horizontal and vertical microchannel heat exchange experimental section;

in the figure, micro-pipe 781; a first insulating sleeve 782; a second insulative sleeve 783; a thermal insulation layer 784; a heating unit 785.

FIG. 4 is a sectional view of a horizontal and vertical microchannel heat exchange experimental section;

in the figure, micro-pipe 781; a first insulating sleeve 782; a second insulative sleeve 783; a thermal insulation layer 784; a heating unit 785.

FIG. 5 is an exploded view of the heating unit;

in the figure, the heat-conducting block 7851; a heating plate 7853; a thermally conductive clip 7852; a temperature thermocouple 7854.

FIG. 6 is a schematic diagram of the working principle of the heating experimental section;

in the figure, the direction of the arrows and their magnitudes represent the heat flow conduction direction and their magnitudes; the same heating unit 785 has a uniform heat flow on the inner cylindrical surface in contact with the micro-pipe 781.

FIG. 7 is a schematic diagram of a heating unit arrangement for heating an experimental section;

in the figure, the distance between the heating units 785 can be adjusted according to the experimental heat flow requirement, and a plurality of heating units 785 can be closely attached to use, so that local or overall uniform heat flow is realized.

Detailed Description

The invention is further described with reference to the following detailed description and the accompanying drawings.

As shown in fig. 1, a supercritical carbon dioxide micro-channel heat exchange experimental system comprises a carbon dioxide gas supply system and a carbon dioxide working medium circulation test system; the device comprises a carbon dioxide gas storage cylinder 1, a liquid storage tank 2, a high-pressure pump 3, a filter 4, a mass flow meter 5, a preheater 6, a vertical micro-channel heat exchange experimental section 7, a horizontal micro-channel heat exchange experimental section 8, a cooler 9, a pressure transmitter, a temperature transmitter, a valve and other auxiliary equipment.

Carbon dioxide working medium used for experimental circulation test is stored in a liquid storage tank 2, a connector above the liquid storage tank 2 is respectively communicated with a carbon dioxide gas storage bottle 1 and a cooler 9, a stop valve v1 and a check valve v2 are arranged on an air outlet pipeline of the carbon dioxide gas storage bottle 1, and a stop valve v19 is arranged on a pipeline between the liquid storage tank 2 and the cooler 9; an exhaust pipeline is arranged above the liquid storage tank 2, a pressure transmitter p1 is arranged on the exhaust pipeline and is divided into two branches, one branch is provided with a safety valve v21, and the other branch is provided with a stop valve v20 and an exhaust port; the outlet at the lower part of the liquid storage tank 2 is connected with the high-pressure pump 3, and a stop valve v3 is arranged on the pipeline; the outlet of the high-pressure pump 3 is communicated with the inlet end of the filter 4.

The carbon dioxide working medium circulation test system is divided into an experiment section main path and a main bypass, and the experiment section main path and the main bypass are both connected with the outlet of the filter 4; the main path and the main bypass of the experimental section are finally gathered at the front end of a back pressure valve v 17; the back pressure valve v17 has its rear end connected to the cooler 9, and a shutoff valve v18 is provided on the pipe.

A bypass throttle valve v16 is arranged on the main bypass, and a main throttle valve v4 is arranged on the main road; the high-pressure pump 3, the main path throttle valve v4, the bypass throttle valve v16 and the backpressure valve v17 work together to adjust the pressure and flow required by the experiment in the experimental section.

In the main path, the rear end of the main path throttle valve is connected with the inlet of a mass flowmeter 5, and the outlet of the mass flowmeter 5 is connected with the inlet of a preheater 6; an outlet pipeline of the preheater 6 is divided into two paths, one branch is a first branch of the vertical microchannel heat exchange experimental section 7, and a stop valve v7 is arranged; the other branch is communicated with the stop valve v6, the rear end of the stop valve v6 is divided into two branches again, one branch is a second bypass v11 of the vertical micro-channel heat exchange experimental section 8, and the other branch is a main branch of the vertical micro-channel heat exchange experimental section 8.

A stop valve v11 is arranged on a second bypass of the vertical micro-channel heat exchange experimental section 7; a stop valve v8 is arranged on the main path of the vertical micro-channel heat exchange experimental section 7 and is communicated with an interface below the vertical micro-channel heat exchange experimental section 7; the upper part of the vertical microchannel heat exchange experimental section 8 is communicated with a stop valve v9, and the stop valve v10 is gathered at the front end of the stop valve v10 together with the first bypass of the vertical microchannel heat exchange experimental section 7.

The second bypass of the vertical micro-channel heat exchange experimental section 7 and the rear end of the stop valve v10 are gathered in the main path of the experimental section and communicated with the main path of the horizontal micro-channel heat exchange experimental section 8 and the bypass of the horizontal micro-channel heat exchange experimental section 8.

A stop valve v13 is arranged on a bypass of the horizontal micro-channel heat exchange experimental section 8, and two ends of the stop valve v13 are respectively gathered with the main circuit of the horizontal micro-channel heat exchange experimental section 8 in the main circuit of the experimental section; the inlet of the main path of the horizontal micro-channel heat exchange experimental section 8 is communicated with a stop valve v12, and the outlet of the main path is communicated with a stop valve v 14;

the main path of the horizontal micro-channel heat exchange experimental section 8 and the bypass outlet end of the horizontal micro-channel heat exchange experimental section 8 are gathered in the main path of the experimental section and are communicated with a stop valve v 15; the back end outlet and the main bypass of the stop valve v15 are gathered at the front end of the back pressure valve v 17.

The vertical microchannel heat exchange experimental section 7 and the horizontal microchannel heat exchange experimental section 8 have the same structural composition, and as shown in fig. 2 to 4, each vertical microchannel heat exchange experimental section consists of a micro pipeline 781, a first heat insulation sleeve 782, a second heat insulation sleeve 783, a heating unit 785 and a heat insulation layer 784.

The two ends of the micro pipeline 781 are communicated with the pipeline of the experimental system, a plurality of heating units 785 are tightly sleeved in the middle of the micro pipeline 781, all the heating units 785 are tightly wrapped by a heat insulating layer 784 to form a heating experimental section, a first heat insulating sleeve 782 and a second heat insulating sleeve 783 are tightly sleeved on the micro pipeline 781, and the two ends of each heating unit 785 form first and second heat insulating forgings. Each hole shaft is matched between the original pieces and can move.

The first insulating sleeve 782, the second insulating sleeve 783 and the insulating layer 784 are made of a thick, extremely low thermal conductivity insulating material, and can reduce the experimental heat loss to an extremely low value. The first heat insulation section and the second heat insulation section are set so that fluid flow of the inlet and the outlet can be fully developed. The wall surface of the heat insulation layer 784 is provided with a narrow gap for connecting the heating plate 7853 and the temperature thermocouple 7854.

The heating unit 785 is composed of a heat conduction block 7851, a heating piece 7853, a heat conduction clamping piece 7852 and a temperature thermocouple 7854, and the heat conduction block 7851 and the heat conduction clamping piece 7852 are made of the same material with high heat conductivity and are formed in a machining mode. The heat conducting block 7851, the heating plate 7853 and the heat conducting clamping piece 7852 are all disc-shaped, a protruding shaft is arranged in the middle of the heat conducting block 7851, a first through hole is formed in the axis of the protruding shaft and used for being sleeved on the micro pipeline 781, and a second through hole is formed in the middle of the heating plate 7853 and the heat conducting clamping piece 7852 and used for being sleeved on the protruding shaft. The second through hole of the heating plate 7853 is larger than the outer diameter of the protruding shaft, and the second through hole of the heat conduction clamping piece is tightly matched with the protruding shaft, so that heat flow of the heating plate 7853 is mainly and uniformly conducted to the heat conduction block 7851 and the heat conduction clamping piece 7852 from two sides, and the heating plate 7853 does not generate installation interference on the temperature thermocouple 7854 attached to the surface of the protruding shaft, which is involved in temperature measurement. As shown in fig. 5, the heat conducting block 7851, the heating plate 7853 and the heat conducting clip 7852 are coaxially and closely mounted, the heat conducting clip 7852 is tightly sleeved on the protruding shaft of the heat conducting block 7851, and the heating plate 7853 is clamped between the heat conducting block 7851 and the heat conducting clip 7852. Temperature thermocouple 7854 is mounted on the convex shaft surface of heat conducting block 7851 and is axially mounted in the center of heat conducting block 7851 and heat conducting clip 7852.

The heating power of the heating units 785 is provided by electrically controlled heating fins 7853, each heating unit 785 being independently controllable, the heating power being adjusted by the electrical circuit. Different heating powers correspond to different heat flux densities input to the surface of the micro-duct 781. Under the condition of certain heating power, the temperature of the inner diameter surface of the heating unit 785 is uniformly distributed, and the heat flow conducted to the interior of the micro-tube is uniformly distributed. Due to the high thermal conductivity characteristics of the heat-conducting block 7851 and the heat-conducting clips 7852, and the fact that most of the surface of the heat-conducting plate 7853 is in contact with the heat-conducting block 7851 and the heat-conducting clips 7852, the heat generated by the heat-conducting plate 7853 is mainly conducted to the heat-conducting block 7851 and the heat-conducting clips 7852. Because the outer ring of the heating unit 785 is wrapped by the heat insulation layer 784, and the inner diameter surface of the heating unit is in close contact with the micro-pipeline 781 with high heat conduction capacity, and meanwhile, the medium in the pipeline continuously takes away heat during the experiment, so that the main heat is conducted to the fluid medium in the pipeline through the contact surface of the heating unit 785 and the micro-pipeline 781. The temperature thermocouple 7854 is installed on the surface of the protruding shaft of the heat conducting block 7851, and the temperature data of the inner wall surface of the micro-pipeline 781, which is obtained through experimental analysis, can be calculated by directly measuring the temperature of the surface of the protruding shaft and utilizing the steady-state heat conducting condition.

Different heat flux density conditions of the surface of the micro pipeline 781 are realized by using the heating unit 785 with adjustable heating power. The axial distribution adjustment between local heat flow input areas on the wall surface of the fluid in the micro-pipeline 781 is realized by utilizing the characteristic that the heating element can move and adjust relative to the micro-pipeline 781 in the axial direction.

As shown in fig. 6-7, by utilizing the feature that the heating unit 785 can be adjusted by moving axially relative to the micro-pipe 781, a plurality of heating units 785 can be closely attached and combined, each heating unit 785 provides the same heating power to realize local uniform heat flow, the axial size of the uniform heat flow input area can be adjusted by increasing or decreasing the number of the attached heating units 785, and the distance between the uniform input areas can be adjusted by moving. A plurality of heating units 785 are tightly attached to fill the whole heating experiment section, and heating conditions for heating the experiment section to achieve uniform heat flux density can be achieved. Meanwhile, non-uniform heating may be achieved by adjusting heating power, distribution, etc. of the heating unit 785.

The vertical micro-channel heat exchange experiment section 7 and the horizontal micro-channel heat exchange experiment section 8 can respectively conduct research on supercritical carbon dioxide in the channel based on complex wall surface heat flow conditions in a vertical and horizontal state, such as uniform heat flow conditions, different heat flow density conditions, non-uniform heat flow distribution, periodic heat flow distribution, axial size of a heat flow area and the like.

After the experiment system is built, the experiment system is required to be well carried out for the normal operation of the experiment: pipeline cleaning, heat preservation measures and experimental working condition pre-estimation, and distribution and interval adjustment work of the heating units 785 in the micro-channel heat exchange experimental section.

After the preparation work is finished, the experimental operation process is as follows:

(1) the cooler 9 is started, a cooling coil valve on the liquid storage tank 2 is opened, the liquid storage tank 2 is pre-cooled, and the temperature is kept at 5-10 DEG C

And (5) cold state.

(2) And opening the carbon dioxide gas cylinder to charge the liquid storage tank 2 until the pressure reaches 4MPa, and keeping the gas cylinder valve open to continuously charge gas so as to condense and liquefy the carbon dioxide gas entering the liquid storage tank 2.

(3) Closing the stop valve v15 and the throttle valve v4, opening the throttle valve v16, adjusting the pressure of a back pressure valve v17 to 4-5 MPa, opening the stop valves v3, v18 and v19, operating the high-pressure pump 3 at a low flow rate to enable carbon dioxide gas in the carbon dioxide gas cylinder to continuously enter a pipeline, closing the stop valve v1 at the outlet of the carbon dioxide gas storage cylinder 1 after a period of time, and then stopping operating the high-pressure pump 3, wherein liquid carbon dioxide which meets the experimental operation demand is fully contained in the liquid storage cylinder 2 at the moment.

(4) And powering up the experimental data acquisition system.

(5) And (3) opening a corresponding pipeline valve, selecting a horizontal micro-channel heat exchange experimental section 8 or a vertical micro-channel heat exchange experimental section 7 through the opening and closing of the stop valves v 6-v 14, and selecting the flow direction of the working medium from bottom to top or from top to bottom through the opening and closing of the stop valves v 6-v 11 if the vertical micro-channel heat exchange experimental section 7 is selected.

(6) The high-pressure pump 3 is started, the flow is set, the backpressure valve v17 and the throttle valves v4 and v16 on the main bypass are adjusted, and the pressure flow parameters of the experimental section meet the experimental requirements.

(7) And starting a power supply system corresponding to the preheater 6 and each heating unit 785 of the micro-channel experimental section, adjusting the power of the preheater 6 until the inlet temperature of the experimental section reaches an experimental preset value, and adjusting the heating power of each heating unit 785 to reach the experimental preset value.

(8) And when the temperature of the inlet and the outlet of the fluid at the experimental section and the temperature measured by a thermocouple temperature sensor on the heating unit 785 are stable, recording experimental data.

(9) And adjusting the experimental parameters to the next working condition.

(10) After the experimental data acquisition is finished, the heating system and the preheater 6 are firstly closed, then the back pressure valve v17 is adjusted to reduce the pipeline pressure to 5MPa, the high-pressure pump 3 is closed, and finally the cooler 9 and the data acquisition system are closed.

(11) The power supply of each device of the experimental system is cut off, and if the experimental system does not carry out experiments for a long time, the carbon dioxide in the loop and the liquid storage tank 2 needs to be emptied.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should all embodiments be exhaustive. And obvious variations or modifications of the invention may be made without departing from the scope of the invention.