A platform for measuring characteristics of forced heat exchange of a cross-flow tube bundle

Abstract

The application provides a cross-flow tube bundle forced heat exchange characteristic test platform, which comprises a low-temperature conveying system, a high-temperature conveying system and a high-air-tightness experimental device; the high-air-tightness experimental device comprises an air distributor, a stabilizing section, a compression section, an air rectifier, a transverse pitch scale, a longitudinal pitch scale, a cross-flow tube bundle and a differential pressure gauge; one end of the air distributor is communicated with the high-temperature conveying system; the other end of the air distributor is communicated with a convection heat exchange area through the stabilizing section, the compression section and the air rectifier in sequence; the convection heat exchange area is composed of a plurality of cross-flow tube bundles which are distributed in a three-dimensional staggered manner; the cross-flow tube bundle is clamped and installed on a wall surface through the transverse pitch scale and the longitudinal pitch scale; the low-temperature conveying system is communicated with an inlet of the convection heat exchange area; the differential pressure gauge is installed at the inlet and outlet of the cross-flow tube bundle and is used for measuring the pressure difference in the cross-flow tube bundle. The application can realize cross-flow tube bundle forced heat exchange characteristic experiments of large heat exchange temperature difference, various flexible tube bundle pitches and various heat exchange materials.

Description

Technical Field

[0001] This invention relates to the field of heat exchanger testing technology, and in particular to a test platform for the forced heat transfer characteristics of swept tube bundles. Background Technology

[0002] Low energy efficiency, poor economic benefits, and severe environmental pollution are the main problems in my country's energy development and utilization. The industrial waste heat generated during my country's economic construction and industrial production has not been fully recovered and utilized, resulting in a significant waste of thermal energy resources. Currently, waste heat recovery technologies mainly include heat exchange technology, waste heat refrigeration and heating technology, and heat-to-work conversion technology.

[0003] As a typical device for recovering waste heat most directly and efficiently in heat exchange technology, the core technology of heat pipe heat exchangers—forced heat transfer characteristics across tube bundles—is a key focus of experimental research. Existing technologies disclose devices for testing the flow and boiling characteristics of refrigerants across tube bundles, but these cannot achieve temperature regulation and multi-condition control. Existing technologies disclose a teaching experimental device and method for forced convection of air across a single tube, but this can only study the heat transfer characteristics of a single tube bundle, has a small temperature difference, and lacks supporting facilities such as pre-experiment airtightness checks and device initialization.

[0004] Existing forced heat transfer experimental devices with transverse tube bundles suffer from problems such as small convective heat transfer temperature difference and limited heat transfer materials, which restrict the heat transfer optimization design of heat pipe heat exchangers and reduce waste heat recovery efficiency. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a transverse tube bundle forced heat transfer characteristic testing platform that is easy to install and test, has convenient and reliable tube bundle pitch adjustment, large convective heat transfer temperature difference, and can also be used to test the heat transfer performance of various heat transfer materials.

[0006] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0007] A test platform for forced heat transfer characteristics of swept tube bundles includes a cryogenic delivery system, a high-temperature delivery system, and a high-airtightness experimental device.

[0008] The high airtightness experimental apparatus includes an air distributor, a stabilization section, a compression section, an air rectifier, a transverse pitch gauge, a longitudinal pitch gauge, a transverse tube bundle, and a differential pressure gauge. One end of the air distributor is connected to the high-temperature delivery system. The other end of the air distributor is connected to the convective heat transfer region via the stabilization section, the compression section, and the air rectifier. The convective heat transfer region is composed of several transverse tube bundles arranged in a three-dimensional staggered pattern. The transverse tube bundles are clamped and installed on the wall surface by the transverse pitch gauge and the longitudinal pitch gauge. The fastening bolts are used to fix the longitudinal pitch. The low-temperature delivery system is connected to the inlet of the convective heat transfer region. The differential pressure gauge is installed at the inlet and outlet ends of the transverse tube bundles to measure the pressure difference within the transverse tube bundles.

[0009] Furthermore, the cryogenic delivery system includes a nitrogen cylinder, a subcooling section, and a molecular pump; the subcooling section includes a subcooler, a second thermometer, a second pressure gauge, and a third pressure gauge; the inlet of the subcooling section is connected to the nitrogen cylinder, and the nitrogen temperature is adjusted through the subcooler; the outlet of the subcooling section is connected to the inlet of the convection heat transfer zone, used to check the airtightness of the high airtightness experimental device and adjust the temperature distribution within the convection heat transfer zone; the jacket of the subcooler is connected to the inlet of the molecular pump through the third pressure gauge and the vacuum valve of the subcooler insulation jacket; the inlet of the molecular pump is connected to the inlet of the convection heat transfer zone through the vacuum valve, used to evacuate air from the high airtightness experimental device; a second thermometer and a second pressure gauge are respectively installed between the outlet of the subcooler and the inlet of the convection heat transfer zone.

[0010] Furthermore, the high-temperature conveying system includes an electric heating boiler, a centrifugal pump, and a temperature regulator; the electric heating boiler is located at the inlet of the centrifugal pump and is used to heat the medium entering the centrifugal pump; the outlet of the centrifugal pump is divided into two branches by an inlet three-way valve, one branch of the centrifugal pump outlet is connected to the inlet of a pressure relief three-way valve through a first flow meter and a first shut-off valve; the other branch of the centrifugal pump outlet is connected to the inlet of a pressure relief three-way valve through a temperature regulator, a second flow meter, and a second shut-off valve; one outlet of the pressure relief three-way valve is connected to an air distributor, and the other outlet of the pressure relief three-way valve is used to discharge steam.

[0011] Furthermore, the anti-slip coating is applied to the clamping surface of the transverse pitch ruler that holds the transverse tube bundle.

[0012] Furthermore, the swept tube bundle includes a graphite tube and a thermocouple, the graphite tube having a heat transfer material coating on its outer side; and at least one thermocouple is installed on the inner surface of the graphite tube.

[0013] Furthermore, a condensate drain valve is provided at the bottom of the convection heat exchange area to collect and drain the condensate generated during the heat exchange experiment.

[0014] Furthermore, the subcooler is used for nitrogen cooling based on the principle of reduced pressure refrigeration, and the formula for calculating the refrigeration power Q of the subcooler is as follows:

[0015] Q = (Q 漏 +c p工 ΩA(T1-T2)) / t

[0016] Among them, Q 漏 The unavoidable heat leakage from the subcooler; c p工 Ω is the specific heat capacity of nitrogen in the subcooler at the working pressure; A is the cross-sectional area of ​​the pipeline; T1 is the nitrogen temperature at the inlet of the subcooler; T2 is the nitrogen temperature at the outlet of the subcooler; and t is the time for depressurization and cooling.

[0017] Furthermore, the pumping speed required by the molecular pump during the heat exchange experiment is not less than the pumping speed S required for the subcooler's refrigeration operation. The formula for calculating the subcooler's refrigeration pumping speed S is as follows:

[0018]

[0019] Where Q is the cooling power of the subcooler, r sen The sensible heat of nitrogen gas during pressure changes within the subcooler, ρ g The density of nitrogen gas at the outlet of the subcooler is given.

[0020] Furthermore, it also includes a data acquisition system, which acquires the current signals generated by the first flow meter and the second flow meter; the data acquisition system acquires the current signals of the pressure sensors on the first pressure gauge, the second pressure gauge, the third pressure gauge, and the differential pressure gauge; the data acquisition system acquires the voltage signals of the temperature sensors on the first thermometer and the second thermometer; and the data acquisition system acquires the voltage signals generated by the thermocouples on the transverse tube bundle.

[0021] An experimental method for testing the forced heat transfer characteristics of a transverse tube bundle includes the following steps:

[0022] Air tightness check: Control the first shut-off valve, the second shut-off valve, the supercooler jacket evacuation valve and the experimental section regulating valve to close, and control the molecular pump and the experimental section vacuum evacuation valve to evacuate the air from the high air tightness experimental device.

[0023] After the air is evacuated from the high airtightness experimental device, the vacuum evacuation valve of the control experimental section is closed, and the regulating valve and nitrogen inlet valve of the control experimental section are activated to check for leaks in the high airtightness experimental device and remove the remaining air.

[0024] Tube bundle temperature control and precooling: Control the operation of the molecular pump and the vacuum pump valve in the supercooler jacket, and close the vacuum pump valve in the experimental section to keep the pressure inside the supercooler jacket below 10. -3 Pa; control the nitrogen inlet valve to adjust the nitrogen temperature in the subcooler to a set value T2', and use the second thermometer to check the nitrogen temperature; when the nitrogen temperature is stable, close the subcooler jacket exhaust valve and molecular pump, and monitor the pressure index of the third pressure gauge; the nitrogen in the subcooler enters the convection heat transfer area through the experimental section regulating valve, and the real-time temperature of the tube bundle is monitored by thermocouples on the inner wall of the tube bundle until it drops to the predetermined temperature T2, and the input of low-temperature nitrogen is maintained;

[0025] Temperature-controlled steam input: Determine the steam temperature as T1 based on the predetermined heat exchange temperature difference ΔT; open the electric heating boiler, boiler exhaust valve, and first shut-off valve; control the inlet three-way valve to connect the centrifugal pump outlet to the pressure relief three-way valve inlet through the first flow meter and the first shut-off valve; control the pressure relief three-way valve outlet to connect to the discharge circuit; determine whether the steam temperature has reached the predetermined temperature T1 by reading the temperature value of the first thermometer; if the temperature does not match, control the inlet three-way valve to connect the centrifugal pump outlet to the pressure relief three-way valve inlet through the temperature regulator, the second flow meter, and the second shut-off valve; adjust the steam temperature to T1 using the temperature regulator, and monitor the steam indicators of the first thermometer and the first pressure gauge; simultaneously monitor the first or second flow meter to adjust the centrifugal pump to achieve the required steam flow rate;

[0026] Convection heat transfer experiment: When the steam temperature and flow rate meet the experimental requirements, open the condensate drain valve, close the nitrogen inlet valve and the experimental section regulating valve, and control the outlet of the pressure relief three-way valve to connect with the high airtightness experimental device, so that steam at temperature T1 enters the transverse tube bundle to start forced convection heat transfer. The data acquisition system records the temperature change on the transverse tube bundle and the pressure difference change of the differential pressure gauge; adjust the pressure and flow rate of the steam input into the high airtightness experimental device for experiments under different steam conditions at different temperatures.

[0027] The beneficial effects of this invention are as follows:

[0028] The forced heat transfer characteristic testing platform for swept tube bundles described in this invention utilizes uncooled nitrogen gas to check the airtightness of the swept tube bundle convective heat transfer experimental system. A three-way valve is installed at the centrifugal pump outlet, allowing for steam temperature regulation using a temperature controller; nitrogen gas, after being regulated by the subcooler, can regulate the temperature of the swept tube bundle, thereby adjusting the convective heat transfer temperature difference between the tube bundle and the steam. Graduations are machined on both the transverse and longitudinal pitch rulers, and the clamping surface of the transverse pitch ruler is coated with an anti-slip coating. Combined with the fastening bolts, various pitch combinations, such as staggered and parallel arrangements of the swept tube bundles, can be achieved. The swept tubes use graphite as a substrate, with heat transfer materials of varying thicknesses sprayed onto the outer wall, enabling forced heat transfer characteristic experiments with various heat transfer materials. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are some embodiments of the present invention. For those skilled in the art, it is obvious that other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 This is a frame diagram of the transverse tube bundle forced heat transfer characteristic testing platform described in this invention.

[0031] Figure 2 This is a partial schematic diagram of the sweep tube described in this invention.

[0032] Figure 3 This is a schematic diagram of the data acquisition system described in this invention.

[0033] In the picture:

[0034] 1-Electric heating boiler; 101-Boiler exhaust valve; 102-Inlet three-way valve; 103-First shut-off valve; 104-Second shut-off valve; 2-Nitrogen cylinder; 201-Nitrogen inlet valve; 3-High airtightness experimental device; 301-Air distributor; 302-Stabilization section; 303-Compression section; 304-Air rectifier; 305-Transverse pitch gauge; 306-Longitudinal pitch gauge; 307-Swept tube bundle; 3071-Graphite round tube; 3072-Heat transfer material coating; 3073-Thermocouple; 308-Differential pressure gauge; 309- Fastening bolts; 310 - Anti-slip coating; 311 - First thermometer; 312 - First pressure gauge; 313 - Condensate drain valve; 314 - Experimental section vacuum extraction valve; 315 - Pressure relief three-way valve; 4 - Subcooling section; 401 - Subcooler; 402 - Second thermometer; 403 - Second pressure gauge; 404 - Third pressure gauge; 405 - Subcooler insulation jacket extraction valve; 406 - Experimental section regulating valve; 5 - Centrifugal pump; 6 - First flow meter; 7 - Second flow meter; 8 - Temperature regulator; 9 - Molecular pump; 10 - Data acquisition system. Detailed Implementation

[0035] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0036] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "axial," "radial," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0037] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0038] like Figure 1 As shown, the transverse tube bundle forced heat transfer characteristic test platform of the present invention includes a low temperature conveying system, a high temperature conveying system and a high airtightness test device 3.

[0039] The high airtightness experimental device 3 includes an air distributor 301, a stabilizing section 302, a compression section 303, an air rectifier 304, a transverse pitch gauge 305, a longitudinal pitch gauge 306, a cross-flow tube bundle 307, and a differential pressure gauge 308. One end of the air distributor 301 is connected to the high-temperature delivery system. The other end of the air distributor 301 is connected to the convective heat transfer region via the stabilizing section 302, the compression section 303, and the air rectifier 304. The convective heat transfer region is composed of several cross-flow tube bundles 307 arranged in a three-dimensional staggered pattern. The cross-flow tube bundles 307 are clamped and installed on the wall surface by the transverse pitch gauge 305 and the longitudinal pitch gauge 306. The low-temperature delivery system is connected to the inlet of the convective heat transfer region. The differential pressure gauge 308 is installed at the inlet and outlet ends of the cross-flow tube bundles 307 and is used to measure the pressure difference within the cross-flow tube bundles 307. The constant-temperature steam is uniformly fed into the stabilization section 302 through the air distributor 301, and then compressed by the compression section 303 before entering the convection heat transfer zone for convection heat transfer and related parameter measurement. A condensate drain valve 313 is provided at the bottom of the convection heat transfer zone to collect and drain the condensate generated during the heat transfer experiment.

[0040] The longitudinal pitch gauge 306 is movably mounted on the upper and lower walls of the convective heat transfer region. Several transverse pitch gauges 305 are arranged on the longitudinal pitch gauges 306 on the upper and lower walls, forming a three-dimensional staggered convective heat transfer region. The transverse pitch gauges 305 are fixed with fastening bolts 309 to clamp the transverse tube bundle 307; the clamping surface of the transverse pitch gauges 305 is coated with the anti-slip coating 310. By adjusting the spacing of the transverse tube bundle 307, the forced heat transfer characteristics of the transverse tube bundle 307 at different pitches can be studied.

[0041] like Figure 2 As shown, the transverse tube bundle 307 includes a graphite tube 3071 and thermocouples 3073. The graphite tube 3071 is provided with a heat transfer material coating 3072 on its outer side; and several thermocouples 3073 are installed on the inner surface of the graphite tube 3071.

[0042] The cryogenic delivery system includes a nitrogen cylinder 2, a subcooling section 4, and a molecular pump 9. The subcooling section 4 includes a subcooler 401, a second thermometer 402, a second pressure gauge 403, and a third pressure gauge 404. The inlet of the subcooling section 4 is connected to the nitrogen cylinder 2, and the nitrogen temperature is regulated by the subcooler 401. A nitrogen inlet valve 201 is installed at the outlet of the nitrogen cylinder 2. The outlet of the subcooling section 4 is connected to the inlet of the convection heat transfer zone, used to check the airtightness of the high airtightness experimental device 3 and to regulate the temperature distribution within the convection heat transfer zone. The jacket of the subcooler 401 is connected to the inlet of the molecular pump 9 through the third pressure gauge 404 and the subcooler insulation jacket evacuation valve 405. The inlet of the molecular pump 9 is connected to the inlet of the convection heat transfer zone through a vacuum evacuation valve 314, used to evacuate air from the high airtightness experimental device 3. The second thermometer 402 and the second pressure gauge 403 are respectively installed between the outlet of the subcooler 401 and the inlet of the convection heat transfer zone.

[0043] The high-temperature conveying system includes an electric heating boiler 1, a centrifugal pump 5, and a temperature regulator 8. The electric heating boiler 1 is located at the inlet of the centrifugal pump 5 and is used to heat the medium entering the centrifugal pump 5. A grate waste valve 101 is provided at the inlet of the electric heating boiler 1 to regulate wastewater discharge. One branch of the outlet of the centrifugal pump 5 is connected to the inlet of a pressure relief three-way valve 315 through a first flow meter 6 and a first shut-off valve 103. The other branch of the outlet of the centrifugal pump 5 is connected to the inlet of the pressure relief three-way valve 315 through the temperature regulator 8, a second flow meter 7, and a second shut-off valve 104. One outlet of the pressure relief three-way valve 315 is connected to an air distributor 301, and the other outlet of the pressure relief three-way valve 315 is used to discharge steam. The pressure relief three-way valve 315 can be used to regulate the steam before the experiment.

[0044] like Figure 1 As shown, the outlet of the centrifugal pump 5 is connected to the inlet three-way valve 102. One outlet of the inlet three-way valve 102 is connected to the inlet of the pressure relief three-way valve 315 through the first flow meter 6 and the first shut-off valve 103. The other outlet of the inlet three-way valve 102 is connected to the inlet of the pressure relief three-way valve 315 through the temperature regulator 8, the second flow meter 7 and the second shut-off valve 104.

[0045] The subcooler 401 is used for nitrogen cooling based on the principle of reduced pressure refrigeration. The calculation formula for the refrigeration power Q of the subcooler 401 is as follows:

[0046] Q = (Q 漏 +c p工 ΩA(T1-T2)) / t

[0047] Among them, Q 漏 The heat leakage from the subcooler 401 due to radiation, conduction, and residual gas transfer in the insulation jacket is unavoidable and is generally determined by referring to a table; c p工Ω is the specific heat capacity of nitrogen in the subcooler 401 at the working pressure; A is the total mass flow rate of nitrogen required to check the airtightness of the high airtightness test device 3; T1 is the nitrogen temperature at the inlet of the subcooler 401, which can be obtained by a temperature sensor; T2 is the nitrogen temperature at the outlet of the subcooler 401; and t is the time for depressurization and cooling.

[0048] The pumping speed required by the molecular pump 9 during the heat exchange experiment shall not be less than the pumping speed S required by the subcooler 401 for refrigeration operation. The formula for calculating the refrigeration pumping speed S of the subcooler 401 is as follows:

[0049]

[0050] Where Q is the cooling power of the subcooler 401, and r sen The sensible heat of nitrogen gas during pressure changes within the subcooler 401, ρ g The density of nitrogen at the outlet of the supercooler 401.

[0051] like Figure 3 As shown, it also includes a data acquisition system 10, which acquires the current signals generated by the first flow meter 6 and the second flow meter 7; the data acquisition system 10 acquires the current signals of the pressure sensors on the first pressure gauge 312, the second pressure gauge 403, the third pressure gauge 404, and the differential pressure gauge 308; the data acquisition system 10 acquires the voltage signals of the temperature sensors on the first thermometer 311 and the second thermometer 402; and the data acquisition system 10 acquires the voltage signal generated by the thermocouple 3071 on the transverse tube bundle 307.

[0052] An experimental method for testing the forced heat transfer characteristics of a transverse tube bundle includes the following steps:

[0053] (1) Pre-experimental preparation: Centered on the inlet three-way valve 102, check the pipe connections of its left inlet circuit, right outlet circuit, lower outlet circuit, and steam discharge circuit; centered on the subcooler 401, check the pipe connections of its vacuum insulation jacket evacuation circuit and nitrogen charging circuit for the experimental section; centered on the high airtightness experimental device 3, check the pipe connections of the experimental section vacuum evacuation circuit and condensate discharge circuit. Adjust the transverse tube bundle pitch flexibly according to experimental requirements, and spray a heat transfer material coating onto the graphite tubes. Close the first shut-off valve 103, the second shut-off valve 104, the subcooler jacket evacuation valve 405, and the experimental section regulating valve 406, and turn on the molecular pump 9 and the experimental section vacuum evacuation valve 314 to pre-evacuate the air from the experimental section. Provided that nitrogen cylinder 2 is filled with the nitrogen required for the experiment, open nitrogen inlet valve 201 and experimental section regulating valve 406, close experimental section vacuum extraction valve 314, and at the same time, supercooler 401 does not need to work. It supplies high-pressure nitrogen to the experimental section for leak detection and completely purges the air in the experimental system to prevent freezing and blockage.

[0054] (2) Tube bundle temperature control and pre-cooling: After completing the airtightness check, open the supercooler jacket evacuation valve 405 and the molecular pump 9, keep the experimental section vacuum evacuation valve 314 closed, and evacuate the vacuum insulation jacket pressure of the supercooler 401 to 10. -3 Below Pa, the subcooler 401 is activated to adjust the nitrogen temperature to a set value T2', and the nitrogen temperature is checked using the second thermometer 402. When the nitrogen temperature remains stable, the subcooler jacket evacuation valve 405 and the molecular pump 9 are closed, and the pressure reading of the third pressure gauge 404 is monitored. The real-time temperature of the tube bundle is monitored using the patch thermocouple 3073 on the inner wall of the tube bundle until it drops to the predetermined temperature T2, while maintaining the input of cryogenic nitrogen.

[0055] (3) Temperature-adjusting steam input: The steam temperature T1 is calculated based on the predetermined heat exchange temperature difference ΔT. The electric heating boiler 1, boiler exhaust valve 101, and first shut-off valve 103 are opened. The inlet three-way valve 102 is turned to the right inlet circuit, and the pressure relief three-way valve 315 is turned to the steam discharge circuit. The steam temperature is checked by reading the temperature value of the first thermometer 311 to determine if the predetermined temperature T1 has been reached. If the temperature does not match, the inlet three-way valve 102 is switched to the lower outlet circuit, and the second shut-off valve 104 is opened. The steam temperature is adjusted to T1 by the temperature regulator 8, and the steam parameters of the first thermometer 311 and the first pressure gauge 312 are monitored. Simultaneously, the first flow meter 6 or the second flow meter 7 needs to be monitored to adjust the centrifugal pump 5 to achieve the required steam flow rate.

[0056] (4) Convection heat transfer experiment: When the steam temperature and flow rate meet the experimental requirements, open the condensate drain valve 313, close the nitrogen inlet valve 201 and the experimental section regulating valve 406, and simultaneously quickly switch the pressure relief three-way valve 315 to the inlet pipeline of the high airtightness experimental device 3, so that steam at temperature T1 enters the transverse tube bundle to begin forced convection heat transfer. Input instructions to the data acquisition system 10 to start recording experimental data such as temperature changes on the transverse tube bundle 307 and pressure difference changes on the differential pressure gauge 308. Adjusting the first shut-off valve 103 (no temperature adjustment) or the second shut-off valve 104 (temperature adjustment) can achieve steam conditions with different pressures and flow rates, and adjusting the temperature regulator 8 can achieve steam conditions with different temperatures.

[0057] (5) Heat exchange experiment stops: When the temperature data fed back by the patch thermocouple 3703 no longer changes, it indicates that the convective heat exchange has been completed. Then, turn the pressure relief three-way valve 315 to the steam discharge circuit and turn off the power to the electric heating boiler 1. When the value of the first pressure gauge 312 gradually decreases to zero or the values ​​of the first flow meter 6 and the second flow meter 7 gradually approach zero, turn off the power to the centrifugal pump 5. After all pipelines and the cross tube bundle 307 return to normal temperature, close the condensate discharge valve 313 after all the condensate has been discharged. After using the nitrogen in the nitrogen cylinder 2 to purge the residual air in the high airtightness test section 3, close the nitrogen inlet valve 201 and the test section regulating valve 406. Zero all measuring instruments in preparation for the next experiment.

[0058] The forced heat transfer characteristic testing platform for swept tube bundles described in this invention utilizes uncooled nitrogen gas to check the airtightness of the swept tube bundle convective heat transfer experimental system. A three-way valve is installed at the centrifugal pump outlet, allowing for steam temperature regulation using a temperature controller; nitrogen gas, after being regulated by the subcooler, can regulate the temperature of the swept tube bundle, thereby adjusting the convective heat transfer temperature difference between the tube bundle and the steam. Graduations are machined on both the transverse and longitudinal pitch rulers, and the clamping surface of the transverse pitch ruler is coated with an anti-slip coating. Combined with the fastening bolts, various pitch combinations, such as staggered and parallel arrangements of the swept tube bundles, can be achieved. The swept tubes use graphite as a substrate, with heat transfer materials of varying thicknesses sprayed onto the outer wall, enabling forced heat transfer characteristic experiments with various heat transfer materials.

[0059] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0060] The detailed descriptions listed above are merely specific illustrations of feasible embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A test platform for forced heat transfer characteristics of swept-over tube bundles, characterized in that, Including a cryogenic transport system, a high-temperature transport system, and a high-airtightness experimental device (3); The high airtightness experimental device (3) includes an air distributor (301), a stabilizing section (302), a compression section (303), an air rectifier (304), a transverse pitch gauge (305), a longitudinal pitch gauge (306), a transverse tube bundle (307), and a differential pressure gauge (308); one end of the air distributor (301) is connected to a high-temperature conveying system; the other end of the air distributor (301) is connected to the stabilizing section (302), the compression section (303), and the air rectifier in sequence. The gas rectifier (304) is connected to the convection heat exchange region; the convection heat exchange region is composed of several cross-sectionally distributed transverse tube bundles (307); the cross-tube bundles (307) are clamped and installed on the wall by transverse pitch gauges (305) and longitudinal pitch gauges (306); the cryogenic delivery system is connected to the inlet of the convection heat exchange region; the differential pressure gauge (308) is installed at the inlet and outlet ends of the cross-tube bundles (307) to measure the pressure difference inside the cross-tube bundles (307); The cryogenic delivery system includes a nitrogen cylinder (2), a subcooling section (4), and a molecular pump (9); the subcooling section (4) includes a subcooler (401), a second thermometer (402), a second pressure gauge (403), and a third pressure gauge (404); the inlet of the subcooling section (4) is connected to the nitrogen cylinder (2), and the nitrogen temperature is adjusted by the subcooler (401); the outlet of the subcooling section (4) is connected to the inlet of the convection heat exchange zone, and is used to check the airtightness and adjustment of the high airtightness experimental device (3). Temperature distribution within the convective heat transfer region; the jacket of the supercooler (401) is connected to the inlet of the molecular pump (9) via a third pressure gauge (404) and a supercooler insulation jacket evacuation valve (405); the inlet of the molecular pump (9) is connected to the convective heat transfer region via a vacuum evacuation valve (314) for evacuating air from the high airtightness experimental device (3); a second thermometer (402) and a second pressure gauge (403) are installed between the outlet of the supercooler (401) and the inlet of the convective heat transfer region, respectively. The high-temperature conveying system includes an electric heating boiler (1), a centrifugal pump (5), and a temperature regulator (8); the electric heating boiler (1) is located at the inlet of the centrifugal pump (5) and is used to heat the medium entering the centrifugal pump (5); the outlet of the centrifugal pump (5) is divided into two branches by an inlet three-way valve (102), one branch of the outlet of the centrifugal pump (5) is connected to the inlet of the pressure relief three-way valve (315) through a first flow meter (6) and a first shut-off valve (103); the other branch of the outlet of the centrifugal pump (5) is connected to the inlet of the pressure relief three-way valve (315) through a temperature regulator (8), a second flow meter (7), and a second shut-off valve (104); one outlet of the pressure relief three-way valve (315) is connected to an air distributor (301), and the other outlet of the pressure relief three-way valve (315) is used to discharge steam.

2. The test platform for forced heat transfer characteristics of swept-over tube bundles according to claim 1, characterized in that, The clamping surface of the transverse pitch ruler (305) that holds the transverse tube bundle (307) is coated with an anti-slip coating (310).

3. The test platform for forced heat transfer characteristics of swept-over tube bundles according to claim 1, characterized in that, The swept tube bundle (307) includes a graphite tube (3071) and a thermocouple (3073). The graphite tube (3071) is coated with a heat transfer material (3072) on its outer side. At least one thermocouple (3073) is installed on the inner surface of the graphite tube (3071).

4. The test platform for forced heat transfer characteristics of swept tube bundles according to claim 1, characterized in that, The bottom of the convection heat exchange area is equipped with a condensate drain valve (313) for collecting and draining the condensate generated during the heat exchange experiment.

5. The test platform for forced heat transfer characteristics of swept-over tube bundles according to claim 1, characterized in that, The subcooler (401) is used for nitrogen cooling based on the principle of reduced pressure refrigeration. The formula for calculating the refrigeration power Q of the subcooler (401) is as follows: ， Among them, Q 漏 The unavoidable heat leakage from the subcooler (401); The specific heat capacity of nitrogen gas in the subcooler (401) at the operating pressure is given by [the specific heat capacity of nitrogen gas in the subcooler (401)]. The total mass flow rate of nitrogen required to check the airtightness of the high airtightness test device (3); A is the cross-sectional area of ​​the pipeline, T1 is the nitrogen temperature at the inlet of the supercooler (401), T2 is the nitrogen temperature at the outlet of the supercooler (401); t is the time for depressurization and cooling.

6. The test platform for forced heat transfer characteristics of swept-over tube bundles according to claim 5, characterized in that, The pumping speed required by the molecular pump (9) during the heat exchange experiment shall not be less than the pumping speed S required by the supercooler (401) for refrigeration operation. The formula for calculating the refrigeration pumping speed S of the supercooler (401) is as follows: ， Where Q is the cooling power of the subcooler (401), The sensible heat of nitrogen gas is due to the pressure change inside the subcooler (401). The density of nitrogen at the outlet of the supercooler (401).

7. The test platform for forced heat transfer characteristics of swept-over tube bundles according to claim 1, characterized in that, It also includes a data acquisition system (10), which acquires the current signals generated by the first flow meter (6) and the second flow meter (7); the data acquisition system (10) acquires the current signals of the pressure sensors on the first pressure gauge (312), the second pressure gauge (403), the third pressure gauge (404), and the differential pressure gauge (308); the data acquisition system (10) acquires the voltage signals of the temperature sensors on the first thermometer (311) and the second thermometer (402); the data acquisition system (10) acquires the voltage signals generated by the thermocouple (3071) on the transverse tube bundle (307).

8. The test platform for forced heat transfer characteristics of swept tube bundles according to claim 7, characterized in that, The data acquisition system (10) controls the first shut-off valve (103), the second shut-off valve (104), the subcooler jacket evacuation valve (405), and the experimental section regulating valve (406) to close, and controls the molecular pump (9) and the experimental section vacuum evacuation valve (314) to operate for evacuation of the high airtightness experimental device (3); after evacuation in the high airtightness experimental device (3), the data acquisition system (10) controls the experimental section vacuum evacuation valve (314) to close, and controls the experimental section regulating valve (406) to operate for leak detection of the high airtightness experimental device (3), discharge of remaining air, and adjustment of temperature distribution in the convective heat transfer area; the data acquisition system (10) controls the subcooler jacket evacuation valve (405) and the molecular pump (9) to operate to keep the pressure inside the jacket of the subcooler (401) below 10. -3 Pa.

9. An experimental method for testing the forced heat transfer characteristics of a swept-over tube bundle according to claim 7, characterized in that, Includes the following steps: Air tightness check: Control the first shut-off valve (103), the second shut-off valve (104), the supercooler jacket evacuation valve (405) and the experimental section regulating valve (406) to close, and control the molecular pump (9) and the experimental section vacuum evacuation valve (314) to evacuate the air from the high air tightness experimental device (3). After the air is pumped out of the high airtightness test device (3), the vacuum pumping valve (314) of the control test section is closed, and the control test section regulating valve (406) and nitrogen inlet valve (201) are operated to check for leaks in the high airtightness test device (3) and discharge the remaining air. Tube bundle temperature control and precooling: Control the operation of molecular pump (9) and supercooler jacket evacuation valve (405), and close the experimental section vacuum evacuation valve (314) to make the pressure inside the jacket of supercooler (401) lower than 10. -3 Pa; control the nitrogen inlet valve (201) to adjust the nitrogen temperature in the supercooler (401) to a set value T2', and use the second thermometer (402) to check the nitrogen temperature; when the nitrogen temperature is stable, close the supercooler jacket exhaust valve (405) and the molecular pump (9), and monitor the pressure index of the third pressure gauge (404); the nitrogen in the supercooler (401) enters the convection heat transfer area through the experimental section regulating valve (406), and the real-time temperature of the tube bundle is monitored by the thermocouple (3073) on the inner wall of the tube bundle until it drops to the predetermined temperature T2, and the input of low-temperature nitrogen is maintained; Temperature-adjusting steam input: Based on the predetermined heat exchange temperature difference △T, determine the steam temperature as T1; open the electric heating boiler (1), boiler exhaust valve (101) and first shut-off valve (103), control the inlet three-way valve (102), so that the outlet of the centrifugal pump (5) is connected to the inlet of the pressure relief three-way valve (315) through the first flow meter (6) and the first shut-off valve (103), control the outlet of the pressure relief three-way valve (315) to be connected to the discharge circuit, and determine whether the steam temperature has reached the set temperature by reading the temperature value of the first thermometer (311). If the predetermined temperature T1 is not met, control the inlet three-way valve (102) to connect the outlet of the centrifugal pump (5) to the inlet of the pressure relief three-way valve (315) through the temperature regulator (8), the second flow meter (7), and the second shut-off valve (104); adjust the steam temperature to T1 through the temperature regulator (8) and monitor the steam indicators of the first thermometer (311) and the first pressure gauge (312); at the same time, monitor the first flow meter (6) or the second flow meter (7) to adjust the centrifugal pump (5) to achieve the required steam flow rate; Convection heat transfer experiment: When the temperature and flow rate of the steam meet the experimental requirements, open the condensate drain valve (313), close the nitrogen inlet valve (201) and the experimental section regulating valve (406), control the outlet of the pressure relief three-way valve (315) to connect with the high airtightness experimental device (3), so that the steam at temperature T1 enters the transverse tube bundle to start forced convection heat transfer. The data acquisition system (10) records the temperature change on the transverse tube bundle (307) and the pressure difference change of the differential pressure gauge (308); adjust the pressure and flow rate of the steam input into the high airtightness experimental device (3) for experiments under different steam conditions at different temperatures.

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