System and method for testing heat exchange efficiency of heat exchange sheet

Abstract

The invention discloses a system and a method for testing the heat exchange efficiency of a heat exchange sheet. The automatic dust generating device, the temperature control panel, the gantry support, the infrared thickness gauge, the thermal imager, the humidity control device and the dust recycling and weighing device are installed in the glass box, and the master control box, the constant-temperature water tank, the recycling and temperature measuring water tank and the data collecting device are arranged outside the glass box. The data collection device is connected with all parts of the system and collects corresponding data. According to the invention, the heat exchange efficiency change of the heat exchange sheet under different heat source temperatures and environment humidity conditions and the dust moisture content under different humidity conditions can be measured, and the influence degree on the heat exchange efficiency of the heat exchange sheet after dust is accumulated on an air cooler fin in an industrial and mining dust environment can be simulated.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat dissipation of heat exchanger fins, and in particular relates to a system and method for testing the heat exchange efficiency of heat exchanger fins. Background Art

[0002] At present, a large amount of dust is generated in industrial production, mining and other workplaces. The dust concentration and composition generated in different industrial and mining workplaces are different, and the temperature and humidity of the environment are also different. Dust will adhere to the surface of cooling equipment such as air cooler fins, resulting in a decrease in the cooling effect of the air cooler, and then cause the temperature in the workplace to rise; the imperfect structure of the heat exchange fins of the air cooler will significantly reduce its cooling effect, and the temperature rise will endanger the occupational health of the operators, thereby reducing work efficiency and increasing the risk of misoperation, posing a great safety hazard. Summary of the invention

[0003] The purpose of the present invention is to provide a heat exchange efficiency testing system and method for heat exchangers, which can measure the changes in heat exchange efficiency of heat exchangers under different heat source temperatures and ambient humidity conditions and the moisture content of dust under different humidity conditions, and can also simulate the influence of dust accumulation on the heat exchange efficiency of heat exchangers in industrial and mining dust environments.

[0004] To achieve the above object, the present invention provides a heat exchange efficiency test system for heat exchanger fins, comprising a glass box and further comprising:

[0005] The automatic dust generating device is installed in the glass box, and includes a fixed bracket and a rotating motor connected to the glass box. A sliding device is connected above the fixed bracket. A transmission shaft is connected above the sliding device through the sliding bracket. One end of the transmission shaft is connected to a vibrating screen equipped with a vibrator, and the other end is connected to a power output end of the rotating motor through a crank mechanism.

[0006] The temperature control panel is installed on the bottom plate of the glass box;

[0007] The gantry bracket is installed in the glass box, and the front end drive is connected to the heat exchanger. A thin plate is placed above the heat exchanger, and the thin plate is driven and controlled by the gantry bracket. The heat exchanger is placed corresponding to the temperature control plate, and the heat exchanger is connected in series to the pipe connecting the constant temperature water tank and the recovery temperature measuring water tank. The constant temperature water tank and the recovery temperature measuring water tank are arranged outside the glass box.

[0008] Infrared thickness gauge, installed in the glass box, located in front of the gantry support;

[0009] Thermal imager, installed in the glass box, above the heat exchanger, to monitor the temperature of the sheet or heat exchanger;

[0010] A humidity control device is installed in the glass box to adjust the humidity in the glass box;

[0011] The dust recovery weighing device is installed in the glass box, on the right side of the heat exchanger;

[0012] The main control box is located outside the glass box and connects various components of the control system;

[0013] The data collection device is arranged outside the glass box and connected with each component of the system to collect corresponding data.

[0014] As a further solution of the present invention: the infrared thickness gauge includes a C-frame, the C-frame opening faces the gantry bracket, an infrared generator is symmetrically installed at one end of the inner side of the C-frame opening close to the gantry bracket, and a monitoring camera is connected to one end of the inner side of the C-frame opening away from the gantry bracket.

[0015] As a further solution of the present invention: the dust recovery weighing device comprises a drying box, a weighing mechanism is arranged in the drying box, and an operating door is arranged on the side wall of the drying box close to the heat exchange plate.

[0016] As a further solution of the present invention: the heat exchanger is composed of a plurality of corrugated fins, each of which is provided with a through hole, and parallel first auxiliary heat dissipation fins and second auxiliary heat dissipation fins are respectively provided on both sides of the corrugated fins along the length direction, and a heat dissipation groove is provided between the first auxiliary heat dissipation fins and the second auxiliary heat dissipation fins.

[0017] A method for testing the heat exchange efficiency of a heat exchanger is based on the above-mentioned heat exchange efficiency testing system. First, without placing a thin plate on the heat exchanger, the heat exchange efficiency of the heat exchanger is measured without dust accumulation. Then, a thin plate is placed on the heat exchanger, and dust is evenly spread on the surface of the thin plate by an automatic dust generating device. The heat exchange efficiency of the heat exchanger under different dust accumulation thicknesses is measured. Specifically, the following steps are included:

[0018] Step 1: After the test system is debugged, use the main control box to control the gantry bracket to lower the heat exchanger as a whole to the top of the temperature control board, then use the temperature control board to heat the heat exchanger, and after heating to the specified temperature, raise it to the initial position, then pass the water in the constant temperature water tank into the pipeline, and the water enters the recovery temperature measuring water tank after passing through the pipeline;

[0019] Step 2: When the water after heat exchange enters the recovery temperature measuring water tank, measure the temperature of the water inside the recovery temperature measuring water tank at this time, and calculate the actual heat exchange amount by the following formula:

[0020] Q=U·A·ΔT LMTD

[0021] Where: Q is the actual heat transfer, W; U is the total heat transfer coefficient, W / (m 2 ·K); A is the heat exchange area, m 2 ; ΔT LMTD is the logarithmic mean temperature difference, k;

[0022] The calculation formula of logarithmic mean temperature difference ΔTLMTD is:

[0023]

[0024] Where: ΔT1 and ΔT2 are the temperature differences at both ends of the pipe during the heat exchange process;

[0025] The overall heat transfer coefficient U can be further refined as:

[0026]

[0027] Where: h in and h out are the heat transfer coefficients of the inner and outer sides of the heat exchanger, W / (m 2 ·K); d1 and d2 are the thickness of the heat exchanger and the dust layer, m; k1 and k2 are the thermal conductivity of the heat exchanger and the dust layer, W / (m 2 K);

[0028] Since dust accumulation will affect thermal conductivity, the thermal conductivity under dust accumulation is calculated here. The effect of dust accumulation on thermal conductivity can be fitted into an empirical formula through experimental data:

[0029]

[0030] Where: k is the thermal conductivity of dust under accumulation state, W / (m 2 ·K); k0 is the thermal conductivity in the clean state, W / (m 2 ·K); α is the dust influence coefficient; δ is the dust accumulation thickness, m;

[0031] Step 3: After calculating the actual heat transfer amount Q, the heat transfer efficiency of the heat exchanger can be calculated by the following formula:

[0032]

[0033] Where: η is the heat transfer efficiency; Q is the actual heat transfer, W; Q total is the theoretical maximum heat transfer capacity, W;

[0034] The theoretical maximum heat transfer can be calculated by the following formula:

[0035] Q total =m·c p ΔT max

[0036] Where: m is the fluid mass flow rate, kg / s; c p is the specific heat capacity of the fluid, J (kg·K); ΔTmax is the maximum theoretical temperature difference, K;

[0037] Step 4: Based on step 1, step 2 and step 3, multiple groups of experiments are carried out in parallel, and the average heat transfer efficiency of the multiple groups of experiments is measured to obtain the initial heat transfer efficiency of the heat exchanger;

[0038] Step 5: Use the humidity control device to adjust the humidity in the glass box. Based on Step 1, Step 2 and Step 3, measure the heat exchange efficiency of the heat exchanger under different humidity conditions to obtain the heat exchange efficiency of the heat exchanger under different humidity conditions, and compare it with the result measured in Step 4;

[0039] Step 6: Change the temperature of the temperature control plate, and measure the heat transfer efficiency of the heat exchanger at different heat source temperatures under the humidity adjustment in step 5, so as to obtain the heat transfer efficiency of the heat exchanger under different humidity and temperature conditions;

[0040] Step 7: After all the above test processes are completed, the system is debugged to the initial state. After debugging is completed, the thin plate is placed directly above the heat exchanger and directly below the vibrating screen using the gantry bracket, and the vibrator and the sliding device are started. Under the action of the sliding bracket, the vibrating screen is reciprocated left and right, and the dust in the vibrating screen is evenly spread on the thin plate. Then, the thin plate is controlled by the gantry bracket to measure the dust accumulation thickness on the thin plate using an infrared thickness gauge. After measuring the dust accumulation thickness, the gantry bracket is used to make the dusty thin plate close to the top of the heat exchanger;

[0041] Step 8: First, test under the same experimental conditions as steps 1, 2, 3, and 4 to obtain the initial heat exchange efficiency of the heat exchanger under dust coverage conditions. Then, measure the heat exchange efficiency of the heat exchanger under the conditions of step 5 to obtain the heat exchange efficiency of the heat exchanger under different humidity conditions when dust is covered. Finally, measure the heat exchange efficiency of the heat exchanger under different humidity and temperature conditions when dust is covered.

[0042] Step 9: Adjust the vibration and reciprocating time of the vibrating screen and vibrator so that different amounts of dust are accumulated on the thin plate, and then measure according to step 8 to obtain the initial heat exchange efficiency of the heat exchanger when covered with different thicknesses of dust, as well as the heat exchange efficiency of the heat exchanger under different humidity and temperature conditions when covered with different thicknesses of dust;

[0043] Step 10: During steps 8 and 9, when the experimental measurement of changing humidity conditions is completed, open the operating door, collect the dust with a certain humidity into the dust recovery weighing device, and use a drying oven to dry it. The mass of the dust before and after drying can be obtained from the weighing mechanism, and then the moisture content of the dust can be obtained, and the initial heat exchange efficiency of the heat exchanger under different moisture contents can be obtained.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] It can measure the changes in the heat transfer efficiency of the heat exchanger under different heat source temperatures, environmental humidity and different dust compositions. It can also simulate the influence of dust accumulation on the air cooler fins in industrial and mining dust environments on the heat transfer efficiency of the heat exchanger. At the same time, it can also measure the heat transfer efficiency and changes of heat exchange fins with different structures in this case, thereby providing a basis for subsequent cooling and comfortable working environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a structural schematic diagram of a heat exchange efficiency test system for heat exchanger plates of the present invention;

[0047] Figure 2 It is a structural schematic diagram of the automatic dust generating device of the present invention.

[0048] Figure 3 It is a schematic diagram of the structure of the changing state of the automatic dust generating device of the present invention.

[0049] Figure 4 It is a schematic structural diagram of the heat exchange plate of the present invention.

[0050] Figure 5 yes Figure 4 Schematic diagram of the structure of part A in the middle.

[0051] Figure 6 It is a structural schematic diagram of the infrared thickness gauge of the present invention.

[0052] Figure 7 It is a structural schematic diagram of the dust recovery weighing device of the present invention.

[0053] In the figure: 1. Data collection device, 2. Automatic dust generation device, 3. General control box, 4. Thermal imager, 5. Heat exchanger, 6. Gantry bracket, 7. Humidity control device, 8. Constant temperature water tank, 9. Infrared thickness gauge, 10. Recycling temperature measuring water tank, 11. Glass box, 12. Temperature control board, 13. Dust recovery weighing device, 14. Thin plate;

[0054] 21. vibrating screen, 22. vibrator, 23. sliding device, 24. fixed bracket, 25. sliding bracket, 26. crank mechanism, 27. rotating motor;

[0055] 51. corrugated fins, 52. through holes;

[0056] 511, first auxiliary heat dissipation fin, 512, second auxiliary heat dissipation fin, 513, heat dissipation groove;

[0057] 91. Infrared generator, 92. Monitoring camera, 93. C-type frame;

[0058] 131. Drying box, 132. Weighing mechanism, 133. Operating door. DETAILED DESCRIPTION

[0059] The present invention will be further described below by way of examples.

[0060] like Figures 1 to 3 As shown, a heat exchange efficiency test system for a heat exchanger comprises a glass box 11, and further comprises:

[0061] The automatic dust generating device 2 is installed in the glass box 11, and includes a fixed bracket 24 and a rotating motor 27 connected to the glass box 11. A sliding device 23 is connected above the fixed bracket 24. A transmission shaft is connected above the sliding device 23 through a sliding bracket 25. One end of the transmission shaft is connected to a vibrating screen 21 equipped with a vibrator 22, and the other end is connected to a power output end of the rotating motor 27 through a crank mechanism 26.

[0062] A temperature control panel 12 is mounted on the bottom plate of the glass box 11;

[0063] The gantry bracket 6 is installed in the glass box 11, and the front end is driven to connect the heat exchange plate 5. A thin plate 14 is placed above the heat exchange plate 5, and the thin plate 14 is driven and controlled by the gantry bracket 6; the heat exchange plate 5 is placed corresponding to the temperature control plate 12, and the heat exchange plate 5 is connected in series to the pipeline connecting the constant temperature water tank 8 and the recovery temperature measuring water tank 10, and the constant temperature water tank 8 and the recovery temperature measuring water tank 10 are arranged outside the glass box 11; the constant temperature water tank 8 is provided with an automatic temperature control device to ensure that the water temperature in the constant temperature water tank 8 remains constant during the test;

[0064] The infrared thickness gauge 9 is installed in the glass box 11 and is located in front of the gantry support 6; it is used to measure the dust thickness on the thin plate 14;

[0065] The thermal imager 4 is installed in the glass box 11 and located above the heat exchanger 5 to monitor the temperature of the thin plate 14 or the heat exchanger 5; the temperature of the thin plate 14 or the heat exchanger 5 monitored in real time is displayed on the data collection device 1 using a high-precision sensor;

[0066] The humidity control device 7 is installed in the glass box 11 to adjust the humidity in the glass box 11;

[0067] The dust recovery weighing device 13 is installed in the glass box 11 and is located on the right side of the heat exchange fin 5;

[0068] The main control box 3 is arranged outside the glass box 11 and is connected to various components of the control system;

[0069] The data collection device 1 is arranged outside the glass box 11, connected with each component of the system to collect corresponding data; it is connected with each component in the system through various sensors, and adopts high-precision data acquisition cards and high-speed data transmission interfaces to ensure the accuracy and real-time performance of data collection.

[0070] Further, such as Figure 6 As shown, the infrared thickness gauge 9 includes a C-frame 93, the opening of the C-frame 93 faces the gantry bracket 6, an infrared generator 91 is symmetrically installed on the inner side of the opening of the C-frame 93 close to the gantry bracket 6, and a monitoring camera 92 is connected to the inner side of the opening of the C-frame 93 away from the gantry bracket 6.

[0071] The measuring principle and steps of infrared thickness gauge 9 are as follows:

[0072] S1: After the automatic dust generating device 2 evenly spreads the dust on the thin plate 14, the main control box 3 controls the gantry support 6 to place the thin plate 14 in the middle position of the C-shaped frame 93;

[0073] S2: Turn on the infrared generator 91 and the monitoring camera 92, observe through the data collection device 1, and adjust the position of the thin plate 14 so that the monitoring camera 92 connected to the data collection device 1 can display two infrared rays; then measure the length D1 of the infrared ray at the upper end of the thin plate 14, and then measure the length D2 of the infrared ray at the lower end;

[0074] S3: After the measurement is completed, according to the measured distances D1 and D2, the thickness D3 of the thin plate 14 and the height D0 of the C-frame 93, the dust accumulation thickness δ=D0-D1-D2-D3 is obtained by subtracting the lengths D1 and D2 of the two infrared rays and the thickness D3 of the thin plate 14 from the height D0 of the C-frame 93;

[0075] S4: According to S2 and S3, the accumulation thickness of dust at multiple locations on the thin plate 14 is measured and the final average value is taken as the final accumulation thickness of the dust, so as to prevent errors caused by other factors when the dust falls in the automatic dust generating device 2 and improve the accuracy of the test.

[0076] Further, such as Figure 7 As shown, the dust recovery weighing device 13 includes a drying box 131, a weighing mechanism 132 is provided in the drying box 131, and an operating door 133 is provided on the side wall of the drying box 131 close to the heat exchange fin 5. After the test is completed, the dust with a certain humidity is collected in the drying box 131, and the dust mass before and after drying can be measured by the weighing mechanism 132.

[0077] Further, such as Figure 4 and Figure 5As shown, the heat exchanger 5 is composed of a plurality of corrugated fins 51, each of which is provided with a through hole 52. A first auxiliary heat dissipation fin 511 and a second auxiliary heat dissipation fin 512 are provided in parallel along the length direction on both sides of the corrugated fin 51, and a heat dissipation groove 513 is provided between the first auxiliary heat dissipation fin 511 and the second auxiliary heat dissipation fin 512. The heat exchanger 5 is installed on a pipeline through which a working fluid flows through the through hole 52, and the first auxiliary heat dissipation fin 511 and the second auxiliary heat dissipation fin 512 provided on both sides can improve the heat dissipation effect.

[0078] A method for testing the heat exchange efficiency of a heat exchanger fin is based on the above-mentioned heat exchange efficiency testing system. First, when no thin plate 14 is placed on the heat exchanger fin 5, the heat exchange efficiency of the heat exchanger fin 5 is measured without dust accumulation. Then, a thin plate 14 is placed on the heat exchanger fin 5, and dust is evenly spread on the upper surface of the thin plate 14 by an automatic dust generating device 2. The heat exchange efficiency of the heat exchanger fin 5 under different dust accumulation thicknesses is measured. Specifically, the following steps are included:

[0079] Step 1: After the test system is debugged, the main control box 3 is used to control the gantry bracket 6 to lower the heat exchanger 5 as a whole to above the temperature control board 12, and then the temperature control board 12 is used to heat the heat exchanger 5. After heating to the specified temperature, it rises to the initial position, and then the water in the constant temperature water tank 8 is passed into the pipeline, and the water enters the recovery temperature measuring water tank 10 after passing through the pipeline;

[0080] Step 2: After the water after heat exchange enters the recovery temperature measuring water tank 10, the temperature of the water inside the recovery temperature measuring water tank 10 is measured, and the actual heat exchange amount is calculated by the following formula:

[0081] Q=U·A·ΔT LMTD

[0082] Where: Q is the actual heat transfer, W; U is the function of the heat exchanger, dust environment and environmental conditions, and is the total heat transfer coefficient, W / (m 2 ·K); A is the heat exchange area, m 2 ; ΔT LMTD is the logarithmic mean temperature difference, k;

[0083] The calculation formula of logarithmic mean temperature difference ΔTLMTD is:

[0084]

[0085] Where: ΔT1 and ΔT2 are the temperature differences at both ends of the pipe during the heat exchange process (i.e., the temperature difference between the water inlet and outlet sides of the pipe, and the initial water outlet temperature is the ambient temperature);

[0086] The overall heat transfer coefficient U can be further refined as:

[0087]

[0088] Where: h in and h out are the heat transfer coefficients of the inner and outer sides of the heat exchanger fin 5, W / (m 2 ·K); d1 and d2 are the thickness of the heat exchanger 5 and the dust layer, m; k1 and k2 are the thermal conductivity of the heat exchanger 5 and the dust layer, W / (m 2 K);

[0089] Since dust accumulation will affect thermal conductivity, the thermal conductivity under dust accumulation is calculated here. The effect of dust accumulation on thermal conductivity can be fitted into an empirical formula through experimental data:

[0090]

[0091] Where: k is the thermal conductivity of dust under accumulation state, W / (m 2 ·K); k0 is the thermal conductivity in the clean state, W / (m 2 ·K); α is the dust influence coefficient, confirmed by experiments; δ is the dust accumulation thickness, m;

[0092] Step 3: After calculating the actual heat transfer amount Q, the heat transfer efficiency of the heat exchanger 5 can be calculated by the following formula:

[0093]

[0094] Where: η is the heat transfer efficiency; Q is the actual heat transfer, W; Q total is the theoretical maximum heat transfer capacity, W;

[0095] The theoretical maximum heat transfer can be calculated by the following formula:

[0096] Q total =m·c p ΔT max

[0097] Where: m is the fluid mass flow rate, kg / s; c p is the specific heat capacity of the fluid, J (kg·K); ΔTmax is the maximum theoretical temperature difference, K;

[0098] Step 4: Based on step 1, step 2 and step 3, multiple groups of experiments are performed in parallel, and the average heat exchange efficiency of the multiple groups of experiments is measured to obtain the initial heat exchange efficiency of the heat exchange plate 5;

[0099] Step 5: The humidity in the glass box 11 is adjusted by using the humidity control device 7. An appropriate humidity gradient can be selected. Based on steps 1, 2, and 3, the heat exchange efficiency of the heat exchange fin 5 under different humidity conditions is measured to obtain the heat exchange efficiency of the heat exchange fin 5 under different humidity conditions, and the result is compared with the measurement result in step 4.

[0100] Step 6: Change the temperature at which the temperature control plate 12 is heated. You can select a temperature gradient or customize different temperatures for measurement. Under the humidity adjustment in step 5, measure the heat exchange efficiency of the heat exchange plate 5 at different heat source temperatures to obtain the heat exchange efficiency of the heat exchange plate 5 under different humidity and temperature conditions.

[0101] Step 7: After all the above test processes are completed, the system is debugged to the initial state. After the debugging is completed, the thin plate 14 is placed directly above the heat exchange plate 5 and directly below the vibrating screen 21 by using the gantry bracket 6, and the vibrator 22 and the sliding device 23 are started. Under the action of the sliding bracket 25, the vibrating screen 21 is reciprocated left and right, and the dust in the vibrating screen 21 is evenly spread on the thin plate 14. Then, the thin plate 14 is controlled by the gantry bracket 6 to measure the accumulation thickness of the dust on the thin plate 14 by using the infrared thickness gauge 9. After measuring the dust accumulation thickness, the gantry bracket 6 is used to make the thin plate 14 with dust close to the top of the heat exchange plate 5;

[0102] Step 8: First, test under the same experimental conditions as steps 1, 2, 3, and 4 to obtain the initial heat exchange efficiency of the heat exchanger 5 under the dust coverage condition, then measure the heat exchange efficiency of the heat exchanger 5 under the conditions of step 5 to obtain the heat exchange efficiency of the heat exchanger 5 under different humidity conditions when covered by dust, and finally measure under the same conditions as step 6 to obtain the heat exchange efficiency of the heat exchanger 5 under different humidity and temperature conditions when covered by dust;

[0103] Step 9: Adjust the vibration and reciprocating time of the vibrating screen 21 and the vibrator 22 so that different amounts of dust are accumulated on the thin plate 14, and then measure according to step 8 to obtain the initial heat exchange efficiency of the heat exchange plate 5 when covered with dust of different thicknesses, and the heat exchange efficiency of the heat exchange plate 5 under different humidity and temperature conditions when covered with dust of different thicknesses;

[0104] Step 10: During steps 8 and 9, when the experimental measurement of changing humidity conditions is completed, open the operating door 133, collect the dust with a certain humidity into the dust recovery weighing device 13, and use the drying box 131 to dry it. The mass of the dust before and after drying can be obtained by the weighing mechanism 132, and then the moisture content of the dust can be obtained, and the initial heat exchange efficiency of the heat exchange plate 5 under different moisture content conditions can be obtained.

[0105] By comparing the measurement results of all parallel measurement experiments, we can draw the final conclusion on the change and degree of heat exchange efficiency, and provide a basis for excellent cooling and providing a comfortable working environment.

[0106] Implementation Cases:

[0107] The heat transfer efficiency of the heat exchanger fin 5 is tested under specific dust accumulation thickness and different conditions (temperature, humidity).

[0108] Step 1: After the system is debugged, the humidity in the system is adjusted to 40% using the humidity control device 7. The main control box 3 controls the gantry bracket 6 to place the heat exchange plate 5 directly above the temperature control board 12. The temperature control board 12 is then used to heat it to 60°C and then raised to the initial position. Then, the water at 0°C in the water tank is introduced through a pipe (the initial ambient temperature is 10°C), and after heat exchange, it flows into the recovery temperature measuring water tank 10.

[0109] Step 2: Turn on the infrared generator 91 and the monitoring camera 92, observe the information sent back through the data collection device 1, and adjust the position of the thin plate 14 so that the monitoring camera 92 can clearly display the two infrared rays. The length D1 of the upper infrared ray emitted by the infrared generator 91 is measured to be 120 mm, and the length D2 of the lower infrared ray is 110 mm. The height D0 of the C-frame is 250 mm, and the thickness D3 of the thin plate is 10 mm. According to the thickness measurement principle, the dust accumulation thickness δ=D0-D1-D2-D3=250mm-120mm-110mm-10mm=10mm is intelligently calculated.

[0110] Step 3: The water after heat exchange enters the recovery temperature measuring water tank 10, and the temperature of the water inside is measured to be 45°C, and the heat exchange area A is 0.5m 2 , the fluid mass flow rate m is 0.01 kg / s, the fluid specific heat capacity c p is 4186J / (kg·K), the theoretical maximum temperature difference ΔT max is 50K.

[0111] (1) Calculation of logarithmic mean temperature difference ΔT LMTD During the heat exchange process, the temperature differences at both ends are ΔT1 = 50K and ΔT2 = 15K; we can get:

[0112]

[0113] (2) Calculate the total heat transfer coefficient U. Assume that the heat transfer coefficient h inside the heat exchanger 5 is in 50W / (m 2 ·K), external heat transfer coefficient h out 20W / (m 2 ·K), the thermal conductivity k1 of the heat exchanger 5 is 0.03W / (m 2·K), the thermal conductivity of the dust layer k2 is 0.01W / (m 2 ·K), the thickness d1 of the heat exchanger 5 is 0.001m, and the thickness d2 of the dust layer is 0.01m. The dust influence coefficient α is measured to be 0.3. The thermal conductivity k0 in the clean state is 0.03W / (m 2 K), the thermal conductivity of the dust accumulation can be calculated:

[0114]

[0115] Next, calculate the overall heat transfer coefficient U:

[0116]

[0117] Calculate the actual heat transfer Q:

[0118] Q=U·A·ΔT LMDT =119×0.5×29=1725.5W

[0119] (3) Calculation of Q total :

[0120] Q total =m·c p ΔT max =0.01×4186×50=2093W

[0121] (4) Calculate heat transfer efficiency:

[0122]

[0123] This implementation case calculates the heat transfer efficiency of the heat exchanger fin 5 when the initial ambient humidity is 40%, the initial temperature is 60°C and the dust accumulation is 10 mm. Other groups of parallel experiments can be calculated according to the above steps after changing the measurement influencing factors.

Claims

1. A heat exchange efficiency test system for a heat exchanger, comprising a glass box (11), characterized in that: Also includes: The automatic dust generating device (2) is installed in the glass box (11), and comprises a fixed bracket (24) and a rotating motor (27) connected to the glass box (11); a sliding device (23) is connected above the fixed bracket (24); a transmission shaft is connected above the sliding device (23) through a sliding bracket (25); one end of the transmission shaft is connected to a vibrating screen (21) equipped with a vibrator (22); and the other end is connected to a power output end of the rotating motor (27) through a crank mechanism (26); A temperature control panel (12) is mounted on the inner bottom panel of the glass box (11); A gantry bracket (6) is installed in the glass box (11), and the front end is driven to connect the heat exchange plate (5). A thin plate (14) is placed above the heat exchange plate (5), and the thin plate (14) is driven and controlled by the gantry bracket (6); the heat exchange plate (5) is placed corresponding to the temperature control plate (12), and the heat exchange plate (5) is connected in series to a pipeline connecting a constant temperature water tank (8) and a recovery temperature measuring water tank (10). The constant temperature water tank (8) and the recovery temperature measuring water tank (10) are arranged outside the glass box (11); An infrared thickness gauge (9) is installed in the glass box (11) and is located in front of the gantry support (6); A thermal imager (4) is installed in the glass box (11) and located above the heat exchanger (5) to monitor the temperature of the thin plate (14) or the heat exchanger (5); A humidity control device (7) is installed in the glass box (11) to adjust the humidity in the glass box (11); A dust recovery weighing device (13) is installed in the glass box (11) and is located on the right side of the heat exchange fin (5); A main control box (3) is arranged outside the glass box (11) and is connected to various components of the control system; The data collection device (1) is arranged outside the glass box (11), connected with various components of the system, and collects corresponding data.

2. A heat exchange efficiency test system for heat exchanger fins according to claim 1, characterized in that: The infrared thickness gauge (9) comprises a C-shaped frame (93), the opening of the C-shaped frame (93) faces the gantry support (6), an infrared generator (91) is symmetrically mounted on one end of the inner side of the opening of the C-shaped frame (93) close to the gantry support (6), and a monitoring camera (92) is connected to one end of the inner side of the opening of the C-shaped frame (93) away from the gantry support (6).

3. A heat exchange efficiency test system for heat exchanger fins according to claim 1, characterized in that: The dust recovery weighing device (13) comprises a drying box (131), a weighing mechanism (132) is arranged inside the drying box (131), and an operating door (133) is provided on a side wall of the drying box (131) close to the heat exchange fins (5).

4. A heat exchange efficiency test system for heat exchanger fins according to claim 1, characterized in that: The heat exchanger (5) is composed of a plurality of corrugated fins (51), each of which is provided with a through hole (52), and parallel first auxiliary heat dissipation fins (511) and second auxiliary heat dissipation fins (512) are respectively provided on both sides of the corrugated fins (51) along the length direction, and a heat dissipation groove (513) is provided between the first auxiliary heat dissipation fins (511) and the second auxiliary heat dissipation fins (512).

5. A method for testing the heat exchange efficiency of a heat exchanger, characterized in that: A heat exchange efficiency test system for a heat exchanger fin according to any one of claims 1 to 4, firstly, without placing a thin plate (14) above the heat exchanger fin (5), the heat exchange efficiency of the heat exchanger fin (5) is measured without dust accumulation; secondly, a thin plate (14) is placed above the heat exchanger fin (5), and dust is evenly spread on the upper surface of the thin plate (14) by an automatic dust generating device (2), and the heat exchange efficiency of the heat exchanger fin (5) is measured under different dust accumulation thicknesses, specifically comprising the following steps: Step 1: After the test system is debugged, the main control box (3) is used to control the gantry bracket (6) to lower the heat exchange plate (5) as a whole to the top of the temperature control plate (12), and then the temperature control plate (12) is used to heat the heat exchange plate (5). After heating to a specified temperature, the heat exchange plate (5) is raised to the initial position, and then the water in the constant temperature water tank (8) is passed into the pipeline, and the water enters the recovery temperature measuring water tank (10) after passing through the pipeline; Step 2: After the water after heat exchange enters the recovery temperature measuring water tank (10), the temperature of the water inside the recovery temperature measuring water tank (10) is measured, and the actual heat exchange amount is calculated by the following formula: Q=U·A·ΔT LMTD Where: Q is the actual heat transfer, W; U is the total heat transfer coefficient, W / (m 2 ·K); A is the heat exchange area, m 2 ; ΔT LMTD is the logarithmic mean temperature difference, k; Logarithmic mean temperature difference ΔT LMTD The calculation formula is: Where: ΔT1 and ΔT2 are the temperature differences at both ends of the pipe during the heat exchange process; The total heat transfer coefficient U can be further refined as: Where: h in and h out are the heat transfer coefficients of the inner and outer sides of the heat exchanger (5), W / (m 2 ·K); d1 and d2 are the thickness of the heat exchanger (5) and the dust layer, m; k1 and k2 are the thermal conductivity of the heat exchanger (5) and the dust layer, W / (m 2 K); Since dust accumulation will affect thermal conductivity, the thermal conductivity under dust accumulation is calculated here. The effect of dust accumulation on thermal conductivity can be fitted into an empirical formula through experimental data: Where: k is the thermal conductivity of dust under accumulation state, W / (m 2 ·K); k0 is the thermal conductivity in the clean state, W / (m 2 ·K); α is the dust influence coefficient; δ is the dust accumulation thickness, m; Step 3: After calculating the actual heat transfer amount Q, the heat transfer efficiency of the heat exchanger can be calculated by the following formula: Where: η is the heat transfer efficiency; Q is the actual heat transfer, W; Q total is the theoretical maximum heat transfer capacity, W; The theoretical maximum heat transfer can be calculated by the following formula: Q total =m·c p ·ΔT max Where: m is the fluid mass flow rate, kg / s; c p is the specific heat capacity of the fluid, J (kg·K); ΔTmax is the maximum theoretical temperature difference, K; Step 4: Based on step 1, step 2 and step 3, multiple groups of experiments are carried out in parallel, and the average heat transfer efficiency of the multiple groups of experiments is measured to obtain the initial heat transfer efficiency of the heat exchanger (5); Step 5: The humidity in the glass box (11) is adjusted by using the humidity control device (7), and the heat exchange efficiency of the heat exchange fin (5) under different humidity conditions is measured on the basis of steps 1, 2 and 3, so that the heat exchange efficiency of the heat exchange fin (5) under different humidity conditions can be obtained, and compared with the result measured in step 4; Step 6: changing the temperature of the temperature control plate (12) while heating, and measuring the heat exchange efficiency of the heat exchange plate (5) at different heat source temperatures under the humidity adjustment in step 5, so as to obtain the heat exchange efficiency of the heat exchange plate (5) under different humidity and temperature conditions; Step 7: After all the above test processes are completed, the system is debugged to the initial state. After the debugging is completed, the thin plate (14) is placed directly above the heat exchange plate (5) and directly below the vibrating screen (21) using the gantry bracket (6), and the vibrator (22) and the sliding device (23) are started. Under the action of the sliding bracket (25), the vibrating screen (21) is made to reciprocate left and right, and at the same time, the dust in the vibrating screen (21) is evenly spread on the thin plate (14). Then, the thin plate (14) is controlled by the gantry bracket (6) to measure the accumulation thickness of the dust on the thin plate (14) using the infrared thickness gauge (9). After measuring the accumulation thickness of the dust, the gantry bracket (6) is used to make the thin plate (14) with dust close to the top of the heat exchange plate (5); Step 8: First, the test is carried out under the same experimental conditions as steps 1, 2, 3 and 4, so as to obtain the initial heat exchange efficiency of the heat exchange plate (5) under the dust covering condition. Then, the heat exchange efficiency of the heat exchange plate (5) is measured again under the conditions of step 5, so as to obtain the heat exchange efficiency of the heat exchange plate (5) under different humidity conditions when the dust is covered. Finally, the measurement is carried out in the same manner as step 6, so as to obtain the heat exchange efficiency of the heat exchange plate (5) under different humidity and different temperature conditions when the dust is covered. Step 9: adjusting the vibration and reciprocating time of the vibrating screen (21) and the vibrator (22) so that different amounts of dust are accumulated on the thin plate (14), and then measuring according to step 8 to obtain the initial heat exchange efficiency of the heat exchange plate (5) when covered with dust of different thicknesses, and the heat exchange efficiency of the heat exchange plate (5) under different humidity and temperature conditions when covered with dust of different thicknesses; Step 10: During steps 8 and 9, when the experimental measurement of changing the humidity conditions is completed, the operating door (133) is opened, and the dust with a certain humidity is collected in the dust recovery weighing device (13), and the dust is dried using a drying box (131). The mass of the dust before and after drying can be obtained by the weighing mechanism (132), and the moisture content of the dust can be obtained, and the initial heat exchange efficiency of the heat exchange plate (5) under different moisture content conditions can be obtained.

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