A heat exchange fin heat exchange efficiency testing system and method

Abstract

This invention discloses a heat exchanger efficiency testing system and method, comprising a glass box, and further comprising an automatic dust generation device, a temperature control board, a gantry support, an infrared thickness gauge, a thermal imager, a humidity control device, a dust recovery and weighing device installed inside the glass box, and a main control box, a constant temperature water tank, a recovery and temperature measurement water tank, and a data collection device located outside the glass box. The main control box is connected to each component of the control system, and the data collection device is connected to each component of the system to collect relevant data. This invention can measure the change in heat exchanger efficiency of heat exchangers under different heat source temperatures and ambient humidity conditions, as well as the moisture content of dust under different humidity conditions. It can also simulate the impact of dust accumulation on the heat exchanger fins in industrial and mining dust environments on the heat exchanger efficiency.

Description

Technical Field

[0001] This invention belongs to the field of heat exchanger heat dissipation technology, specifically relating to a heat exchanger heat exchange efficiency testing system and method. Background Technology

[0002] Currently, large amounts of dust are generated in industrial production, mining, and other work sites. The concentration and composition of dust vary from site to site, and the temperature and humidity of the environment also differ. Dust adheres to the surface of cooling equipment such as air cooler fins, reducing the cooling effect of the air cooler and causing the temperature in the work area to rise. Imperfect heat exchange fin structures of air coolers can significantly reduce their cooling effect. The temperature rise can endanger the occupational health of workers, thereby reducing work efficiency, increasing the risk of misoperation, and posing significant safety hazards. Summary of the Invention

[0003] The purpose of this invention is to provide a heat exchanger efficiency testing system and method, which can measure the change in heat exchanger efficiency under different heat source temperatures and ambient humidity conditions, as well as the dust moisture content under different humidity conditions. It can also simulate the impact of dust accumulation on the heat exchanger efficiency in industrial and mining dust environments.

[0004] To achieve the above objectives, the present invention provides a heat exchanger efficiency testing system, comprising a glass chamber, and further comprising:

[0005] An automatic dust generation device is installed inside a glass box. It includes a fixed bracket and a rotary motor connected inside the glass box. A sliding device is connected above the fixed bracket. A drive shaft is connected above the sliding device through the sliding bracket. One end of the drive shaft is connected to a vibrating screen equipped with a vibrator, and the other end is connected to the power output end of the rotary motor through a crank mechanism.

[0006] Temperature control panel, installed on the bottom plate inside the glass box;

[0007] The gantry support is installed inside the glass box. The front drive connects to the heat exchange fins. A thin plate is placed on top of the heat exchange fins and is controlled by the gantry support drive. The heat exchange fins are placed corresponding to the temperature control board. The heat exchange fins are connected in series to the pipes connecting the constant temperature water tank and the recovery temperature measurement water tank. The constant temperature water tank and the recovery temperature measurement water tank are located outside the glass box.

[0008] The infrared thickness gauge is installed inside a glass case and located on the front side of the gantry frame;

[0009] A thermal imager, installed inside a glass enclosure and positioned above the heat exchange fins, monitors the temperature of the thin plate or heat exchange fins.

[0010] A humidity control device is installed inside the glass box to regulate the humidity inside the glass box;

[0011] The dust recovery weighing device is installed inside the glass box, located on the right side of the heat exchange fins;

[0012] The main control box, located on the outside of the glass enclosure, connects all components of the control system.

[0013] The data collection device is located on the outside of the glass box and is connected to various components of the system to collect relevant data.

[0014] As a further aspect of the present invention: the infrared thickness gauge includes a C-shaped frame, the opening of the C-shaped frame facing the gantry support, infrared generators are symmetrically installed at the top and bottom of the inner side of the opening of the C-shaped frame near the gantry support, and a monitoring camera is connected to the inner side of the opening of the C-shaped frame away from the gantry support.

[0015] As a further embodiment of the present invention: the dust recovery weighing device includes a drying box, a weighing mechanism is provided inside the drying box, and an operating door is provided on the side wall of the drying box near the heat exchange plate.

[0016] As a further aspect of the present invention: the heat exchange plate is composed of multiple corrugated fins, the corrugated fins are provided with through holes, 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 heat dissipation grooves are 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 fin, based on the aforementioned heat exchange efficiency testing system, firstly, without placing a thin plate above the heat exchanger fin, the heat exchange efficiency of the heat exchanger fin is measured when there is no dust accumulation. Secondly, with a thin plate placed above the heat exchanger fin, and dust evenly spread on the surface of the thin plate using an automatic dust generation device, the heat exchange efficiency of the heat exchanger fin is measured under different dust accumulation thicknesses. The method specifically includes the following steps:

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

[0019] Step Two: After the water undergoes heat exchange and enters the recovery temperature measuring tank, measure the temperature of the water inside the tank and calculate the actual heat exchange using the following formula:

[0020] Q=U·A·ΔT LMTD

[0021] In the formula: Q is the actual heat exchange, W; U is the overall heat transfer coefficient, W / (m²). 2 ·K); A is the heat exchange area, m 2 ;ΔT LMTD The logarithmic mean temperature difference, k;

[0022] The formula for calculating the logarithmic mean temperature difference ΔTLMTD is:

[0023]

[0024] In the formula: ΔT1 and ΔT2 are the temperature differences between the two ends of the pipe during the heat exchange process;

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

[0026]

[0027] Where: h in and h out These are the heat transfer coefficients for the inner and outer sides of the heat exchanger, respectively, in W / (m²). 2 ·K); d1 and d2 are the thicknesses of the heat exchanger and dust layer, respectively, in meters; k1 and k2 are the thermal conductivity of the heat exchanger and dust layer, respectively, in W / (m²). 2 ·K);

[0028] Since dust accumulation affects thermal conductivity, the thermal conductivity under dust accumulation conditions is calculated here. The effect of dust accumulation on thermal conductivity can be derived from experimental data using an empirical formula:

[0029]

[0030] In the formula: k is the thermal conductivity under dust accumulation conditions, W / (m²). 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 exchange Q, the heat exchange efficiency of the heat exchanger can be calculated using the following formula:

[0032]

[0033] In the formula: η is the heat exchange efficiency; Q is the actual heat exchanged, W; Q total The theoretical maximum heat exchange capacity is W;

[0034] The theoretical maximum heat exchange can be calculated using the following formula:

[0035] Q total =m·c p ·ΔT max

[0036] Where: m is the fluid mass flow rate, kg / s; c p ΔTmax 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, conduct multiple sets of experiments in parallel and measure the average heat transfer efficiency of the multiple sets of experiments to obtain the initial heat transfer efficiency of the heat exchanger.

[0038] Step 5: Adjust the humidity inside the glass box using a humidity control device. Based on steps 1, 2, and 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 results measured in step 4.

[0039] Step 6: Change the heating temperature of the temperature control board. Under the humidity adjustment in step 5, measure the heat exchange efficiency of the heat exchange plate at different heat source temperatures to obtain the heat exchange efficiency of the heat exchange plate under different humidity and temperature conditions.

[0040] Step 7: After all the above tests are completed, adjust the system to the initial state. After the adjustment is completed, use the gantry bracket to place the thin plate directly above the heat exchange plate and directly below the vibrating screen. Start the vibrator and sliding device. Under the action of the sliding bracket, the vibrating screen will move back and forth left and right. At the same time, the dust in the vibrating screen will be evenly spread on the thin plate. Then, control the thin plate with the gantry bracket and use an infrared thickness gauge to measure the dust accumulation thickness on the thin plate. After measuring the dust accumulation thickness, use the gantry bracket to make the thin plate with dust stick tightly to the top of the heat exchange plate.

[0041] Step 8: First, conduct tests under the same experimental conditions as in Steps 1, 2, 3, and 4 to obtain the initial heat exchange efficiency of the heat exchanger under dust coverage. Then, measure the heat exchange efficiency of the heat exchanger under the conditions in Step 5 to obtain the heat exchange efficiency of the heat exchanger under different humidity conditions when covered by dust. Finally, perform the same measurements as in Step 6 to obtain the heat exchange efficiency of the heat exchanger under different humidity and temperature conditions when covered by dust.

[0042] Step 9: Adjust the vibration and reciprocating motion time of the vibrating screen and vibrator to make different amounts of dust accumulate on the thin plate. Then, measure according to Step 8 to obtain the initial heat exchange efficiency of the heat exchange plate when covered with different thicknesses of dust, as well as the heat exchange efficiency of the heat exchange plate under different humidity and temperature conditions when covered with different thicknesses of dust.

[0043] Step 10: After the experimental measurement of changing humidity conditions is completed in steps 8 and 9, open the operating door and collect the dust with a certain humidity into the dust recovery weighing device. Dry it in a drying oven and obtain the mass of the dust before and after drying from the weighing mechanism. Then, the moisture content of the dust can be obtained, and the initial heat exchange efficiency of the heat exchange plate under different moisture content conditions can be obtained.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] It can measure the changes in heat exchange efficiency of heat exchange fins under different heat source temperatures, ambient humidity, and dust compositions. It can also simulate the impact of dust accumulation on the heat exchange efficiency of heat exchange fins in industrial and mining dust environments. At the same time, it can measure the heat exchange efficiency and changes of heat exchange fins with different structures under these conditions, thus providing a basis for subsequent cooling and ensuring a comfortable working environment. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the heat exchange efficiency testing system for heat exchange plates of the present invention;

[0047] Figure 2 This is a schematic diagram of the automatic dust generation device of the present invention.

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

[0049] Figure 4 This is a schematic diagram of the structure of the heat exchanger of the present invention.

[0050] Figure 5 yes Figure 4 Schematic diagram of the structure of section A.

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

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

[0053] In the diagram: 1. Data collection device, 2. Automatic dust generation device, 3. Main control box, 4. Thermal imager, 5. Heat exchanger, 6. Gantry support, 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 recycling weighing device, 14. Thin plate;

[0054] 21. Vibrating screen; 22. Vibrator; 23. Sliding device; 24. Fixed support; 25. Sliding support; 26. Crank mechanism; 27. Rotary 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-frame;

[0058] 131. Drying oven; 132. Weighing mechanism; 133. Operating door. Detailed Implementation

[0059] The present invention will be further illustrated by the following examples.

[0060] like Figures 1 to 3 As shown, a heat exchanger efficiency testing system includes a glass box 11, and further includes:

[0061] Automatic dust generation device 2 is installed inside glass box 11, including fixed bracket 24 and rotary motor 27 connected inside glass box 11. A sliding device 23 is connected above the fixed bracket 24. A drive shaft is connected above the sliding device 23 through sliding bracket 25. One end of the drive shaft is connected to a vibrating screen 21 equipped with vibrator 22, and the other end is connected to the power output end of rotary motor 27 through crank mechanism 26.

[0062] Temperature control panel 12 is installed on the inner bottom plate of glass box 11;

[0063] A gantry bracket 6 is installed inside the glass box 11. The front end of the bracket is connected to the heat exchange plate 5. A thin plate 14 is placed on top of the heat exchange plate 5 and is controlled by the gantry bracket 6. The heat exchange plate 5 is placed in relation to the temperature control plate 12. The heat exchange plate 5 is connected in series to the pipe connecting the constant temperature water tank 8 and the recovery temperature measuring water tank 10. The constant temperature water tank 8 and the recovery temperature measuring water tank 10 are located outside the glass box 11. The constant temperature water tank 8 is equipped 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] Infrared thickness gauge 9 is installed inside glass box 11 and located on the front side of gantry bracket 6; it is used to measure the thickness of dust on thin plate 14.

[0065] Thermal imager 4 is installed inside glass box 11, located above heat exchange plate 5, to monitor the temperature of thin plate 14 or heat exchange plate 5; and displays the real-time monitored temperature of thin plate 14 or heat exchange plate 5 on data collection device 1 using a high-precision sensor.

[0066] Humidity control device 7 is installed inside the glass box 11 to regulate the humidity inside the glass box 11;

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

[0068] The main control box 3 is located on the outside of the glass box 11 and connects to the various components of the control system.

[0069] The data collection device 1 is located outside the glass box 11 and is connected to various components of the system to collect corresponding data. It is connected to various components within the system through various sensors, and uses a high-precision data acquisition card and a high-speed data transmission interface to ensure the accuracy and real-time performance of data collection.

[0070] Furthermore, such as Figure 6 As shown, the infrared thickness gauge 9 includes a C-shaped frame 93 with its opening facing the gantry support 6. Infrared generators 91 are symmetrically installed at the top and bottom of the opening of the C-shaped frame 93 near the gantry support 6, and a monitoring camera 92 is connected to the opening of the C-shaped frame 93 away from the gantry support 6.

[0071] The measurement principle and steps of the 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 gantry bracket 6 is controlled by the main control box 3 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 at the same time 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, based on the measured distances D1 and D2, the thickness of the thin plate 14 D3, and the height D0 of the C-frame 93, the dust accumulation thickness δ = D0 - D1 - D2 - D3 can be 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, measure the thickness of dust accumulation at multiple points on the thin plate 14 and take the final average value as the final dust accumulation thickness to prevent errors caused by other factors when dust falls in the automatic dust generation device 2 and improve the accuracy of the test.

[0076] Furthermore, such as Figure 7 As shown, the dust recovery weighing device 13 includes a drying chamber 131, a weighing mechanism 132 inside the drying chamber 131, and an operating door 133 on the side wall of the drying chamber 131 near the heat exchange plate 5. After the test is completed, dust with a certain humidity is collected into the drying chamber 131, and the mass of the dust before and after drying can be measured by the weighing mechanism 132.

[0077] Furthermore, such as Figure 4 and Figure 5As shown, the heat exchanger 5 is composed of multiple corrugated fins 51. Each corrugated fin 51 has through holes 52. 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 their length. A heat dissipation groove 513 is provided between the first auxiliary heat dissipation fins 511 and the second auxiliary heat dissipation fins 512. The heat exchanger 5 is installed on a pipe through the through holes 52, and the first and second auxiliary heat dissipation fins 511 and 512 on both sides can improve heat dissipation.

[0078] A method for testing the heat exchange efficiency of a heat exchanger fin, based on the aforementioned heat exchange efficiency testing system, 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 when there is no 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 generation device 2. The heat exchange efficiency of the heat exchanger fin 5 is measured under different dust accumulation thicknesses. The method specifically includes the following steps:

[0079] Step 1: After the test system is debugged, use the main control box 3 to control the gantry bracket 6 to lower the heat exchange plate 5 as a whole to above the temperature control board 12. Then use the temperature control board 12 to heat the heat exchange plate 5. After heating to the specified temperature, raise it to the initial position. Then, put the water in the constant temperature water tank 8 into the pipeline. After the water passes through the pipeline, it enters the recovery temperature measuring water tank 10.

[0080] Step 2: After the water undergoes heat exchange and 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 is calculated using the following formula:

[0081] Q=U·A·ΔT LMTD

[0082] In the formula: Q is the actual heat exchange, W; U is a function of the heat exchange fins, dust environment, and environmental conditions, and is the overall heat transfer coefficient, W / (m²). 2 ·K); A is the heat exchange area, m 2 ;ΔT LMTD The logarithmic mean temperature difference, k;

[0083] The formula for calculating the logarithmic mean temperature difference ΔTLMTD is:

[0084]

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

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

[0087]

[0088] Where: h in and h out The heat transfer coefficients, W / (m²), are for the inner and outer sides of heat exchanger 5, respectively. 2 ·K); d1 and d2 are the thicknesses of heat exchanger 5 and dust layer, respectively, in meters; k1 and k2 are the thermal conductivity of heat exchanger 5 and dust layer, respectively, in W / (m). 2 ·K);

[0089] Since dust accumulation affects thermal conductivity, the thermal conductivity under dust accumulation conditions is calculated here. The effect of dust accumulation on thermal conductivity can be derived from experimental data using an empirical formula:

[0090]

[0091] In the formula: k is the thermal conductivity under dust accumulation conditions, W / (m²). 2 ·K); k0 is the thermal conductivity in the clean state, W / (m 2 ·K); α is the dust influence coefficient, confirmed experimentally; δ is the dust accumulation thickness, in meters;

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

[0093]

[0094] In the formula: η is the heat exchange efficiency; Q is the actual heat exchanged, W; Q total The theoretical maximum heat exchange capacity is W;

[0095] The theoretical maximum heat exchange can be calculated using the following formula:

[0096] Q total =m·c p ·ΔT max

[0097] Where: m is the fluid mass flow rate, kg / s; c p ΔTmax 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, conduct multiple sets of experiments in parallel and measure the average heat transfer efficiency of the multiple sets of experiments to obtain the initial heat transfer efficiency of heat exchanger 5.

[0099] Step 5: Adjust the humidity inside the glass box 11 using the humidity control device 7. Select an appropriate humidity gradient. Based on steps 1, 2 and 3, measure the heat exchange efficiency of the heat exchange plate 5 under different humidity conditions. The heat exchange efficiency of the heat exchange plate 5 under different humidity conditions can be obtained and compared with the results measured in step 4.

[0100] Step 6: Change the heating temperature of the temperature control board 12. 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 heat exchange plate 5 at different heat source temperatures to obtain the heat exchange efficiency of heat exchange plate 5 under different humidity and temperature conditions.

[0101] Step 7: After all the above tests are completed, the system is debugged to the initial state. After debugging, 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. 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 move back and forth. At the same time, the dust in the vibrating screen 21 is evenly spread on the thin plate 14. Then, the gantry bracket 6 controls the thin plate 14 to measure the thickness of the dust accumulation on the thin plate 14 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 tightly attached to the top of the heat exchange plate 5.

[0102] Step 8: First, conduct tests under the same experimental conditions as in Steps 1, 2, 3, and 4 to obtain the initial heat exchange efficiency of heat exchange plate 5 under dust coverage. Then, measure the heat exchange efficiency of heat exchange plate 5 under the conditions in Step 5 to obtain the heat exchange efficiency of heat exchange plate 5 under different humidity conditions when covered by dust. Finally, perform the same measurements as in Step 6 to obtain the heat exchange efficiency of heat exchange plate 5 under different humidity and temperature conditions when covered by dust.

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

[0104] Step 10: During steps 8 and 9, after the experimental measurement of changing humidity conditions is completed, open the operation door 133 and collect the dust with a certain humidity into the dust recovery weighing device 13. Dry it using the drying box 131. 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. Thus, 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 conclusions about the changes and extent of heat exchange efficiency, providing a basis for excellent cooling and providing a comfortable working environment.

[0106] Implementation Case:

[0107] The heat exchange efficiency of heat exchange plate 5 was tested under specific dust accumulation thickness and different conditions (temperature, humidity).

[0108] Step 1: After the system is debugged, use the humidity control device 7 to adjust the humidity in the system to 40%. Use the main control box 3 to control the gantry bracket 6 to place the heat exchange plate 5 directly above the temperature control board 12. Then use the temperature control board 12 to heat it to 60°C and raise it to the initial position. Next, put the 0°C water in the water tank into the tank through the pipe (the initial ambient temperature is 10°C). 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 transmitted information 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. Measure the length D1 of the upper infrared ray emitted by the infrared generator 91 as 120mm, the length D2 of the lower infrared ray as 110mm, the height D0 of the C-frame as 250mm, and the thickness D3 of the thin plate as 10mm. Based on the thickness measurement principle, intelligently calculate the dust accumulation thickness δ=D0-D1-D2-D3=250mm-120mm-110mm-10mm=10mm.

[0110] Step 3: After heat exchange, the water enters the recovery and temperature measurement tank 10, where the internal water temperature is measured to be 45℃, and the heat exchange area A is 0.5m². 2 The fluid mass flow rate m is 0.01 kg / s, and the fluid specific heat capacity c p The theoretical maximum temperature difference is ΔT, which is 4186 J / (kg·K). max It is 50K.

[0111] (1) Calculate the logarithmic mean temperature difference ΔT LMTD The temperature differences at both ends during the heat exchange process are ΔT1 = 50K and ΔT2 = 15K, respectively; therefore, we can obtain:

[0112]

[0113] (2) Calculate the overall heat transfer coefficient U. Assume the heat transfer coefficient h inside heat exchanger 5 is... in 50W / (m 2 ·K), outer heat transfer coefficient h out 20W / (m 2 The thermal conductivity k1 of heat exchanger fin 5 is 0.03 W / (m²). 2The thermal conductivity k2 of the dust layer is 0.01 W / (m²). 2 The thickness of heat exchanger fin 5 (d1) is 0.001 m, and the thickness of the dust layer (d2) is 0.01 m. The dust influence coefficient α is measured to be 0.3. The thermal conductivity k0 under clean conditions is 0.03 W / (m²). 2 ·K), at this point, the thermal conductivity under dust accumulation conditions can be calculated:

[0114]

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

[0116]

[0117] Calculate the actual heat exchange Q:

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

[0119] (3) Calculate Q total :

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

[0121] (4) Calculate the heat transfer efficiency:

[0122]

[0123] This implementation case calculated the heat exchange efficiency of heat exchanger 5 under the conditions of initial ambient humidity of 40%, initial temperature of 60℃ and dust accumulation of 10mm. Other parallel experiments can be calculated according to the above steps after changing the measurement influencing factors.

Claims

1. A heat exchanger efficiency testing system, comprising a glass box (11), characterized in that, Also includes: Automatic dust generation device (2) is installed inside a glass box (11) and includes a fixed bracket (24) and a rotary motor (27) connected inside the glass box (11). A sliding device (23) is connected above the fixed bracket (24). A drive shaft is connected above the sliding device (23) via a sliding bracket (25). One end of the drive shaft is connected to a vibrating screen (21) equipped with a vibrator (22), and the other end is connected to the power output end of the rotary motor (27) via a crank mechanism (26). Temperature control panel (12) is installed on the bottom plate inside the glass box (11); A gantry bracket (6) is installed inside a glass box (11). The front end is driven and connected to a heat exchange plate (5). A thin plate (14) is placed above the heat exchange plate (5). The thin plate (14) is driven and controlled by the gantry bracket (6). The heat exchange plate (5) is placed in relation to the temperature control plate (12). The heat exchange plate (5) is connected in series to the pipe connecting the constant temperature water tank (8) and the recovery temperature measuring water tank (10). The constant temperature water tank (8) and the recovery temperature measuring water tank (10) are located outside the glass box (11). The infrared thickness gauge (9) is installed inside the glass box (11) and located on the front side of the gantry bracket (6); A thermal imager (4) is installed inside a glass box (11) and located above the heat exchange plate (5) to monitor the temperature of the thin plate (14) or the heat exchange plate (5); A humidity control device (7) is installed inside a glass box (11) to regulate the humidity inside the glass box (11); The dust recovery weighing device (13) is installed inside the glass box (11) and located on the right side of the heat exchange plate (5); The main control box (3) is located outside the glass box (11) and connects to the various components of the control system; The data collection device (1) is located outside the glass box (11) and is connected to each component of the system to collect corresponding data.

2. The heat exchange efficiency testing system for heat exchanger plates according to claim 1, characterized in that, The infrared thickness gauge (9) includes a C-frame (93), with the opening of the C-frame (93) facing the gantry support (6). Infrared generators (91) are symmetrically installed at the inner side of the opening of the C-frame (93) near the gantry support (6), and a monitoring camera (92) is connected to the inner side of the opening of the C-frame (93) away from the gantry support (6).

3. The heat exchange efficiency testing system for heat exchanger plates according to claim 1, characterized in that, The dust recovery weighing device (13) includes a drying box (131), a weighing mechanism (132) is provided inside the drying box (131), and an operating door (133) is provided on the side wall of the drying box (131) near the heat exchange plate (5).

4. The heat exchange efficiency testing system for heat exchanger plates according to claim 1, characterized in that, The heat exchange plate (5) is composed of multiple corrugated fins (51). The corrugated fins (51) are provided with through holes (52). The corrugated fins (51) are provided with parallel first auxiliary heat dissipation fins (511) and second auxiliary heat dissipation fins (512) on both sides along the length direction. 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 plate, characterized in that, Based on the heat exchange efficiency testing system of claim 3, firstly, without placing a thin plate (14) above the heat exchange plate (5), the heat exchange efficiency of the heat exchange plate (5) without dust accumulation is measured. Secondly, a thin plate (14) is placed above the heat exchange plate (5), and dust is evenly spread on the upper surface of the thin plate (14) by an automatic dust generation device (2). The heat exchange efficiency of the heat exchange plate (5) under different dust accumulation thicknesses is measured. Specifically, the system includes the following steps: Step 1: After the test system is debugged, the gantry bracket (6) is controlled by the main control box (3) to lower the heat exchange plate (5) as a whole to the top of the temperature control board (12). Then the heat exchange plate (5) is heated by the temperature control board (12) and raised to the initial position after being heated to the specified temperature. Then the water in the constant temperature water tank (8) is introduced into the pipeline and enters the recovery temperature measurement water tank (10) after passing through the pipeline. Step 2: After the water undergoes heat exchange, it enters the recovery temperature measuring tank (10). The temperature of the water inside the recovery temperature measuring tank (10) is measured, and the actual heat exchange is calculated using the following formula: Q = U·A·∆T LMTD； Where: Q is the actual heat exchange, W; U is the overall heat transfer coefficient, W / (m²·K); A is the heat exchange area, m²; ∆T LMTD The logarithmic mean temperature difference, k; Logarithmic mean temperature difference ∆T LMTD The calculation formula is: ； In the formula: ∆T1 and ∆T2 are the temperature differences between the two ends of the pipe during the heat exchange process; The overall heat transfer coefficient U is further refined as follows: ； Where: h in and h out d1 and d2 are the heat transfer coefficients of the inner and outer sides of the heat exchange plate (5), respectively, in W / (m²·K); d1 and d2 are the thicknesses of the heat exchange plate (5) and the dust layer, respectively, in m; k1 and k2 are the thermal conductivity of the heat exchange plate (5) and the dust layer, respectively, in W / (m²·K); Since dust accumulation affects thermal conductivity, the thermal conductivity under dust accumulation conditions is calculated here. The effect of dust accumulation on thermal conductivity is derived from an empirical formula by fitting experimental data: ； Where: k is the thermal conductivity under dust accumulation, W / (m²·K); k0 is the thermal conductivity under clean conditions, W / (m²·K); α is the dust influence coefficient; δ is the dust accumulation thickness, m; Step 3: After calculating the actual heat exchange Q, the heat exchange efficiency of the heat exchanger can be calculated using the following formula: ； In the formula: Q represents the heat exchange efficiency; Q represents the actual heat exchanged (in W). total The theoretical maximum heat exchange capacity is W; The theoretical maximum heat exchange can be calculated using the following formula: ；； Where: m is the fluid mass flow rate, kg / s; c p ΔTmax 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, conduct multiple sets of experiments in parallel and measure the average heat exchange efficiency of the multiple sets of experiments to obtain the initial heat exchange efficiency of the heat exchange plate (5). Step 5: Use the humidity control device (7) to adjust the humidity in the glass box (11). Based on Step 1, Step 2 and Step 3, measure the heat exchange efficiency of the heat exchange plate (5) under different humidity conditions. The heat exchange efficiency of the heat exchange plate (5) under different humidity conditions can be obtained and compared with the results measured in Step 4. Step 6: Change the heating temperature of the temperature control board (12). Under the humidity adjustment in step 5, measure the heat exchange efficiency of the heat exchange plate (5) at different heat source temperatures. The heat exchange efficiency of the heat exchange plate (5) under different humidity and temperature conditions can be obtained. Step 7: After all the above test processes are completed, the system is debugged to the initial state. After debugging, 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). 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 move back and forth. At the same time, the dust in the vibrating screen (21) is evenly spread on the thin plate (14). Then, the gantry bracket (6) is used to control the thin plate (14) to measure the thickness of the dust accumulation on the thin plate (14) using an infrared thickness gauge (9). After measuring the dust accumulation thickness, the gantry bracket (6) is used to make the thin plate (14) with dust stick tightly to the top of the heat exchange plate (5). Step 8: First, test under the same experimental conditions as in Step 1, 2, 3, and 4 to obtain the initial heat exchange efficiency of the heat exchange plate (5) under dust coverage. Then, measure the heat exchange efficiency of the heat exchange plate (5) under the conditions in Step 5 to obtain the heat exchange efficiency of the heat exchange plate (5) under different humidity conditions when covered by dust. Finally, measure in the same way as in Step 6 to obtain the heat exchange efficiency of the heat exchange plate (5) under different humidity and temperature conditions when covered by dust. Step 9: Adjust the vibration and reciprocating motion time of the vibrating screen (21) and the vibrator (22) so that different amounts of dust accumulate on the thin plate (14). Then measure according to step 8 to obtain the initial heat exchange efficiency of the heat exchange plate (5) when covered with different thicknesses of dust, as well as the heat exchange efficiency of the heat exchange plate (5) under different humidity and temperature conditions when covered with different thicknesses of dust. Step 10: In steps 8 and 9, after the experimental measurement of changing humidity conditions is completed, open the operation door (133) and collect the dust with a certain humidity into the dust recovery weighing device (13). Dry it using the drying box (131). 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. The initial heat exchange efficiency of the heat exchange plate (5) under different moisture content conditions can be obtained.

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