Heat and moisture transfer characteristics testing system and method based on evaporative medium wettability

Abstract

The present invention provides a heat and moisture transfer characteristics test system and method based on the wettability of an evaporative medium. The test system includes: an air pretreatment device, including a first air channel; a second air channel, in which an air pressure sensing device for sensing air pressure is provided; a fan; a placement platform, which is provided in the second air channel and is provided with a table for placing the evaporative medium to be tested; a solar radiation simulator, in which the simulated sunlight emitted by the light source can be radiated on the surface of the evaporative medium to be tested; an automatic water replenishment system, including a liquid level water tank; the automatic water replenishment system also includes a water replenishment container; the test system also includes: a weighing device; a temperature sensor and a humidity sensor; a temperature measuring device; an air flow meter; and a water film thickness measuring device. The test system and method provided by the present invention can accurately obtain the heat and mass transfer characteristics of the roof evaporative medium under different surface wettability and different environmental conditions, and thus obtain the optimal water supply under different conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of heat and moisture transfer characteristics testing, and in particular to a heat and moisture transfer characteristics testing system and method based on evaporative medium wettability. Background Art

[0002] High energy consumption and carbon emissions of building air conditioning are difficult problems faced by my country and many countries in the world. Studies have shown that 50% of the heat obtained in a single-story building comes from the roof. Applying passive evaporative cooling technology to the roof is an effective means to reduce the heat load of the building, reduce air conditioning energy consumption, and improve the indoor thermal environment. According to the classification of evaporative media, evaporative roof technology includes planting roofs, water storage roofs, spray roofs, floating fibers and wet fiber roofs. These different forms of evaporative roofs all use the principle of evaporating water in the evaporative medium and taking away the latent heat of vaporization to reduce the roof temperature in summer. Among them, compared with water storage roofs and floating fiber roofs, wet fiber roofs can obtain the lowest indoor temperature under various climatic conditions (humid heat, dry heat and mild), and the water consumption is only 1 / 37 of that of water storage roofs and floating fiber roofs, and it has almost no effect on the building load. The structure of the wet fiber roof is simple, and a thin fiber layer is laid on the roof waterproof layer. The fiber layer is a water-absorbing layer and is a medium for achieving evaporative cooling.

[0003] As a porous evaporation medium, the fiber layer has the advantages of strong water absorption and water retention capacity, and its heat and mass transfer characteristics have an important influence on the roof cooling effect. In the field of evaporative roof technology, building a roof heat and moisture transfer calculation model is an important task to predict the indoor thermal environment. The model usually assumes that the wet surface of the roof evaporative medium is similar to the evaporation of the free water surface. Under any working condition and water supply conditions, its surface is fully wetted to meet the heat and mass transfer ratio, that is, the Lewis number is approximately equal to 1 to obtain the mass transfer coefficient corresponding to the heat transfer coefficient. In the actual heat and moisture transfer process, the degree of wetting of the evaporative material surface varies due to the influence of the wettability of the evaporative material, the water supply method and the environmental conditions. The assumption of sufficient surface wetting is one of the main reasons for the prediction error of the calculation model. Prediction errors often lead to excessive water supply to the evaporative roof, which is of no benefit to reducing the indoor load and can only increase additional water consumption.

[0004] Therefore, how to accurately obtain the heat and mass transfer characteristics of the roof evaporation medium under different surface wetness and different environmental conditions to obtain the optimal water supply under different conditions is an important technical problem that technical personnel in this field need to solve urgently. Summary of the invention

[0005] The present invention provides a heat and moisture transfer characteristics testing system and method based on the wettability of evaporative media, which can accurately obtain the heat and mass transfer characteristics of roof evaporative media under different surface wettability and different environmental conditions, and then obtain the optimal water supply under different conditions.

[0006] A first aspect of the present invention provides a heat and moisture transfer characteristics testing system based on evaporative medium wettability, comprising:

[0007] an air pretreatment device, comprising a first air passage provided with an air inlet and an air outlet, an air filtering device arranged in the first air passage, a temperature control device for heating and cooling the air in the first air passage, and a humidity control device for humidifying the air in the first air passage;

[0008] a second air channel, provided with an air inlet and an air outlet, the air inlet of the second air channel being connected to the air outlet of the first air channel, and an air pressure sensing device for sensing air pressure being provided in the second air channel;

[0009] A fan, used for driving air flow from the air inlet of the first air channel to the air outlet of the second air channel;

[0010] A placement platform, which is arranged in the second air channel and is provided with a table surface for placing the evaporation medium to be tested;

[0011] A solar radiation simulator, comprising a light source and a dimmer for adjusting the radiation intensity of the light source, an isolation device for isolating heat conduction and heat convection is provided between the light source and the second air channel, and the simulated sunlight emitted by the light source can be radiated on the surface of the evaporation medium to be tested;

[0012] The automatic water replenishment system comprises a liquid level water tank provided with a water temperature measuring device therein, the table top of the placement platform is provided with a water replenishment hole which penetrates downwards, the liquid level water tank is connected with the water replenishment hole through a pipeline, the pipeline is provided with a water pressure sensing device for sensing water pressure and a flow regulating valve for regulating the water replenishment flow, the water level in the liquid level water tank can be at the same horizontal plane as the lower surface of the evaporative medium to be tested; the automatic water replenishment system also comprises a water replenishment container, the water replenishment container is connected with the liquid level water tank, the liquid level water tank is provided with a liquid level switch for controlling the water replenishment container to replenish water to the liquid level water tank, and the opening condition of the liquid level switch is that the water level of the liquid level water tank is lower than the lower surface of the evaporative medium to be tested;

[0013] A weighing device, used for weighing the water replenishment container;

[0014] a temperature sensor and a humidity sensor, disposed in the second air passage and used to measure the air temperature and humidity in the second air passage;

[0015] A temperature measuring device, used to measure the surface temperature of the evaporative medium to be tested;

[0016] an air flow meter, used for measuring the air flow delivered from the first air passage to the second air passage;

[0017] The water film thickness measuring device is used to measure the thickness of the water film formed on the surface of the evaporation medium to be tested.

[0018] According to the heat and moisture transfer characteristics testing system based on the wettability of the evaporative medium provided by the present invention, a plurality of the water replenishment holes are distributed on the table matrix of the placement platform, and the pipeline includes a main circuit connected to the liquid level water tank, and a plurality of branches connected to the main circuit at one end and to the water replenishment holes at the other end in a one-to-one correspondence, and each of the branches is provided with the water pressure sensing device and the flow regulating valve.

[0019] According to the heat and moisture transfer characteristics testing system based on evaporative medium wettability provided by the present invention, the isolation device includes a box with an opening on one side, the light source is arranged in the box, the inner wall of the box is provided with a reflective film, the inner side of the reflective film is provided with a thermal insulation film, and the opening is closed by a light-transmitting partition.

[0020] According to the heat and moisture transfer characteristics testing system based on the wettability of the evaporative medium provided by the present invention, the water film thickness measuring device includes an image acquisition device for photographing the surface of the evaporative medium to be tested and a cold light source for providing shooting light, and the water film thickness on the surface of the evaporative medium to be tested can be obtained from the image captured by the image acquisition device.

[0021] According to the heat and moisture transfer characteristics testing system based on evaporative medium wettability provided by the present invention, the fan is arranged in the second air channel, and the fan is close to the air outlet position of the second air channel.

[0022] The heat and moisture transfer characteristics testing system based on evaporative medium wettability provided by the present invention further includes a flow mixer arranged in the second air channel, and the flow mixer is arranged at a position close to the air inlet end of the second air channel.

[0023] According to the heat and moisture transfer characteristics testing system based on evaporative medium wettability provided by the present invention, the placement platform includes a thermal insulation layer, the upper surface of the thermal insulation layer is provided with a groove, and the table top is arranged in the groove.

[0024] The heat and moisture transfer characteristics testing system based on the wettability of the evaporative medium provided by the present invention also includes a data acquisition and processing device, which is communicatively connected to the image acquisition device, the air flow meter, the temperature sensor, the humidity sensor, the temperature measuring device, the water temperature measuring device, and the weighing device.

[0025] A second aspect of the present invention provides a method for testing heat and moisture transfer characteristics based on evaporative medium wettability, using a heat and moisture transfer characteristics testing system based on evaporative medium wettability as described in any of the above items, including multiple groups of experiments, each group of experiments including the steps of:

[0026] Fixing the evaporation medium to be tested on the table of the placement platform;

[0027] Add water to the liquid level water tank, and adjust the water surface in the liquid level water tank to be at the same level as the lower surface of the evaporative medium to be tested, and adjust the flow regulating valve to make the lower surface pressure of the evaporative medium to be tested equal to the upper surface pressure, so as to wet the evaporative medium to be tested only by capillary action;

[0028] The air is filtered, temperature-regulated and humidity-regulated by the air pretreatment device, and after reaching a preset air temperature and a preset air humidity, the air is driven by the fan to enter the second air channel, and the fan is controlled so that the air flow rate from the first air channel to the second air channel is a preset air flow rate, and the radiation intensity of the light source of the solar radiation simulator is adjusted to a preset radiation intensity;

[0029] The water film thickness formed on the surface of the evaporative medium to be tested is measured continuously by the water film thickness measuring device, and it is determined whether the water film thicknesses measured multiple times adjacently are equal. If they are equal, the measured water film thickness is used as the reference water film thickness of the evaporative medium to be tested in a water absorption saturation state; and / or, the weight of the water replenishment container is measured continuously by the weighing device, and it is determined whether the weights of the water replenishment container measured multiple times adjacently are equal. If they are equal, the water film thickness formed on the surface of the evaporative medium to be tested is measured by the water film measuring device, and the measured water film thickness is used as the reference water film thickness of the evaporative medium to be tested in a water absorption saturation state;

[0030] Under the working conditions of the preset air temperature, the preset air humidity, the preset air flow rate and the preset radiation intensity, continuously measure the water film thickness formed on the surface of the evaporative medium to be tested within a preset time, compare the measured water film thickness with the reference water film thickness, and adjust the flow control valve to adjust the water replenishment amount according to the comparison result, so that the evaporative medium to be tested is always in a water-saturated state, and then the water replenishment amount is equal to the surface evaporation amount of the evaporative medium to be tested;

[0031] The evaporation amount of the evaporation medium to be tested within a preset time is obtained by the weight reduction of the water replenishment container; and the average water film thickness is calculated by combining the reference water film thickness, the water absorption amount of the evaporation medium to be tested from the beginning of water absorption to water absorption saturation, and the volume, porosity, and surface area of ​​the evaporation medium to be tested;

[0032] The surface temperature of the evaporative medium to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank, and all or part of the parameters of the preset air flow rate in each group of experiments are different. According to the evaporation amount of the evaporative medium to be tested, the water film thickness of the evaporative medium to be tested, the surface temperature of the evaporative medium to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank, and the preset air flow rate in each group of experiments, the surface evaporation rate, convective heat transfer coefficient, convective mass transfer coefficient, and Lewis number of the evaporative medium to be tested are calculated, and then a quantitative relationship between the surface wettability, water supply and evaporation rate of the evaporative medium to be tested is established.

[0033] According to a method for testing heat and moisture transfer characteristics based on evaporative medium wettability provided by the present invention, a heat and moisture transfer characteristics testing system based on evaporative medium wettability as described above is used, including multiple groups of experiments, each group of experiments including the following steps:

[0034] Fixing the evaporation medium to be tested on the table of the placement platform;

[0035] Adding water to the liquid level water tank and adding fluorescent material to the liquid level water tank, and adjusting the water surface in the liquid level water tank and the lower surface of the evaporation medium to be tested to be at the same level;

[0036] The air is filtered, temperature-regulated and humidity-regulated by the air pretreatment device, and after reaching a preset air temperature and a preset air humidity, the air is driven by the fan to enter the second air channel, the flow rate of the flow regulating valve is adjusted, and the fan is controlled to make the air flow rate from the first air channel to the second air channel equal to the preset air flow rate, so that the lower surface pressure of the water film on the evaporative medium to be tested is equal to the upper surface pressure, the evaporative medium to be tested is wetted only by capillary action, and the radiation intensity of the light source of the solar radiation simulator is adjusted to the preset radiation intensity;

[0037] The water film thickness formed on the surface of the evaporative medium to be tested is measured continuously by the water film thickness measuring device, and it is determined whether the water film thicknesses measured several times adjacently are equal. If they are equal, the measured water film thickness is used as the reference water film thickness of the evaporative medium to be tested in a water absorption saturation state; and / or, the weight of the water replenishment container is measured continuously by the weighing device, and it is determined whether the weights of the water replenishment container measured several times adjacently are equal. If they are equal, the water film thickness formed on the surface of the evaporative medium to be tested is measured by the water film measuring device, and the measured water film thickness is used as the reference water film thickness of the evaporative medium to be tested in a water absorption saturation state;

[0038] Clean the liquid level water tank, replace the evaporation medium to be tested with the same size, and add water without fluorescent material into the liquid level water tank;

[0039] Under the working conditions of the preset air temperature, the preset air humidity, the preset air flow rate and the preset radiation intensity, continuously measure the water film thickness formed on the surface of the evaporative medium to be tested within a preset time, compare the measured water film thickness with the reference water film thickness, and adjust the flow control valve to adjust the water replenishment amount according to the comparison result, so that the evaporative medium to be tested is always in a water-saturated state, and then the water replenishment amount is equal to the surface evaporation amount of the evaporative medium to be tested;

[0040] The evaporation amount of the evaporation medium to be tested within a preset time is obtained by the weight reduction of the water replenishment container; and the average water film thickness is calculated by combining the reference water film thickness, the water absorption amount of the evaporation medium to be tested from the beginning of water absorption to water absorption saturation, and the volume, porosity, and surface area of ​​the evaporation medium to be tested;

[0041] The surface temperature of the evaporative medium to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank, and the preset air flow rate parameters in each group of experiments are different or some parameters are different. According to the evaporation amount of the evaporative medium to be tested, the water film thickness of the evaporative medium to be tested, the surface temperature of the evaporative medium to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank, and the preset air flow rate in each group of experiments, the surface evaporation rate, convective heat transfer coefficient, convective mass transfer coefficient, and Lewis number of the evaporative medium to be tested are calculated, and then a quantitative relationship between the surface wettability, water supply and evaporation rate of the evaporative medium to be tested is established.

[0042] The heat and moisture transfer characteristic testing system based on the wettability of an evaporative medium provided by the present invention comprises an air pretreatment device for filtering, adjusting the temperature and adjusting the humidity of air and a second air channel. The air treated by the air pretreatment device can reach a preset temperature and a preset humidity. The air inlet of the second air channel is connected to the air outlet of the first air channel. The air treated by the air pretreatment device can flow into the second air channel by driving a fan, and the air flow and air pressure can be controlled by controlling the rotation speed of the fan. An air pressure sensing device for sensing air pressure is provided in the second air channel; a placement platform is provided in the second air channel, and the placement platform is provided with a table top for placing the evaporative medium to be tested; and a solar radiation simulator can simulate sunlight irradiating the evaporative medium to be tested. The present invention also includes an automatic water replenishment system, including a liquid level water tank with a water temperature measuring device inside, a table top of the placement platform is provided with a water replenishment hole that penetrates downward, the liquid level water tank is connected with the water replenishment hole through a pipeline, a water pressure sensing device for sensing water pressure and a flow regulating valve for adjusting the water replenishment flow rate are provided on the pipeline, the water level in the liquid level water tank can be in the same horizontal plane as the lower surface of the evaporation medium to be tested, when the water level in the liquid level water tank is in the same horizontal plane as the lower surface of the evaporation medium to be tested, the flow rate of the flow regulating valve and the rotation speed of the fan are adjusted to make the lower surface pressure of the water film on the evaporation medium to be tested equal to the upper surface pressure, the evaporation medium to be tested can only absorb water through capillary action to achieve a wetting effect, thereby avoiding the influence of the water replenishment pressure on the water absorption of the evaporation medium to be tested. The automatic water replenishment system also includes a water replenishment container, which is connected to a liquid level water tank. The liquid level water tank is provided with a liquid level switch for controlling the water replenishment container to replenish water to the liquid level water tank. The condition for the water replenishment container to replenish water to the liquid level water tank is that the water level of the liquid level water tank is lower than the lower surface of the evaporation medium to be tested. When the water level of the liquid level water tank is lower than the lower surface of the evaporation medium to be tested, the liquid level switch is opened, and the water replenishment container replenishes water into the liquid level water tank until the water level of the liquid level water tank is flush with the lower surface of the evaporation medium to be tested, and the liquid level switch is closed to stop replenishing water. The present invention also includes a weighing device, a temperature sensor and a humidity sensor, a temperature measuring device, an air flow meter, and a water film thickness measuring device, wherein the weighing device is used to weigh the water replenishment container; the temperature sensor and the humidity sensor are arranged in the second air channel and are used to measure the air temperature and humidity in the second air channel; the temperature measuring device is used to measure the surface temperature of the evaporation medium to be tested; the air flow meter is used to measure the air flow transported from the first air channel to the second air channel; and the water film thickness measuring device is used to measure the water film thickness formed on the surface of the evaporation medium to be tested. When using the heat and moisture transfer characteristics testing system provided by the present invention, multiple groups of experimental tests need to be performed, and the steps of each group of experimental tests are as follows:

[0043] Fix the evaporation medium to be tested on the table of the placement platform;

[0044] Add water to the liquid level tank and adjust the water level in the liquid level tank to be at the same level as the lower surface of the evaporation medium to be tested;

[0045] The air is filtered, temperature-regulated and humidity-regulated by an air pretreatment device, and after reaching a preset air temperature and a preset air humidity, the air is driven by a fan to enter a second air channel, the flow rate of a flow regulating valve is adjusted, and the fan is controlled so that the air flow rate from the first air channel to the second air channel is a preset air flow rate, so that the lower surface pressure of the water film on the evaporation medium to be tested is equal to the upper surface pressure, the evaporation medium to be tested is wetted only by capillary action, and the radiation intensity of the light source of the solar radiation simulator is adjusted to a preset radiation intensity;

[0046] The thickness of the water film formed on the surface of the evaporative medium to be tested is continuously measured by a water film thickness measuring device, and it is determined whether the water film thicknesses measured multiple times adjacent to each other are equal. If they are equal, the measured water film thickness is used as the reference water film thickness of the evaporative medium to be tested in a water absorption saturation state; and / or, the weight of the water replenishment container is continuously measured by a weighing device, and it is determined whether the weights of the water replenishment container measured multiple times adjacent to each other are equal. If they are equal, the thickness of the water film formed on the surface of the evaporative medium to be tested is measured by a water film measuring device, and the measured water film thickness is used as the reference water film thickness of the evaporative medium to be tested in a water absorption saturation state;

[0047] Under the working conditions of preset air temperature, preset air humidity, preset air flow rate and preset radiation intensity, the thickness of the water film formed on the surface of the evaporation medium to be tested is continuously measured within a preset time, the measured water film thickness is compared with the reference water film thickness, and the flow control valve is adjusted to adjust the water replenishment amount according to the comparison result, so that the evaporation medium to be tested is always in a state of water absorption saturation, and the water replenishment amount is equal to the surface evaporation amount of the evaporation medium to be tested;

[0048] The evaporation amount of the evaporation medium to be tested within the preset time is obtained by the weight reduction of the water replenishment container; and the average water film thickness is calculated by combining the reference water film thickness, the water absorption amount of the evaporation medium to be tested from the beginning of water absorption to water absorption saturation, and the volume, porosity, and surface area of ​​the evaporation medium to be tested;

[0049] The surface temperature of the evaporative medium to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank, and the preset air flow rate parameters in each group of experiments are different or some parameters are different. According to the evaporation amount of the evaporative medium to be tested, the water film thickness of the evaporative medium to be tested, the surface temperature of the evaporative medium to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank, and the preset air flow rate in each group of experiments, the surface evaporation rate, the convective heat transfer coefficient, the convective mass transfer coefficient, and the Lewis number of the evaporative medium to be tested are calculated, and then the quantitative relationship between the surface wettability, the water supply and the evaporation rate of the evaporative medium to be tested is established. Furthermore, the heat and moisture transfer characteristics test system based on the wettability of the evaporative medium provided by the present invention can accurately obtain the heat and mass transfer characteristics of the roof evaporative medium under different surface wettability and different environmental conditions, and then obtain the optimal water supply under different conditions.

[0050] The present invention also provides a method for testing heat and moisture transfer characteristics based on the wettability of an evaporative medium. Based on the above test system, the test method provided by the present invention can accurately obtain the heat and mass transfer characteristics of the roof evaporative medium under different surface wettability and different environmental conditions, and then obtain the optimal water supply under different conditions. The derivation process of this beneficial effect is generally similar to the derivation process of the beneficial effect brought by the above test system, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0052] Figure 1 Schematic diagram of a heat and moisture transfer characteristics testing system based on evaporative medium wettability provided by the present invention;

[0053] Figure 2 is a top view of the placement platform provided by the present invention;

[0054] Figure 3 It is a schematic longitudinal section diagram of the placement platform provided by the present invention;

[0055] Figure 4 is a schematic diagram of a solar radiation simulator provided by the present invention;

[0056] Figure 5 The hourly measurement results of the air inlet and outlet temperature and humidity of the second air channel in the embodiment of the present invention;

[0057] Figure 6 The hourly measurement results of the surface temperature of the evaporation medium to be tested in the embodiment of the present invention;

[0058] Figure 7 The hourly measurement result of the weight of the water replenishment container in the embodiment of the present invention;

[0059] Figure 8 This is a graph showing the hourly measurement of the amount of water absorbed by the evaporation medium to be tested when the evaporation medium reaches saturation state in an embodiment of the present invention;

[0060] Reference numerals:

[0061] 1: First air channel; 2: Air filter device; 3: Temperature control device;

[0062] 4: humidity control device; 5: first flow mixer; 6: second air channel;

[0063] 7: fan; 8: second mixer; 9: air pressure sensing device;

[0064] 10: Placement platform; 11: Evaporation medium to be tested; 12: Liquid level water tank;

[0065] 13: Water temperature measuring device; 14: Water filling hole; 15: Water pressure sensing device;

[0066] 16: Flow regulating valve; 17: Water supply container; 18: Liquid level switch;

[0067] 19: weighing device; 20: temperature sensor; 21: humidity sensor;

[0068] 22: Trunk road; 23: Branch road; 24: Light source;

[0069] 25: Reflective film; 26: Thermal insulation film; 27: Translucent partition;

[0070] 28: Image acquisition device; 29: Cold light source; 30: Barometer;

[0071] 31: thermal insulation layer; 32: data acquisition and processing device; 33: air flow meter;

[0072] 34: Temperature measuring device; 35: Solar radiation simulator. DETAILED DESCRIPTION

[0073] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0074] Combine the following Figure 1-Figure 4 Describe the heat and moisture transfer characteristics test system based on evaporative medium wettability of the present invention, please refer to Figure 1 The test system provided in this embodiment includes an air pretreatment device for filtering, adjusting the temperature and humidity of the air. The air pretreatment device may include a first air channel 1, an air filtering device 2 arranged in the first air channel 1, a temperature control device 3 for heating and cooling the air in the first air channel 1, and a humidity control device 4 for humidifying the air in the first air channel 1.

[0075] In some embodiments, the air filter device 2 of the air pretreatment device is arranged at the air inlet and / or air outlet of the first air channel 1 to clean the air impurities and dust entering the first air channel 1. The heating unit of the temperature control device 3 may include a heating rod and a voltage regulator, and the voltage regulator adjusts the output power of the heating rod by adjusting the voltage to achieve the purpose of adjusting the heating temperature. The refrigeration unit of the temperature control device 3 may include a Peltier and a voltage regulator, and the Peltier semiconductor voltage is adjusted by the voltage regulator to control the cold output to achieve the purpose of air cooling. The humidity control device 4 can use an ultrasonic atomizer for humidification, and adjust the amount of mist to achieve the purpose of adjusting the air humidity. It should be noted that the air filter device 2, the heating unit, the refrigeration unit, and the humidity control device 4 can be separate modules, and two adjacent modules can be connected modularly. A first mixer 5 can be provided at the air outlet of the first air channel 1, and the first mixer 5 can be a porous sponge, a wire mesh, etc., which can make the air mixed and the flow rate more uniform.

[0076] The test system provided in this embodiment further includes a second air channel 6, the air inlet of the second air channel 6 is connected to the air outlet of the first air channel 1 through a pipeline, and the air treated by the air pretreatment device can flow into the second air channel 6 by driving the fan 7. The fan 7 can be arranged in the second air channel 6, and the fan 7 is close to the air outlet position of the second air channel 6.

[0077] Similarly, in order to make the air flow rate flowing into the second air channel 6 more uniform, a second mixer 8 can be provided at the entrance of the second air channel 6. The second mixer 8 can be a porous sponge, a wire mesh, etc., which can mix the air and make the flow rate more uniform. The air flow rate and air pressure can be controlled by controlling the speed of the fan 7. The second air channel 6 is provided with an air pressure sensing device 9 for sensing the air pressure.

[0078] The test system provided in this embodiment also includes a solar radiation simulator 35, an automatic water replenishment system, a placement platform 10, a weighing device 19, a temperature sensor 20 and a humidity sensor 21, a temperature measuring device 34, an air flow meter 33, and a water film thickness measuring device. The placement platform 10 is arranged in the second air channel 6, and the placement platform 10 is provided with a table for placing the evaporation medium 11 to be tested. The solar radiation simulator 35 can simulate sunlight irradiating the evaporation medium 11 to be tested. The automatic water replenishment system includes a liquid level water tank 12 with a water temperature measuring device 13 inside, a table top of the placement platform 10 is provided with a water replenishment hole 14 penetrating downward, the liquid level water tank 12 is connected to the water replenishment hole 14 through a pipeline, and a water pressure sensing device 15 for sensing water pressure and a flow regulating valve 16 for adjusting the water replenishment flow rate are provided on the pipeline. The water level in the liquid level water tank 12 can be at the same horizontal plane as the lower surface of the evaporative medium 11 to be tested. When the water level in the liquid level water tank 12 is at the same horizontal plane as the lower surface of the evaporative medium 11 to be tested, the flow rate of the flow regulating valve 16 and the rotation speed of the fan 7 are adjusted to make the lower surface pressure of the water film on the evaporative medium 11 to be tested equal to the upper surface pressure, and the evaporative medium 11 to be tested can only absorb water through capillary action to achieve a wetting effect, avoiding the influence of the water replenishment pressure and the air pressure difference on the water absorption of the evaporative medium 11 to be tested. The automatic water replenishment system also includes a water replenishment container 17, which is connected to the liquid level water tank 12. The liquid level water tank 12 is provided with a liquid level switch 18 for controlling the water replenishment container 17 to replenish water to the liquid level water tank 12, and the condition for the water replenishment container 17 to replenish water to the liquid level water tank 12 is that the water level of the liquid level water tank 12 is lower than the lower surface of the evaporation medium 11 to be tested. When the water level of the liquid level water tank 12 is lower than the lower surface of the evaporation medium 11 to be tested, the liquid level switch 18 is opened, and the water replenishment container 17 replenishes water into the liquid level water tank 12 until the water level of the liquid level water tank 12 is flush with the lower surface of the evaporation medium 11 to be tested, and the liquid level switch 18 is closed to stop replenishing water.

[0079] The weighing device 19 is used to weigh the water replenishment container 17, and specifically, an electronic scale with high precision can be used; the temperature sensor 20 and the humidity sensor 21 are arranged in the second air channel 6 and are used to measure the air temperature and humidity in the second air channel 6; the temperature measuring device 34 is used to measure the surface temperature of the evaporative medium 11 to be tested, and specifically, it can be set to a thermocouple that can be attached to the surface of the evaporative medium 11 to be tested; the air flow meter 33 is used to measure the air flow delivered from the first air channel 1 to the second air channel 6, and specifically, it can be set on the connecting pipe between the first air channel 1 and the second air channel 6; the water film thickness measuring device is used to measure the thickness of the water film formed on the surface of the evaporative medium 11 to be tested.

[0080] When using the heat and moisture transfer characteristics testing system provided in this embodiment, multiple groups of experimental tests need to be performed, and the steps of each group of experimental tests are as follows:

[0081] Fix the evaporation medium 11 to be tested on the table of the placement platform 10;

[0082] Add water to the liquid level water tank 12, and adjust the water surface in the liquid level water tank 12 to be at the same level as the lower surface of the evaporation medium 11 to be tested;

[0083] The air is filtered, temperature-regulated and humidity-regulated by the air pretreatment device, and after reaching the preset air temperature and preset air humidity, the air is driven by the fan 7 to enter the second air channel 6, the flow rate of the flow regulating valve 16 is adjusted, and the fan 7 is controlled to make the air flow rate delivered from the first air channel 1 to the second air channel 6 equal to the preset air flow rate, so that the lower surface pressure of the water film on the evaporation medium 11 to be tested is equal to the upper surface pressure, the evaporation medium 11 to be tested is wetted only by capillary action, and the radiation intensity of the light source 24 of the solar radiation simulator 35 is adjusted to the preset radiation intensity;

[0084] The water film thickness formed on the surface of the evaporation medium 11 to be tested is continuously measured by a water film thickness measuring device, and it is determined whether the water film thicknesses measured multiple times adjacent to each other are equal. If they are equal, the measured water film thickness is used as the reference water film thickness of the evaporation medium 11 to be tested in a water absorption saturation state; and / or, the weight of the water replenishment container 17 is continuously measured by a weighing device 19, and it is determined whether the weights of the water replenishment container 17 measured multiple times adjacent to each other are equal. If they are equal, the water film thickness formed on the surface of the evaporation medium 11 to be tested is measured by a water film measuring device, and the measured water film thickness is used as the reference water film thickness of the evaporation medium 11 to be tested in a water absorption saturation state;

[0085] Under the working conditions of preset air temperature, preset air humidity, preset air flow rate and preset radiation intensity, the thickness of the water film formed on the surface of the evaporative medium 11 to be tested is continuously measured within a preset time, and the water replenishment amount is adjusted by adjusting the flow regulating valve 16 according to the measured water film thickness and the reference water film thickness, so that the evaporative medium 11 to be tested is always in a water-saturated state, and thus the water replenishment amount is equal to the surface evaporation amount of the evaporative medium 11 to be tested;

[0086] The evaporation amount of the evaporation medium 11 to be tested within the preset time is obtained by the weight reduction of the water replenishment container 17; and the average water film thickness is calculated by combining the reference water film thickness, the water absorption amount of the evaporation medium 11 to be tested from the beginning of water absorption to water absorption saturation, and the volume, porosity, and surface area of ​​the evaporation medium 11 to be tested;

[0087] The surface temperature of the evaporative medium 11 to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank 12, and the preset air flow rate parameters in each group of experiments are different or some parameters are different. According to the evaporation amount of the evaporative medium 11 to be tested, the water film thickness of the evaporative medium 11 to be tested, the surface temperature of the evaporative medium 11 to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank 12, and the preset air flow rate in each group of experiments, the surface evaporation rate, the convective heat transfer coefficient, the convective mass transfer coefficient, and the Lewis number of the evaporative medium 11 to be tested are calculated, so that the quantitative relationship between the surface wettability, the water supply and the evaporation rate of the evaporative medium 11 to be tested can be established. Furthermore, the heat and moisture transfer characteristics test system based on the wettability of the evaporative medium provided in this embodiment can accurately obtain the heat and mass transfer characteristics of the roof evaporative medium under different surface wettability and different environmental conditions, and obtain the optimal water supply under different conditions.

[0088] It should be emphasized that in the process of determining the reference water film thickness, the reference water film thickness can be determined by multiple shots to determine whether the water film thickness of the multiple shots is stable. When the water film thickness of the multiple shots is equal, it means that the evaporation medium 11 to be tested is in a water absorption saturation state. At this time, the measured water film thickness can be used as the reference water film thickness. Similarly, the reference water film thickness can also be determined by multiple weighing methods at the same time. When the weights of the water replenishment containers weighed multiple times are equal, it means that the evaporation medium to be tested has completed water absorption and is in a water absorption saturation state. At this time, the measured water film thickness can also be used as the reference water film thickness. In a further embodiment, the table matrix of the placement platform 10 is distributed with multiple water replenishment holes 14, and the pipeline includes a main road 22 and multiple branches 23, wherein the main road 22 is connected to the liquid level water tank 12, one end of each branch road 23 is connected to the main road 22, and the other end is connected to the water replenishment hole 14 one by one, and each branch road 23 is provided with a water pressure sensing device 15 and a flow regulating valve 16.

[0089] In this way, when the evaporation amount of the evaporation medium 11 to be tested is small, only one branch 23 can be opened for water replenishment, and the other branches 23 are closed. When the evaporation amount of the evaporation medium 11 to be tested is large, several branches 23 can be appropriately added for water replenishment, and each branch 23 is provided with a water pressure sensing device 15 and a flow regulating valve 16, which can achieve fine adjustment of the water replenishment amount.

[0090] In a further embodiment, the solar radiation simulator 35 further includes a box with an opening on one side. Figure 4 The light source 24 is arranged in the box, the inner wall of the box is provided with a reflective film 25, the inner side of the reflective film 25 is provided with a heat preservation and insulation film 26, and the opening is closed by a light-transmitting partition 27.

[0091] The inner wall of the box body includes a reflective film 25 and a heat-insulating film 26. The material of the reflective film 25 needs to have a high reflectivity to light, and can be a PET aluminized film with a reflectivity of ≈95%. The material of the heat-insulating film 26 can be PET polyester, which has a visible light transmittance of 1%, an infrared heat blocking rate of 99%, and an ultraviolet blocking rate of 99%. Its function is to prevent the high temperature generated by the light source 24 from causing thermal stress damage to the box body. In order to prevent the airflow in the second air channel 6 from entering the light box, a light-transmitting partition 27 is used to separate the box body from the second air channel 6. The material of the light-transmitting partition 27 can be high-temperature resistant and highly light-transmitting organic glass or optical glass, and has no effect on the radiation intensity of the light source 24.

[0092] In a further embodiment, the water film thickness measuring device includes an image acquisition device 28 for photographing the surface of the evaporation medium 11 to be tested and a cold light source 29 for providing shooting light, and the image captured by the image acquisition device 28 can be used to obtain the water film thickness on the surface of the evaporation medium 11 to be tested.

[0093] The image acquisition device 28 and the cold light source 29 can be respectively arranged on both sides of the second air channel 6. Optical glass windows can be arranged on both sides of the second air channel 6. The light emitted by the cold light source 29 irradiates the surface of the evaporation medium 11 to be tested without affecting its surface temperature, and thus will not cause errors in the test results.

[0094] It should be noted that, in the above test process, the reference water film thickness is used as a reference standard for subsequent water film thickness tests and needs to have high accuracy. In order to improve the accuracy of the reference water film thickness, the present embodiment can use a laser induced fluorescence method to photograph the water film thickness, that is, before obtaining the above reference water film thickness, a fluorescent substance is added to the liquid level water tank 12, and then a water film containing the fluorescent substance is formed on the surface of the evaporation medium 11 to be tested. When the image acquisition device 28 photographs the water film containing the fluorescent substance, the image obtained can more realistically correspond to the actual thickness of the water film, and then an accurate water film thickness can be obtained as the reference water film thickness.

[0095] In the subsequent process of testing the evaporation of the water film, since the influence of the fluorescent substance on the evaporation rate of the water film needs to be eliminated, the water in the liquid level tank 12 needs to be replaced with water without fluorescent substance before the stage of testing the evaporation of the water film.

[0096] In a further embodiment, in order to prevent the evaporation of water in the liquid level water tank 12 and the water replenishment container 17 from affecting the test accuracy, a cover body may be provided on the liquid level water tank 12 and the water replenishment container 17, and a vent hole may be provided on the cover body. In addition, the liquid level water tank 12 may also be provided with a barometer 30, which is provided above the liquid surface of the liquid level water tank 12. In this way, the air pressure in the liquid level water tank 12 can be monitored by the barometer 30.

[0097] Also, please refer to Figure 2 and Figure 3 In this embodiment, the placement platform 10 further includes a heat-insulating layer 31, the upper surface of the heat-insulating layer 31 is provided with a groove, and the table top is arranged in the groove. The table top is arranged in the groove, which is more convenient for positioning the evaporation medium 11 to be tested. The placement platform 10 is provided with the heat-insulating layer 31, which can prevent the external temperature from affecting the ambient temperature of the evaporation medium 11 to be tested through heat conduction, thereby causing the problem of test error.

[0098] In a further embodiment, a data acquisition processing device 32 is also included, and the data acquisition processing device 32 is communicatively connected to the image acquisition device 28, the air flow meter 33, the temperature sensor 20, the humidity sensor 21, the temperature measuring device 34, the water temperature measuring device 13, and the weighing device 19.

[0099] The data acquisition and processing device 32 has data acquisition and data processing functions. The data acquisition and processing device 32 can automatically obtain the data of the above-mentioned devices or sensors, and automatically process the data to obtain the heat and mass transfer characteristics of the evaporating medium under different surface wetness and different environmental conditions, and then automatically obtain the optimal water supply under different conditions.

[0100] The embodiment of the present invention further provides a method for testing heat and moisture transfer characteristics based on the wettability of an evaporative medium, using a heat and moisture transfer characteristics testing system based on the wettability of an evaporative medium as described in any of the above embodiments, including multiple groups of experiments, each group of experiments including the steps of:

[0101] Fix the evaporation medium 11 to be tested on the table of the placement platform 10;

[0102] Add water to the liquid level water tank 12, and adjust the water surface in the liquid level water tank 12 to be at the same level as the lower surface of the evaporation medium 11 to be tested;

[0103] The air is filtered, temperature-regulated and humidity-regulated by the air pretreatment device, and after reaching the preset air temperature and preset air humidity, the air is driven by the fan 7 to enter the second air channel 6, the flow rate of the flow regulating valve 16 is adjusted, and the fan 7 is controlled to make the air flow rate delivered from the first air channel 1 to the second air channel 6 equal to the preset air flow rate, so that the lower surface pressure of the water film on the evaporation medium 11 to be tested is equal to the upper surface pressure, the evaporation medium 11 to be tested is wetted only by capillary action, and the radiation intensity of the light source 24 of the solar radiation simulator 35 is adjusted to the preset radiation intensity;

[0104] The water film thickness formed on the surface of the evaporation medium 11 to be tested is continuously measured by a water film thickness measuring device, and it is determined whether the water film thicknesses measured multiple times adjacent to each other are equal. If they are equal, the measured water film thickness is used as the reference water film thickness of the evaporation medium 11 to be tested in a water absorption saturation state; and / or, the weight of the water replenishment container 17 is continuously measured by a weighing device 19, and it is determined whether the weights of the water replenishment container 17 measured multiple times adjacent to each other are equal. If they are equal, the water film thickness formed on the surface of the evaporation medium 11 to be tested is measured by a water film measuring device, and the measured water film thickness is used as the reference water film thickness of the evaporation medium 11 to be tested in a water absorption saturation state;

[0105] Under the working conditions of preset air temperature, preset air humidity, preset air flow rate and preset radiation intensity, the thickness of the water film formed on the surface of the evaporative medium 11 to be tested is continuously measured within a preset time, and the water replenishment amount is adjusted by adjusting the flow regulating valve 16 according to the measured water film thickness and the reference water film thickness, so that the evaporative medium 11 to be tested is always in a water-saturated state, and thus the water replenishment amount is equal to the surface evaporation amount of the evaporative medium 11 to be tested;

[0106] The evaporation amount of the evaporation medium 11 to be tested within the preset time is obtained by the weight reduction of the water replenishment container 17; and the average water film thickness is calculated by combining the reference water film thickness, the water absorption amount of the evaporation medium 11 to be tested from the beginning of water absorption to water absorption saturation, and the volume, porosity, and surface area of ​​the evaporation medium 11 to be tested;

[0107] The surface temperature of the evaporation medium 11 to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank 12, and the preset air flow rate parameters in each group of experiments are different or some parameters are different. According to the evaporation amount of the evaporation medium 11 to be tested, the water film thickness of the evaporation medium 11 to be tested, the surface temperature of the evaporation medium 11 to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank 12, and the preset air flow rate in each group of experiments, the surface evaporation rate, convective heat transfer coefficient, convective mass transfer coefficient, and Lewis number of the evaporation medium 11 to be tested are calculated, and then a quantitative relationship between the surface wettability, water supply and evaporation rate of the evaporation medium 11 to be tested is established.

[0108] Similarly, in order to improve the accuracy of the reference water film thickness, the test method provided in a further embodiment can use the laser induced fluorescence method to photograph the water film thickness, that is, before obtaining the above-mentioned reference water film thickness, a fluorescent substance is added to the liquid level water tank 12, and then a water film containing the fluorescent substance is formed on the surface of the evaporation medium 11 to be tested. When the image acquisition device 28 photographs the water film containing the fluorescent substance, the image obtained can more realistically correspond to the actual thickness of the water film, and then the accurate water film thickness can be obtained as the reference water film thickness. In the subsequent process of testing the evaporation amount of the water film, since it is necessary to eliminate the influence of the fluorescent substance on the evaporation rate of the water film, before the stage of testing the evaporation amount of the water film, it is necessary to replace the water in the liquid level water tank 12 with water without fluorescent substance. The heat and moisture transfer characteristics test method based on the wettability of the evaporation medium provided in this embodiment adopts the heat and moisture transfer characteristics test system based on the wettability of the evaporation medium as described in any of the above embodiments, including multiple groups of experiments, each group of experiments including the steps of:

[0109] Fix the evaporation medium 11 to be tested on the table of the placement platform 10;

[0110] Add water to the liquid level water tank 12, and add fluorescent material to the liquid level water tank 12, and adjust the water surface in the liquid level water tank 12 to be at the same level as the lower surface of the evaporation medium 11 to be tested;

[0111] The air is filtered, temperature-regulated and humidity-regulated by the air pretreatment device, and after reaching the preset air temperature and preset air humidity, the air is driven by the fan 7 to enter the second air channel 6, the flow rate of the flow regulating valve 16 is adjusted, and the fan 7 is controlled to make the air flow rate delivered from the first air channel 1 to the second air channel 6 equal to the preset air flow rate, so that the lower surface pressure of the water film on the evaporation medium 11 to be tested is equal to the upper surface pressure, the evaporation medium 11 to be tested is wetted only by capillary action, and the radiation intensity of the light source 24 of the solar radiation simulator 35 is adjusted to the preset radiation intensity;

[0112] The water film thickness formed on the surface of the evaporation medium 11 to be tested is continuously measured by a water film thickness measuring device, and it is determined whether the water film thicknesses measured multiple times adjacent to each other are equal. If they are equal, the measured water film thickness is used as the reference water film thickness of the evaporation medium 11 to be tested in a water absorption saturation state; and / or, the weight of the water replenishment container 17 is continuously measured by a weighing device 19, and it is determined whether the weights of the water replenishment container 17 measured multiple times adjacent to each other are equal. If they are equal, the water film thickness formed on the surface of the evaporation medium 11 to be tested is measured by a water film measuring device, and the measured water film thickness is used as the reference water film thickness of the evaporation medium 11 to be tested in a water absorption saturation state;

[0113] Clean the liquid level water tank 12, replace the evaporation medium 11 to be tested with the same size, and add water without fluorescent material into the liquid level water tank 12;

[0114] Under the working conditions of preset air temperature, preset air humidity, preset air flow rate and preset radiation intensity, the thickness of the water film formed on the surface of the evaporative medium 11 to be tested is continuously measured within a preset time, and the water replenishment amount is adjusted by adjusting the flow regulating valve 16 according to the measured water film thickness and the reference water film thickness, so that the evaporative medium 11 to be tested is always in a water-saturated state, and thus the water replenishment amount is equal to the surface evaporation amount of the evaporative medium 11 to be tested;

[0115] The evaporation amount of the evaporation medium 11 to be tested within the preset time is obtained by the weight reduction of the water replenishment container 17; and the average water film thickness is calculated by combining the reference water film thickness, the water absorption amount of the evaporation medium 11 to be tested from the beginning of water absorption to water absorption saturation, and the volume, porosity, and surface area of ​​the evaporation medium 11 to be tested;

[0116] The surface temperature of the evaporation medium 11 to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank 12, and the preset air flow rate parameters in each group of experiments are different or some parameters are different. According to the evaporation amount of the evaporation medium 11 to be tested, the water film thickness of the evaporation medium 11 to be tested, the surface temperature of the evaporation medium 11 to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank 12, and the preset air flow rate in each group of experiments, the surface evaporation rate, convective heat transfer coefficient, convective mass transfer coefficient, and Lewis number of the evaporation medium 11 to be tested are calculated, and then a quantitative relationship between the surface wettability, water supply and evaporation rate of the evaporation medium 11 to be tested is established.

[0117] In addition, it should be noted that, in a further embodiment, the surface evaporation rate, convective heat transfer coefficient, convective mass transfer coefficient, and Lewis number of the evaporation medium 11 to be tested are calculated, and then a quantitative relationship between the surface wettability, water supply, and evaporation rate of the evaporation medium 11 to be tested is established. The specific process can be described as follows:

[0118] The length L of the second air channel 6, the equivalent diameter d of the pipe, and the surface area A of the evaporation medium 11 to be tested are measured. By presetting the air flow rate m f , and thus obtain the average air flow rate ν in the tube. The viscosity coefficient μ and thermal conductivity coefficient λ of the air can be obtained by looking up the physical parameter table. Thus, the Reynolds number Re of the fluid is calculated. According to the preset air temperature and preset air humidity, the enthalpy-humidity diagram is consulted to obtain the moisture content d before and after the evaporation medium 11 to be tested in d out The saturated water vapor density ρ under different working conditions can be obtained from the saturated water vapor density table and the wet air density table. sat,s 、Density of moist air ρ f,ν . ;

[0119] The evaporation rate m of the surface of the evaporation medium 11 to be tested is calculated based on the experimental test data and the empirical correlation formula of the convective heat transfer in the second air channel 6. w , convective heat transfer coefficient h, convective mass transfer coefficient h m : Substituting the experimental parameters into the following equations (3)(4)(5), we can obtain the convective heat transfer coefficient h of the evaporation medium 11 to be tested, the evaporation rate m of the evaporation medium 11 to be tested, respectively. w , and the convective mass transfer coefficient h m , the Lewis number Le is determined by Lewis relation (7). ;

[0120] The water absorption V of the evaporation medium 11 to be tested is obtained by the weighing device 19. w According to the porosity P, volume V, and surface area A of the evaporation medium 11 to be tested, the theoretical average water film thickness H of the evaporation medium 11 to be tested can be calculated by substituting into formula (6): t The data acquisition and processing device processes the image through image processing technology, converts the true color image into a grayscale image, and determines the real image of the water film thickness by comparing the difference between the fluorescent band and the surrounding grayscale. Finally, the real water film thickness observed by the image is compared with the average water film thickness calculated by the semi-empirical method, and the quantitative relationship between the water film thickness and the evaporation heat transfer characteristics of the evaporation medium (evaporation material) to be tested is established.

[0121] The formula quoted in the above steps is as follows:

[0122] The empirical correlation formula for convective heat transfer in the tube in the turbulent zone is:

[0123]

[0124] Where: Reynolds number

[0125] Prandtl number Pr≈0.7

[0126] Because the Nussell number

[0127] From formula (1) (2) we get:

[0128] Convective heat transfer coefficient:

[0129] According to the mass conservation relationship, the evaporation amount of the evaporation medium 11 to be tested per unit time is equal to the change in the moisture content of the flowing air:

[0130] Then the evaporation rate of the evaporation medium 11 to be tested is:

[0131] m w =h m A(ρ sat，s -ρ f，v)=m f (d out -d in ) (4)

[0132] From formula (4), we can get:

[0133] Convective mass transfer coefficient:

[0134] The surface water film thickness of the evaporation medium 11 to be tested:

[0135]

[0136] And because heat and mass transfer satisfy the Lewis relationship:

[0137]

[0138] Then the Lewis number is:

[0139]

[0140] The following is an example of the present invention in combination with specific data and the above calculation process. In this embodiment, the thickness of the evaporation medium 11 to be tested is 0.2 mm, the porosity of the evaporation medium 11 to be tested is 0.863, and the surface area of ​​the evaporation medium 11 to be tested is 2.56×10 -2 m 2 The experimental data are as follows: Figure 6 As shown, when the surface radiation intensity of the evaporation medium 11 (evaporation material) to be tested is 500w and the air flow rate in the second air channel 6 is 0.5m / s: the temperature at the air inlet position of the second air channel 6 is 25.9°C, the relative humidity is 48.5%, the temperature at the air outlet position of the second air channel 6 is 24.75°C, the relative humidity is 54.33%, the air flow rate is 0.0035kg / s, and the water temperature in the liquid level water tank 12 is 22°C. Figure 5 The hourly temperatures at each measuring point indicate that the average temperature of the surface of the evaporation medium 11 (evaporation material) to be tested in a stable state is 20.5°C.

[0141] according to Figure 6 The experimental test data is obtained by consulting the enthalpy-humidity diagram and the moisture content of the inlet and outlet are 10.05 g / kg and 10.59 g / kg respectively. Substituting the moisture content value into formula (4) to calculate the evaporation rate m of the saturated state of the evaporation medium 11 to be tested w The evaporation rate per unit area is 4.86×10 -5 kg / s·m 2 , to compare the theoretical calculation results with the experimental measurement results, please refer to Figure 7 , the evaporation rate of the material in the saturated state can be obtained more accurately. Figure 8The weight change curve of the water replenishment container 17 during the water film test experiment is shown, that is, the water absorption of the evaporation medium 11 to be tested from a dry state to a saturated state. According to the weight change of the water replenishment container 17, the water absorption of the evaporation medium 11 to be tested when it reaches a saturated state is 8.68g. Substituting it into formula (6), the theoretical water film thickness H can be obtained. t By comparing with the water film thickness observation value obtained by digital image processing technology, the real water film thickness H on the surface of the evaporation medium 11 to be tested can be obtained more accurately. t The convective heat transfer coefficient (h = 9.73 w / m·k) and convective mass transfer coefficient (h m =7.05×10 -3 Substituting 100 m / s into the Lewis relation (8), we can obtain the Lewis number Le as 1.09.

[0142] This embodiment can accurately obtain the evaporation rate, average water film thickness, convective heat transfer coefficient, convective mass transfer coefficient and Lewis number of the evaporation medium to be tested under saturated state by combining experiments with theoretical calculations.

[0143] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A heat and moisture transfer characteristics testing system based on evaporative medium wettability, characterized in that: include: an air pretreatment device, comprising a first air passage provided with an air inlet and an air outlet, an air filtering device arranged in the first air passage, a temperature control device for heating and cooling the air in the first air passage, and a humidity control device for humidifying the air in the first air passage; a second air channel, provided with an air inlet and an air outlet, the air inlet of the second air channel being connected to the air outlet of the first air channel, and an air pressure sensing device for sensing air pressure being provided in the second air channel; A fan, used for driving air flow from the air inlet of the first air channel to the air outlet of the second air channel; A placement platform, which is arranged in the second air channel and is provided with a table surface for placing the evaporation medium to be tested; A solar radiation simulator, comprising a light source and a dimmer for adjusting the radiation intensity of the light source, wherein the simulated sunlight emitted by the light source can be radiated on the surface of the evaporation medium to be tested; The automatic water replenishment system comprises a liquid level water tank provided with a water temperature measuring device therein, the table top of the placement platform is provided with a water replenishment hole which penetrates downwards, the liquid level water tank is connected with the water replenishment hole through a pipeline, the pipeline is provided with a water pressure sensing device for sensing water pressure and a flow regulating valve for regulating the water replenishment flow, the water level in the liquid level water tank can be at the same horizontal plane as the lower surface of the evaporative medium to be tested; the automatic water replenishment system also comprises a water replenishment container, the water replenishment container is connected with the liquid level water tank, the liquid level water tank is provided with a liquid level switch for controlling the water replenishment container to replenish water to the liquid level water tank, and the opening condition of the liquid level switch is that the water level of the liquid level water tank is lower than the lower surface of the evaporative medium to be tested; A weighing device, used for weighing the water replenishment container; a temperature sensor and a humidity sensor, disposed in the second air passage and used to measure the air temperature and humidity in the second air passage; A temperature measuring device, used to measure the surface temperature of the evaporative medium to be tested; an air flow meter, used for measuring the air flow delivered from the first air passage to the second air passage; A water film thickness measuring device is used to measure the thickness of a water film formed on the surface of the evaporative medium to be tested; the water film thickness measuring device comprises an image acquisition device for photographing the surface of the evaporative medium to be tested and a cold light source for providing shooting light, and the image photographed by the image acquisition device can be used to obtain the water film thickness on the surface of the evaporative medium to be tested; the image acquisition device and the cold light source can be respectively arranged on both sides of the second air channel, and optical glass windows can be arranged on both sides of the second air channel, and the light emitted by the cold light source irradiating the surface of the evaporative medium to be tested will not affect its surface temperature, and thus will not cause errors in the test results.

2. The heat and moisture transfer characteristics testing system based on evaporative medium wettability according to claim 1, characterized in that: The tabletop matrix of the placement platform is distributed with multiple water supply holes, and the pipeline includes a main line connected to the liquid level water tank, and multiple branches connected to the main line at one end and the water supply holes at the other end, and each of the branches is provided with the water pressure sensing device and the flow regulating valve.

3. The heat and moisture transfer characteristics testing system based on evaporative medium wettability according to claim 1, characterized in that: The solar radiation simulator also includes a box with an opening on one side, the light source is arranged in the box, the inner wall of the box is provided with a reflective film, the inner side of the reflective film is provided with a heat preservation and heat insulation film, and the opening is closed by a light-transmitting partition.

4. The heat and moisture transfer characteristics testing system based on evaporative medium wettability according to claim 1, characterized in that: The fan is disposed in the second air passage, and the fan is close to an air outlet position of the second air passage.

5. The heat and moisture transfer characteristics testing system based on evaporative medium wettability according to claim 1, characterized in that: The invention also includes a flow mixer disposed in the second air channel, wherein the flow mixer is disposed at a position close to an air inlet end of the second air channel.

6. The heat and moisture transfer characteristics testing system based on evaporative medium wettability according to claim 1, characterized in that: The placement platform comprises a heat-insulating layer, the upper surface of the heat-insulating layer is provided with a groove, and the table top is arranged in the groove.

7. The heat and moisture transfer characteristics testing system based on evaporative medium wettability according to claim 1, characterized in that: It also includes a data acquisition and processing device, which is communicatively connected to the image acquisition device, the air flow meter, the temperature sensor, the humidity sensor, the temperature measuring device, the water temperature measuring device, and the weighing device.

8. A method for testing heat and moisture transfer characteristics based on the wettability of evaporative media, characterized in that: The heat and moisture transfer characteristics testing system based on the wettability of the evaporative medium as described in any one of claims 1 to 7 is used, including multiple groups of experiments, each group of experiments including the steps of: Fixing the evaporation medium to be tested on the table of the placement platform; Adding water to the liquid level water tank, and adjusting the water level in the liquid level water tank to be at the same level as the lower surface of the evaporative medium to be tested; The air is filtered, temperature-regulated and humidity-regulated by the air pretreatment device, and after reaching a preset air temperature and a preset air humidity, the air is driven by the fan to enter the second air channel, the flow rate of the flow regulating valve is adjusted, and the fan is controlled to make the air flow rate from the first air channel to the second air channel equal to the preset air flow rate, so that the lower surface pressure of the water film on the evaporative medium to be tested is equal to the upper surface pressure, the evaporative medium to be tested is wetted only by capillary action, and the radiation intensity of the light source of the solar radiation simulator is adjusted to the preset radiation intensity; The water film thickness formed on the surface of the evaporative medium to be tested is measured continuously by the water film thickness measuring device, and it is determined whether the water film thicknesses measured multiple times adjacently are equal. If they are equal, the measured water film thickness is used as the reference water film thickness of the evaporative medium to be tested in a water absorption saturation state; and / or, the weight of the water replenishment container is measured continuously by the weighing device, and it is determined whether the weights of the water replenishment container measured multiple times adjacently are equal. If they are equal, the water film thickness formed on the surface of the evaporative medium to be tested is measured by the water film measuring device, and the measured water film thickness is used as the reference water film thickness of the evaporative medium to be tested in a water absorption saturation state; Under the working conditions of the preset air temperature, the preset air humidity, the preset air flow rate and the preset radiation intensity, continuously measure the water film thickness formed on the surface of the evaporative medium to be tested within a preset time, compare the measured water film thickness with the reference water film thickness, and adjust the flow control valve to adjust the water replenishment amount according to the comparison result, so that the evaporative medium to be tested is always in a water-saturated state, and then the water replenishment amount is equal to the surface evaporation amount of the evaporative medium to be tested; The evaporation amount of the evaporation medium to be tested within a preset time is obtained by the weight reduction of the water replenishment container; and the average water film thickness is calculated by combining the reference water film thickness, the water absorption amount of the evaporation medium to be tested from the beginning of water absorption to water absorption saturation, and the volume, porosity, and surface area of ​​the evaporation medium to be tested; The surface temperature of the evaporative medium to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank, and the preset air flow rate parameters in each group of experiments are different or some parameters are different. According to the evaporation amount of the evaporative medium to be tested, the water film thickness of the evaporative medium to be tested, the surface temperature of the evaporative medium to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank, and the preset air flow rate in each group of experiments, the surface evaporation rate, convective heat transfer coefficient, convective mass transfer coefficient, and Lewis number of the evaporative medium to be tested are calculated, and then a quantitative relationship between the surface wettability, water supply and evaporation rate of the evaporative medium to be tested is established.

9. A method for testing heat and moisture transfer characteristics based on the wettability of evaporative media, characterized in that: The heat and moisture transfer characteristics testing system based on the wettability of the evaporative medium as claimed in claim 1 includes multiple groups of experiments, each group of experiments including the steps of: Fixing the evaporation medium to be tested on the table of the placement platform; Adding water to the liquid level water tank and adding fluorescent material to the liquid level water tank, and adjusting the water surface in the liquid level water tank and the lower surface of the evaporation medium to be tested to be at the same level; The air is filtered, temperature-regulated and humidity-regulated by the air pretreatment device, and after reaching a preset air temperature and a preset air humidity, the air is driven by the fan to enter the second air channel, the flow rate of the flow regulating valve is adjusted, and the fan is controlled to make the air flow rate from the first air channel to the second air channel equal to the preset air flow rate, so that the lower surface pressure of the water film on the evaporative medium to be tested is equal to the upper surface pressure, the evaporative medium to be tested is wetted only by capillary action, and the radiation intensity of the light source of the solar radiation simulator is adjusted to the preset radiation intensity; The water film thickness formed on the surface of the evaporative medium to be tested is measured continuously by the water film thickness measuring device, and it is determined whether the water film thicknesses measured several times adjacently are equal. If they are equal, the measured water film thickness is used as the reference water film thickness of the evaporative medium to be tested in a water absorption saturation state; and / or, the weight of the water replenishment container is measured continuously by the weighing device, and it is determined whether the weights of the water replenishment container measured several times adjacently are equal. If they are equal, the water film thickness formed on the surface of the evaporative medium to be tested is measured by the water film measuring device, and the measured water film thickness is used as the reference water film thickness of the evaporative medium to be tested in a water absorption saturation state; Clean the liquid level water tank, replace the evaporation medium to be tested with the same size, and add water without fluorescent material into the liquid level water tank; Under the working conditions of the preset air temperature, the preset air humidity, the preset air flow rate and the preset radiation intensity, continuously measure the water film thickness formed on the surface of the evaporative medium to be tested within a preset time, compare the measured water film thickness with the reference water film thickness, and adjust the flow control valve to adjust the water replenishment amount according to the comparison result, so that the evaporative medium to be tested is always in a water-saturated state, and then the water replenishment amount is equal to the surface evaporation amount of the evaporative medium to be tested; The evaporation amount of the evaporation medium to be tested within a preset time is obtained by the weight reduction of the water replenishment container; and the average water film thickness is calculated by combining the reference water film thickness, the water absorption amount of the evaporation medium to be tested from the beginning of water absorption to water absorption saturation, and the volume, porosity, and surface area of ​​the evaporation medium to be tested; The surface temperature of the evaporative medium to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank, and the preset air flow rate parameters in each group of experiments are different or some parameters are different. According to the evaporation amount of the evaporative medium to be tested, the water film thickness of the evaporative medium to be tested, the surface temperature of the evaporative medium to be tested, the preset air temperature, the preset air humidity, the water temperature of the liquid level water tank, and the preset air flow rate in each group of experiments, the surface evaporation rate, convective heat transfer coefficient, convective mass transfer coefficient, and Lewis number of the evaporative medium to be tested are calculated, and then a quantitative relationship between the surface wettability, water supply and evaporation rate of the evaporative medium to be tested is established.

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