Portable greenhouse covering material heat transfer coefficient testing device and using method thereof

Abstract

The invention belongs to the technical field of greenhouse covering material testing, and relates to a portable greenhouse covering material heat transfer coefficient testing device and a using method thereof.The testing device comprises a heat preservation box body, a direct current power supply system and a data collecting and processing system, an upper cavity and a lower cavity are formed in the heat preservation box body, and a film pressing device is arranged in the upper cavity; an electric heating wire and an anti-radiation layer are arranged in the lower cavity; the direct-current power supply system is used for providing stable direct current and adjusting the heating power of the electric heating wire; the data acquisition and processing system comprises a data acquisition module, a data analysis module, a data storage module and a data display module, the data acquisition module is used for acquiring temperature and wind speed data, and the data analysis module is used for measuring and calculating a heat transfer coefficient and transmitting a result to the data display module and the data storage module; the data storage module is used for storing and exporting data; the testing device can be used for carrying out real-time dynamic monitoring on the covering material in an actual production environment, and the testing precision is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of greenhouse covering material testing, and in particular relates to a portable greenhouse covering material heat transfer coefficient testing device and a use method thereof. Background Art

[0002] The primary function of horticultural facilities such as plastic greenhouses, solar greenhouses, and multi-span glass greenhouses is to break through the limitations of natural climate conditions and provide crops with a hot and humid environment suitable for their growth. When the temperature is too low, crops will suffer from frost, resulting in low yields or even death; when the temperature is too high, crops will suffer from diseases and pests, thus affecting production performance. The covering layer of horticultural facilities is the key to affecting the indoor thermal and humid environment, mainly including plastic film, insulation blanket, PC sun panel, glass and other materials. Therefore, accurately testing and obtaining the heat transfer coefficient of these covering materials during actual production is of great significance for the regulation of greenhouse thermal and humid environment and the efficient production of horticultural crops.

[0003] The heat transfer coefficient of greenhouse covering materials refers to a performance parameter defined by comprehensively considering the external surface convection heat transfer, external surface radiation heat transfer, self-heat conduction, internal surface convection heat transfer, and internal surface radiation heat transfer. It is used to quantitatively characterize the intensity of the heat transfer process of the covering material. It is not only related to the type and thickness of the covering material itself, but also closely related to indoor and outdoor environmental conditions such as wind speed, sky background radiation temperature, and atmospheric pressure. In particular, for covering materials such as plastic films, the thermal conductivity can be ignored due to their very small thickness (0.07mm~0.20mm), and the radiation heat exchange between them and the sky background is the main heat dissipation method for greenhouses at night. At present, the test of heat transfer coefficient of covering materials is mainly carried out under laboratory conditions, such as the method for improving the test accuracy of the test bench for thermal insulation performance of covering materials disclosed in document 2013104821008. First, specific indoor and outdoor environmental conditions are simulated by experiments, such as outdoor wind speed of 4m / s, sky background radiation temperature of -20℃, indoor and outdoor temperature difference ≥20℃, etc.; secondly, the temperature in the cold box and hot box is adjusted to reach the preset value and tend to be stable by adjusting the cooling and heating power; finally, the heat transfer coefficient of the covering material is calculated based on the thermal balance. However, in actual production, the outdoor environmental conditions of the greenhouse vary with different regions and different times, so that the heat transfer coefficient of the covering material (especially plastic film) is constantly changing. Therefore, the existing test method cannot truly reflect the actual on-site environmental conditions (especially the sky background radiation temperature) in greenhouse production, resulting in large measurement errors. In addition, for high-altitude special climatic conditions such as Tibet and Qinghai, the existing test device is difficult to simulate environmental conditions such as low pressure and fails. In summary, the existing covering material heat transfer coefficient test device has great limitations and cannot objectively reflect the actual production environment conditions of the greenhouse covering layer, resulting in large measurement errors.

[0004] More importantly, the existing covering material heat transfer coefficient testing device cannot accurately test the heat transfer coefficient of greenhouse covering (flexible) materials during use, and it is particularly difficult to reduce the impact of refractive index errors on the test results. Summary of the invention

[0005] In view of the technical problems in the background technology, the purpose of the present invention includes providing a portable greenhouse covering material heat transfer coefficient testing device and its use method, which can be carried to the actual production environment to realize on-site and real-time monitoring of the heat transfer coefficient of the covering material, and provide key data and technical support for the creation and regulation of the greenhouse thermal and humid environment, so as to reduce measurement errors and solve the shortcomings of existing testing devices.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: A portable greenhouse covering material heat transfer coefficient testing device, comprising a heat preservation box, a DC power supply system, and a data acquisition and processing system; The thermal insulation box is provided with a partition, and a plurality of heat dissipation holes are provided on the partition, and the partition divides the thermal insulation box into an upper chamber and a lower chamber; the inner wall of the upper chamber is provided with a wall plate, and the top of the upper chamber is provided with a baffle plate, and at least one film press for mounting the test piece is provided between the wall plate and the baffle plate, and first rollers are provided on both sides of the film press, and the first rollers can slide up and down between the baffle plate and the wall plate, and a sealing strip is provided at the interface between the film press and the baffle plate; a heating assembly is provided in the lower chamber, and the heating assembly includes a fixed column located at the center of the lower chamber, and a heating wire is wound around the fixed column, and an anti-radiation layer is provided on the upper part of the heating wire, and the anti-radiation layer is used to prevent the heating wire from exchanging radiation heat with the sky background; The DC power supply system is electrically connected to the heating wire, and the DC power supply system includes a mobile power supply module and a power regulation module, the mobile power supply module is used to provide stable DC power, and the power regulation module is used to regulate the heating power of the heating wire; The data acquisition and processing system includes an electrically connected data acquisition module, a data analysis module, a data storage module and a data display module; the data acquisition module is used to collect the surface temperature of the outer wall and wall panel of the insulation box, the air temperature inside the upper chamber, and the air temperature and wind speed outside the insulation box; the data analysis module is used to calculate the heat transfer coefficient based on the data collected by the data acquisition module, and transmit the measured heat transfer coefficient to the data display module and the data storage module; the data storage module is used to store and export the data collected by the data acquisition module and the heat transfer coefficient calculated by the data analysis module; the data display module is used to display the data collected by the data acquisition module and the heat transfer coefficient calculated by the data analysis module.

[0007] Furthermore, a retractable bottom plate is provided at the bottom of the upper chamber, and second rollers are provided on both sides of the bottom plate, and the second rollers can slide up and down along the wall plate.

[0008] Furthermore, the data acquisition module includes a first sensor, a second sensor, a third sensor and a fourth sensor. The first sensor is used to detect the surface temperature of the upper chamber wall panel, the second sensor is used to detect the surface temperature of the outer wall of the insulation box, the third sensor is used to detect the air temperature inside the upper chamber, and the fourth sensor is used to detect the air temperature and wind speed outside the insulation box.

[0009] Furthermore, the data display module includes a display screen, which is used to display in real time the air temperature inside the insulation box, the air temperature and wind speed outside the insulation box, the surface temperature of the wall panel and the outer wall of the insulation box, the heating power of the heating wire and the heat transfer coefficient of the test piece.

[0010] Furthermore, the bottom of the insulated box is provided with a plurality of wheels, and the side of the insulated box is provided with a plurality of storage compartments, and the wheels can be folded and supported at the bottom of the insulated box or stored in the storage compartments. A detachable lifting assembly is also included, and the lifting assembly includes a scissor bracket, and the top of the scissor bracket is provided with a storage plate for placing the insulated box, and one side of the storage plate is provided with a lifting switch, and the lifting switch adopts a gas spring to provide support force for the scissor bracket, and the bottom of the scissor bracket is provided with a soft pad.

[0011] In order to accurately test the heat transfer coefficient of greenhouse covering (flexible) materials during use, the influence of refractive coefficient error on the test results is minimized as much as possible. A plurality of groups of vertically arranged lifting rods are arranged in the heat preservation box, and each group of lifting rods includes a first lifting rod and a second lifting rod. The first lifting rod and the second lifting rod are located on both sides of the test piece, and the tops of the first lifting rod and the second lifting rod are connected by a straight wire. When the lifting rod rises to the target height, the wire presses against the bottom surface of the test piece in an arc state. In this scheme, the wire used is a cotton thread with a diameter not greater than 2 mm, which is not only convenient for accurately, flexibly and stably adjusting the posture of the test piece, but also has almost no effect on the test results.

[0012] A method for using the portable greenhouse covering material heat transfer coefficient testing device comprises the following steps: Step S1, move the heat preservation box to the actual production environment of the test piece, and fix the test piece on the laminator to ensure the flatness of the test piece, and fix the first rollers on both sides of the uppermost laminator to the bottom of the baffle, and use a sealing strip to seal the interface between the baffle and the laminator; Step S2, at night, the DC power supply system is turned on to start heating the heating component, and the data acquisition module starts to measure data, and at the same time transmits the temperature data, heating power and wind speed data to the data display module, and the air temperature and heating power inside the insulation box are monitored in real time through the data display module, and the internal air temperature is preset according to the external air temperature of the insulation box to ensure that the temperature difference between the internal air temperature of the insulation box and the external air temperature is ≥20°C; Step S3: When the heat preservation box reaches thermal equilibrium, the data analysis module calculates the heat transfer coefficient and transmits the measured heat transfer coefficient to the data display module and the data storage module; Step S4: After the test is completed, turn off the DC power supply system, remove the test piece from the laminator, and wait until the internal air temperature of the insulation box cools to the same as the external air temperature, then repeat steps S1-S3 to start the next test.

[0013] Furthermore, the thermal equilibrium condition of step S3 is that after the internal air temperature of the heat preservation box reaches a preset value, the value fluctuates and the fluctuation change has no continuous increasing or decreasing trend.

[0014] Furthermore, the formula for calculating the heat transfer coefficient by the data analysis module in step S3 is: Where U 0 is the heat transfer coefficient of the test piece, W / (m 2 ℃); A 0 is the area of ​​the test piece, m 2 ; ΔT 0 is the temperature difference between the air inside and outside the insulation box, ℃; Q is the heating power, W; ΔT i is the temperature difference between the inner and outer walls of the ith insulation box, ℃; U i is the heat transfer coefficient of the ith box wall of the insulation box, which can be obtained according to the material and thickness of the wall, W / (m 2 ℃); A i is the area of ​​the ith box wall of the insulation box, m 2 .

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention is based on a semi-open hot box method. By installing a test device in a greenhouse in actual production, continuous real-time monitoring and on-site testing of the heat transfer coefficient of the greenhouse covering material can be achieved, and the dynamic influence under different environmental conditions can be fully reflected, and the test error can be effectively reduced, so that the test result is more real and accurate; and by arranging a retractable bottom plate and a second roller in the heat preservation box, the length and inclination of the bottom plate can be changed by adjusting the relative positions of the two second rollers during the heat transfer coefficient test, so as to achieve the change of the internal space of the upper chamber of the heat preservation box, so as to simulate the internal shapes of different greenhouse types, reflect the real production environment, and further improve the accuracy of the test result; The present invention can realize the measurement of the heat transfer coefficient of single-layer or multi-layer covering materials, has good versatility, and can easily and conveniently move the insulation box to different locations without the aid of tools, thereby realizing on-site testing and real-time monitoring of the heat transfer coefficient, and can ensure that the insulation box remains stable during the test. It also has the advantages of small footprint and simple results. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a plan view of the testing device in the first embodiment of the present invention; Figure 2 It is a top view of the film pressing device in Example 1 and a schematic diagram of the installation of the test piece; Figure 3 is a schematic diagram of the data acquisition and processing system in Example 1; Figure 4 This is a plan view of the test device in Example 2. Figure 5 Schematic diagram of the top view of the test device in Example 3 during use.

[0017] In the figure: insulation box 1, partition 11, heat dissipation hole 111, upper chamber 12, lower chamber 13, wall panel 14, baffle 15, sealing strip 16, wheel 17, storage compartment 18; film press 2, winding roller 21, first roller 22; bottom plate 3, second roller 31; heating component 4, fixing column 41, heating wire 42, radiation protection layer 43; data acquisition and processing system 5, first sensor 51, third sensor 52, fourth sensor 53, display screen 54; lifting component 6, scissor bracket 61, storage plate 62, lifting switch 63, test piece 7, lifting rod 80, first lifting rod 81, second lifting rod 82, silk thread 83. DETAILED DESCRIPTION

[0018] The following is further explained in detail through specific implementation methods. Example 1

[0019] A portable greenhouse covering material heat transfer coefficient testing device comprises a heat preservation box 1, a DC power supply system, and a data acquisition and processing system 5. Figure 1 As shown, a partition 11 is provided in the heat preservation box 1, and a plurality of heat dissipation holes 111 are evenly distributed on the partition 11. The partition 11 divides the heat preservation box 1 into an upper chamber 12 and a lower chamber 13; a wall plate 14 is provided on the inner wall of the upper chamber 12, and a baffle 15 is provided on the top of the upper chamber 12. Two film pressing devices 2 are provided between the wall plate 14 and the baffle 15, as shown in FIG. Figure 2As shown, each laminator 2 includes two winding rollers 21, and the ends of the test piece 7 can be fixed on the two winding rollers 21 respectively. Both ends of each winding roller 22 are installed with first rollers 22, and the first rollers 22 can slide up and down between the baffle 15 and the wall plate 14. A sealing strip 16 is provided at the interface between the uppermost laminator 2 and the baffle 15; a retractable bottom plate 3 is provided at the bottom of the upper chamber 12, and second rollers 31 are provided on both sides of the bottom plate 3. The second rollers 31 can slide up and down along the wall plate 14, and buckles are provided on the first roller 22 and the second roller 31, through which the first roller 22 and the second roller 31 can be clamped. The roller 22 and the second roller 31 are fixed on the inner wall or wall panel 14 of the insulation box body 1; a heating component 4 is arranged in the lower chamber 13, and the heating component 4 includes a fixed column 41 located in the center of the lower chamber 13, and a heating wire 42 is wound on the fixed column 41, and an anti-radiation layer 43 is arranged on the upper part of the heating wire 42, and the anti-radiation layer 43 is used to prevent the heating wire 42 from exchanging radiation heat with the sky background; a plurality of foldable wheels 17 are installed at the bottom of the insulation box body 1, and a plurality of storage grids 18 are arranged on the side of the insulation box body 1, and the wheels 17 can be folded and supported at the bottom of the insulation box body 1 or stored in the storage grid 18.

[0020] In this embodiment, the heat preservation box 1 is made of a material with good heat preservation, relatively stable physical properties and non-corrosive properties; the emissivity of the surface material of the wall panel 14 is 0.7-0.9, which is used to simulate the surface emissivity of crops and soil in the greenhouse; by rotating the two winding rollers 21 of the film press 2, the test piece 7 can be fixed horizontally and flatly in the heat preservation box 1, which can effectively reduce the eddy current effect caused by the unevenness of the test piece 7; before the heat transfer coefficient test is performed, the position of the first roller 22 of each film press 2 can be adjusted to change the position of the two film presses 2 The spacing between the two second rollers 31 can be adjusted to control the different distances of the multi-layer test pieces 7; by changing the relative positions of the two second rollers 31, the length and inclination of the bottom plate 3 can be adjusted, thereby changing the internal space of the heat preservation box 1 to simulate the internal shapes of different greenhouse types; the heat preservation box 1 can be quickly and conveniently moved to the test site by the wheels 17, and can be stored in the storage compartment 18 when the wheels 17 are not in use, thereby ensuring the stability of the heat preservation box 1 during the test, and avoiding damage to the wheels 17 when transporting the heat preservation box 1, thereby saving space.

[0021] like Figure 3 As shown, the DC power supply system includes an electrically connected mobile power module and a power regulation module. The mobile power module is used to provide stable DC power. The power regulation module is electrically connected to the heating wire 42. The power regulation module is used to adjust the heating power of the heating wire 42 to achieve precise control of the heating power of the heating wire 42. Compared with the AC power supply system, the DC power supply system is more stable and has no fluctuations, has high power regulation accuracy and is easy to carry and move.

[0022] like Figure 1 and3 As shown, the data acquisition and processing system 5 includes an electrically connected data acquisition module, a data analysis module, a data storage module and a data display module; the data acquisition module includes a first sensor 51, a second sensor, a third sensor 52 and a fourth sensor 53, the first sensor 51 is installed on the inner side of the wall plate 14, the first sensor 51 is used to detect the surface temperature of the wall plate 14 of the upper chamber 12, the second sensor (not shown in the figure) is installed on the outer wall of the heat preservation box 1, the second sensor is used to detect the surface temperature of the outer wall of the heat preservation box 1, the third sensor 52 is installed inside the upper chamber 12, the third sensor 52 is used to detect the air temperature inside the upper chamber 12, and the fourth sensor 53 is installed outside the heat preservation box 1 near At the test piece 7, the fourth sensor 53 is used to detect the air temperature and wind speed outside the insulation box 1; the data analysis module is used to calculate the heat transfer coefficient based on the data collected by the data acquisition module, and transmit the measured heat transfer coefficient to the data display module and the data storage module; the data display module includes a display screen 54, and the display screen 54 is used to display the internal air temperature of the upper chamber 12, the external air temperature of the insulation box 1, the surface temperature of the outer wall of the insulation box 1 and the wall panel 14, the heating power of the heating wire 42 and the heat transfer coefficient of the test piece 7 in real time; the data storage module is used to store and export the data collected by the data acquisition module and the heat transfer coefficient calculated by the data analysis module, and the data storage module is provided with a data export interface.

[0023] A method for using the portable greenhouse covering material heat transfer coefficient test device of this embodiment, in which a double-layer plastic film is used as a test piece 7, comprises the following steps: Step S1, install the inner plastic film on a laminator 2, rotate the two winding rollers 21 to keep the inner plastic film in a horizontal tensioned state, and slide the laminator 2 to the bottom of the insulation box 1 through the first rollers 22 on both sides, and fix it at a position 10 cm away from the upper surface of the insulation box 1; then install the outer plastic film on another laminator 2, rotate the two winding rollers 21 to keep the outer plastic film in a horizontal tensioned state, and fix the laminator 2 at a position 10 cm away from the upper surface of the insulation box 1 through the first rollers 22 on both sides. At the bottom of the baffle 15, the interface between the film press 2 and the baffle 15 is sealed by the sealing strip 16, so that the distance between the two layers of plastic film is 10 cm; the test device with the plastic film fixed is moved to an open outdoor environment through the wheels 17 at the bottom of the insulation box 1, so that both layers of plastic film face the sky and perform complete radiation heat exchange with the sky; after the test device is moved, the wheels 17 at the bottom of the insulation box 1 are folded and stored in the storage compartment 18 to prevent the insulation box 1 from being displaced due to excessive wind speed; Step S2, wait until night (when the sun has completely set) to turn on the DC power supply system, and the heating wire 42 starts to heat, so that the inside of the heat preservation box 1 is evenly heated; when the heating wire 42 starts to heat, the first sensor 51, the second sensor and the third sensor 52 of the data acquisition module start to measure data, and at the same time transmit the temperature data, the heating power and the wind speed data to the data display module, and monitor the air temperature and the heating power inside the heat preservation box 1 in real time through the display screen 54; preset the internal air temperature according to the external air temperature of the heat preservation box 1, and ensure that the temperature difference between the internal air temperature of the heat preservation box 1 and the external air temperature is ≥20°C; Step S3, the tester determines whether the heat preservation box 1 reaches thermal equilibrium by observing the air temperature and heating power inside the heat preservation box 1. The condition for determining thermal equilibrium is: after the air temperature inside the heat preservation box 1 reaches the preset value, the value fluctuates and the fluctuation does not have a continuous increasing or decreasing trend; when thermal equilibrium is reached, the data analysis module uses formula (1) to calculate the heat transfer coefficient, and transmits the measured heat transfer coefficient to the data display module and the data storage module; the temperature data and wind speed data before reaching thermal equilibrium are stored in the data storage module every 5 minutes, and the subsequent test data can be exported through the data export structure; Where U 0 is the heat transfer coefficient of the test piece, W / (m 2 ℃); A 0 is the area of ​​the test piece, m 2 ; ΔT 0 is the temperature difference between the air inside and outside the insulation box, ℃; Q is the heating power, W; ΔT i is the temperature difference between the inner and outer walls of the ith insulation box, ℃; U i is the heat transfer coefficient of the ith box wall of the insulation box, which can be obtained according to the material and thickness of the wall, W / (m 2 ℃); A i is the area of ​​the ith box wall of the insulation box, m 2 ; Step S4, after one test is completed, the DC power supply system is turned off, the plastic film on the laminator 2 is removed, and the next test can be started after the internal air temperature of the heat preservation box 1 cools to the same as the external air temperature.

[0024] It is impossible to quantitatively evaluate the effect of solar radiation heat exchange on the heat transfer coefficient of the test piece 7 during the day, so the heat transfer coefficient of the test piece 7 needs to be tested using the above-mentioned test device at night to ensure the accuracy of the test results. Example 2

[0025] like Figure 4As shown, a portable device for testing heat transfer coefficient of greenhouse covering materials is provided. The difference between this embodiment and embodiment 1 is that only one film press 2 is arranged in the upper chamber 12 of the insulation box body 1, and a detachable lifting component 6 is arranged at the bottom of the insulation box body 1. The lifting component 6 includes a scissor bracket 61, and a placement plate 62 for placing the insulation box body 1 is fixed on the top of the scissor bracket 61. A lifting switch 63 is arranged on one side of the placement plate 62. The lifting switch 63 adopts a gas spring to provide support force for the scissor bracket 61, and a soft pad is arranged at the bottom of the scissor bracket 61.

[0026] When in use, holding the lifting switch 63 and pulling it upward or pushing it downward can control the flow rate of the air flow inside the gas spring to adjust the lifting rate of the lifting component 6, making the lifting process more stable and controllable, and facilitating the adjustment of the height of the insulation box 1, so that it can be used for the heat transfer coefficient test of the covering material on the top of a higher greenhouse, making the test device have better versatility; by arranging a soft pad at the bottom of the scissor bracket 61, the scissor bracket 61 can be kept stable during the test, and the lifting component 6 is detachable and foldable, which is convenient for carrying and on-site installation.

[0027] A method for using the portable greenhouse covering material heat transfer coefficient test device in this embodiment, using a single-layer plastic film on the top of the greenhouse as a test piece 7, comprises the following steps: Step S1, move the test device into the greenhouse to be tested via the wheels 17, and after storing the wheels 17 in the storage compartment 18, install the insulation box 1 on the storage plate 62 of the lifting assembly 6, and lift the insulation box 1 upward until the top is flush with the top of the greenhouse through the lifting switch 63 and the scissor bracket 61, so that the film press 2 on the top of the insulation box 1 is in close contact with the single-layer plastic film on the top of the greenhouse, and the single-layer plastic film to be tested is fixed on the upper surface of the insulation box 1 through two winding rollers 21 to ensure that the single-layer plastic film to be tested is flat, fix the first rollers 22 on both sides of the film press 2 to the bottom of the baffle 15, and use the sealing strip 16 to seal the interface between the film press 2 and the baffle 15 to ensure that the overall air tightness of the insulation box 1 is good; Steps S2-S4 are the same as Example 1.

[0028] It is worth noting that the provided test device can be used to test the heat transfer coefficient of the covering materials of greenhouse structures such as plastic greenhouses, solar greenhouses, large-span greenhouses, multi-span plastic greenhouses, and multi-span glass greenhouses. The covering materials include plastic films such as PE, PO, and EVA, sun panels such as PE and PVC, tempered glass, float glass, double-layer hollow glass, and thermal insulation quilts composed of materials such as space cotton, non-woven fabrics, pearl cotton, rainproof cloth, and coated felt; the covering materials can also be multi-layer, including double-layer inflatable plastic films, three-layer inflatable plastic films, a comprehensive covering layer composed of plastic films and thermal insulation quilts, and thermal insulation quilts composed of multi-layer materials. In addition, during the test, the heat in the thermal insulation box 1 should be prevented from overflowing with the airflow as much as possible. In particular, in Example 3, when the test piece 7 is in an arc state, the highest point of the test piece 7 should be lower than the top surface of the thermal insulation box 1. Example 3

[0029] Combination Figure 5 As shown, a portable greenhouse covering material heat transfer coefficient test device is shown. The difference between this embodiment and embodiment 1 is that in order to accurately test the heat transfer coefficient of the greenhouse covering (flexible) material during use and minimize the influence of the refractive index error on the test result, a plurality of vertical lifting rods 80 ( Figure 5 The figure schematically shows five groups of lifting rods 80, each group of lifting rods 80 includes a first lifting rod 81 and a second lifting rod 82, the first lifting rod 81 and the second lifting rod 82 are located on both sides of the test piece 7, and the tops of the first lifting rod 81 and the second lifting rod 82 are connected by a straightened wire 83; when the lifting rod 80 rises to the target height, the wire 83 presses against the bottom surface of the test piece 7 in an arc state, and the wire 83 used is a cotton thread with a diameter of 1 mm, which is not only convenient for accurately, flexibly and stably adjusting the posture of the test piece, but also has almost no effect on the test results. When the test piece 7 is a plastic film in the greenhouse, the height of each group of lifting rods 80 is calculated and adjusted in advance according to the curvature of the plastic film in the use process, so that the plastic film (test piece 7) can be kept in an arc state (arched state) with the help of the wire 83, so that the plastic film in the test process is consistent with the plastic film in the use state. Since the plastic film is supported by the wire 83, the influence of the wire 83 on the radiation is cleverly avoided, so that the heat transfer coefficient of the greenhouse covering (flexible) material during use can be accurately tested.

Claims

1. A portable greenhouse covering material heat transfer coefficient test device, characterized in that: It comprises a heat preservation box (1), a DC power supply system, and a data acquisition and processing system (5); The heat preservation box (1) is provided with a partition (11), the partition (11) is provided with a plurality of heat dissipation holes (111), and the partition (11) divides the heat preservation box (1) into an upper chamber (12) and a lower chamber (13); the inner wall of the upper chamber (12) is provided with a wall plate (14), the top of the upper chamber (12) is provided with a baffle plate (15), at least one film press (2) for mounting a test piece (7) is provided between the wall plate (14) and the baffle plate (15), and first rollers (22) are provided on both sides of the film press (2). The roller (22) can slide up and down between the baffle (15) and the wall plate (14), and a sealing strip (16) is provided at the interface between the film pressing device (2) and the baffle (15); a heating component (4) is provided in the lower chamber (13), and the heating component (4) includes a fixed column (41) located at the center of the lower chamber (13), and a heating wire (42) is wound around the fixed column (41), and an anti-radiation layer (43) is provided on the upper part of the heating wire (42), and the anti-radiation layer (43) is used to prevent the heating wire (42) from exchanging radiation heat with the sky background; The DC power supply system is electrically connected to the heating wire (42), and the DC power supply system comprises a mobile power supply module and a power regulation module, the mobile power supply module is used to provide stable DC power, and the power regulation module is used to regulate the heating power of the heating wire (42); The data acquisition and processing system (5) comprises an electrically connected data acquisition module, a data analysis module, a data storage module and a data display module; the data acquisition module is used to collect the surface temperature of the outer wall and the wall plate (14) of the thermal insulation box (1), the air temperature inside the upper chamber (12), and the air temperature and wind speed outside the thermal insulation box (1); The data analysis module is used to measure the heat transfer coefficient based on the data collected by the data acquisition module, and transmit the measured heat transfer coefficient to the data display module and the data storage module; The data storage module is used to store and export the data collected by the data acquisition module and the heat transfer coefficient calculated by the data analysis module; the data display module is used to display the data collected by the data acquisition module and the heat transfer coefficient calculated by the data analysis module.

2. The portable greenhouse covering material heat transfer coefficient testing device according to claim 1, characterized in that: A retractable bottom plate (3) is provided at the bottom of the upper chamber (12), and second rollers (31) are provided on both sides of the bottom plate (3). The second rollers (31) can slide up and down along the wall plate (14).

3. The portable greenhouse covering material heat transfer coefficient testing device according to claim 2, characterized in that: The data acquisition module comprises a first sensor (51), a second sensor, a third sensor (52) and a fourth sensor (53); the first sensor (51) is used to detect the surface temperature of the wall plate of the upper chamber (12); the second sensor is used to detect the surface temperature of the outer wall of the heat preservation box (1); the third sensor (52) is used to detect the air temperature inside the upper chamber (12); and the fourth sensor (53) is used to detect the air temperature and wind speed outside the heat preservation box (1).

4. The portable greenhouse covering material heat transfer coefficient testing device according to claim 3 is characterized in that: The data display module comprises a display screen (54), wherein the display screen (54) is used to display in real time the air temperature inside the heat preservation box (1), the air temperature and wind speed outside the heat preservation box (1), the surface temperature of the wall panel (14) and the outer wall of the heat preservation box (1), the heating power of the electric heating wire (42), and the heat transfer coefficient of the test piece (7).

5. The portable greenhouse covering material heat transfer coefficient testing device according to claim 4, characterized in that: The bottom of the thermal insulation box (1) is provided with a plurality of wheels (17), and the side of the thermal insulation box (1) is provided with a plurality of storage compartments (18), the wheels (17) can be folded and supported at the bottom of the thermal insulation box (1) or stored in the storage compartments (18); the thermal insulation box (1) also includes a detachable lifting assembly (6), the lifting assembly (6) includes a scissor bracket (61), the top of the scissor bracket (61) is provided with a storage plate (62) for placing the thermal insulation box (1), one side of the storage plate (62) is provided with a lifting switch (63), the lifting switch (63) uses a gas spring to provide support force for the scissor bracket (61), and the bottom of the scissor bracket (61) is provided with a soft pad.

6. The portable greenhouse covering material heat transfer coefficient testing device according to any one of claims 1 to 5, characterized in that: A plurality of groups of vertically arranged lifting rods (80) are arranged in the heat preservation box (1), each group of lifting rods (80) comprising a first lifting rod (81) and a second lifting rod (82), the first lifting rod (81) and the second lifting rod (82) being located on both sides of the test piece (7), the tops of the first lifting rod (81) and the second lifting rod (82) being connected by a straightened wire (83); when the lifting rod (80) rises to a target height, the wire (83) presses against the bottom surface of the test piece (7) in an arc-shaped state.

7. A method for using the portable greenhouse covering material heat transfer coefficient testing device according to claim 1, comprising the following steps: Step S1, moving the heat preservation box (1) to the actual production environment of the test piece (7), and fixing the test piece (7) on the film press (2) to ensure the flatness of the test piece (7), and fixing the first rollers (22) on both sides of the uppermost film press (2) on the bottom of the baffle (15), and using a sealing strip (16) to seal the interface between the baffle (15) and the film press (2); Step S2, at night, the DC power supply system is turned on to start heating the heating component (4), and the data acquisition module starts measuring data, and at the same time transmits the temperature data, heating power and wind speed data to the data display module, and the internal air temperature and heating power of the heat preservation box (1) are monitored in real time through the data display module, and the internal air temperature is preset according to the external air temperature of the heat preservation box (1), so as to ensure that the temperature difference between the internal air temperature of the heat preservation box (1) and the external air temperature is ≥20°C; Step S3: when the heat preservation box (1) reaches thermal equilibrium, the data analysis module measures the heat transfer coefficient and transmits the measured heat transfer coefficient to the data display module and the data storage module; Step S4: After the test is completed, the DC power supply system is turned off, the test piece (7) on the film pressing device (2) is removed, and after the internal air temperature of the heat preservation box (1) cools to the same temperature as the external air temperature, steps S1-S3 are repeated to start the next test.

8. The method for using the portable greenhouse covering material heat transfer coefficient testing device according to claim 7, characterized in that: The thermal equilibrium condition of step S3 is that after the internal air temperature of the heat preservation box (1) reaches a preset value, the value fluctuates and the fluctuation does not have a continuous increasing or decreasing trend.

9. The method for using the portable greenhouse covering material heat transfer coefficient testing device according to claim 7, characterized in that: The formula for calculating the heat transfer coefficient by the data analysis module in step S3 is: In the formula, is the heat transfer coefficient of the test piece, W / (m²·℃); is the area of ​​the test piece, m²; is the temperature difference between the air inside and outside the insulation box, ℃; is the heating power, W; is the temperature difference between the inner and outer walls of the ith box of the insulation box, ℃; is the heat transfer coefficient of the ith box wall of the insulation box, which can be obtained according to the material, thickness and other conditions of the wall, W / (m²·℃); is the area of ​​the ith box wall panel of the insulation box, m².

Images