A heat transfer analysis method and system for a composite thermal insulation blanket for a solar greenhouse

Abstract

This invention provides a method and system for analyzing heat transfer in composite insulation blankets in solar greenhouses, belonging to the field of greenhouse environmental technology. The method includes: meshing the internal structure of the composite insulation blanket along its thickness; establishing a transient heat conduction differential equation as the governing equation based on the law of conservation of energy; determining initial and boundary conditions; and solving for the temperature distribution and overall heat transfer coefficient of the composite insulation blanket by coupling four heat transfer processes: conduction, convection, radiation, and latent heat exchange due to water vapor condensation. This invention solves the problem that existing models lack clear heat transfer mechanisms and cannot accurately reflect actual heat transfer processes. By comprehensively considering dynamic environmental factors and the structural characteristics of the insulation blanket, it achieves a realistic simulation of the heat transfer process under actual working conditions, providing a reliable theoretical tool for the structural optimization and material selection of the insulation blanket.

Description

Technical Field

[0001] This invention belongs to the field of greenhouse environment technology, specifically relating to a method and system for analyzing the heat transfer of composite insulation blankets in solar greenhouses. Background Technology

[0002] As a highly efficient and energy-saving agricultural facility, solar greenhouses play a crucial role in overcoming seasonal climate constraints and ensuring year-round crop production. Their core function lies in providing suitable conditions for crop growth through optimized thermal environment management. The greenhouse envelope, as the core interface for heat exchange between the greenhouse and the external environment, directly affects the stability of the indoor thermal environment and energy utilization efficiency. Given the winter insulation and production needs of crops in northern my country, thick composite insulation blankets are often required to reduce heat loss.

[0003] Composite insulation blankets are widely used due to their significant advantages such as high efficiency and energy saving, cold protection and insulation, and low cost. The rapid development of composite insulation blankets has driven the diversification of their materials and structures. The presence of moisture in the insulation blanket significantly alters the thermal conductivity of the material, affecting its insulation effect. During production, changes in porosity and moisture content of the insulation blanket are common due to material aging, mechanical crushing, and changes in the external environment (such as temperature, humidity, wind speed, and radiation), leading to a decline in insulation performance. The heat transfer coefficient is a key comprehensive parameter characterizing the overall insulation performance of composite insulation blankets in solar greenhouses under the coupled effects of multiple processes. Traditional methods for determining the heat transfer coefficient of composite insulation blankets mainly include field testing and laboratory determination. Field testing is entirely dependent on environmental conditions, parameters are difficult to control, test results are easily affected by interference, and errors are relatively large. While laboratory devices, mainly based on the hot box method, can autonomously control environmental parameters and produce relatively accurate and stable results, their testing conditions are usually stable and singular, and they still require physical samples of composite insulation blankets, increasing the economic and time costs of the determination. More importantly, the heat transfer process of composite insulation blankets in practical applications changes dynamically with the external environment (temperature, humidity, wind speed, radiation, etc.), and experimental results under static or simplified conditions are difficult to accurately describe the heat transfer process of greenhouse composite insulation blankets. Researchers have established methods for solving the heat transfer coefficient of greenhouse covering layers from different perspectives using models. They usually simplify the internal structure of composite insulation blankets, treating them as a homogeneous whole, and ignoring the influence of differences in the structure, density, porosity, and interface characteristics of different material layers on the heat transfer process, resulting in inaccurate analysis of the heat transfer process. Summary of the Invention

[0004] To address the problem of poor heat transfer analysis results in existing composite insulation blankets, this invention provides a method and system for analyzing the heat transfer of composite insulation blankets in solar greenhouses.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for analyzing heat transfer of composite insulation blankets in a solar greenhouse includes the following steps: Acquire the thermal properties of materials, structural parameters of the greenhouse, and indoor and outdoor environmental parameters in the solar greenhouse; Using the transient thermal conductivity differential equation as the governing equation, the multi-layer structure of the greenhouse, consisting of a light-transmitting covering layer and a composite insulation blanket, is divided into layers according to material density. The layers are then meshed along the thickness direction to obtain an upper boundary mesh, a lower boundary mesh, and an intermediate mesh. Based on the mesh parameters of different boundaries, the governing equation is transformed into a set of equations. Based on the physical properties, structural parameters, and environmental parameters of the solar greenhouse, the inner and outer surface temperatures of the composite insulation blanket are obtained by solving the equations; and the comprehensive heat transfer coefficient is obtained based on the inner and outer surface temperatures of the blanket.

[0006] Preferably, the system of equations specifically comprises: ; in, For the first The specific heat capacity of the material in each grid; and and Temperature at time; a, b, c, and d are all equation coefficients; when When, represents the mesh equation of the lower boundary, when When, it represents the mesh equation of the upper boundary.

[0007] Preferably, the heat exchange at the lower boundary includes radiative heat exchange, convective heat exchange, and latent heat of water vapor condensation between the inner surface of the composite insulation blanket and the greenhouse environment; the heat exchange at the upper boundary includes radiative heat exchange and convective heat exchange between the outer surface of the composite insulation blanket and the outdoor environment.

[0008] Preferably, the process of solving the equations based on the physical properties, structural parameters, and environmental parameters of the solar greenhouse to obtain the inner and outer surface temperatures of the composite insulation blanket involves programming the equations using Python, inputting the physical properties, structural parameters, and environmental parameters of the solar greenhouse into a solver for numerical solution, and obtaining the inner and outer surface temperatures of the composite insulation blanket.

[0009] Preferably, the comprehensive heat transfer coefficient is obtained based on the inner and outer surface temperatures. Specifically, the heat flow through the cover layer from the inside is calculated using the following formula: ; The overall heat transfer coefficient is calculated based on heat flow, specifically using the following formula: ; in, for The heat flow that constantly passes through the inside of the cover layer. and They are respectively , The average temperature of the overlay at any given time, for The overall heat transfer coefficient of the overlay layer at any given time; It is the radiation projected from the upper surface of the crop, the insulation blanket itself, and the wall; for Convective heat transfer between indoor air and the inner surface of the covering layer at time 1; for Latent heat transfer occurs on the inner surface of the cover layer due to water vapor condensation. For the inner surface of the coating layer in Effective radiation at all times.

[0010] This invention also provides a heat transfer analysis system for composite insulation blankets in a solar greenhouse, specifically comprising: The data module is used to acquire the thermophysical properties of materials, greenhouse structural parameters, and indoor and outdoor environmental parameters in the solar greenhouse.

[0011] The model building module is used to divide the multi-layer structure of the greenhouse, consisting of a light-transmitting covering layer and a composite insulation blanket, into layers according to the material density, using the transient thermal conductivity differential equation as the governing equation. The module then divides the structure into meshes along the thickness direction to obtain upper boundary meshes, lower boundary meshes, and intermediate meshes. Based on the mesh parameters of different boundaries, the governing equations are transformed into a set of equations.

[0012] The heat transfer analysis module solves the equations based on the physical properties, structural parameters, and environmental parameters of the greenhouse to obtain the inner and outer surface temperatures of the composite insulation blanket; and obtains the comprehensive heat transfer coefficient based on the inner and outer surface temperatures of the blanket.

[0013] The present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps described in the method for analyzing the heat transfer of composite insulation blankets in a solar greenhouse.

[0014] The present invention also provides a computer-readable storage medium storing a computer program, which, when loaded by a processor, is capable of executing the steps described in the method for analyzing the heat transfer of composite insulation blankets in a solar greenhouse.

[0015] The heat transfer analysis method for composite insulation blankets in a solar greenhouse provided by this invention has the following beneficial effects: This invention, based on the solution of a system of one-dimensional transient heat conduction differential equations, simulates the dynamic response of thermal insulation blankets under all-weather variations (such as diurnal temperature variation, wind speed variation, and solar radiation substitution terms). By dividing the continuous thickness space into a finite number of independent virtual grids, the differential equations are transformed into algebraic recursive formulas between the grids, making the theoretical formulas a computable numerical model. The grid boundaries comprehensively consider all coupled heat transfer forms between the inner / outer surfaces of the insulation blanket and the surrounding environment, reflecting the dynamic heat transfer process of the composite insulation blanket in a real greenhouse under complex operating conditions. Solving the system of equations yields the inner and outer surface temperatures of the composite insulation blanket and the overall heat transfer coefficient, enabling a comprehensive quantitative analysis of the heat transfer process of the composite insulation blanket in a real greenhouse environment. This provides a physically interpretable theoretical tool for optimizing the layered structure of the insulation blanket, selecting suitable surface and core materials, and formulating reasonable operation and management strategies. It helps improve the nighttime insulation performance and energy efficiency of greenhouses, and has high practical value. Attached Figure Description

[0016] To more clearly illustrate the embodiments and design schemes of the present invention, the accompanying drawings required for this embodiment will be briefly described below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of heat transfer inside the solar greenhouse in an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of the grid of a composite insulation blanket covering a solar greenhouse in an embodiment of the present invention.

[0019] Figure 3 This is a simplified schematic diagram of the internal path of the fiber porous material in an embodiment of the present invention.

[0020] Figure 4 This is a schematic diagram of greenhouse 1 in an embodiment of the present invention. Figure 4 (a) refers to the outdoor environment; Figure 4 (b) is the indoor environment.

[0021] Figure 5 This is a schematic diagram of greenhouse 2 in an embodiment of the present invention. Figure 5 (a) refers to the outdoor environment; Figure 5 (b) is the indoor environment.

[0022] Figure 6 This is a schematic diagram showing the locations of various measuring points in a traditional brick-walled greenhouse according to an embodiment of the present invention.

[0023] Figure 7This is a schematic diagram showing the locations of various measuring points in the novel flexible solar greenhouse according to an embodiment of the present invention.

[0024] Figure 8 This paper compares and analyzes the measured and simulated values ​​of the inner surface temperature of the insulation blanket for the traditional brick-walled greenhouse in Area A and the novel flexible greenhouse in Area B from January 20th to January 27th, 2025, in this embodiment of the invention. Figure 8 (a) shows the comparative analysis results of traditional brick-walled greenhouses in Area A; Figure 8 (b) shows the comparative analysis results of the new flexible solar greenhouse in area B.

[0025] Figure 9 This is a flowchart of a heat transfer analysis method for composite insulation blankets in a solar greenhouse according to the present invention.

[0026] Figure 10 This is a comparison chart of the thermal conductivity of materials with different porosities in embodiments of the present invention. Figure 10 (a) is spray-bonded cotton; Figure 10 (b) is pearl cotton; Figure 10 (c) is needle-punched felt.

[0027] Figure 11 This is a comparison chart of the thermal conductivity of materials with different water contents at the same porosity in embodiments of the present invention. Figure 11 (a) is spray-bonded cotton; Figure 11 (b) is pearl cotton; Figure 11 (c) is needle-punched felt. Detailed Implementation

[0028] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0029] Example The internal environment of a solar greenhouse is a closed space composed of a covering layer, a soil layer, and walls (including the north wall, north roof, east wall, and west wall). The actual thermal environment inside the greenhouse is the result of the coupling of four heat transfer mechanisms: heat conduction, heat convection, heat radiation, and latent heat transfer. Its dynamic equilibrium is influenced by both external meteorological conditions and internal control strategies. During winter production, a composite insulation blanket is typically added over the light-transmitting covering layer to reduce heat loss and achieve insulation. The heat transfer process of the composite insulation blanket involves multiple aspects, such as... Figure 1As shown: The interior of the composite insulation blanket is mainly heat conduction; its inner surface undergoes radiative heat exchange with the wall and crop surface, and convective heat exchange with the indoor air, and may generate latent heat exchange due to water vapor condensation; the outer surface undergoes long-wave radiation heat exchange with the sky background and convective heat exchange with the outdoor air.

[0030] This invention provides a method for analyzing the heat transfer of composite insulation blankets in solar greenhouses, such as... Figure 1 As shown, the specific steps include: Step 1: Obtain the surface thermal properties of each object, the greenhouse structural parameters, and the environmental parameters.

[0031] Step Two: When constructing the mathematical model of the internal heat conduction process of the composite insulation blanket covering the front roof of the greenhouse, the core governing equation is the transient heat conduction differential equation based on the law of conservation of energy. The specific calculation equation is as follows:

[0032] (1); The multi-layered structure, consisting of a light-transmitting covering layer and a composite insulation blanket, is divided into layers along its thickness according to the actual materials, creating a grid pattern from the indoor side to the outdoor side based on material density. This results in a structure with sparser layers in the middle and denser layers at the edges. Specifically, as shown below... Figure 2 As shown. The mesh volume is represented by Gi (i=1, 2, ..., n-1, n), and the thickness between the center points of each mesh is... The internal structure of the composite insulation blanket is gridded along the thickness direction to form multiple grid bodies.

[0033] Based on the finite difference method, the difference form of the governing equations is as follows: (2); In the formula, For the first The material density of each grid, in units of ; For the first The specific heat capacity of the material in each grid, in units of ; This is the grid length, in mm; The time step is expressed in seconds (s). , The first , Thermal conductivity at the center point of each grid, in units of ; For the first The grid and the first The distance between the center points of each grid, in mm; For the first The grid and the first The distance between the center points of each grid, in mm; , , The first , , A grid G ​​in Temperature at any given time, expressed in Kelvin (K). For the first Each grid in A constant source of heat.

[0034] In this configuration, the heat exchanger in the middle grid only exchanges heat with the upper and lower grids through conduction. The calculation formula is as follows: (3); The lower boundary grid exchanges heat with the grid above it via conductive heat transfer, and with the indoor surfaces below it via radiative heat transfer, convective heat transfer with the surrounding air, and condensation heat transfer with indoor water vapor. This portion of heat exchange on the lower side exists as a heat source for the grid, affecting its heat transfer. The expression for the lower boundary grid is as follows (i.e....). ):

[0035] (4); The upper boundary grid undergoes heat conduction and heat exchange with the next grid below it, and radiation and convection heat exchange with the outdoor sky background and the surrounding outdoor air above it. This portion of heat exchange on the upper side acts as a heat source for the grid, affecting its heat exchange. The expression for ) is as follows: (5); make: , , , , The resulting system of equations is: (6); (7); (8); Initial conditions can be directly substituted into measured data. For new materials and new structural samples that are in the development stage and cannot be tested, the initial conditions can be determined by the pre-testing method.

[0036] The boundary conditions of the governing equations are the radiation, convection, and water vapor condensation heat transfer between the inner and outer surfaces of the composite insulation blanket and the surrounding environment. The lower boundary condition is the convection, radiation, and water vapor condensation heat transfer between the inner surface of the insulation blanket and the indoor environment; the upper boundary condition is the convection and radiation heat transfer between the outer surface of the composite insulation blanket and the outdoor air.

[0037] (1) Lower boundary conditions Radiative heat transfer: As opaque surfaces, the composite insulation blanket and wall structure's effective radiation includes its own radiation and the reflected portion of effective radiation from other surfaces. The projected radiation from the inner surface of the insulation blanket... Projected radiation from the crop surface, the insulation blanket itself, and the wall; projected radiation from the wall. The radiation comes from the upper surface of the crop, the wall itself, and the inner surface of the covering layer.

[0038] (9); (10); (11); (12); As three-dimensional radiators, crops in greenhouses have diverse leaf angles, making it difficult to accurately calculate their angular coefficients with surrounding surfaces. Therefore, in simulating crop radiative heat transfer, based on the theory of plant canopy radiative transfer, the three-dimensional crop canopy is equivalent to a translucent medium layer with a certain characteristic thickness H and an equivalent extinction coefficient k, with its upper and lower boundaries considered as gray bodies satisfying diffuse reflection conditions. The effective radiation from the upper and lower surfaces of the crops... , This includes intrinsic radiation, reflected radiation from the inner surface of the composite insulation blanket or the soil surface, and transmitted radiation. Projected radiation from the crop's upper surface... It mainly exchanges radiation with the inner walls of the greenhouse and the inner surface of the composite insulation blanket, while the lower surface... It then only exchanges heat with the soil surface through radiation.

[0039] (13); (14); (15); (16); In actual production conditions, greenhouses are often covered with mulch film. When conducting radiative heat transfer analysis, the mulch film and soil inside the greenhouse are considered as equivalent composite surfaces. The emissivity and reflectivity of the mulch film surface are used, while the soil surface is considered an opaque surface, and its effective radiation... The projected radiation is the radiation emitted by the crop itself and the reflection of effective radiation from the lower surface of the crop. It only exchanges heat with the lower surface of the crop layer through radiation.

[0040] (17); (18); In the formula, , , , , These are the inner surface of the cover layer, the inner surface of the wall, the upper and lower surfaces of the crop layer, and the soil surface. Effective radiation at any given time, in units of ; , , , , Each surface at Projected radiation at time, in units of ; Let be the blackbody radiation constant, with a value of . ; , , , The surface areas of the cover layer, wall, crop, and soil are respectively expressed in units of ; Let be the radiation angle coefficient of surface a to surface b; , , , The emissivity of each surface; , , , Let be the reflectivity of each surface; The transmittance of the crop layer to long-wave radiation; , , , , Each surface is in Temperature at any given time, expressed in Kelvin (K).

[0041] Convective heat transfer: Indoor air undergoes natural convection due to temperature differences, or forced convection due to ventilation systems, crop transpiration, etc., resulting in convective heat transfer with the inner surface of the composite insulation blanket. The formula for convective heat transfer between indoor air and the inner surface of the insulation blanket is as follows:

[0042] (19); (20); In the formula, for The convective heat transfer between indoor air and the inner surface of the covering layer at time 1, in units of ; inner surface of the coating layer The convective heat transfer coefficient at any given time; for Indoor air temperature at any given time, expressed in Kelvin (K). for The temperature of the inner surface of the coating at any given time, expressed in Kelvin (K).

[0043] Water vapor condensation heat transfer: When indoor humidity is high, water vapor may condense on the inner surface of the insulation blanket because the temperature is lower than the dew point temperature, releasing latent heat and further affecting surface heat exchange. This process is coupled with convective heat transfer, jointly determining the overall heat transfer characteristics of the covering layer.

[0044] The formula for calculating dew point temperature is: (twenty one); Latent heat transfer due to water vapor condensation on the inner surface of the covering layer: (twenty two); (twenty three); Saturated vapor pressure at the inner surface temperature of the capping layer: (twenty four); In the formula, for Dew point temperature at any given time, in Kelvin (K). for Indoor air temperature at any given time, expressed in Kelvin (K). for Latent heat transfer due to water vapor condensation on the inner surface of the cover layer, W / m2; This is a humidity calculation constant, with units of Pa / K; for The air vapor pressure inside the greenhouse at any given time, expressed in Pa. inner surface of the coating layer The saturated vapor pressure at a given temperature, expressed in Pa.

[0045] (2) Upper boundary conditions: Radiative heat transfer: outer surface of the insulation blanket Against the sky background They radiate to each other.

[0046] (25); (26); (27); (28); In the formula , The sky background and the outer surface of the overlay are respectively... Effective radiation at any given time, in units of ; , Each surface at Projected radiation at time, in units of ; The surface area of ​​the sky background, in units of ; , , where represents the emissivity of each surface; , Let be the reflectivity of each surface; , Each surface is in Temperature at any given time, expressed in Kelvin (K).

[0047] Convective heat transfer: Forced convection heat transfer occurs between the outer surface of the covering layer and the outdoor air, mainly due to the action of external wind.

[0048] The formula for convective heat transfer between the outdoor environment and the outer surface of the insulation blanket is as follows: (29); In the formula, for The convective heat transfer between outdoor air and the outer surface of the covering layer at a given time, in units of ; for Outdoor wind speed at any given time, in m / s; for The outdoor air temperature at any given time, expressed in Kelvin (K). for The temperature of the inner surface of the coating at any given time, expressed in Kelvin (K).

[0049] The program is written based on the governing equations. The initial and boundary conditions are substituted into the program to calculate the inner and outer surface temperatures of the composite insulation blanket, and then the comprehensive heat transfer coefficient and heat loss are determined.

[0050] Step 3: The heat transfer paths of the insulation blanket include conduction, radiation, convection, and water vapor condensation. These four heat transfer mechanisms occur simultaneously and collectively affect the heat transferred by the insulation blanket. For heat transfer within the insulation blanket, only conduction is considered. The radiation, convection, and water vapor condensation processes between the upper and lower surfaces of the insulation blanket and the surrounding environment are analyzed using boundary conditions within the insulation blanket.

[0051] The composite insulation blanket used as a covering layer in solar greenhouses is typically composed of a multifunctional surface material and a porous fiber core. Its core thermal function lies in significantly increasing the overall thermal resistance of the covering layer through its porous media properties, thereby suppressing heat dissipation primarily through conduction. Therefore, composite insulation blankets are calculated using two types of materials: dense surface materials and porous materials.

[0052] Its heat transfer caused by thermal conduction The calculation formula is as follows: (30); For porous fibrous materials, the internal fibers are mostly randomly and non-directionally distributed. The heat conduction paths are tortuous and complex, making accurate calculation difficult. In quantitative analysis, the internal paths are simplified proportionally to a random arrangement of solids, liquids, and gases, with the heat conduction paths being randomly distributed horizontally and vertically. This means that the thermal resistances in series and in parallel are added proportionally. For example... Figure 3 As shown.

[0053] The simplified thermal conductivity of the porous fiber material is: (31); in, c .

[0054] In the formula, , These are the thicknesses of the surface material and the porous, fluffy fiber material, respectively, in meters (m). , These are the thermal conductivity coefficients of the surface material and the porous, fluffy fibrous material, respectively, in units of... ; The pore channel distribution coefficient; , , These are the thermal conductivity coefficients of solid, liquid, and gaseous media, respectively, in units of... ; Porosity; Moisture content; For tortuosity; Fill rate; Weight is expressed in grams, and the unit is... H represents the filter media thickness, in units of... , The density of the filter media fiber is expressed in units of... .

[0055] Step Four: The overall heat transfer coefficient is a key parameter for evaluating the thermal insulation performance of the covering layer, and its numerical calculation directly reflects the overall thermal insulation performance of the composite structure. When there is a temperature difference between indoors and outdoors, heat is continuously transferred from the high-temperature indoor environment to the low-temperature outdoor environment through four coupled mechanisms: radiation, convection, conduction, and latent heat transfer. Based on key thermophysical properties such as the material's apparent thermal conductivity, density, and specific heat capacity, the overall heat transfer coefficient is quantified by calculating the heat flow through the composite structure under a given indoor-outdoor temperature difference.

[0056] The heat flow through the cover layer from the inside at any given time is calculated by the following formula: (32); The formula for calculating the overall heat transfer coefficient of the overlay layer at any given time is as follows: (33); In the formula, for The heat flow rate through the cover layer from the inside at any given time, in units of ; , They are respectively , The average temperature of the overlying layer at any given time, expressed in Kelvin (K). for The overall heat transfer coefficient of the overlay layer at any given time, in units of .

[0057] The multi-process coupled heat transfer model of composite insulation blanket for solar greenhouses was validated. Greenhouse 1 in Area A is a traditional brick-walled solar greenhouse. The indoor and outdoor environments of the greenhouse are as follows: Figure 4 As shown. The greenhouse is oriented east-west, with a length of 85 m and a north-south span of 9 m. The north wall is 3.1 m high, and the roof ridge is 4.6 m high. The south roof is covered with a 0.1 mm thick PO (Polyolefin) film at the bottom, and the upper layer is a composite insulation blanket consisting of silver aluminized PE woven fabric + pearl cotton + 1050 g of spray-bonded cotton + silver PE (Polyethylene) woven fabric, with a thickness of 45 cm. In January 2025, tomatoes will be grown in the greenhouse and will be in harvest season. The composite insulation blanket will be turned on around 9:30 AM and turned off around 4:30 PM daily, with the specific times adjusted according to the sunrise and sunset times.

[0058] Greenhouse 2 in Zone B is a new type of flexible solar greenhouse. The indoor and outdoor environments of the greenhouse are as follows: Figure 5As shown. The greenhouse is oriented east-west, with a length of 75 m and a span of 12 m, and a ridge height of 5.8 m. The south roof is covered with a PO film at the bottom, and a composite insulation blanket structure consisting of brown PVC (Polyvinyl chloride) cloth + spray-bonded cotton + pearl cotton + black PVC cloth, with a thickness of 32 cm. The north wall and east and west walls are composed of two layers of black felt + two layers of recycled cotton blankets + two layers of PO film + one layer of 0.5 cm cement mortar + 3 cm PVC insulation blanket. In January 2025, tomatoes will be grown in the greenhouse and will be in harvest season. The composite insulation blanket will be turned on around 9:30 am and turned off around 4:30 pm daily.

[0059] The locations of various measuring points in a traditional brick-walled greenhouse are as follows: Figure 6 As shown in the diagram, four temperature measuring points on the inner and outer surfaces of the composite insulation blanket were symmetrically arranged at heights of 2.25 m and 1.25 m. A cross-section 30 m from the east wall of the greenhouse was selected as the test section. Air temperature and soil temperature measuring points were evenly set along the south, center, and north directions of the cross-section, with a spacing of 2.7 m between adjacent measuring points. Two relative humidity measuring points were set along the south and north directions, and one total solar radiation measuring point was set at the midpoint of the greenhouse. The air temperature measuring points were at heights of 2.25 m and 1.25 m, the soil temperature measuring point was at a depth of 0.05 m, and the wall temperature, total solar radiation, and relative humidity measuring points were at a height of 2.25 m. Outdoor weather stations were set up at the south side of the greenhouse and the roof ridge to simultaneously record outdoor meteorological data.

[0060] The locations of the measuring points in the new flexible solar greenhouse are as follows: Figure 7 As shown in the diagram, four temperature measuring points were symmetrically arranged at heights of 1.8 m and 1 m on the inner and outer surfaces of the composite insulation blanket. Similarly, a section 30 m from the east wall of the greenhouse was selected as the test section, and air temperature and soil temperature measuring points were evenly set along the south, center, and north directions of the section, with a spacing of 3.5 m between adjacent measuring points. One solar total radiation measuring point and one relative humidity measuring point were set at the midpoint of the greenhouse. The air temperature measuring point was at heights of 1.8 m and 1 m, the soil temperature measuring point was at a depth of 0.05 m, and the wall temperature measuring point, solar total radiation measuring point, and relative humidity measuring point were at a height of 1.8 m. Outdoor weather stations were set up at the southern part of the greenhouse and at the roof ridge to simultaneously record outdoor meteorological data.

[0061] A multi-process coupled heat transfer model for the composite insulation blanket in a solar greenhouse was constructed. The input parameters included the temperatures of the walls, soil surface, crop surface, indoor and outdoor air, as well as outdoor solar radiation, outdoor wind speed, and indoor relative humidity. The model was validated based on measured data, with the weighted average temperature of the walls and soil surface substituted. The equations (6)-(8) were solved using Python programming, and the model output was the inner surface temperature of the composite insulation blanket.

[0062] To verify the accuracy and stability of the model, a traditional brick-walled greenhouse in Area A and a new flexible greenhouse in Area B were selected as research objects. Measured data from January 20th to January 27th, 2025 were used to validate the model, and the measured values ​​of the inner surface temperature of the insulation blanket were compared and analyzed with the simulated values. The results are as follows: Figure 8 As shown in the figure. This period falls around the time of the Great Cold (January 20th-21st-27th) and includes a wide range of weather conditions, encompassing sunny (January 22nd-24th) and cloudy (January 25th-26th) days, making it highly representative of meteorological conditions. This study focuses on the heat transfer process after covering the area with thermal blankets at night; therefore, the daily analysis period is defined as 17:00 to 8:00 the following day.

[0063] The simulation accuracy was quantitatively evaluated by calculating the Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and Coefficient of Determination (R²) between the simulated and measured values. The results showed that the MAE for the Fangshan greenhouse was 1.21℃, the RMSE was 1.27℃, and the R² was 0.97; while the MAE for the Miyun greenhouse was 0.56℃, the RMSE was 1.08℃, and the R² was 0.85. Overall, the error indices for both greenhouses were at low levels, demonstrating that the constructed model has good predictive ability for both types of greenhouse structures. However, in the traditional brick-walled greenhouse, the joints of the composite insulation blanket had insufficient sealing, leading to localized cold bridging effects. Furthermore, due to the continuous heat loss from the greenhouse at night, these localized heat leaks accumulated over time, causing the measured data to gradually fall below the simulated values, and the deviation between the two gradually widened over time. Further analysis of the model's performance under different weather conditions revealed that: under sunny conditions, the simulated values ​​matched the measured values ​​best and had the smallest error; while under cloudy and overcast conditions, despite significant changes in sky radiation, the model maintained high stability, with only slight deviations occurring during a few instantaneous meteorological abrupt changes, and the overall simulation trend was consistent with the measured data.

[0064] Analyze the influence of material porosity, such as Figure 10As shown, when the spray-bonded cotton is at a low moisture content (≤0.05), its thermal conductivity decreases with increasing porosity. When the moisture content is 0, as the porosity increases from 0.75 to 0.975, the thermal conductivity decreases from 0.034 W / (m·K) to 0.024 W / (m·K), a decrease of 27.4%. At intermediate moisture contents (0.1, 0.15), the porosity has little effect on the thermal conductivity. At high moisture contents (≥0.2), the thermal conductivity increases slightly with increasing porosity. When the moisture content is 0.25, as the porosity increases from 0.75 to 0.975, the thermal conductivity decreases from 0.093 W / (m·K) to 0.1 W / (m·K), an increase of 7.7%. For pearl cotton, as the moisture content increases from 0 to 0.25, the thermal conductivity continuously decreases with the increase of porosity. When the moisture content is 0, as the porosity increases from 0.7 to 0.95, the thermal conductivity decreases from 0.073 W / (m·K) to 0.031 W / (m·K), a decrease of 57.6%. When the moisture content is 0.25, as the porosity increases from 0.7 to 0.95, the thermal conductivity decreases from 0.12 W / (m·K) to 0.1 W / (m·K), a decrease of 19.6%. When the moisture content of the needle-punched felt is in the range of 0 to 0.15, the thermal conductivity decreases with increasing porosity. When the moisture content is 0, as the porosity increases from 0.3 to 0.85, the thermal conductivity decreases from 0.063 W / (m·K) to 0.03 W / (m·K), a decrease of 52.4%. When the moisture content is 0.2, the effect of porosity on thermal conductivity is relatively small. When the moisture content is 0.25, the thermal conductivity increases slightly with increasing porosity. As the porosity increases from 0.3 to 0.85, the thermal conductivity increases from 0.089 W / (m·K) to 0.095 W / (m·K), an increase of 6.5%. The reason for this is that the greater the porosity of a material, the more air with poor thermal conductivity it contains, and the lower its thermal conductivity. When the moisture content of the material increases, the high thermal conductivity of water replaces the low thermal conductivity of air in the pores. Therefore, the overall thermal conductivity of the material increases with the increase in moisture content. Spray-bonded cotton and needle-punched felt have a loose fibrous structure with interconnected pores. At low moisture content, the pores are mainly composed of air. The greater the porosity, the higher the proportion of air, and the lower the thermal conductivity. At intermediate moisture content (0.1% and 0.15%), the water does not fill the interconnected pores, and the thermal conductivity contributions of air and pores cancel each other out. The impact of porosity changes on overall thermal conductivity is weakened, and the thermal conductivity remains basically stable. At high moisture content, the interconnected pores allow water to form continuous thermal conduction channels. The greater the porosity, the more continuous water channels there are, and the thermal conductivity actually increases. Because pearl cotton is EPE foam, its pores are closed, independent cells. The closed cells restrict the flow of water between the pores, making it difficult for water to form continuous heat conduction channels. Therefore, as the porosity increases, the thermal conductivity continues to decrease.

[0065] The effect of material moisture content, such as Figure 11 As shown, when the material porosity is constant, as the moisture content increases from 0 to 0.225: For spray-bonded cotton with a porosity of 0.7, the thermal conductivity increases from 0.036 to 0.086 W / (m·K), an increase of 138.9%; when the porosity is 0.95, the thermal conductivity increases from 0.025 to 0.091 W / (m·K), an increase of 264%. For pearl cotton with a porosity of 0.7, the thermal conductivity increases from 0.073 to 0.123 W / (m·K), an increase of 68.5%; when the porosity is 0.95, the thermal conductivity increases from 0.031 to 0.096 W / (m·K), an increase of 209.6%. When the porosity of needle-punched felt is 0.35, the thermal conductivity increases from 0.059 to 0.086, an increase of 45.8%; when the porosity is 0.85, the thermal conductivity increases from 0.03 to 0.089 W / (m·K), an increase of 196.7%. The results show that under humid conditions, the thermal conductivity of all three materials—spray-bonded cotton, pearl cotton, and needle-punched felt—increases linearly with increasing moisture content. Furthermore, the higher the porosity, the more significant the effect of increasing moisture content on thermal conductivity, meaning the faster the rate of increase. For materials with higher porosity, when the moisture content increases, a small amount of liquid water can replace a large amount of air with low thermal conductivity, resulting in an enhanced heat conduction effect. This leads to a rapid increase in thermal conductivity, eventually surpassing that of materials with lower porosity.

[0066] By comparing the heat loss ratio of the composite insulation blankets in traditional brick-walled solar greenhouses and new flexible solar greenhouses, the differences and patterns in their heat transfer mechanisms are revealed.

[0067] Traditional brick-walled greenhouses primarily experience nighttime heat loss through radiation and condensation, with radiative heat loss accounting for approximately 26%-56%, latent heat loss for approximately 26%-59%, and convective heat loss for approximately 8%-32%. In contrast, the heat transfer characteristics of the covering layer in new flexible greenhouses differ: radiation accounts for approximately 45%-73%, latent heat for approximately 27%-55%, and convection is extremely low. This difference stems from the fact that traditional brick-walled greenhouses use nylon Velcro fasteners for their insulation, resulting in poor sealing and convective heat loss. The new flexible greenhouses, with their composite insulation using a combination of nylon Velcro and surface adhesive, offer superior sealing, significantly reducing air convection. Furthermore, the higher emissivity of the covering material in the new flexible greenhouse allows heat to dissipate more easily through radiation, while the traditional brick walls provide stronger radiation barrier properties, further reducing radiative heat loss. Both types of greenhouses experience some condensation heat loss during winter nights due to high indoor humidity and low surface temperature of the covering layer.

[0068] Therefore, traditional brick-walled greenhouses, while maintaining basic insulation performance using materials with a certain porosity, must focus on suppressing radiation, condensation, and convective heat loss. The surface layer of the insulation blanket can use high-reflectivity, high-density, and waterproof materials to reduce radiative heat loss and protect the interior; ventilation and dehumidification should be strengthened to control humidity within the greenhouse and reduce condensation heat loss; the splicing method should be improved, and insulating core materials such as foam plastic and porous materials should be added inside the insulation blanket to utilize still air to block convection and conduction heat loss. New flexible solar greenhouses, while maintaining the advantages of high sealing performance and low convective heat loss of the insulation blanket, are advised to use a high-reflectivity surface layer to optimize the radiation performance of the composite insulation blanket and reduce the proportion of radiative heat loss; refined humidity management (such as timed dehumidification) should also be implemented to reduce condensation heat loss.

[0069] This invention also provides a heat transfer analysis system for composite insulation blankets in a solar greenhouse, comprising: The data module is used to acquire the thermophysical properties of materials, greenhouse structural parameters, and indoor and outdoor environmental parameters in the solar greenhouse.

[0070] The model building module is used to divide the multi-layer structure of the greenhouse, consisting of a light-transmitting covering layer and a composite insulation blanket, into layers according to the material density, using the transient heat conduction differential equation as the governing equation. The module then divides the structure into meshes along the thickness direction to obtain the upper boundary mesh, the lower boundary mesh, and the intermediate mesh. Based on the mesh parameters of different boundaries, the governing equation is transformed into a set of equations.

[0071] The heat transfer analysis module solves the equations based on the physical properties, structural parameters, and environmental parameters of the greenhouse to obtain the inner and outer surface temperatures of the composite insulation blanket; and obtains the comprehensive heat transfer coefficient based on the inner and outer surface temperatures of the blanket.

[0072] The various modules in the aforementioned composite insulation blanket heat transfer analysis system for a solar greenhouse can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the computer device's memory as software, so that the processor can call and execute the corresponding operations of each module.

[0073] The present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory. The processor executes the computer program to implement the steps in an embodiment of a method for analyzing the heat transfer of a composite insulation blanket in a solar greenhouse. Specific implementation methods can be found in the method embodiments, and will not be repeated here.

[0074] Furthermore, the present invention also provides a non-transitory computer-readable storage medium containing instructions, on which a computer program is stored. For example, a memory containing instructions that can be executed by a processor of a computer device to perform the above-described method. For example, the non-transitory computer-readable storage medium may be a ROM, random access memory (RAM), CD-ROM, magnetic tape, floppy disk, and optical data storage device, etc. When the computer program is executed by the processor, it can implement the steps in an embodiment of a method for analyzing the heat transfer of composite insulation blankets in a solar greenhouse. Specific implementation methods can be found in the method embodiments, which will not be repeated here.

[0075] Those skilled in the art will understand that embodiments of the present invention can provide methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0076] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, as well as combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0077] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0078] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0079] It should be noted that the specific embodiments described above enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way. Therefore, although the present invention has been described in detail in this specification and embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention are covered within the protection scope of the present invention patent. No reference numerals in the claims should be construed as limiting the scope of the claims. Any simple variations or equivalent substitutions of technical solutions that can be readily obtained by those skilled in the art within the scope of the technology disclosed in the present invention are within the protection scope of the present invention.

Claims

1. A method for analyzing heat transfer in composite insulation blankets in a solar greenhouse, characterized in that, Includes the following steps: Acquire the thermal properties of materials, structural parameters of the greenhouse, and indoor and outdoor environmental parameters in the solar greenhouse; Using the transient thermal conductivity differential equation as the governing equation, the multi-layer structure of the greenhouse, consisting of a light-transmitting covering layer and a composite insulation blanket, is divided into layers according to material density. The layers are then meshed along the thickness direction to obtain an upper boundary mesh, a lower boundary mesh, and an intermediate mesh. Based on the mesh parameters of different boundaries, the governing equation is transformed into a set of equations. Based on the physical properties, structural parameters, and environmental parameters of the solar greenhouse, the inner and outer surface temperatures of the composite insulation blanket are obtained by solving the equations. The combined heat transfer coefficient is obtained based on the inner surface temperature and the outer surface temperature.

2. The method for analyzing heat transfer of composite insulation blankets in a solar greenhouse according to claim 1, characterized in that, The system of equations is specifically as follows: ； in, For the first The specific heat capacity of the material in each grid; and The first and Each grid in Temperature at time; a, b, c, and d are all equation coefficients; when When, represents the mesh equation of the lower boundary, when When, it represents the mesh equation of the upper boundary.

3. The method for analyzing heat transfer of composite insulation blankets in a solar greenhouse according to claim 1, characterized in that, The heat exchange at the lower boundary includes radiative heat exchange, convective heat exchange, and latent heat of water vapor condensation between the inner surface of the composite insulation blanket and the greenhouse environment; the heat exchange at the upper boundary includes radiative heat exchange and convective heat exchange between the outer surface of the composite insulation blanket and the outdoor environment.

4. The method for analyzing heat transfer of composite insulation blankets in a solar greenhouse according to claim 1, characterized in that, The method involves solving a set of equations based on the physical properties, structural parameters, and environmental parameters of the solar greenhouse to obtain the inner and outer surface temperatures of the composite insulation blanket. Specifically, the equations are programmed using Python, and the physical properties, structural parameters, and environmental parameters of the solar greenhouse are input into a solver for numerical solution to obtain the inner and outer surface temperatures of the composite insulation blanket.

5. The method for analyzing heat transfer of composite insulation blankets in a solar greenhouse according to claim 1, characterized in that, The combined heat transfer coefficient is obtained based on the inner and outer surface temperatures. Specifically, the heat flow through the cover layer from the inside is calculated using the following formula: ； The overall heat transfer coefficient is calculated based on heat flow, specifically using the following formula: ； in, for The heat flow that constantly passes through the inside of the cover layer. and They are respectively , The average temperature of the overlay at any given time, for The overall heat transfer coefficient of the overlay layer at any given time; It is the radiation projected from the upper surface of the crop, the insulation blanket itself, and the wall; for Convective heat transfer between indoor air and the inner surface of the covering layer at time 1; for Latent heat transfer occurs on the inner surface of the cover layer due to water vapor condensation. For the inner surface of the coating layer in Effective radiation at all times.

6. A heat transfer analysis system for composite insulation blankets in a solar greenhouse, characterized in that, include: The data module is used to acquire the thermophysical properties of materials, structural parameters of the greenhouse, and indoor and outdoor environmental parameters in the solar greenhouse. The model building module is used to divide the multi-layer structure of the greenhouse, consisting of a light-transmitting covering layer and a composite insulation blanket, into layers according to the material density, using the transient heat conduction differential equation as the governing equation. The module then divides the structure into meshes along the thickness direction to obtain upper boundary meshes, lower boundary meshes, and intermediate meshes. Based on the mesh parameters of different boundaries, the governing equations are transformed into a set of equations. The heat transfer analysis module solves the equations based on the physical properties, structural parameters, and environmental parameters of the greenhouse to obtain the inner and outer surface temperatures of the composite insulation blanket. The combined heat transfer coefficient is obtained based on the inner surface temperature and the outer surface temperature.

7. A computer device, comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is loaded by the processor, it is able to perform the steps of the method according to any one of claims 1 to 5.

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