Numerical calculation method for heat transfer coefficient of building thermal insulation wall

Abstract

This invention belongs to the field of building insulation wall construction technology, and specifically relates to a numerical calculation method for the heat transfer coefficient of building insulation walls. The method includes the following steps: 1. Using finite element modeling or importing drawings using drawing software; 2. Setting material properties in the finite element software based on the measured performance index of the building insulation wall; 3. Setting loads and boundaries; 4. Setting the analysis step; 5. Meshing the building insulation wall according to its structure; 6. By setting the basic parameter values ​​of internal and external temperatures and heat transfer coefficients, and then using the unit heat flow results given in the field output of the numerical analysis software, a numerical calculation formula for the heat transfer coefficient of different materials in the building insulation wall is constructed, and the heat transfer coefficient of different materials in the complex structure of the wall insulation as a function of the output heat flow value is calculated. This calculation method, through numerical calculation, solves the problems of long test cycles, high costs, and human measurement errors inherent in experimental methods.

Description

Technical Field

[0001] This invention belongs to the field of building insulation wall construction technology, and specifically relates to a numerical calculation method for the heat transfer coefficient of building insulation walls. Background Technology

[0002] The heat transfer coefficient of a building wall is defined as the amount of heat transferred per unit time per unit area under steady-state heat transfer conditions, where the temperature difference between the air on both sides of the building wall is 1 degree Celsius (K or °C). Current technologies generally use experimental testing and standard formula calculation methods to test the heat transfer coefficient of building walls. Each method has its advantages and disadvantages, mainly as follows:

[0003] While experimental testing methods yield accurate and reliable data, they also have significant limitations: long testing cycles, high costs, and the possibility of human measurement errors. Standard formula calculation methods, which use existing formulas to calculate heat transfer coefficients from known data, are widely accepted in the industry, but their limitation lies in considering only heat transfer in one direction and being suitable only for simple models—thin sheet structures. For building insulation walls, which are mostly complex structures with heat transfer not limited to one dimension, such as porous block self-insulating walls and sandwich insulation walls, the standard-recommended formula calculation method is not practical.

[0004] Therefore, existing testing methods all have their limitations, which to some extent affect the accuracy of the final conclusions. There is an urgent need for a simpler, faster, more economical, more accurate method for calculating the heat transfer coefficient of building insulation walls that can be applied to complex real-world 3D models. Summary of the Invention

[0005] This invention provides a numerical calculation method for the heat transfer coefficient of building insulation walls, used to determine the thermal insulation performance of building insulation walls. It is applicable to determining insulation methods and optimizing structural systems for different types of walls in different climate zones. The numerical calculation method overcomes the problems of long testing cycles, high costs, and human measurement errors inherent in experimental methods. Using finite element analysis software, complex detailed models of building walls can be constructed, overcoming the limitations of standard-recommended formula calculation methods that only consider heat transfer in one direction, and the limitation of calculating only simple, thin-sheet models based on a single type of insulation material. This calculation method is simple, fast, economical, accurate, and applicable to complex real-world three-dimensional models.

[0006] To solve the above technical problems, the present invention includes the following technical solutions:

[0007] A numerical calculation method for the heat transfer coefficient of building insulation walls includes the following steps:

[0008] Step S1: Model the building insulation wall using finite element software or import drawings using drawing software;

[0009] Step S2: Set material properties in the finite element software based on the measured performance index of the building insulation wall;

[0010] Step S3: Add different boundary conditions to the inner and outer ends of the building's thermal insulation wall to represent the hot surface temperature and cold surface temperature, respectively.

[0011] Step S4: Set up the analysis step, select the mesh size and heat transfer calculation model, and perform mesh generation;

[0012] Step S5: Based on the mesh division in step S4, by setting the basic parameter values ​​of internal and external temperatures and heat transfer coefficients, and using the unit heat flow results given in the field output of the numerical analysis software, a numerical calculation formula for the heat transfer coefficient of different materials in building insulation walls is constructed. The heat transfer coefficients of different materials in the complex structure of the wall insulation as a function of the output heat flow value are calculated, as shown in equation (1):

[0013] K i =(Q i ×n i ×S i ) / (S0×ΔT) (1)

[0014] In the formula, K i The heat transfer coefficients of different materials in the complex structural parts of the wall insulation are represented by the integers i = 1 to n, where the number of i equals the number of wall material types n, and the unit is W·m. -2 ·K -1 Q i This represents the heat transfer of a single mesh element in the wall structure under study, considering different material components, at steady state. The unit is W, and the result is derived from the finite element simulation software. i S represents the number of grid cells occupied by the materials in each part of the wall; i The area of ​​a single grid of material in each part of the wall is expressed in m². 2 S0 represents the original total cross-sectional area of ​​the wall, in m². 2 ΔT is the temperature difference between the inner and outer surfaces of the wall under steady state, in K.

[0015] Furthermore, it also includes step S6:

[0016] Based on the general heat transfer formula for ordinary walls, the overall heat transfer coefficient of building insulation walls is derived, as shown in equation (2):

[0017] (2)

[0018] In the formula, K S The overall heat transfer coefficient of the building's thermal insulation wall, expressed in W·m. -2 ·K -1 ;K1…K nThe heat transfer coefficients of different materials in the wall insulation structure are given by i, which are integers from 1 to n, and the unit is W·m. -2 ·K -1 ;l in l out These are the widths of the inner and outer heat transfer surfaces, respectively, in meters (m); K in K out These are the heat transfer coefficients for the inner and outer sides, respectively, in W·m. -1 ·K -1 λs is the correction coefficient for the overall heat transfer coefficient of the building insulation wall. The heat transfer correction coefficient for complex walls composed of different pore shapes is obtained through comparison and verification with a large number of relevant numerical models and experimental values, and the values ​​are as follows:

[0019]

[0020] Furthermore, in step S1, the drawing software is either CAD drawing software or SKETCHUP drawing software.

[0021] Furthermore, in step S2, the building insulation wall is composed of several different perforated bricks. The perforated bricks can be a combination of KM1, KM2, KP1, and KP2 blocks, or a combination of blocks with square, round, and rectangular holes of different sizes. During assembly, the different combinations of perforated bricks are filled with mortar joints. The mortar joints are made of masonry mortar material. The plastering material on both sides of the perforated bricks is determined according to the actual building insulation wall project requirements. The plastering material can be unplastered material, 10mm-30mm thick ordinary plastering mortar material, or 10mm-50mm thick insulation mortar material.

[0022] Furthermore, the thermal conductivity of the different combinations of porous bricks ranges from 0.03 to 1.20 (W·m). -1 ·K -1 The thermal conductivity of masonry mortar and plastering mortar ranges from 0.50 to 1.00 (W·m). -1 ·K -1 The thermal conductivity of the insulating mortar ranges from 0.03 to 0.30 (W·m). -1 ·K -1 ).

[0023] Furthermore, in step S4, the grid size is 1mm, and the grid is divided into squares or near-squares.

[0024] Furthermore, the method includes step S7, which compares the simulated numerical solution of the overall heat transfer coefficient of the building insulation wall with the experimental measured value. For KM1 type block and KP2 type block wall, the deviation between the calculated simulated numerical solution and the experimental measured value after formula correction is less than 2%; for complex 3-hole composite structure block wall, the deviation between the calculated simulated numerical solution and the experimental measured value after formula correction is less than 4%.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] (1) This invention provides a numerical calculation method for the heat transfer coefficient of building insulation walls. The method comprises: 1) using finite element modeling or importing drawings using drawing software; 2) setting material properties in the finite element software based on the measured performance index of the building insulation wall; 3) setting loads and boundaries; 4) setting analysis steps; 5) meshing based on the building insulation wall; and 6) constructing a numerical calculation formula for the heat transfer coefficient of different materials in the building insulation wall by setting the basic parameters of internal and external temperatures and heat transfer coefficients, and then using the unit heat flow results given in the field output of the numerical analysis software. This formula calculates the heat transfer coefficient of different materials in the complex structure of the wall insulation as a function of the output heat flow value. This calculation method is simple, fast, economical, and practical, solving the problems of high purchase and maintenance costs due to the high price of thermal conductivity meters and field heat transfer meters currently on the market, as well as the high labor costs caused by long testing cycles and frequent human error in detection.

[0027] (2) This invention provides a numerical calculation method for the heat transfer coefficient of building insulation walls. With the help of finite element analysis software, a complex detailed model of building walls can be constructed to calculate the heat transfer of different material components inside the complex insulation wall structure and their respective heat transfer coefficients, and then calculate the overall heat transfer coefficient. This solves the limitations of the heat conduction formula calculation method in the standard, which only considers heat transfer in one direction and the single type of insulation structure material, which can only calculate simple thin sheet models. It also expands the applicability of the thermal simulation results of finite element software, and the calculated heat transfer results are more accurate and reliable.

[0028] (3) This invention provides a numerical calculation method for the heat transfer coefficient of building insulation walls. The applicability and accuracy of the formula for complex porous block walls are greatly improved. It is applicable not only to commercially available brick-type walls, but also to innovative multi-material, multi-porous composite block walls. Compared with existing numerical calculation methods for heat transfer coefficients, based on the different heat transfer in different areas of the wall, an independent calculation formula is proposed for the heat transfer coefficient of different wall materials, i.e., the heat transfer coefficient of different materials in the complex insulation structure of the wall as the output heat flow value changes. Based on complex walls with different porous structure combinations, through verification by a large number of related numerical models, different heat transfer coefficient correction coefficients are proposed for complex walls composed of different porous combinations. Therefore, the heat transfer coefficient calculation formula is more refined and accurate, and has stronger universality, so that the overall deviation of the numerical calculation method for the heat transfer coefficient of complex walls is reduced to below 4%, and the overall accuracy is improved to above 96%. It is applicable to complex thermal insulation structures of buildings constructed with different hole types, sizes, masonry structures, and masonry materials on the market. It is also easy and quick to set up different types of materials. It is of great significance for the preliminary feasibility assessment and subsequent qualification verification of the overall building wall insulation structure performance and has broad application prospects. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of KM1 type masonry block in a numerical calculation method for the heat transfer coefficient of building insulation wall according to an embodiment of the present invention.

[0030] Figure 2 This is a schematic diagram of the construction of KP2 type blocks in a numerical calculation method for the heat transfer coefficient of building insulation walls according to an embodiment of the present invention.

[0031] Figure 3 This is a schematic diagram of the construction of a three-hole composite structure block in a numerical calculation method for the heat transfer coefficient of a building insulation wall according to an embodiment of the present invention.

[0032] Figure 4 This is a schematic diagram of the construction of a three-hole composite structure block II in a numerical calculation method for the heat transfer coefficient of a building insulation wall according to an embodiment of the present invention. Detailed Implementation

[0033] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a numerical calculation method for the heat transfer coefficient of building insulation walls provided by the present invention. The advantages and features of the present invention will become clearer from the following description. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise proportions, used only to facilitate and clarify the illustration of the embodiments of the present invention. For ease of description, the terms "upper" and "lower" used below correspond to the upper and lower directions in the accompanying drawings, but this should not be construed as a limitation of the technical solution of the present invention.

[0034] The numerical calculation method for the heat transfer coefficient of building insulation walls of this invention mainly includes: establishing a geometric model of the building insulation wall in finite element software, assigning general properties of each material to different parts, setting the analysis step size and calculation cycle, dividing all non-rigid parts into meshes and defining mesh element properties, as well as the heat transfer coefficients of the inner and outer surfaces. In the process of numerically calculating the building wall using finite element numerical analysis software, the research object is divided into countless tiny elements. The heat transfer situation of the entire building wall can be reflected by the interference superposition of the heat transfer situations of a large number of elements under steady state.

[0035] Example 1

[0036] Please refer to Figures 1 to 4 This invention provides a numerical calculation method for the heat transfer coefficient of building insulation walls, comprising the following steps:

[0037] Step S1: Model the building insulation wall using finite element software or import drawings using drawing software;

[0038] Step S2: Set material properties in the finite element software based on the measured performance index of the building insulation wall;

[0039] Step S3: Add different boundary conditions to the inner and outer ends of the building's thermal insulation wall to represent the hot surface temperature and cold surface temperature, respectively.

[0040] Step S4: Set up the analysis step, select the mesh size and heat transfer calculation model, and perform mesh generation;

[0041] Step S5: Based on the mesh division in step S4, by setting the basic parameter values ​​of internal and external temperatures and heat transfer coefficients, and using the unit heat flow results given in the field output of the numerical analysis software, a numerical calculation formula for the heat transfer coefficient of different materials in building insulation walls is constructed. The heat transfer coefficients of different materials in the complex structure of the wall insulation as a function of the output heat flow value are calculated, as shown in equation (1):

[0042] K i =(Q i ×n i ×S i ) / (S0×ΔT) (1)

[0043] In the formula, K i The heat transfer coefficients of different materials in the complex structural parts of the wall insulation are represented by the integers i = 1 to n, where the number of i equals the number of wall material types n, and the unit is W·m. -2 ·K -1 Q i This represents the heat transfer of a single mesh element in the wall structure under study, considering different material components, at steady state. The unit is W, and the result is derived from the finite element simulation software. iS represents the number of grid cells occupied by the materials in each part of the wall; i The area of ​​a single grid of material in each part of the wall is expressed in m². 2 S0 represents the original total cross-sectional area of ​​the wall, in m². 2 ΔT is the temperature difference between the inner and outer surfaces of the wall under steady state, in K.

[0044] In this embodiment, more preferably, step S6 is also included:

[0045] Based on the general heat transfer formula for ordinary walls, the overall heat transfer coefficient of building insulation walls is derived, as shown in equation (2):

[0046] (2)

[0047] In the formula, K S The overall heat transfer coefficient of the building's thermal insulation wall, expressed in W·m. -2 ·K -1 ;K1…K n The heat transfer coefficients of different materials in the wall insulation structure are given by i, which are integers from 1 to n, and the unit is W·m. -2 ·K -1 ;l in l out These are the widths of the inner and outer heat transfer surfaces, respectively, in meters (m); K in K out These are the heat transfer coefficients for the inner and outer sides, respectively, in W·m. -1 ·K -1 λs is the correction coefficient for the overall heat transfer coefficient of the building insulation wall. The heat transfer correction coefficient for complex walls composed of different pore shapes is obtained through comparison and verification with a large number of relevant numerical models and experimental values, and the values ​​are as follows:

[0048]

[0049] Specifically, in step S1, the drawing software can be CAD drawing software or SKETCHUP drawing software, etc., and there is no limitation here.

[0050] In this embodiment, more preferably, in step S2, the building insulation wall is composed of several different combinations of porous bricks. The porous bricks can be existing blocks such as KM1, KM2, KP1, and KP2, or complex combinations of porous bricks composed of square, round, and rectangular holes of different sizes with greatly increased porosity. When assembling, the different combinations of porous bricks are filled with mortar joints, which can be set as masonry mortar material. The plastering material on both sides of the porous bricks is determined according to the actual building insulation wall project needs, and can be set as no plastering material, 10mm to 30mm plastering ordinary mortar material, or 10mm to 50mm insulation mortar material. For example, the building insulation wall can be constructed by assembling several KM1 type blocks, KP2 type blocks, and combined perforated bricks. The KM1 type blocks and the combined 3-hole structural blocks have 20mm of finishing mortar and 30mm of insulation mortar on their left and right sides, respectively. The KP2 type blocks and the combined 3-hole structural blocks have no mortar on their left and right sides. All four types of wall blocks are joined by mortar joints. To ensure the feasibility and accuracy of the simulation, material properties are set in the finite element software according to the measured performance indices of the laboratory wall materials. For example, the entire block can be treated as concrete, while the gaps can be treated as air, extruded polystyrene board, or polyethylene. The wall measures 2.0m x 2.0m x 0.24m and is composed of several complex structural blocks of types KM1, KP2, and 3-hole. The KM1 blocks and the first 3-hole structural block have 20mm of finishing mortar on the left and right sides, and 30mm of insulating mortar on the right and left sides, respectively. The KP2 blocks and the second 3-hole structural block have no mortar on the left and right sides. All four types of wall blocks have joints filled with masonry mortar. However, since heat transfer mainly occurs along the thickness direction and is primarily affected by the internal structure, only the top view is considered here.

[0051] In this embodiment, more preferably, the thermal conductivity of the KM1 type block is set to 0.60 (W·m). -1 ·K -1 The thermal conductivity of KP2 type blocks is set to 0.03 (W·m). -1 ·K -1 The thermal conductivity of both the masonry mortar and the plastering mortar was set to 0.50 (W·m). -1 ·K -1 The thermal conductivity of the insulating mortar was set to 0.08 (W·m). -1 ·K -1 Different boundary conditions were added to the inner and outer ends of the masonry wall to represent the hot and cold surface temperatures, respectively. The hot and cold surface temperatures for the three stages are set as shown in Table 1 below. Table 1 shows the simulated data of heat transfer coefficients and thermal resistances for four different types of masonry blocks: Type I, Type II, Type III, and Type IV.

[0052]

[0053] Table 1

[0054] In this embodiment, more preferably, in step S4, the grid size is 1mm, and the grid is divided into squares or near-squares.

[0055] In this embodiment, more preferably, step S7 is also included, comparing the simulated numerical solution of the overall heat transfer coefficient of the building insulation wall with the experimentally measured value. It can be found that for mainstream common masonry blocks such as KM1 and KP2 type masonry walls, the deviation between the calculated simulated numerical solution after formula correction and the experimentally measured value is less than 2%; while for more complex three-hole composite structure masonry walls, such as masonry walls with three or more hole types (square holes, combinations of multiple rectangular holes, or round holes, combinations of multiple rectangular holes), the deviation between the calculated simulated numerical solution after formula correction and the experimentally measured value is less than 4%. See Table 2 for details. Table 2 compares the heat transfer coefficients of the four wall types (I, II, III, and IV) tested.

[0056]

[0057] Table 2

[0058] As shown in Table 2, for mainstream common blocks on the market, such as KM1 and KP2 blocks, the deviation between the calculated simulation solution and the experimental measured value after formula correction is less than 2%. For more complex block walls with different hole types, such as those with three or more hole types, such as square holes, combinations of multiple rectangular holes, or circular holes, combinations of multiple rectangular holes, the deviation between the calculated simulation solution and the experimental measured value after formula correction is less than 4%. Therefore, it can be concluded that the numerical method for calculating the heat transfer coefficient of walls is feasible and effective. Furthermore, the applicability and accuracy of the formula for complex porous block walls are greatly improved. It is applicable not only to commercially available brick-type walls but also to innovative multi-material, multi-porous composite block walls. Compared to existing numerical methods for calculating heat transfer coefficients, this method proposes independent calculation formulas (Equation 1) for the heat transfer coefficients of different wall materials to account for variations in heat transfer in different areas. It also proposes different heat transfer coefficient correction coefficients (Equation 2) for complex walls composed of different porous structures to account for variations in porous structures (wherein, the correction coefficients are verified through numerous relevant numerical models). Therefore, the heat transfer coefficient calculation formula is more refined and accurate, with stronger versatility, reducing the overall deviation of the numerical calculation method for the heat transfer coefficient of complex walls to below 4% and improving the overall accuracy to over 96%.

[0059] In summary, this invention provides a numerical calculation method for the heat transfer coefficient of building insulation walls, which is simple, fast, economical, practical, accurate, and applicable to complex real-world 3D models. It primarily solves two problems: First, the numerical calculation method addresses the limitations of experimental methods, such as long testing cycles, high costs, and the presence of human measurement errors. Second, by utilizing finite element analysis software, it enables the construction of complex and detailed models of building walls, overcoming the limitations of standard-recommended formulas that only consider heat transfer in one direction and are limited to simple, thin-sheet models due to the limited variety of insulation materials.

[0060] The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples. The above embodiments only illustrate several implementations of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A numerical calculation method for the heat transfer coefficient of building insulation walls, characterized in that, Includes the following steps: Step S1: Use finite element software to model the building insulation wall or import drawings through drawing software; Step S2: Set material properties in the finite element software based on the measured performance index of the building insulation wall; Step S3: Add different boundary conditions to the inner and outer ends of the building's thermal insulation wall to represent the hot surface temperature and cold surface temperature, respectively. Step S4: Set up the analysis step, select the mesh size and heat transfer calculation model, and perform mesh generation; Step S5: Based on the mesh division in step S4, by setting the basic parameter values ​​of internal and external temperature and heat transfer coefficient, and using the unit heat flow results given in the field output of the numerical analysis software, a numerical calculation formula for the heat transfer coefficient of different materials in building insulation walls is constructed. The heat transfer coefficients of different materials in the complex structure of the wall insulation as a function of the output heat flow value are calculated, as shown in equation (1): K i =( Q i ×n i × S i ) / ( S 0×∆T) (1) In the formula, K i The heat transfer coefficients of different materials in the complex structural parts of the wall insulation are represented by the integers i = 1 to n, where the number of i equals the number of wall material types n, and the unit is W·m. -2 ·K -1 ; Q i This represents the heat transfer of a single mesh element in the wall structure under study, considering different material components, at steady state. The unit is W, and the result is derived from the finite element simulation software. i This represents the number of grid cells occupied by the materials in each part of the wall. S i The area of ​​a single grid of material in each part of the wall is expressed in m². 2 ; S 0 represents the original total cross-sectional area of ​​the wall, in m². 2 ΔT represents the temperature difference between the inner and outer surfaces of the wall under steady-state conditions, in K. Step S6 Based on the general heat transfer formula for ordinary walls, the overall heat transfer coefficient of building insulation walls is derived, as shown in equation (2): （2） In the formula, The overall heat transfer coefficient of the building's thermal insulation wall, expressed in W·m. -2 ·K -1 ; The heat transfer coefficients of different materials in the wall insulation structure are given in W·m. -2 ·K -1 ; , These are the widths of the inner and outer heat transfer surfaces, respectively, in meters (m). , These are the heat transfer coefficients for the inner and outer sides, respectively, in W·m. -1 ·K -1 ; 's' is the overall heat transfer coefficient correction factor for building insulation walls. The heat transfer correction factor for complex walls composed of different pore shapes is obtained through verification using a large number of relevant numerical models, and the values ​​are as follows: 。 2. The method according to claim 1, characterized in that, In step S1, the drawing software is either CAD drawing software or SKETCHUP drawing software.

3. The method according to claim 1, characterized in that, In step S2, the building insulation wall is composed of several different porous bricks. The porous bricks can be combinations of KM1, KM2, KP1, and KP2 blocks, or combinations of blocks with square, round, or rectangular holes of different sizes. During assembly, the different combinations of porous bricks are filled with mortar joints. The mortar joints are made of masonry mortar material. The plastering material on both sides of the porous bricks is determined according to the actual building insulation wall project requirements. The plastering material can be unplastered material, 10mm~30mm thick ordinary plastering mortar material, or 10mm~50mm thick insulation mortar material.

4. The method according to claim 3, characterized in that, The thermal conductivity of the KM1 type block is set to 0.60 (W•m). -1 •K -1 The thermal conductivity of KP2 type blocks is set to 0.03 (W•m). -1 •K -1 The thermal conductivity of both masonry mortar and ordinary plastering mortar was set to 0.50 (W•m). -1 •K -1 The thermal conductivity of the insulating mortar was set to 0.08 (W•m). -1 •K -1 ).

5. The method according to claim 1, characterized in that, In step S4, the grid size is 1mm, and the grid is divided into squares or near-squares.

6. The method according to claim 1, characterized in that, The method also includes step S7, which compares the simulated numerical solution of the overall heat transfer coefficient of the building insulation wall with the experimental measured value. For KM1 type masonry wall and KP2 type masonry wall, the deviation between the calculated simulated numerical solution and the experimental measured value after formula correction is less than 2%; for complex 3-hole type combined structure masonry wall, the deviation between the calculated simulated numerical solution and the experimental measured value after formula correction is less than 4%.

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