Method for testing thermal performance of heterogeneous building wall material

Abstract

The invention relates to the technical field of building thermal testing, and discloses a method for testing the thermal performance of a heterogeneous building wall material, an adopted testing device comprises a hot box and a cold box which are located on the two sides of a test piece frame, and the testing method comprises the following steps that S1, a filling body with known thermal resistance is placed in the test piece frame, and the heat flow QT passing through the filling body is measured; s2, measuring the heat flow QS passing through the filling body embedded with the n test pieces, and respectively measuring the hot side surface temperature Thi of the ith test piece to be tested; s3, the heat flow Qsi passing through the n to-be-tested pieces is obtained through calculation; s4, calculating to obtain a heat transfer coefficient and heat transfer resistance; and S5, calculating the equivalent heat conductivity coefficient of the test piece to be tested. According to the testing method, the heat flow passing through the to-be-tested piece is indirectly obtained by means of the relative relation between the surface temperature of the test piece and the surface temperature of the filling body, the heat transfer resistance, the heat transfer coefficient and the equivalent heat conductivity coefficient parameters of the to-be-tested piece can be tested, and the requirements of existing building material specifications are met.

Description

Technical Field

[0001] The invention relates to the technical field of building thermal testing, and in particular to a method for testing the thermal performance of a non-homogeneous building wall material. Background Art

[0002] With the development of building energy-saving technology, the wall self-insulation technology with composite materials such as hollow blocks, insulation bricks, insulation hollow blocks, composite insulation bricks, composite insulation hollow blocks as the core insulation layer has developed rapidly. These wall composite insulation materials are composed of blocks and insulation materials and are non-homogeneous wall materials. The heterogeneity of wall materials will affect the heat flux pattern, which is neither one-dimensional nor uniform. Changes in specimen thickness will also cause significant local changes in the specimen heat flux pattern.

[0003] The laboratory test of thermal performance of heterogeneous wall materials mainly uses the method of building heterogeneous wall materials into walls, and converting the thermal resistance R value of the heterogeneous wall materials by testing the thermal resistance of the wall. The measurement method of equivalent thermal conductivity is mainly to convert and calculate the equivalent thermal conductivity λe value based on the thermal resistance R value of the measured wall. There are two commonly used methods: the protective hot box method and the calibrated hot box method. These two methods require the samples to be built into walls. Because of the involvement of masonry mortar and plastering mortar, the curing time of the masonry wall is long, and the curing placement time is at least 28 days, and the existing equipment can only test one wall material at a time. This test method has a long detection cycle, and is greatly affected by human and environmental factors, and cannot keep up with the development needs of building energy-saving acceptance.

[0004] The thermal performance test of heterogeneous wall materials is currently mainly based on the steady-state thermal balance method. The indirect test method is to first test the thermal resistance R value of the wall built with heterogeneous wall materials, and then convert and calculate the thermal performance of the heterogeneous wall materials through the relationship between the thermal resistance of the heterogeneous wall materials and the thermal resistance of the wall. Direct detection of the thermal performance of the composite insulation material itself can effectively reduce the influence of human and environmental factors. In the document GB / T 32981-2016, a method for measuring the equivalent thermal conductivity of wall materials is proposed. Specifically, the filler (the thermal conductivity of the material is known) and the test piece (placed in the filler) are installed between the cold box and the metering box, and the temperature of the cold box and the metering box is controlled to maintain the heat conduction balance. Under the same working conditions, the heat flow through the filler and the test piece is measured respectively, and the equivalent thermal conductivity of the test piece is calculated according to the changes in temperature and power.

[0005] The indirect test method involves wet wall construction operations, a long cycle, many influencing factors, and relatively large test errors. In the existing direct test method, the equivalent thermal conductivity obtained is the surface thermal resistance on both sides calculated into the wall thermal resistance, which is inconsistent with the equivalent thermal conductivity of the wall material itself; the specimen frame size is 500mm×500mm. When the specimen size is larger than the specimen frame, the material needs to be cut and prepared, which is easy to destroy the integrity of the non-homogeneous wall material; the test parameters are too single, only the equivalent thermal conductivity; each test can only detect the thermal performance of one wall material, and the test cost is high. Summary of the invention

[0006] The purpose of the present invention is to provide a method for testing the thermal performance of heterogeneous building wall materials. The testing device forms a multi-cavity structure and can simultaneously test the thermal performance of at least two heterogeneous wall materials.

[0007] The present invention provides the following technical solutions:

[0008] A method for testing thermal performance of heterogeneous building wall materials is based on a testing device, the testing device comprising a hot box and a cold box located on both sides of a specimen frame, at least one specimen is arranged in the specimen frame, the remaining cavities of the specimen frame are filled with a filling body with known thermal resistance, the temperature of the hot box and the cold box are adjustable, temperature sensors for detecting temperature are arranged in the hot box and the cold box and on the surface of the specimen, a power meter for measuring heat flow is connected to the heating device of the hot box, and the method comprises the following steps:

[0009] S1: Place a filler with known thermal resistance in a test piece frame. The effective area of ​​the test piece frame is F. The thickness of the filler and the test piece are both d (m). The test piece frame is connected to the cold and hot chambers as a whole. After the air temperatures T1 and T2 in the cold and hot chambers reach equilibrium, measure the heat flow Q through the filler. T ;

[0010] S2: seal and embed n test pieces in the filling body 6 in the test piece frame, where n is a natural number greater than or equal to 1, and the area occupied by the i-th test piece is F i , i is a natural number less than or equal to n; the specimen frame is connected to the cold and hot chambers as a whole. After the air temperatures T1 and T2 in the cold and hot chambers reach equilibrium, the heat flux Q passing through the filling body inlaid with n specimens is measured. S , measure the hot side surface temperature of the i-th test piece as T hi ;

[0011] S3: The measured heat flow Q T and Q S Substituting into the following formula, we can get the heat flux Q passing through n test pieces: si :

[0012] Q1=QS -Q T

[0013]

[0014] Where:

[0015] Q1——The difference in heat flow between two tests;

[0016] Q2 – the heat flux generated by a filler with the same area as the test piece;

[0017] Q si ——The heat flux passing through the i-th test piece;

[0018] T hi ——The surface temperature of the hot side of the i-th test piece under steady state;

[0019] S4: Based on the heat flow of the test specimen and the air temperature on both sides of the hot and cold chambers, the heat transfer coefficient and heat transfer resistance are calculated using the following formula:

[0020]

[0021] R i =1 / K i

[0022] Where:

[0023] K i ——The heat transfer coefficient of the i-th test piece;

[0024] R i ——Thermal resistance of the ith test piece;

[0025] S5: The equivalent thermal conductivity of the test piece is calculated according to the following formula

[0026] λ ei =d / (R i ×F i )

[0027] Where:

[0028] λ ei is the equivalent thermal conductivity through the i-th test piece.

[0029] According to some embodiments, the outer surface of the specimen is wrapped with a temperature equalizing plate.

[0030] According to some embodiments, the temperature homogenizing plate is made of copper.

[0031] According to some embodiments, the temperature homogenizing plate has a thickness ranging from 0.5 to 5 mm.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention provides a test method for the thermal performance of heterogeneous building wall materials. The test method forms a multi-cavity structure according to the size of the heterogeneous wall materials, and can test the thermal performance of multiple heterogeneous wall materials at the same time. The thermal parameters tested include thermal resistance, heat transfer coefficient and equivalent thermal conductivity. By setting a copper temperature equalizing plate on the hot side surface of the test piece, the surface temperature of the hot side of the test piece and the heat flow value passing through are obtained by means of the test, and the thermal performance of multiple heterogeneous wall materials is obtained at the same time. This test method indirectly obtains the heat flow passing through the test piece by means of the relative relationship between the surface temperatures of the test piece and the filler, and can test the thermal resistance, heat transfer coefficient, and equivalent thermal conductivity parameters of the test piece to be tested, meeting the requirements of existing building material specifications. Compared with the test methods provided by the prior art, the present invention has the following advantages:

[0034] 1. The detection cycle is greatly shortened, and there is no need for on-site wall maintenance. Direct testing methods are used for test samples, and results can be obtained within 24 hours.

[0035] 2. The number of detectable parameters has increased. Not only can the equivalent thermal conductivity of the sample be tested be tested, but also its thermal resistance and thermal transfer coefficient can be tested to meet the requirements of existing building wall material specifications.

[0036] 3. Effectively reduce the detection error. The heat flow of the entire test piece frame is directly measured. Due to the non-uniformity of the test piece, the heat flow through the test piece is not directly obtained by a heat flow meter, but is converted through the surface temperature, which can improve the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of a thermal performance testing device for heterogeneous building wall materials provided in an embodiment of the present invention.

[0038] Figure 2 A schematic diagram of a test piece frame provided in an embodiment of the present invention.

[0039] Figure 3 A schematic diagram of ultra-fine grid division provided in an embodiment of the present invention.

[0040] Figure 4 The temperature distribution on the hot side of the specimen provided in the embodiment of the present invention.

[0041] Figure 5 A flow chart of a method for testing thermal performance of a heterogeneous building wall material provided in an embodiment of the present invention.

[0042] In the figure:

[0043] Protective hot box 1; cold box 2; metering box 3; specimen frame 4; temperature equalizing plate 5; filling body 6; specimen 7; first specimen 7-1; second specimen 7-2; third specimen 7-3; fourth specimen 7-4; power meter 8; temperature sensor 9; guide screen 10; air conditioner 11; electric heater 12. DETAILED DESCRIPTION

[0044] The present invention is described in detail below in conjunction with the embodiments and drawings, but it should be understood that the embodiments and drawings are only used to exemplify the present invention and do not constitute any limitation on the protection scope of the present invention. All reasonable changes and combinations within the scope of the inventive concept of the present invention fall within the protection scope of the present invention.

[0045] The present invention will be further described below in conjunction with the accompanying drawings.

[0046] Example 1

[0047] The present embodiment provides a testing device for thermal performance of heterogeneous building wall materials, hereinafter referred to as the testing device, which is used to directly measure the thermal performance of 1-4 kinds of heterogeneous wall materials.

[0048] like Figure 1 The test device includes a protective hot box 1 on the left and a cold box 2 on the right, and the left and right boxes clamp a test piece frame 4.

[0049] like Figure 2 The specimen frame 4 is provided with specimens 7 made of different building wall materials, namely a first specimen 7 - 1 , a second specimen 7 - 2 , a third specimen 7 - 3 and a fourth specimen 7 - 4 , and the remaining cavities in the specimen frame 4 are filled with a filling body 6 .

[0050] The entire test piece frame 4 can be freely moved and pulled out. The inner length or width of the entire test piece frame 4 is in the range of 1500mm to 1800mm, which is convenient for the installation of the filling body 6 and the test piece 7. The distance between the test piece 7 and the test piece frame 4 is not less than 200mm, and the distance between different test pieces 7 is not less than 300mm. The number of tested pieces is set according to the test piece size and the installation spacing limit requirements. Figure 1 and Figure 2 The following description takes the installation of 4 test pieces as an example.

[0051] The air temperature of the protective hot box 1 and the cold box 2 is adjusted by the air conditioner 11, the hot environment temperature is 20℃~30℃, and the cold environment temperature is -10℃~-20℃. The metering box 3 is arranged in the protective hot box 1, covering the first to fourth test pieces, and the internal air temperature is controlled by the electric heater 12, and the environment temperature is 20℃~30℃. A copper temperature averaging plate 5 with a thickness of 0.5mm is arranged on the hot side surface of each test piece 7, and temperature sensors 9 are arranged in the protective hot box 1, the cold box 2, the metering box 3 and the temperature averaging plate 5 to measure the air temperature in the hot and cold rooms and the surface temperature of the test piece. The filling body 6 is a homogeneous EPS board with known thermal resistance, and the thickness is the same as that of the test piece. The two surfaces of the filling body 6 adopt a surface layer that can block the penetration of air and moisture. The electric heater 12 in the metering box 3 is shielded by an insulating reflective cover. In order to adjust the air velocity parallel to the surface of the test piece 7, a guide screen 10 is set in the metering box 3. The guide screen 10 is the same width as the test piece 7 and can move in the direction perpendicular to its surface. The guide screen is a prior art, and there is a similar description in the national standard GBT 13475-2008 Determination and calibration of adiabatic steady-state heat transfer properties and protective hot box method, 2.3.2. It is regulated and moved by a bracket fixed on the inner wall of the metering box 3. It will not be repeated here.

[0052] The whole equipment consists of four parts, namely, the protective hot box, the cold box, the specimen frame, and the control and data acquisition processing system. The protective hot box 1, the cold box 2 and the specimen frame 4 are composed of polyurethane foam color steel plates. The structure does not produce cold and hot bridges and has good sealing performance. The heat transfer resistance is not less than 3.5㎡.K / W. The test specimen 7 to be tested is installed in the filling body 6. The temperature sensors 9 are distributed in the protective hot box 1, the cold box 2 and the metering box 3 to monitor the experimental process.

[0053] The control and data acquisition processing system is used for temperature control management, including an air conditioner 11, an electric heater 12 and a temperature sensor 9. Electric heaters 12 and air conditioners 11 are installed in the protective hot box 1, cold box 2 and metering box 3 respectively to simulate the experimental conditions of the constant cold room temperature effect. The temperature sensor 9 is used to monitor and collect the air temperature in the protective hot box 1 and cold box 2 and the hot side surface temperature data of the test piece. The electric heater 12 is connected to a power meter 8, and the power meter 8 and temperature sensor 9 are used to measure the heat flow through the test. The air temperature in the protective hot box 1 and the metering box 3 is set to be consistent, so as to reduce the influence of the laboratory ambient temperature on the air temperature in the hot and cold rooms and reduce the heat loss.

[0054] like Figure 5 A flow chart of a method for testing the thermal performance of a heterogeneous building wall material based on the above test device provided in this embodiment. Four test pieces are selected in this embodiment, and the steps of testing using the above test device are as follows:

[0055] Step 1: Place a homogeneous EPS board filler 6 with known thermal resistance in the test frame 4. The effective area of ​​the test frame 4 is F. The thickness of the filler 6 and the test piece are the same, both d (m). The test frame 4 is connected to the cold and hot chambers as a whole. After the air temperatures T1 and T2 in the cold and hot chambers reach equilibrium, measure the heat flow Q through the filler 6. T ;

[0056] Step 2: Four test pieces are sealed and embedded in the filling body 6 in the test piece frame. The areas occupied by the test pieces are F1, F2, F3, and F4 respectively. The test piece frame is connected to the cold and hot chambers as a whole. After the air temperatures T1 and T2 in the cold and hot chambers reach equilibrium, the heat flow Q passing through the filling body 6 embedded with the four test pieces is measured. S , measure the hot side surface temperature T of the test pieces 7-1, 7-2, 7-3, and 7-4 h1 , T h2 , T h3 , T h4 .

[0057] Step 3: Convert the measured heat flow Q T and Q S Substituting into the following formula, we can get the heat flux Q passing through the four test pieces: s1 , Q s2 , Q s3 , Q s4 :

[0058] Q1=Q S -Q T (1)

[0059] Q2=(F1+F2+F3+F4) × Q T / F (2)

[0060] Q s1 =(Q1+Q2)*(T1-T h1 ) * F1 / [(T1-T h1 )*F1+(T1-T h2 )*F2+(T1-T h3 ) *F3+( T1-T h4 ) *F4] (3)

[0061] Q s2 =(Q1+Q2)*(T1-T h2 ) * F2 / [(T1-T h1 )*F1+(T1-T h2 )*F2+(T1-T h3 ) *F3+( T1-T h4 ) *F4] (4)

[0062] Q s3 =(Q1+Q2)*(T1-T h3 ) * F3 / [(T1-T h1 )*F1+(T1-T h2 )*F2+(T1-T h3 ) *F3+( T1-T h4 ) *F4] (5)

[0063] Q s4 =(Q1+Q2)*(T1-T h4 ) * F4 / [(T1-T h1 )*F1+(T1-T h2 )*F2+(T1-T h3 ) *F3+( T1-T h4 ) *F4] (6)

[0064] Where:

[0065] Q1——The difference in heat flow between two tests;

[0066] Q2 - the heat flux generated by the filling body 6 of the same area as the test piece 7;

[0067] Q s1 ——The heat flux through the test piece 7-1;

[0068] Q s2 ——The heat flux through the test piece 7-2;

[0069] Q s3 ——The heat flux through the test piece 7-3;

[0070] Q s4 ——The heat flux through the test piece 7-4;

[0071] T h1 ——The surface temperature of the hot side of the test piece 7-1 under stable condition;

[0072] T h2 ——The surface temperature of the hot side of the test piece 7-2 under stable conditions;

[0073] T h3 ——The surface temperature of the hot side of the test piece 7-3 under stable condition;

[0074] T h4 ——The surface temperature of the hot side of the test piece 7-4 under stable condition;

[0075] Step 4: Based on the heat flux of the sample and the air temperature on both sides of the hot and cold chambers obtained from the test, the heat transfer coefficient and heat transfer resistance are calculated according to the following formula:

[0076] K1=(Q1+Q2)*(T1-T h1 ) / {[(T1-T h1 )*F1+(T1-T h2 )*F2+(T1-T h3 ) *F3+( T1-T h4 ) *F4]* ( T1- T2)} (7)

[0077] K2=(Q1+Q2)*(T1-T h2 ) / {[(T1-T h1 )*F1+(T1-T h2 )*F2+(T1-T h3 ) *F3+( T1-T h4 ) *F4]* ( T1- T2)} (8)

[0078] K3=(Q1+Q2)*(T1-T h3 ) / {[(T1-T h1 )*F1+(T1-T h2 )*F2+(T1-T h3 ) *F3+( T1-T h4 ) *F4]* ( T1- T2)} (9)

[0079] K4=(Q1+Q2)*(T1-T h4 ) / {[(T1-T h1 )*F1+(T1-T h2 )*F2+(T1-T h3 ) *F3+( T1-T h4 ) *F4]* ( T1- T2)} (10)

[0080] R1=1 / K1 (11)

[0081] R2=1 / K2 (12)

[0082] R3=1 / K3 (13)

[0083] R4=1 / K4 (14)

[0084] Where:

[0085] K1——heat transfer coefficient of the test piece 7-1;

[0086] K2——heat transfer coefficient of the test piece 7-2;

[0087] K3——heat transfer coefficient of the test piece 7-3;

[0088] K4——heat transfer coefficient of the test piece 7-4;

[0089] R1——Thermal resistance of the test piece 7-1;

[0090] R2——Thermal resistance of the test piece 7-2;

[0091] R3——heat transfer resistance of the test piece 7-3;

[0092] R4——heat transfer resistance of the test piece 7-4;

[0093] Step 5: Calculate the equivalent thermal conductivity of the sample under test according to the following formula

[0094] λ e1 = d / (R1 ×F1) (15)

[0095] λ e2 = d / (R2 ×F2) (16)

[0096] λ e3 = d / (R3 ×F3) (17)

[0097] λ e4 = d / (R4 ×F4) (18)

[0098] Where:

[0099] λ e1 ——Equivalent thermal conductivity through the test piece 7-1;

[0100] λ e2 ——Equivalent thermal conductivity through the test piece 7-2.

[0101] λ e3 ——Equivalent thermal conductivity through the test piece 7-3.

[0102] λ e4 ——Equivalent thermal conductivity through the test piece 7-4.

[0103] Example 2

[0104] This embodiment provides simulation calculation:

[0105] COMSOL was used to construct the filling body in the specimen frame and the 7 (4) models of the specimen to be tested. Figure 3As shown, the left picture is the physical model of the test equipment simulation calculation, and the right picture is the grid processing of the test equipment simulation calculation model. The net size of the test piece frame is 1800mm*1800mm*300mm, and the size of the four test pieces is 300mm*300mm*300mm. The same position inside the test pieces is set with 100mm*100mm*100mm insulation material, and the insulation material is the same material as the filling body. The outer surface of the lower left corner test piece is arranged with a 5mm thick copper plate 5. The hot side air temperature is 25℃, and the cold test air temperature is -15℃.

[0106] like Figure 4 As shown, the calculation results show that: when the temperature balancing plate 5 with a 5 mm thick copper sheet is arranged on the outer surface of the test piece 7, the temperature distribution is more uniform.

[0107] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for testing the thermal performance of a non-homogeneous building wall material, which is based on a testing device, wherein the testing device comprises a hot box and a cold box located on both sides of a specimen frame, wherein at least one specimen is arranged in the specimen frame, and the remaining cavities of the specimen frame are filled with a filling body with a known thermal resistance, wherein the temperature of the hot box and the cold box is adjustable, and temperature sensors for detecting the temperature are arranged in the hot box and the cold box and on the surface of the specimen, and a power meter for measuring the heat flow is connected to the heating device of the hot box, wherein the method is characterized in that: The following steps are involved: S1: Place a filler with known thermal resistance in a test piece frame. The effective area of ​​the test piece frame is F. The thickness of the filler and the test piece are the same, both d. The test piece frame is connected to the cold and hot chambers as a whole. After the air temperatures T1 and T2 in the cold and hot chambers reach equilibrium, measure the heat flow Q through the filler. T ; S2: seal and embed n test pieces in the filling body 6 in the test piece frame, where n is a natural number greater than or equal to 1, and the area occupied by the i-th test piece is F i , i is a natural number less than or equal to n; the specimen frame is connected to the cold and hot chambers as a whole. After the air temperatures T1 and T2 in the cold and hot chambers reach equilibrium, the heat flux Q passing through the filling body inlaid with n specimens is measured. S , measure the hot side surface temperature of the i-th test piece as T hi ; S3: The measured heat flow Q T and Q S Substituting into the following formula, we can get the heat flux Q passing through n test pieces: si : Q1=Q S -Q T Where: Q1——The difference in heat flow between two tests; Q2 – the heat flux generated by a filler with the same area as the test piece; Q si ——The heat flux passing through the i-th test piece; T hi ——The surface temperature of the hot side of the i-th test piece under steady state; S4: Based on the heat flow of the test specimen and the air temperature on both sides of the hot and cold chambers, the heat transfer coefficient and heat transfer resistance are calculated using the following formula: R i =1 / K i Where: K i ——The heat transfer coefficient of the i-th test piece; R i ——Thermal resistance of the ith test piece; S5: The equivalent thermal conductivity of the test piece is calculated according to the following formula l ei =d / (R i ×F i ) Where: λ ei is the equivalent thermal conductivity through the i-th test piece.

2. The method for testing the thermal performance of heterogeneous building wall materials according to claim 1, characterized in that : The outer surface of the specimen is wrapped with a metal temperature-averaging plate.

3. The method for testing the thermal performance of heterogeneous building wall materials according to claim 2, characterized in that :The temperature equalizing plate is made of copper.

4. The method for testing thermal performance of heterogeneous building wall materials according to claim 3, characterized in that : The thickness of the temperature equalizing plate ranges from 0.5 to 5 mm.

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