Research On The Test Of Thermal Conductivity And Thermal Diffusivity For Thermal Insulation Materials For Building Application With Plane Source Method

Abstract:Since lots of new thermal insulation materials for building application emerge these years, less testing methods are available. The thermal conductivities and thermal diffusivities of thermal insulation materials for building application are limited. A testing device for thermal conductivity and thermal diffusivity was designed based on plane heat source method. A visual test software was developed. The thermal conductivities and thermal diffusivities of several kinds of thermal insulation materials were tested here. The results were optimized. The main research work and conclusions are as follows:(1) A testing equipment for thermal conductivity and thermal diffusivity testing was developed based on the testing principle of the plane heat source method. The influences of testing length and width(L), temperature testing point spacing(h) and heat flux(qw) on the testing accuracy were analyzed using Fluent software. The optimal experimental parameters were determined. L is300mm. h is fromlO to20mm, and qw is from30to150W·m-2.(2) A visual test software was designed using Microsoft Visual Studio.NET2008. It can be used for data collection and processing based on constant power plane source method and stepwise plane source method.(3) The effective test time is determined theoretically. The minimum time τmin is100s and the maximum time τmax is the moment when the temperature of the monitor plane increases by0.1℃. The influences of the insulation mantle and heat flux on the accuracy of the thermal conductivity were studied by experiment. The experimental results show that the reproducibilities of the two plane source methods are reliable, and the deviations are within3%. The testing accuracy of the EPS foam increases by0.85%when the insulation mantle is used. The heat flux has great influence on the thermal conductivities of the cement foam plate and foam glass. When the temperature of the cement foam is from20to 43.5℃and the temperature of foam glass is from20to43.5℃, both the thermal conductivities increase with the temperature increasing. The heat flux has less effect on the thermal conductivity of the EPS foam(20-43℃) and aerated concrete block(20-32℃).(4) The thermal conductivities and thermal diffusivities of the organic foam, aerated concrete block, cement foam plate and foam glass were tested by the constant power plane source method and stepwise plane source method respectively. There exists a certain difference between the two methods, but the relative deviations of the thermal conductivity are all within5%, and the relative deviations of the thermal diffusivity are from1.7%to22.2%. There is no proof which method is better. The relative errors between the testing results of thermal conductivity and the corresponding data offered by the factories are-1.95%and2.68%using constant power plane source method and stepwise plane source method respectively. The thermal diffusivities based on two methods are consistent with that of the references. The thermal diffusivities of the golden plate, aerated concrete block, cement foam plate, foam glass were obtained experimentally. The heat storage coefficients of the foam, aerated concrete block, cement foam plate and foam glass were also obtained experimentally based on a new method.(5) The thermal conductivities were revised by combining experimental data and simulation predictions from Fluent. The relative error of the thermal conductivity for the EPS foam decreases from-1.95%to-1.22%and the corresponding accuracy increases by0.73%after optimization.