Transient hot wire measures thermophysical properties of organic foam thermal insulation materials

A device based on the transient hot wire (THW) method was developed to measure thermal conductivity and thermal diffusivity of organic foam thermal insulation materials. EPS board and XPS board were used as the experimental samples. The simulation results show that the calculation errors of thermal conductivities with cross hot wire (CHW) method, parallel hot wire (PHW) method and cross-parallel hot wire (CPHW) method are 0%, and the calculation errors of thermal diffusivities with these three methods are small. The experimental results show that for PHW method, the calculation results of thermal conductivity and thermal diffusivity of EPS board fluctuate greatly with the selection of computation time. For CHW method and CPHW method, the measurement errors of thermal conductivities of EPS board are less than 3.5% and that of XPS board are less than 6.5%. The experimental values of thermal diffusivities with CPHW method are close to the reference values, but the experimental values with CHW method are much smaller than the reference values. The measurement errors of thermal diffusivities with these two methods were analyzed theoretically and experimentally. The measurement error with CPHW method is approximately between 27% and 13% with the error of thermal conductivity from -5% to 5%, however, the measurement error with CHW method is more than 99%. The proposed device offers some significant advantages such as economy, flexibility, and the repeatability of measurement accuracy. If applied properly, CPHW method is promising to measure the thermal conductivity and thermal diffusivity of many other types of solid materials.