Estimation of radiative thermal conductivity of glass wool using high precision GHP apparatus

Abstract

In this study, the effective thermal conductivity of glass wool was measured under different temperature and packing ratio conditions using a high-precision guarded hot plate (GHP) apparatus, which adopted a Peltier module. From the measurement results, it was confirmed that the effective thermal conductivity was linearly proportional to the cubic of absolute temperature. Varying the packing ratio, the influence amount of the radiative heat transfer on the effective thermal conductivity varied from 44 to 66% for different packing ratio. The influence of the radiative heat transfer on the effective thermal conductivity decreases with increasing of the packing ratio. From the variation of the effective thermal conductivity against cubic of the temperature, the Rosseland mean extinction coefficient were evaluated and the equivalent thermal conductivity by the radiation was estimated. The equivalent thermal conductivity by the radiation decreases as increasing of packing ratio of the glass wool and this result could be explained by the increment of the Rossleand mean extinction coefficient. From the comparison between the theoretical and experimental results of the equivalent thermal conductivity by radiation, a correction value that depends on the packing ratio is required. Furthermore, we compared the experimental values and the calculated values by Kunii's formula for the thermal conductivity of the glass wool with different packing ratio and it was confirmed that the quantitative evaluation of the equivalent thermal conductivity by the radiation is important for estimating the total effective thermal conductivity of the glass wool.