Experimental investigation on thermal contact resistance of alumina fibrous insulation material with Ti-6Al-4V alloy at high temperature and its effective thermal conductivity

Abstract

Heat transfer through thermal insulation material is an important process in the design and performance evaluation of an insulation system, which is a key component of space vehicles. Accurate information on heat transfer analysis requires determination of thermal contact resistance (TCR) between the insulation material and the super-alloy plate. In this study, test equipment was designed to measure the TCR as well as the effective thermal conductivity of low thermal conductivity fibrous insulation material at high temperatures and in atmospheric pressure conditions. Two heat-flux meters were used to measure the heat flux from the bottom (high temperature) to the top (low temperature) of a fibrous sample in the test column. The two-thickness method was used to obtain the TCR and the effective thermal conductivity. An uncertainty analysis was also evaluated, which proved that the most important factor in the TCR measurement was the heat flux calculation. The result reveals that the TCR values become high at small contact pressures. The TCR decreased with an increase in the compressive load and significantly contributed to the total thermal resistance of the fibrous sample, approximately 42% and 35% when the average temperature of the sample was 190 °C and 290 °C, respectively. The effective thermal conductivity of the fibrous sample decreased slightly with an increase in the average temperature due to the presence of the carbonization of the binder resin. The numerical method validated the experimental results well. In addition, the micrograph images of the contact surface were investigated.