This apparatus is designed to determine the thermal conductivity of insulating powder. The apparatus consists of two thin walled concentric copper spheres. Inner sphere houses Nichrome Wire heater. Insulating powder is filled between the two spheres. Heat flows radially outwards. Temperature sensors at proper positions are fitted to measure surface temperatures of spheres. Heat input to the heater is given through a variac and measured by energymeter. By varying the heat input rates, data can be obtained.