Astove's walls are made up of a flat inner insulating board 0.01m thick (thermal conductivity: 0.2 w m-1k-1) and a flat outer steel sheet 0.01m thick (thermal conductivity: 26 w m-1k-1). a mineral-wool (thermal conductivity: 0.065 w m-1k-1) is placed between these sheets. the inside temperature of the wall is 773k, how thick does the insulation have to be to maintain the outside wall temperature at 323k ? assume that the ambient air temperature is 293k and the outside convective heat transfer coefficient: 5 w m-2k-1.
determine the heat transfer current and calculate the required length of thw mineral-wool insulation.