3. The wall of a house, 7 m wide and 6 m high is made from 0.3 m thick brick with k = 0.6 W/mK. The surface temperature on the inside of the wall is 16°C and that on the outside is 6°C. Find the heat flux through the wall and the total heat loss through it. 4. A 20 mm diameter copper pipe is used to carry heated water, the external surface of the pipe is subjected to a convective heat transfer coefficient of h = 6 W/m²K, find the heat loss by convection per metre length of the pipe when the external surface temperature is 80°C and the surroundings are at 20°C. Assuming black body radiation what is the heat loss by radiation?