Two large parallel plates at T1 = 1000 K and T2 = 750 K have emissivity e1 = 0.5 and e3.2 = 0.8 respectively. A radiation shield having an emissivity of e3.2 = 0.12 on one side and an emissivity e3.2 = 0.08 on the other side is placed between the plates. Calculate the heat transfer rate by radiation per square metre with and without radiation shield.
Take $\sigma$ = 5.67 ´ 10–8 W/m2k4.