Q5 Thermal diffusion equation 4e + de rsindo rsin e do y 90+do rde dr r sin rde Volume element dV=r'sine de do dr y do 90 (1) Starting from the temperature gradient for spherical coordinates, at 1 1 T VT =+- ar rae rsin ag derive the heat diffusion equation based on the differential control volume shown below. e 1 a aT ( p ar kr207 1 a r sine ag 1 a r sin , ar k sine +9 = pc , at k , ar P (2) For heat conduction in r direction at steady state without energy generation and k as constant, please show the simplified heat diffusion equation