A temperature-measuring instrument consists of a hollow spherical shell consisting of three materials as shown in the figure. The top hemisphere is composed of material A, while the bottom hemisphere consists of an inner layer of material B and an outer layer of material c. These have thermal conductivities of kn, ko and kc W.m.K respectively. A thin layer of highly thermally insulating material separates material A from materials B and C (ie, no heat flows directly from A into B or C. and vice versa). The liquid that fills the space inside the shell is kept at a uniform constant temperature T. and the outer surface of the sphere is at a constant temperature Ta. Insulation 9 1) 1 Calculate the rate of heat transfer expected if temperature at the inner surface of the shell is maintained at 30"C while the outer surface temperature is maintained at 150C (sphere inner diameter = 5 cm, outer diameter = 7 cm, outer diameter of layer B = 6 cm). (4 marks) KA= 250 W.m.K. kg = 50 W.m.K kc=5 W.m.K iv) The sphere is immersed in a fast-flowing fluid at temperature 200"C. What average/overall convective heat transfer coefficient would be required at the outer surface to enable the outer surface temperature of 150C to be reached? (2 marks)