A spherical fuel element has a center temperature of 3600 F. The fuel element is covered by two layers of coating. The fuel ball is cooled by helium. Find the rate of heat transfer. Data: rfuel = 0.5...

 A spherical fuel element has a center temperature of 3600 F. The fuel element is covered by two layers of coating. The fuel ball is cooled by helium. Find the rate of heat transfer. Data: rfuel = 0.5 in, r1 = 0.7 in, r2 = 0.9 in. kfuel = 2 Btu/ft·h·F,

kcoating = 7 Btu/ft·h·F, Tf = 700 F and h = 5000 Btu/ft·h·F.

[Ans.: 4100 Btu/h].