Question

Q1) A sphere of radius 5cm. At t=0 Ti=400C. It is suddenly placed in air of 20C. ha= 100 W/m^2.K. If sphere rho= 3000 kg/m^3 , k= 20W/m.K, c=1000 J/kg.K

How long will it take for its center T=200C? Using LHC and the exact solution to solve this problem.

Q2) A long steel cylinder initial temperature Ti=300K . Steel properties rho=7832 kg/m^3, k=51.2 W/m.K, c=541 J/kg.K, diffusivity alpha = 1.21x10^-5 m^2/s. Tinfinity= 1200K, h= 100 W/m^2.K, D=0.1m. Find the time when the temp at the center reaches 800K. What is the temp at the surface of the cylinder at that time?

Answer 1

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