Question

A stainless steel rod of outer diameter 10mm and length 1m originally at a temperature of 593k is suddenly immersed in a liquid at 393k for which convective heat transfer coefficient is 100w/m2. K. Validating the methodology employed in solving the problem, estimate the time required for the temperature of the rod to reach 473k. Given for the rod material, density=7800 kg/m3, cp=460 j/kg.K, and k=40w/m.K. Why is the name lumped heat capacity model and the physical meaning of the criterion adopted .

Answer 1

Answer:

Given:

force, F=100KN

 radius, L=10mm

length, L=1m

Area A=πr2

Stress σ=AF=π(10−2)2105

Elongation

ΔL=Y(F/A)L=2×1011Nm−2(π(10−2)2105)(1m)=1.59×10−3m=1.59mm

Strain produced in the rod is 

Strain=LΔL=1m1.59×10−3m=1.59×10−3=0.16