The outer pipe is at 280K. Emissivity of inner and outer surfaces is 0.2 and 0.3 respectively. (i)Determine the radiant heat flow rate over a pipe length of 5m. (ii)If a radiation shield of diameter 12mm and emissivity 0.05 on both sides is placed between the pipes, determine the percentage reduction on heat flow. (iii)What is the equilibrium temperature of the shield?

Case 1

Given,

d1=10mm=0.01m (Diameter of inner pipe)

t1=80K=-193℃ (Temperature of inner pipe)

d2=15mm=0.015m (Diameter of outer pipe)

t2=280K=7℃ (Temperature of outer pipe)

ε1=0.2 (Emissivity of inner pipe surface)

ε2=0.3 (Emissivity of outer pipe surface)

l=5m (Length of both pipes)

Find: Q1-2 (Heat flow rate)

Solution:

Heat Transfer from pipe …