Exercises proposed group 5
7. Some people believe that because of' its lower thermal conductivity stainless
steel is appreciably thermally inferior to copper or mild steel as constructional
material for a steam-jacketed pan to heat food materials. The condensing heat
transfer coefficient for the steam and the surface boiling coefficient on the two
sides of the heating surface are respectively 10,000 J m -2 s-1 °C-1 and 700 J m-2 s-1
°C-1. The thickness of all three metal walls is 1.6 mm. Compare the heating rates
from all three constructions (assuming steady state conditions).
[mild steel 2% worse than copper, stainless steel 4.5% worse than copper ]
For stainless steel
But
⁄
Therefore
For mild steel
But
⁄
Therefore
For cooper
But
Therefore
⁄
Further,
Copper Vs mild steel
Copper Vs stainless steel