Question

18. An egg hatchery is preparing to renovate its egg holding room. The room is insulated and cooled to 40 degrees F. They want to compare the rate of heat gain through the room wall when insulating with 3.6 inches of fiberglass insulation (k=0.318 BTU inch/(hr ft² F)) versus 3.3 inches of polystyrene (k=0.2 BTU inch/(hr ft² F)). Determine the heat transfer rate for each material for the two wall types if the outside temperature is 85 degrees F.

Heat Transfer Rate (Fiberglass) = BTU/hr ft²

Heat Transfer Rate (Polystyrene) = BTU/hr ft²

Answer 1

Given

Egg hatchery with inside temperature is T1 = 40 0F
out side the temperature is T2 = 85 0F
when the room is insulated with fiber glass with thickness t = 3.6 in having coefficient of thermal conduction is k = 0.318 BTU inch/(hr ft2 F)
and
when the room is insulated with polystyrene with thickness t = 3.3 in having coefficient of thermal conduction is k = 0.2 BTU inch/(hr ft2 F

from the relation of rate of heat conduction is

   dQ/dt = k*A*(T2-T1)/t

   dQ/dt*A = k (T2-T1)/t

for fiber glass

   dQ/dt*A = 0.318 (85-40)/3.6 = 3.975 BTU/hr ft2

for polystyrene

   dQ/dt*A = 0.2 (85-40)/3.3 = 2.727 BTU/hr ft2