Question

A temperature difference of 85◦c is impressed across a fiberglass layer of 13 cm thickness. the thermal conductivity of the fiberglass is 0.035 w/m · ◦c. compute the heat transferred through the material per hour per unit area

Answer 1

Formula of heat transfer per sec per unit area is $H=\frac{K\Delta{T}}{\Delta{x}}$

Where K is thermal conductivity
∆T is the change in temperature
∆x is the thickness of layer.

Here, K = 0.035 w/m.°C
∆T = 85°C
∆x = 13 cm = 0.13 m

Now, Heat per sec per unit area = 0.035 × 85/0.13 = 22.88 J

so, heat transfer per unit hour per unit area = 3600 × 22.88 J = 82384.6 J

Answer 2

Explanation:

Q/A=∆T/(x/k)

∆T=85℃

x=13cm=0.13m

k=0.035w/(m℃)

Q/A=85/(0.13/0.035)

Q/A=22.88w/m^2=22.88 j/sm^2

=22.88×3600

=82384.61 j/hrm^2