Question

A slab of thermal insulator is 200cm square in cross section and 5cm thick.If thermal conductivity is0.50 and temperature difference is 150 what is the heat flow through the slab in 2 days

Answer 1

Answer: 5184 kJ

Explanation:

Given

Area of cross-section $A=200\ cm^2$

thickness of slab $t=5\ cm$

thermal conductivity $k=0.5\ W/m-K$

temperature difference $\Delta T=150\ K$

Heat flow is given by

$\Rightarrow Q=kA\dfrac{dT}{dx}\\\Rightarrow Q=0.5\times 200\times \dfrac{150}{5}\times 10^{-2}\\\Rightarrow Q=30\ W\ or\ 30\ J/s$

for 2 days time period, it is

$t=2\ days\ or\ 2\times 24\times 60\times 60\ s\\t=1,72,800\ s$

Heat flow in 2 days

$Q=30\times 172800=5184000=5184\ kJ$