Question

A temperature difference of 15°C is impressed across a brick wall of a house which is 15 cm in thickness. The thermal conductivity of the brick is 1.0 W/m °C. The face of the wall is 6 meters high and 12 meters long. Compute both the heat flux and the heat transfer rate through the wall. Why aren't these numerical values the same?

Answer 1

Answer:

Q=7200 W

q=7200/72=100 $W/m^2$

Explanation:

Given that

ΔT=15° C

Thickness ,t=15 cm

Thermal conductivity ,K=1 W/m.°C

Height,h=6 m

Length ,L=12 m

As we know that heat conduction through wall given as

$Q=\dfrac{KA}{t}\Delta T$

Now by putting the values

A= 6 x 12 =72 $m^2$

$Q=\dfrac{KA}{t}\Delta T$

$Q=\dfrac{1\times 72}{0.15}\times 15\ W$

Q=7200 W

Q is the total heat transfer.

Heat flux q

 q=Q/A $W/m^2$

q=7200/72=100 $W/m^2$

q is the heat flux.

As w know that heat flux(q) is the heat transfer rate from per unit area and on the other hand heat transfer(Q) is the total heat transfer from the surface.

Heat flux q=Q/A

That is why these both are different.