Question

A radiator has an emissivity of 0.7 and its exposed area is 1.2 m2. The temperature of the radiator is 850C and the surrounding temperature is 200C. What is the net heat flow rate from the radiator? ( = 5.67x10-8 W/m2K4)

Answer 1

To solve this problem it is necessary to apply the Stefan-Boltzmann equations. This equation describes the power radiated from a black body in terms of its temperature. Mathematically this can be expressed as,

$\frac{\Delta Q}{\Delta t} = e\sigma A(T_1^4-T_2^4)$

Where,

e= Emissivity

$\sigma$ = Stefan Boltzmann constant

A = Surface Area

$T_{1,2}$= Temperature at each state

Replacing our values we have,

$\frac{\Delta Q}{\Delta t} = (0.7)(5.67*10^{-8})(1.2)([273+80]}}^4-[273+20]^4)$

$\frac{\Delta Q}{\Delta t} = 431.317W$

Therefore the neat heat flow rate from the radiator is 431.3W