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,
[tex]\frac{\Delta Q}{\Delta t} = e\sigma A(T_1^4-T_2^4)[/tex]
Where,
e= Emissivity
[tex]\sigma[/tex] = Stefan Boltzmann constant
A = Surface Area
[tex]T_{1,2}[/tex]= Temperature at each state
Replacing our values we have,
[tex]\frac{\Delta Q}{\Delta t} = (0.7)(5.67*10^{-8})(1.2)([273+80]}}^4-[273+20]^4)[/tex]
[tex]\frac{\Delta Q}{\Delta t} = 431.317W[/tex]
Therefore the neat heat flow rate from the radiator is 431.3W
