This module calculates the radiative heat flow per unit surface between two plane surfaces, considering the case when these are separated by a non-absorptive medium.
On account of the Stefan-Boltzmann law, the unit radiative heat flow between the two surfaces is given by
with , the emissivity factors of the first and second surface , the emissivity constant of the black body and , the corresponding absolute temperatures of the two plane surfaces.
In the diagram below is show the radiative heat transfer between two plane surfaces, in which is the radiative energy emitted by the first surface, is the radiative energy emitted by the second surface, is the energy emitted by the first surface and absorbed by the second, is the energy emitted by the second surface and absorbed by the first, is the radiative energy emitted by the first surface and reflected by the second and is the radiative energy emitted by the second surface and reflected by the first.
Example 1
The example below computes the unit radiative heat flow between an oxidated aluminium plane surface at 873.16 degrees Kelvin and an oxidated copper plane surface at 403.16 degrees Kelvin, separated by a non-absorptive medium.
#include <codecogs/engineering/heat_transfer/radiation/flow_noshield.h>#include <stdio.h>int main(){// the temperature of the oxidated aluminium surfacedouble T1 = 873.16;
// the temperature of the oxidated copper surfacedouble T2 = 403.16;
// the emission factor of the aluminium surfacedouble e1 = 0.19;
// the emission factor of the copper surfacedouble e2 = 0.76;
// display radiative heat flow between the two plane surfacesprintf("Radiative heat flow = %.5lf W per sq. meter\n",
Engineering::Heat_Transfer::Radiation::flow_noshield(T1, T2, e1, e2));
return0;
}
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, 
the emissivity factors of the first and second surface 
, 
the emissivity constant of the black body ![\displaystyle \left(C_0 \approx 5.669 \left[\frac{W}{m^2 K^4}\right]\right)](http://www.codecogs.com/images/eqns/67fc33bfe68b5caa3581d0d7912ffcd6.gif)
and 
, 
the corresponding absolute temperatures of the two plane surfaces.
In the diagram below is show the radiative heat transfer between two plane surfaces, in which 
is the radiative energy emitted by the first surface, 
is the radiative energy emitted by the second surface, 
is the energy emitted by the first surface and absorbed by the second, 
is the energy emitted by the second surface and absorbed by the first, 
is the radiative energy emitted by the first surface and reflected by the second and 
is the radiative energy emitted by the second surface and reflected by the first.
![q = e_{1-2} \,\, C_0 \left[\left(\frac{T_1}{100}\right)^4 - \left(\frac{T_2}{100}\right)^4\right] \qquad \left[\frac{W}{m^2}\right]](http://www.codecogs.com/images/eqns/fdcfd62d6f5a52b16bd4496e94376165.gif)
