energy

Computes the total energy radiated by a body with given parameters.

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Contents

Interface
Energy
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Interface

C++

Excel

Energy

doubleenergy(	double	`T`
	double	`e` `= 1.0`	)[inline]

This module calculates the total energy radiated by a body per unit surface area in unit time.

The total radiative energy $\inline E_0$ of a black body is given by the Stefan-Boltzmann law

$E_0 = \int_0^{\infty} I(\lambda) {\rm d}\lambda \qquad \left[\frac{W}{m^2}\right]$

(2)

where $\inline I(\lambda)$ is the radiative intensity of the black body.

In practice, the following formula due to Kirchoff is used

$E_0 = e c_0 \left(\frac{T}{100}\right)^4 \qquad \left[\frac{W}{m^2}\right]$

(3)

where $\inline C_0$ is the emissivity constant of the black body $\inline \displaystyle \left(C_0 \approx 5.669 \left[\frac{W}{m^2 K^4}\right]\right)$ , $\inline e$ is the emissivity factor of the body $\inline (0 < e \leq 1)$ and $\inline T$ is its absolute temperature.

Example 1

The following example calculates the total radiative energy emitted by the Wolfram filament of an incandescent light bulb at 3573.16 degrees Kelvin.

#include <codecogs/engineering/heat_transfer/radiation/energy.h>
#include <stdio.h>
 
int main()
{
  // the temperature of the Wolfram filament
  double T = 3573.16;
 
  // emissivity factor of the filament
  double e = 0.39;
 
  // display the total radiative energy
  printf("Energy = %.5lf kW per sq. meter\n",
  Engineering::Heat_Transfer::Radiation::energy(T, e)/1000.0);
 
  return 0;
}

Output

Energy = 3603.96794 kW per sq. meter

Note

A table with the emissivity factors of various materials at different temperatures can be found at the following link http://www.monarchserver.com/TableofEmissivity.pdf

References

Dan Stefanescu, Mircea Marinescu - "Termotehnica"

Parameters

T	the absolute temperature of the body (Kelvin)
e	Default value = 1.0

Returns

the total radiative energy emitted by the body (Watt per square meter)

Authors

Grigore Bentea, Lucian Bentea (November 2006)

Source Code

Source code is available when you buy a Commercial licence.

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