For every iteration, a radiosity matrix is form and solved. A complete record of the energy balance is provided for every part in the model. This data is written to the “.sol” file for every iteration during the analysis, and to the summary file after the last iteration. This section describes the information that is provided, and discusses the differences for models using transparent boundary conditions and solar heating.
Radiation with no Transparent BC or Solar
The following is a sample energy balance from a radiation analysis containing five parts. There are four parts immersed in an air cavity (part 5). None of the parts has transmissivity. Comments about the meaning of certain items are written below the line and are preceded by a “>>>>” symbol.
Radiosity Solution has converged
Iter=12 ResNorm = 5.85774E-013
CPU time to solve radiosity matrix = 0.719
Radiation heat balance = 2.3363e-008/ 20.437 = 1.1431e-007%
>>>> The 2.3363e-008 is the sum of the radiative energy. This value should be 0 or very close. The 20.437 is the sum of the absolute values of the radiative energy. The 1.1431e-007% is the total radiative energy divided by the sum of the absolute values. This is an indicator of the error in the radiative energy balance.
Radiation Heat Loads by Part ID:
| ID |
Radiation Heat Load (Watts) |
Area (mm^2) |
Surface Temperature (K) |
Emissivity | Transmissivity |
| 1 | -2.583 | 5959.3 | 365.23 | 0.94 | 0 |
| 2 | -2.5318 | 5959.2 | 363.07 | 0.94 | 0 |
| 3 | -2.5806 | 5959.3 | 365.56 | 0.94 | 0 |
| 4 | -2.5148 | 5959.3 | 364.2 | 0.94 | 0 |
| 5 | 10.21 | 1.2296e+005 | 298.25 | 0.7 | 0 |
| Totals | 2.3363e-008 | 1.4679e+005 | 309.01 |
>>>>Parts 1-4 are each losing about 2.5 Watts through radiation, and part 5, the enclosure, is receiving that radiant energy. The totals indicate that the total heat lost equals the sum of the heat gain, indicated by the total heat load summing to 0. The temperature for each part is an area-weighted temperature, and the total temperature is average temperature for all of the parts.
Radiation with Transparent Boundary Conditions
When transparent boundary conditions are included in a radiation analysis, the energy balance information is presented slightly differently as shown in the radiative energy balance from such an analysis. Comments about the meaning of certain items are written below the line and are preceded by a “>>>>” symbol.
Radiation heat balance = -4.5792e-008/ 226.96 = -2.0176e-008%
>>>>As in the previous example, the -4.5792e-008 value is the net radiative heat exchange within the model. A very small value means that a good energy balance has been attained.
Radiation Heat Loads by Part ID
| ID |
Radiation Heat Load (Watts) |
Area (mm^2) |
Surface Temp (K) |
Emissivity | Transmissivity |
| 2 |
-36.289 / 0 transparentBC |
6.917e+005 | 1268.5 | 0.94 | 0 |
| 3 |
-32.062 / 0 transparentBC |
1599.3 | 1015.7 | 0.94 | 0 |
| 4 |
0.18324 / -76.557 transparentBC |
1767.8 | 980.85 | 0.05 | 0.8 |
| 6 |
-8.3889 / 0 transparentBC |
2.029e+005 | 1270.7 | 0.94 | 0 |
| Totals | -76.557/ -76.557 | 8.980e+005 | 1268 |
>>>> Parts 2 and 3 are losing about 36 and 32 Watts, respectively. Part 6, the enclosure, is losing about 8 Watts. The sum of the energy lost from these three parts equals the energy lost through the transparent boundary condition. The transparent part, part 4, is only picking up a small amount of energy because it is losing most of its energy through the transparent boundary condition. Note that the total transparent BC heat load = total radiation heat load. This indicates a good energy balance.