Introduction of a new calculation approach based on the radiosity method.
The 2017 revision of the norm 10077-2 introduces a new method for calculating the heat transfer inside air cavities:
According to the existing method the flags in this example (surface emissivity: 0.9, distance of flags more than 2mm) are not improving the construction. With the new method there is an improvement of 15%, which is realistic.
After calculating hundreds of customer examples with both methods, we have concluded the following:
In day to day use the existing method has some weak points that result from the non-definitive description of the algorithms. This can lead to significant differences in the calculations. On the other hand some effects cannot be simulated with the existing method.
The algorithms of the new method are formulated definitively, without any room for interpretation neither from software manufacturers nor users. The heat transfer by radiation is modeled physically correct.
For comparing the results of different software products and different users, a single, definitively formulated method should be established. Because of the precise modelling of the heat transfer by radiation and the concise formulation, the new method is more appropriate for this purpose.