The hygrothermal whole-building simulation software WUFI® Plus was extended with a new model: the calculation of longwaveradiative heat exchange between surfaces inside a zone. This allows a more detailed calculation of the interior radiativeand surface temperatures, which also results in a better simulation of indoor climate conditions. The model also takes into accountthe optical properties of indoor surfaces, such as low-e coatings. Further benefits are a more comprehensive comfort assessment,for example, for asymmetric radiant temperature. Radiant temperatures can also be calculated for every position inside a zone.The model uses Gebhart factors for the calculations of long-wave heat exchange between surfaces inside a zone. These factorsdescribe the fraction of emitted energy from one surface that is absorbed at another. They are determined from view factors, whichonly describe geometrical relationships between surfaces. WUFI® Plus uses a numerical triangulation method to calculate theview factors. As the Gebhart factors also consider optical properties of surfaces, all possible radiation paths, including multipleand own reflections, are taken into account for the calculations. Single parts of the calculation process are successfully validatedwith analytical solutions: the view factor calculation of a nontrivial room geometry and the long-wave heat exchange betweentwo parallel plates show only minimal deviations from the analytical results. The German standard DIN EN 13791 provides testsfor the validation of interior long-wave heat exchange. The model was successfully validated with them. In an exemplary applicationcase, simulations with the new model are used as a preliminary study to determine the required accuracy and positioningof measurement equipment of a future test room. The simulated surface temperatures were successfully used as a plausibilitycontrol. The measurements will later be used as an experimental validation test for the new model.
Citation: Thermal Performance of Exterior Envelopes of Whole Buildings XIII, Conference Papers
Product Details
- Published:
- 2016
- Number of Pages:
- 9
- Units of Measure:
- Dual
- File Size:
- 1 file , 2.5 MB
- Product Code(s):
- D-BldgConf16-62
