TRNSYS17: New features of the multizone building model

For the upcoming release of TRNSYS 17, one main focus is the improvement of the simulation of highly glazed large spaces such as multi-story atriums with respect to accuracy, user effort and error-proneness. Therefore, the existing multizone building model has been extended to a detailed modelling of 3-dimensional energy transport by radiation and thermal stratification. This paper briefly describes the new model for long-wave and short-wave radiation handling within a thermal zone as well as the multiple airnode approach. The new radiation model applies so-called Gebhart factors, which are based on view factors. The long-wave and short-wave diffuse radiation exchange between all surfaces of a thermal zone are calculated explicitly, including all possible paths. Point sources are treated similarly. To account for stratification effects or local conditions near the facade, multiple airnodes can be defined within each thermal zone. In addition, external sunlit factors of solar radiation can be handled automatically and the incoming beam radiation is distributed depending on the sun’s position, the external shading and the geometry of the thermal zone. For convenient geometry input and visualisation a graphical interface will be available for TRNSYS 17. From the resulting geometric information the required inputs such as view factors, shading factors and distribution factors are calculated in a preprocessing step.