Comparing internal and external run-time coupling of CFD and building energy simulation software

Summary: This paper describes a comparison between internal and external run-time coupling of CFD and building energy simulation software. Internal coupling can be seen as the “traditional” way of developing software, i.e. the capabilities of existing software are expanded by merging codes. With external coupling, two or more software packages run simultaneously while exchanging calculation results at appropriate time intervals. One of the most notable advantages of external coupling is that it is no longer necessary to make major changes to one of the coupled simulation packages should the other one be expanded with new or improved features. Furthermore, it is much easier to externally couple some software than to merge its code into existing software. Obviously in commercial software the code would not even be available. This paper presents the implementation of external coupling between BES and CFD. The external coupling method will be compared with internal coupling method by simulating the IAE Annex 26 Atrium (Yokohama, Japan). The results show the applicability and advantages of the external coupling method.