Dynamic thermal CFD simulation of a typical office by efficient transient solution methods

This paper describes the evolution and application of an efficient dynamic thermal modelling (DTM) procedure, developed within computational fluid dynamics (CFD). The results of a case study to simulate the dynamic thermal conditions within a typical office space using the novel DTM-CFD procedure are reported. The main area of investigation was the ability to account for the time-varying thermal response of building fabrics to internal and external ambient conditions and the consequential effect on the air inside the enclosure. The proposed DTM-CFD procedure utilised a transient time-varying grid schedule, 'Freeze-Flow' and 'Boundary Freeze' techniques. 'Freeze Flow' paused the solution of all governing equations of fluid flow, except temperature; while 'Boundary Freeze' froze temperatures at boundaries of the CFD model whilst solving all equations in the flow domain. The DTM-CFD procedure provides the potential for solving the problem of generating large quantities of data, whilst effectively and accurately modelling heat transfer through the building fabric and internal air simultaneously using CFD alone. An assessment of the performance of the DTM-CFD procedure was made through inter-model comparisons with fully transient CFD solutions. The procedure was successful in providing more detailed dynamic thermal simulations than would have otherwise been obtainable from a DTM and more efficiently (simulation time) than a CFD model.