On the combined application of thermal and CFD modelling in the design of naturally ventilated industrial halls.

For indoor thermal environment engineering and heating system dimensioning, naturally ventilated spaces impose difficulties due to the interaction of indoor and outdoor air flows and due to their variation in time and space. Thermal building simulation models basically assume mixed air flow conditions in the individual zones, but are able to dynamically model the building masses and the heat exchange between them and the zone air. CFD codes on the other hand can predict the air flow field in a zone in great detail - also in transient cases - but the calculations normally are based on pre-set surface temperature boundary conditions. Therefore, in practice, both dynamic building simulation and CFD calculations are used for proper building design. This is illustrated in this paper in two cases, where both simulation methods were used. The first case is a naturally ventilated test laboratory hall, where overheating risk studies were performed by a combination of thermal modelling and multi-zone air flow modelling, while for winter cases, the draft risk from cold air under the roof glazing was studied using transient CPD calculations. The second case is one of three large central parcel distribution centres, newly built by Swiss Post, where CFD simulations were used to study the inflow of cold air from the truck docking stations. Thermal building simulations where made to provide surface temperatures, especially of the floor, and the overall air flow rates through the building leakage, and to allow for the dimensioning of the heating system. The paper concludes with generally applicable recommendations on the combined use of thermal and CFD modelling.