A simplified model for large spaces

In the last years large spaces have been becoming very diffused in new buildings (atria, show- rooms, etc.). The study of the indoor climate in these spaces is very difficult, due to problems related to air stratification. Generally CFD programs (Computational Fluid Dynamics) are used; they are able to solve air motion in accurate way but steady state simulation or simula-tion of only short time periods can be obtained. Furthermore CFD need surface temperatures as input and thermal behaviour in time domain is difficult to obtain, while for energy purposes the dynamic behaviour of the whole environment is needed. In this paper a simplified model taking into account heat balance and air motion for large spaces is presented; it enables to simulate a large room obtaining information about the air stratification in height. It derives from detailed model DigiThon, which is based on transfer function method, and it allows to simulate all types of radiant systems. The room is divided into n volumes one above the other, as to take into account the possible air stratification. It is possible to consider air inlet/outlet and internal loads. In this way one year dynamic simulation may be carried out, thus allowing to get the temperatures of the n volumes in height. A comparison with CFD program is shown, as test the developed model.