A thermal and airflow analysis tool using simplified models based on the zonal method.

The article presents a zonal model called Sim_Zonal which can be used to predict air movement, temperature distribution and comfort characteristics in a room. The model is based on an approximate partitioning of the room, which is divided into a small number of 'cells', usually in the order of 10 to 100, as compared to 10000 or more for typical CFD calculations. Exchanges are calculated between the cells when mass balance and heat balance equations are applied. Empirical laws describe airflow where plumes or jets occur. Flow rates are calculated in respect to the pressure distribution in low velocity domains. The air flow model is coupled with a building envelope model including the calculation of conduction through the walls, convection between inside wall surfaces and cells, and long-wave and short wave radiant interchange among the inside wall surfaces. The start of the article consists of the description of the different heat transfer models used. They are described in the second part. Finally different results of simulations in a 3D room are described and it is shown that the model yields accurate results even with a rough partitioning.