Zonal models for indoor air flow - A critical review

A zonal model is an intermediate approach between computational fluid dynamics (CFD) and single-room models. It can give results faster than CFD and be more accurate than single-zone models. It has been used to provide some global information regarding thermal and flow parameters within a room. In this review, due emphasis is given to the commonly used pressurized zonal model - the power law. Qualitative validations show that the power law model reasonably predicts well for natural convection. Nevertheless, for the case of forced convection it was found that zonal models fail to predict the recirculation loop reasonably. This is due to the fact that the power law model employs a constant flow coefficient throughout the flow field. A validated room CFD simulation was employed to illustrate the variability of the flow coefficient in the flow field.