A Momentum-Zonal Model for Predicting Zone Airflow and Temperature Distributions to Enhance Building Load and Energy Simulations

Abstract

Building load and energy simulation programs based on the complete-mixing air model fail to consider the impact of nonuniform air temperature distributions. A momentum zonal model based on the Eüler equation has been developed to enhance building load and energy simulations by predicting indoor airflows and temperatures. This paper shows some validation exercises by comparing model results to measurements and computational fluid dynamics. The model was found to predict thermal stratification conditions reasonably well and to err on the side of complete mixing. The model has been coupled to the heat balance model and tested on load calculations. Results for cooling and heating loads are compared to the traditional complete-mixing model with minor effects on total load but important differences in air system flow rate and control options. Total computation times for load calculations were two orders of magnitude higher using the momentum zonal model compared to traditional complete mixing.