Calculation of Natural Ventilation in Large Enclosures

Abstract

There is a need for a good analytical model of natural ventilation of large enclosures. This study describes a multi-layer pattern of thermal stratification in high and large spaces driven by natural ventilation. The pattern is then used to construct an analytical model for natural ventilation of large enclosures. A thermal plume developed in the multi-layer environment is investigated based on its development across each density interface. This kind of plume and the airflows along vertical wall surfaces are combined to establish the heat and mass balances in each thermally stratified layer. Two different mathematical models that model the airflows along vertical wall surfaces are presented. These two models are compared for their predictions of the ventilation flow rate and vertical temperature profiles. Results of both present models are also compared with those calculated by computational fluid dynamics (CFD). It is shown from the comparisons that both models predict reasonably the thermal stratification in the large enclosure but only the one that considers continuous airflow along the whole wallsurface gives reliable predictions which agree well with results from the CFD study.