Study on a Multi-Layer Analytical Model of Natural Ventilation in Large Single-Cell Buildings

In large single-cell buildings, a multi-layer analytical model of natural ventilation is presented in this paper. The fluid mechanics of a plume developing in multi-layer environment is investigated based on the plume theory. Using the basic equations for a thermal plume, a mathematical model demonstrating this mechanics is established. Multi-layer thermal stratification of air density or temperature is considered driven by heat flux along wall surfaces. Airflow along vertical walls is modeled with two separate methods, one considering separate wall plumes for each layer and another modeling continuous airflow along the whole wall surface. A multi-layer model is established through balance equations for mass flow rate and heat in each layer. Two separate multi-layer models are presented and then are used to predict the ventilation flow rate and vertical temperature profiles. CFD simulation is also carried out using the RNG κ-ε model, together with an enhanced wall boundary treatment. Results of both present models are compared with those of CFD simulation. Comparisons of the results show that one model using turbulent boundary layer to calculate continuous airflow along vertical walls gives more reasonable and reliable predictions than the other one.