Numerical prediction of indoor temperature stratification

In many buildings, displacement ventilation is used so that contaminants can be separated from occupied space [1, 2]. A fundamental characteristic of displacement ventilation is a layer of stratified fluid that separates the occupied zone from the contaminated zone, marked by a density gradient usually due to temperature differences in the two zones. Because buoyancy is a dominant effect in these situations, natural rather than forced ventilation is commonly used. This paper presents a series of simulations studying the prediction of steady-state stratification in a room ventilation case. Following on from work performed by Iial-Awad [3], numerical simulations coupled with a 2-equation turbulence model were employed to predict the steady-state time-averaged temperature distribution and stratification layer height in a room subject to two momentum sources at different temperatures. The room has been simulated with different levels of idealism to examine the effect boundary condition assumptions have on the predictive accuracy of the simulation compared to the work of Iial-Awad [3]. It was found that the assumption of adiabacity of the room caused the predicted vertical temperature profile to be highly idealistic, with the flow stratified into two discrete layers across a sharp interface. The addition of heat loss boundary conditions and thermal radiation modelling causes the predicted temperature profile to more closely match that produced in the original experimental work.