A new paper by professor Andy Woods and former PhD student Dan Toy has been recently published in the Journal of Fluid Mechanics. In this paper, Andy and Dan investigate the transient ventilation flows which develop in a building with upward mechanical displacement ventilation following variations in the heat load and ventilation rate.
In steady state, thermal plumes that rise from localised heat sources interact with the upward ventilation flow to produce a two-layer stratification. Through new laboratory experiments, the article examines the transient responses to changes in the strength of the heat source or modifications to the ventilation volume flux. Changes to the heat source immediately affect the plume buoyancy, while changes to the ventilation lead to a more gradual evolution of the system. This difference in time scales results in a range of transient flows in the space. Andy and Dan have developed a model for these transient flows that is consistent with the experimental observations. The insights from this work are key for developing control strategies which maintain thermal comfort in buildings subject to frequent changes in heat load.