An Extended Model for Underfloor Air Distribution Systems

Previous work on an Underfloor Air Distribution (UFAD) system with a single heat source anda single cooling diffuser at floor level developed by Lin has been extended to study the effects of the vertical location of the heat source and of multiple cooling diffusers. This is an attempt to produce more realistic models of UFAD systems. Both experimental and theoretical modeling is described in this paper. In the experiments, a plume and fountains represent a heat source and cooling diffusers respectively. The experiments suggest how the entrainment rate of ambient fluid into the fountain at the interface changes with the local Richardson number. They show that for a fixed ventilation rate, as the source elevation is increased, the return temperature remains unchanged and the height of the cooler, lower zone increases. The effect of multiple cooling diffusers is to decrease the height and the temperature of the cooler zone.