Use of low temperature air for cooling of buildings.

The topic of this paper is the use of low temperature air (40 F or 5 C) for room cooling. Cold air systems can offer energy and space savings relative to higher temperature cooling systems. As the supply temperature and flowrate are reduced, considerations such as adequate flowrate, jet dumping or separation, condensation on duct walls, and decreased relative humidity become increasingly important. Cold air jet separation from the ceiling can be a problem resulting in unacceptable thermal discomfort in the occupied zone. In the paper, the behavior of cold air jets , including throw and separation, is examined. A simple jet model is presented, and throw and separation point relationships are developed. The results from the ideal jet model suggest that for the same cooling capacity, the resulting room air motion, jet throw, and jet separation point will be the same for both conventional and cold air jets if the jet momentum is held constant.