Spot Cooling - Part 2: Recommendations for design of spot cooling systems

Abstract

In this paper, the results of human subject and thermal manikin experiments with cooling jets are analyzed and discussed from the viewpoint of the design of spot-cooling systems. Large individual differences among people with regard to their physiological and subjective responses to the thermal environment and the selected preferred jet velocity make it unrealistic to propose one velocity for all persons depending on environmental conditions. A major conclusion of this study is that a spot-cooling system with individual control of the jet velocity and, impossible, control of the jet temperature is the most desirable. The spot cooling should provide a maximum local velocity of 4 meters per second (m/s) in the workplace. The jet outlet should be as close as possible to the person to provide energy-efficient cooling and maximum cooling benefit. The range of local jet air temperatures accepted by the subjects as a function of the room air temperature is given in the paper. A vertical jet has a stronger cooling ability and provides a more uniform cooling of the body than a horizontal jet. Nevertheless, the subjects were able to select an acceptable thermal environment with both vertical and horizontal jets. They found a compromise between decreasedmore » warm discomfort for the whole body and increased local draft discomfort or discomfort due to the pressure of the air movement. A combination of a vertical jet, a helmet, and a clothing ensemble of a design modified to protect the neck and shoulders from draft is recommended for use at room air temperatures above 35 C.« less