Chapter 14 Prediction of Local Discomfort for Man

Abstract

Publisher Summary The main purpose of most heating and air conditioning systems is to provide thermal comfort for human beings. For the design and operation of such systems and for the thermal design of buildings, it is essential to establish quantitative comfort requirements. Thermal comfort is defined in the chapter as that condition of mind that expresses satisfaction with the thermal environment. A first requirement for comfort is that a person feels thermally neutral for the body as a whole—that is, a person does not know whether he/she would prefer a higher or lower ambient temperature level. Man's thermal neutrality depends on his clothing and activity and on the following environmental variables: the mean air temperature, mean radiant temperature, mean air velocity, and water vapor pressure in the ambient air. The thermal neutrality as predicted by the comfort equation is not the only condition for thermal comfort. A person may feel thermally neutral for the body as a whole, but he might not be comfortable if one part of the body is warm and another cold. It is, therefore, a further requirement for thermal comfort that no local area of discomfort exists at any part of the human body. Such local discomfort may be caused by an asymmetric radiant field, by a local convective cooling (draught), by contact with a warm or cool floor, or by a vertical air temperature gradient. Each of these cases are discusses in the chapter, along with limits for avoiding local discomfort.