Chapter 3—Principles of thermal comfort

• Published in: Renewable & sustainable energy reviews Vol. 2; no. 1; pp. 39 - 66
• Main Author: Butera, Federico M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.1998; Elsevier
• Series: Renewable and Sustainable Energy Reviews
• ISSN: 1364-0321; 1879-0690
• DOI: 10.1016/S1364-0321(98)00011-2

The human body, considered as a thermodynamic system, produces mechanical work and low temperature heat, using food (fuel) and oxygen as input. This system requires, in healthy conditions, to maintain a constant internal temperature around 37±0.5°C, otherwise the functionality of important organs like liver, spleen, etc, may be severely damaged. fn2 fn2 During heavy work it rises by a few tenths of degree; under extreme activity it may rise as high as 39.5°C for short durations; temperatures above 40°C maintained for many hours lead to a breakdown of the thermoregulatory system, causing death. Chilling of internal organs to 36°C is possible without damage; below this, muscular weakness, exposure and then death results. In carefully controlled situations, as in surgical hypothermia, 30°C can be reached. In order to achieve this goal, the rate of heat generation of the body must be equal to the rate of heat loss from it. The job of our thermoregulatory system is to maintain the heat balance, that is a fundamental condition for survival and necessary (but not sufficient) for comfort. Skin temperature, otherwise, is not constant, and it varies according to the part of the body and the air temperature; the absolute maximum and the minimum values, however, are 45 and 4°C (pain thresholds).