The assessment of heat radiation

Abstract

Approximately 900 climatic chamber experiments were performed with 16 male subjects to study the thermal strain at climates including increased heat radiation. Based on the reactions of heart rate, rectal temperature and sweat rate, a heat stress index was developed for the assessment of climates with effective heat radiation intensities up to 1400 W m −2. The index considers different combinations of dry air temperature (5–55°C), globe temperature (25–76°C), mean radiant temperature (25–160°C), air velocity (0.5–2.0 m s −1), clothing, physical work load and directions of radiation and air flow. The index integrates combinations of the variables producing the same degree of thermal strain into a single value. This value indicates the temperature of the physiologically equivalent climate in which air and radiant temperature are equal. It can be determined from a simple formula or from correspondent graphs. In comparison, the international recommended heat stress indices are less capable to evaluate heat radiation correctly. The incorporation of the new partial index into the used indices may improve substantially their physiological validity in the assessment of climates with radiant heat stress. Relevance to industry The goal of this paper is to provide an improved assessment of thermal stress in working environments in which heat radiation is an important heat stress factor.