A CORRELATION OF THE WET-BULB GLOBE TEMPERATURE AND BOTSBALL HEAT STRESS INDEXES FOR INDUSTRY

A heat transfer analysis of the instruments used for the measurement of the wet-bulb globe temperature (WBGT) and the Botsball temperature (BBT) was made. By using the analysis, both heat stress indexes were calculated over wide ranges of air temperature, humidity, air speed, and radiant heat flux, thereby simulating different industrial environments. The calculated results were in agreement with measurements taken in industry and in the laboratory. The two heat stress indexes were correlated by the following equation: WBGT=1.5157(BBT) + 0.0112(BBT * Pa) −0.7379(Pa) −2.5591 where Pa is the water vapor pressure of the ambient air. This equation reconciles the divergence of published correlations for industrial environments. The WBGT may be predicted from the Botsball with a precision of ±1.18°C if the water vapor pressure of the ambient air is known. In some industries, the water vapor pressure is the same at different work sites and a single measurement with a psychrometer would be sufficient.