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Józef Wacławik

Comments on wet – bulb globe temperature

Wet-bulb globe temperature (WBGT) index is a function of four factors affecting environmental heat stress: dry-bulb temperature Ta, wet-bulb temperature Tm, radiant temperature Tr and velocity of air va. This index combines in enclosed environment the measurement of two parameters, natural wet-bulb temperature and the globe temperature. Several mathematical formulas are available for predicting WBGT from the environmental factors. W.Turkiewicz (1986) recommended a new one, which called temperature conform of climate TZK: TZK = 0.6Tm + 0.4Ta – va. Unfortunately, values of TZK are unequal WBGT for the same environment parameters. In comparison with C.D.Sullivan & R.L.Gorton’s (1976) formula TZK get values smaller than WBGT. It is known that WBGT is not extremely sensitive to air velocity and that sensitivity decays at higher velocities. For the same environmental parameters be obtained the value of TZK which is references for high metabolic rate and the value of WBGT which is proper for moderate or low metabolic.