Direct and indirect measurement of WBGT index in transversal flow

ISO 7243 considers the WBGT (Wet Bulb Globe Temperature) index as an index of thermal stress in hot environments. It can be evaluated directly by measuring the globe temperature, the natural wet bulb temperature, and the air temperature (only outside in the presence of solar radiation) or, indirectly, by measuring the air temperature, the air velocity, the humidity and the mean radiant temperature. The globe and natural wet bulb temperatures can only be estimated empirically, because they are not thermodynamic properties. The direct method, thus, permits neither very accurate measurements nor direct traceability. The aim of this study is to compare the above-mentioned methodologies experimentally. This analysis was carried out by varying the thermal and fluid dynamic parameters for transversal flow in the common measurement range.