Prediction of Workplace Wet Bulb Global Temperature

The wet bulb globe temperature (WBGT) is the de facto standard to assess environmental contributions to heat stress. A practical problem emerges when the heat stress conditions vary over many locations or during the day. To address this problem, investigators have suggested empirical relationships and thermodynamic models. The purpose of this effort was to examine a thermodynamic model in the laboratory and to predict WBGTs in an aluminum smelter by both the empirical and thermodynamic models. In the laboratory, there was no real difference between the experimental data and the thermodynamic model. In the application to an aluminum smelter, there was a small overall tendency for the predicted values to be greater than the actual values, but there was no practical difference between the models. The empirical model provided a good match with a slight over-prediction by 0.5 degree C with a standard deviation of 3.0 degrees C. For the same data, the thermodynamic model had an average over-prediction of 0.7 degree C with a standard deviation of 2.8 degrees C. Either method of predicting WBGT was effective. The empirical method required less computation and was conceptually simpler.