Environmental index for evaluating thermal sensations in a mist spraying environment

The present study assessed a new index that can evaluate thermal sensations in outdoor and mist spraying environments. Mist spraying systems have been widely used to relieve thermal discomfort in hot weather. However, relatively few studies have investigated the environmental indices to evaluate thermal sensations in mist spraying environments. Therefore, this study carried out experiments to collect data for the environmental factors, physiological responses, and survey results in a mist spraying environment. In the first experiment, subjective assessments and environmental factors measurements were conducted. Based on the experimental analysis, the conventional indices were examined to determine the acceptability in the mist environment. In the second experiment, the thermal state of the subjects was estimated using Gagge's two-node model with the measured environmental conditions. The validity of the prediction model was confirmed by comparison with the measured subject's physiological responses. The results showed that the conventional SET*, PET, WBGT, and UTCI indices could not fully represent the thermal sensation and comfort in the mist spraying environment, while the two-node model showed accurate prediction results for skin temperature. In conclusion, a concept of new index to assess the thermal sensation of the outdoor and mist spraying environment was proposed by comparing the predicted thermal state of the body and the subjects mTSV (modified thermal sensation vote). The proposed index is expected to estimate the thermal sensation inside and outside of the mist spraying environment only using measured environmental factors.