Developing predictive framework for human thermal state based on multilevel fuzzy integrated assessment method: Local thermal radiation environments

Abstract

Local thermal radiation in heat treating, glass melting workshops substantially affect the human thermal comfort and thermal responses, causing even the thermal health risks. The accessibility of an effective assessment of human thermal state is crucial for the thermal safety protection. A scoring for thermal state was developed based on the multilevel fuzzy integrated assessment method at three aspects: thermal environment (Air temperature and mean radiant temperature), physiological responses (Heart rate, sweat rate, auditory canal temperature, mean arterial pressure, and skin temperature), and psychological perceptions (Rating of perceived exertion and thermal perception). Scoring of thermal state (STS) was determined to be dependent on the objective weights of each index and the set of nonlinear weights. Twelve experimental cases, including air temperatures of 33 and 36 °C, mean radiant temperatures of 33.6 to 38.3 °C, and metabolic levels of 1.1, 2.9 and 4.3 met, simulated the situations of different work intensities with exposure to local thermal radiation, which were used for the validation of the STS. Results showed that the remarkable contributions of air temperature, radiant temperature, auditory canal temperature, heart rate, sweat rate, and perceived fatigue were the highest in the STS. The STS, validated with the PHS model and the PSI index, allows a well-assessed human thermal state because of its encompassing multifaceted characteristics. This study contributes to the evaluation of hot discomfort in local thermal radiation environments, revisiting the thermal comfort research method.