The effect of forced convection and PCM on helmets' thermal performance in hot and arid environments

Safety helmets are essential Personal Protecting Equipment (PPE) in all industrial and construction sites. When temperature and humidity levels are high, users' thermal comfort is adversely affected. This paper examines the utilization of forced convection and Phase Changing Material (PCM) to control the thermal comfort of helmet users. An experimentally validated three-dimensional Computational Fluid Dynamics (CFD) model of an industrial helmet and a human head was utilized to assess the helmet thermal performance under different harsh working environments. The standard k-epsilon turbulence model was used to investigate the helmet cooling performance and to assess the user's thermal comfort at different ambient conditions. Energy and mass conservation equations were implemented in the calculation. The effect of solar radiation, forced convection and PCM integration at different incident wind speeds on the helmet's thermal performance was assessed. The effect of sweating on mass and heat transfer of the modeled human head skin was examined. Results concluded that forced convection decreased the maximum temperature on the helmet outer surface by about 10 degrees C. The PCM embedded in the helmet proved to prolong the thermal comfort period. Findings highlighted that the heat generated from the head is the dominant factor affecting the melting time of the PCM. (C) 2016 Elsevier Ltd. All rights reserved.