The effect of four cooling strategies on cooling performance of a hybrid personal cooling system (HPCS) incorporated with phase change materials (PCMs) and electric fans in a hot environment (i.e., Tair = 36 ± 0.5 °C, RH = 59 ± 5%) was investigated. Twelve healthy young male participants underwent four 90-min trials comprising 70 min walking and 20 min resting periods. Cooling strategies adopted in this work were CON (control), PCM-control (PCMs were removed at the end of exercise), Fan-control (fans were switched OFF during the initial 20 min) and PCM&Fan-control (fans were turned ON after 20 min exercising and PCMs were removed after the 70-min exercise). Results demonstrated that the control of electric fans could suppress the mean skin temperature rise to 34.0 °C by over 15 min and also cut down the energy consumption of the HPCS from 15.6 W h to 12.1 W h over the entire 90-min trials. Thus, it is recommended that fans should be turned off at the beginning of hot exposure and switched on once participants felt warm. Our findings also showed that the removal of fully melted PCM packs from the HPCS could enhance the evaporative cooling effect brought about by air circulation. The removal of melted PCMs significantly reduced the physical load by 37.3% and ratings of perceived exertion (RPE) were decreased by 3.5-4.2 RPE units. This could also help quickly restore the PCM energy for future usage. In summary, cooling strategies demonstrated in this work could improve HPCS's overall cooling performance on workers while working in the studied hot environment.
Keywords: Cooling strategy; Electric fan; Hot environment; Hybrid cooling; Perceptual response; Phase change materials (PCMs).
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