Efficacy of a novel phase change material for microclimate body cooling

The present study was conducted in order to evaluate the efficiency of personal body microclimate cooling systems based on a phase change materials (PCM) and its effects on physiological strain in soldiers during exertional heat stress in hot environment. The results are obtained in the experiment conducted in the climatic chamber in the Institute of Hygiene, Military Medical Academy in Belgrade. Ten male soldiers were voluntarily subjected to exertional heat stress tests (EHST) consisted of walking on treadmill (5.5 km/h) in hot conditions (40?C) in climatic chamber. The subjects performed first test while wearing a field camouflage uniform without any cooling system ("CONTROL" group) and in second test they used additional microclimate cooling system with paraffin wax consist of n-hexadecane (C16H34), in a form of cooling packs ("COOL" group). As indicators of thermal strain, mean skin (Tsk) and tympanic (Tty) temperature were determined. Simultaneously, thermal effects of PCM were measured by thermal imaging camera. The exercise in hot conditions induced a physiological response to heat stress, manifested through increased body core and skin temperatures. The results confirmed that the cooling vest worn over the field uniform was able to attenuate the physiological strain during exercise, compared to the identical exposure in the ''control'' group. The results of thermal imaging also indicate that heat generated inside the body is the main factor that will affect the phase change material melting time.