The key local segments of human body for personalized heating and cooling

Thermal characteristics of local body parts of a human subject are markedly different in cold or hot environments. Some body segments are known to be much more susceptible to heat loss than the others, thus strongly influencing the overall thermal sensation of a subject. If these body parts can be effectively cooled in a hot environment or warmed in a cold environment using personal environmental control systems, thermal comfort of human occupants can be achieved at the minimum cost of energy without heavily relying on centralized heating, ventilation, and air conditioning systems. With an objective to understand the influence of local thermal sensation on the subjects' overall thermal comfort perception, experiments in the two sets of climate chambers were carried out simulating summer and winter conditions, respectively. A total of 24 subjects (12 females and 12 males) were recruited for this study, and their local skin temperature, conductive heat flux, and thermal sensations were recorded during the experiments. The local thermal characteristics of the subjects were compared between the 'neutral' and 'hot' conditions to identify predominant body segments in the summer scenario. Moreover, the comparison was also made between the 'neutral' and 'cold' conditions to derive predominant body segments in the winter scenario. The analysis of the results indicated that leg, thigh, and back are the key segments desirable for local cooling; whilst leg, thigh, back, and upper arm are the crucial segments for local heating. The findings can have important implications for the design of low-energy cost-effective personal heating/cooling devices. Finally, the results identified the conductive heat flux of skin as a useful physiological parameter in examining human thermal sensation.