Contact cooling for bare feet using floor cooling systems: Experiment on human thermal physiology and sensation in Japanese hot environment

Abstract

This study clarifies the contact cooling effect of bare feet on human thermal physiology and sensation using a floor cooling system under hot environments. An experiment was conducted with 14 healthy young men and women using a water-cooled floor panel to investigate the cooling effects under Japanese summer conditions. The results revealed that the influences of the room temperature on the physiological parameters including blood flow, mean skin temperature, and sublingual temperature were more sensitive than that of the floor temperature. Nevertheless, the contact cooling of the soles with the floor temperature of 28 °C reduced the percentage of “very hot” and “hot” sensations of the entire body by 15.5 % when the room temperature was 30 °C. Moreover, the contact cooling of the soles at the room temperature of 30 °C increased heat flow from the soles while maintaining constant blood flow when the floor temperature was decreased. Thus, contact cooling of the soles was confirmed to be effective for heat mitigation in hot environments. However, the contact cooling was likely to cause thermal discomfort owing to the cold sensation as the room temperature decreased to 24 °C. Individual differences, in addition to the sex differences, occurred in the contact cooling effects on blood flow and skin temperature. Individual differences in blood flow were primarily caused by differences in basal metabolism and muscle mass. Further energy savings for space cooling and improved thermal comfort will be achieved by considering the individual differences for the floor cooling systems.