Effects of local heating of body on human thermal sensation and thermal comfort

Abstract

Cold climates are conductive to heavy reliance on mechanical heating, increasing energy consumption. The use of personalized local heating can save energy, but the thermal perception capabilities of different body parts to local heating remain unclear. In this study, 32 participants wore clothing with an insulation rating of 0.9 Clo in a cool environment maintained at 19 °C. Each of seven body parts (back, chest, belly, waist, buttock, knee, and foot) was locally heated for 15 min using a heating pad taped to the outside of the undergarment at a temperature of 32±1 °C. The overall and local subjective thermal perceptions were captured using a questionnaire. Local heating devices with fixed surface temperatures significantly improved thermal sensation and comfort in cool environments. Heating the waist was associated with a significant improvement in overall thermal perception (p < 0.05), while heating the knee and chest showed the least improvement. Heating the waist increased the overall thermal sensation from slightly cool (−0.78) to neutral (0.26) and the overall thermal comfort from slightly uncomfortable (−0.50) to slightly comfortable (0.47), which was better than heating the foot. The effect of local heating was different between genders, with improvements being characterized as increased thermal sensation for men and increased thermal comfort for women. Local heating also reduced the heart rate, again with this reduction varying with the body part being heated. The acceptability of local heating was 81%, showing that it can be widely used in practice.