Evaluation of Heating Protocols and Body Regions with Graphene Heater for Cold Protective Clothing

Abstract

The purpose of this study was to evaluate the effects of intermittent and continuous heating protocols using graphene heated clothing and identify the more effective body region for heating in a cold environment. The current study consisted of three parts. First, we examined the permissible temperature of graphene heater on the chest, upper back, respectively for human application. Two young males participated in two experiments consisted of chest heating and upper back heating at an air temperature of 0.4oC with 41%RH. The temperature of graphene heater was increased by controlling the voltage. The permissible temperature of graphene heater for human application was decided to be around 45oC considering pain sensation, subjective perceptions and the prevention of skin burn injury. Second, we developed intermittent heating protocol according to electric power consumption. Electric power was set at 0.18, 0.71, 1.61, and 2.86 W with the voltage of 5, 10, 15, and 20 V per graphene heater, respectively. Tests were conducted at an air temperature of 30oC with 10%RH. Five intermittent heating protocols were developed with different electric power consumptions. For the continuous heating protocol (CP), 20 V during 60 min generated an electric power of 8.58 W from three graphene heaters. For the intermittent heating protocols, electric power was 5.28, 5.49, 2.49, 5.10, and 2.94 W for IP-1, IP-2, IP-3, IP-4, and IP-5, respectively. The results showed that the electric power consumption of the IP-3 (2.49 W) was conserved by 71% compared to the continuous protocol (8.58 W). Based on the results, IP-3 was selected for the following human wear trials. Lastly, we evaluated in the following five graphene heating protocols in human wear trials: no heating, continuous heating the chest, continuous heating the back, intermittent heating the chest, and intermittent heating the back. Eight males participated in the experimental protocol consisting of 10 min rest on a chair at an air temperature of 25oC with 28%RH and 60 min cold exposure at an air temperature of 0.6oC with 40%RH. Rectal temperature, cardiovascular and respiratory responses showed no significant differences among the five heating conditions while heating the back showed more beneficial effects on skin temperatures than heating the chest. In summary, to keep a balance between saving electric power and minimizing thermal discomfort in cold environments, intermittent heating the back is recommended.