Evaluating the cold protective performance (CPP) of an electrically heated garment (EHG) and a chemically heated garment (CHG) in cold environments

This study investigated the cold protective performance (CPP) of two types of heated garments using a Newton manikin operated in constant temperature mode (CT) and thermoregulatory model control (TMC) mode. The effect of two levels of air velocity (i.e., 0.4±0.1 m/s and 1.0±0.1 m/s) on the CPP was discussed. Five scenarios were chosen, the traditional cold protective ensemble (CON), the electrically heated garment (EHG), the non-heated electrically heated garment (EHGCON, heating was turned off), the chemically heated garment (CHG) and the non-heated chemically heated garment (CHGCON) (completely oxidized body warmers were used). All experiments were performed at ta=2.0±0.3 oC and RH=80±5 %. Results demonstrated that both EHG and CHG could provide improved cold protection compared to the nonheated garments, evidenced by the significantly higher thermal insulation in EHG and CHG at both two air velocities (p<0.01). The air velocity has a minor effect on the effective heating power and the heating efficiency, but it significantly reduced the total clothing thermal insulation. EHG exhibited a significantly higher effective heating power and thermal insulation compared to the CHG only under the low air velocity (p<0.05). Additionally, higher skin temperatures and improved whole body and local thermal sensations were observed in both EHG and CHG compared to CON. The EHG compared to CHG, showed similar thermophysiological and psychological responses at 1.0±0.1 m/s (p>0.05). It was thus anticipated that both two heated garments could improve human wear thermal comfort in cold environments.