Study on the Performance of Personal Heating in Extremely Cold Environments Using a Thermal Manikin

Cold protection for outdoor workers is crucial for their health and thermal safety in winter. Personal heating is considered an effective measure to solve the problem, which can significantly improve thermal comfort. However, according to the present studies, a uniform assessment of different personal heating measures is hard to obtain. This study explored four typical types of personal heating measures (electrically heated garment, electrically heated garment with an aerogel layer, electrically heated seat, and chemically heated insole) in different cold environments. Clothing insulation, effective heating power (Peff), and heating efficiency (η) were measured by a thermal manikin with a constant temperature in nine environmental conditions. Three levels of two critical environmental factors (air temperature (Ta): −5 °C, −10 °C, and −15 °C; air velocity (Va): <0.1 m/s, 0.5 m/s, and 1.0 m/s) were crossed orthogonally to form the nine environmental conditions. The results indicated that Ta had no significant effect on clothing insulation, while elevated Va significantly decreased clothing insulation. When Va increased from 0 m/s to 1 m/s, the air layer inside the garment was squeezed, causing a 0.6–0.9 clo decrease in total clothing insulation. Decreased Ta and elevated Va reduced the Peff and η of electrical heating measures while they improved the Peff and η of chemical heating insoles. The Peff and η of the garment dropped to 8.2 W and 21%, respectively, at −15 °C and 1.0 m/s. In addition, the aerogel layer could effectively improve the Peff and η of the garment. The improvement was weakened by decreased Ta and elevated Va. The corrective power values of personal heating measures in different environments were calculated to guide the design and application of personal heating.