Investigation on the thermal insulation and evaporative resistance of outdoor backpacks based on a sweating thermal manikin

The thermal insulation and evaporative resistance of backpacks are vital for users' physical performance and safety. In hot humid weather, users carrying a backpack with high thermal insulation and evaporative resistance may face the risk of heat stress, such as heat stroke. However, few studies have investigated the thermal insulation and evaporative resistance of backpacks. In this study, a sweating thermal manikin was employed to evaluate the thermal insulation and evaporative resistance of backpacks. Four backpack samples with different back panel designs were tested under two load conditions (0 and 5 kg), two wind speeds (0.3 and 1.5 m/s), and two body movement levels (inactive 0 km/h and walking at a 2.5 km/h speed). Test results showed that the back panel designs fundamentally determined the thermal insulation and evaporative resistance. Both the air-permeable design of the back panel's filling material and the ventilation design of the back panel structure could improve the heat dissipation performance of the backpack. However, the ventilation designs that formed tunnels with openings between the backpacks and the human body showed more efficient heat dissipation. In practical application, the resultant thermal insulation and evaporative resistance were affected by the load condition, wind speed, and body movement. However, backpacks with better ventilation were less affected by external conditions. The findings of this study provide fundamental knowledge to improve the heat dissipation property of outdoor backpacks.