Effects of Air Velocity and Clothing Combination on Heating Efficiency of an Electrically Heated Vest (EHV): A Pilot Study

Abstract

Cold endangers the heat balance of the human body. Protective clothing is the natural and most common equipment against cold stress. However, clothing for cold protection may be bulky and heavy, affecting human performance and increasing the work load. In such cases, a heated garment with built-in heating elements may be helpful. This pilot study presents a method based on a thermal manikin to investigate the effects of air velocity and clothing combination on the heating efficiency of an electrically heated vest (EHV). An infrared thermal camera was used to detect surface temperature distributions of the EHV on the front and back. Results show that the heating efficiency of the EHV decreases with increasing air velocity. Changes in EHV sequence in the three-layer clothing combination also significantly affect the heating efficiency: it increases with the increasing number of layers on top of the EHV. The highest mean temperature on the inner surface of the EHV was 40.2°C, which indicates that it is safe for the wearers. For the EHV to heat the human body effectively, we suggest that it be worn as a middle layer. Finally, the EHV is especially suitable for occupational groups whose metabolic rate is below 1.9 Mets.

Keywords:

• air velocity
• clothing combination
• cold environment
• electrically heated vest (EHV)
• heating efficiency
• infrared thermography

ACKNOWLEDGMENTS

This work was financially supported by the China Scholarship Council (CSC) and Taiga AB in Varberg, Sweden. The authors would like to thank Kalev Kuklane for his valuable comments on the manuscript. We thank Eileen Deaner for the English language improvements. We are also grateful to the editors and two anonymous reviewers for their valuable comments on an early draft version.