The relationship between air gap sizes and clothing heat transfer performance

Abstract

The objective of the study is to establish a quantitative relationship between air gap sizes and clothing thermal performance. Using a three-dimensional human body scanner, the thicknesses and volumes of air gaps of 35 experimental shirts were measured. Relationships between the thermal insulations of clothing, measured on a thermal manikin, and air gap volumes were examined by regression analysis. Also, the regression model between clothing surface temperatures, measured by an infrared thermal camera, and air gap thicknesses was established. The results proved that the thermal insulation of experimental shirts increased with air gap sizes but began to decrease as a result of natural convection when the air gap thickness was higher than 1 cm or the air gap volume was greater than 6000 cm3. The 3D human body scanner can accurately measure air gaps under clothing, but it is expensive and is not available everywhere. A substitute method is to build a mathematical model for predicting air gap sizes. In this paper, regression models were established to estimate volumes and thicknesses of air gaps when the ease allowances of chest circumference and fabric properties were known. This study can be used to predict the thermal performance of clothing at the product’s design stage.