Experimental and numerical investigation on the effect of ease allowance of clothing on thermal comfort

Abstract

The heat transfer within the microclimate of clothing directly affects the thermal sensation of the human body, holding significant implications for both heat dissipation and cold protection. To investigate the variations in the heat transfer performance of the microclimate under the clothing influenced by distinct air gap thicknesses and diverse body postures, twelve female subjects participated in experiments wearing T-shirts with various ease allowances, conducting tasks in both sitting and standing positions within a climate chamber set at 20 °C and 50 % RH. Physiological parameters and subjective evaluations of comfort were recorded. Additionally, we constructed a three-dimensional model of the air gap featuring realistic morphology for numerical simulations of microclimatic heat transfer in a standing posture. The experimental results indicate that air gap thickness significantly impacts core temperature, mean skin temperature, local skin temperature, and thermal sensation. While postural differences did not show statistical significance, temperatures and thermal sensations were generally higher in the sitting position. Based on the results of numerical simulation, under this environmental condition, approximately 27 % of heat transfer was through radiation, with both the percentage of radiative heat transfer and the overall heat flux increasing with greater ease allowance. Furthermore, airflow under the clothing became more disorganized at thicker air layers, primarily concentrating in folds, hems, and sides of the body. This study provides a theoretical support for the workwear design and similar clothing and helps to reduce energy consumption in office environments.