A numerical approach to evaluate the personal radiative thermal management of textiles part one: Mid-infrared transmittance, reflection and absorption

Abstract

The infrared radiative heat from the human body accounts for more than 60% of dry heat loss. Textiles with mid-infrared (MIR) transparency can help achieve good radiative personal cooling and potentially save energy on building refrigeration. The interaction between MIR light and textiles is complex, involving fibre materials and yarn structure parameters and a precise computation of the optical characteristics of the textile is required. This paper presents a modelling methodology to predict the MIR transfer behaviour from human skin through a textile by simulating the radiative properties of textiles on the micro-scale. The model was validated qualitatively and quantitatively for transmittance, reflection, and absorption using FTIR data and parametric studies were carried out by varying the yarn diameter and filling factor. The results reveal that: (1) Increasing the yarn diameter results in decreased total transmittance and reflection and increased absorption for both PE and PET fabrics; (2) Increasing the yarn filling factor results in decreased total transmittance and reflection and increased absorption for both PE and PET fabrics; (3) The effect of changing the structural parameters was more dominant for commercial PET fabrics than for radiative cooling PE fabrics.