A new test method for evaluating the evaporative cooling efficiency of fabrics using a dynamic sweating hot plate

Abstract

The lack of direct measures of the ability of a fabric to cool the skin by liquid sweat evaporation is a critical gap in available laboratory tests for evaluating the comfort of active wear clothing materials. This paper describes a novel method designed to evaluate the evaporative cooling performance of fabrics in a protocol that simulates active wear, including sweating and drying periods, in a continuous one-step procedure. It uses a dynamic sweating hot plate to measure the latent heat absorbed by fabrics in sweat evaporation, and in drying after sweat absorption. The efficacy of the method is demonstrated using a selected set of high-wicking polyester and a cotton knit t-shirt material that have different moisture absorption, wicking and drying properties. The cooling efficiency test shows that high-wicking polyester fabrics provide larger evaporative cooling in the sweating phase, where it is more likely to convey cooling benefits to the skin. Cotton fabrics absorb more latent heat in the drying phase, where the cooling effect may contribute to chilling effects. It provides an ideal platform to observe the dynamic relationship between patterns of wicking and liquid moisture spreading in fabrics and the evaporative cooling provided by test materials. It shows that the location of wicked moisture in the fabric is a critical determinant of potential cooling effects. It also shows that a fabric’s wicking ability is not always an accurate predictor of its cooling efficiency. This new test method has provided a unique tool for directly characterizing the cooling efficiency of clothing materials using a protocol that accurately simulate sweating generation and drying in actual active wear scenarios.

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