Inertia Effects on the Modulated Air Layer Heat and Moisture Transport From Clothing With Open Aperture

A two-dimensional model is developed of the modulated internal airflow in the gap between clothing and skin surface due to walking and in presence of clothing end apertures. The normal airflow renewing the air layer through the fabric is conducted in an oscillatory way during body motion without gross environmental air movement using fabric-three node model [1]. The parallel flow is induced by periodic pressure difference between environment pressure at the aperture of the clothing system and trapped air layer pressure. The parallel flow is assumed locally governed by Womersley solution of time-periodic laminar flow in a plane channel. The three-node fabric ventilation model has been modified to include the diffusion-dominated transport processes in the fabric at low normal flow rates. The low flow rates occurred near the opening and during the periodic ventilation cycle when the airflow rate approaches zero before changing direction in and out of the fabric. The fabric ventilation model and the diffusion model completely overlap at the normal airflow rate of 0.00777 kg/m²·s. The new modified-model has been used in the 1-D steady periodic normal flow model and results have shown good agreement with published experimental data. The 2-D model using Womersley-flow model in the parallel direction has predicted significantly lower flow rates than Poisueille flow model. In addition, the 2-D model predicted the sensible and latent heat loss from the sweating skin in presence of openings in the clothing system. The reported results showed that under walking conditions, a clothing system with an open aperture reduced heat loss from the skin when compared to 1-D normal ventilation model (closed aperture). These results were consistent with previously published empirical data of Lotens [2] and Danielsson [3] on air layer resistance for open and closed aperture of high air permeable fabric.