UNCORRECTED PROOF 2 Ventilation rates of micro-climate air annulus of the 3 clothing-skin system under periodic motion 4 N. Ghaddar a, * , K. Ghali b , J. Harathani a , E. Jaroudi a 5 a Department of Mechanical Engineering, American University of Beirut, P.O. Box 11-0236, Beirut 1107-2020, Lebanon 6 b Department of Mechanical Engineering, Beirut Arab University, Beirut, Lebanon 8 Abstract 9 A novel three-dimensional dynamic model is developed from first principles of mass and energy conservation of the 10 modulated internal airflow in the variable annulus size between the clothing and the skin surface in presence of clothing 11 apertures. The developed model solves for the flow and heat transfer problem in a finite length cylindrical annulus 12 where the inner cylinder is oscillating within an outer fixed cylinder of porous fabric boundary. The changing annulus 13 size induces pressure variations that cause air flow in the angular and the radial directions. In addition, axial airflow is 14 present due to clothing open aperture to the atmosphere at one end of the annulus (sleeve or neck opening). The axial 15 and angular flows in the trapped air layer are assumed locally governed by Womersley solution of time-periodic laminar 16 flow in a plane channel in each direction. The 3-D model predicted the ventilation radial airflow through the fabric, the 17 angular and axial airflow induced by the motion of the inner cylinder, and the sensible and latent heat losses from the 18 skin due to ventilation with the presence of an open or closed aperture. Experiments were conducted using tracer gas 19 method to measure time and space-averaged air ventilation rates induced by inner cylinder periodic motion within a 20 fabric cylindrical sleeve at spacing amplitude ratio with respect to the mean of 0.8 for both closed and open aperture 21 cases. 22 The ventilation rates within the annulus predicted by the 3-D model agreed well with experimental data at higher 23 frequencies. For closed aperture situation at an amplitude ratio of 0.8, the mean percentage errors of the measurements 24 compared with the predicted values of the model were 52%, 27.5% and 6.7% corresponding to the frequencies of 30 25 rpm, 40 rpm, and 60 rpm, respectively. Measured ventilation rates for open aperture agreed well with predicted venti- 26 lation rates at high frequencies giving lower values of total air renewal than the closed aperture results where the mea- 27 sured reductions in total ventilation rate compared to closed aperture were 8.5% and 14.3% corresponding to the 28 frequencies of 40 rpm and 60 rpm, respectively. In addition, the model results showed that under walking conditions, 29 a permeable clothing system with an open aperture reduced the heat loss from the skin by less than 1% when compared 30 to the closed aperture clothing system. These results are consistent with previously published empirical data on air layer 31 resistance for open and closed aperture of high air permeable fabric. 32 Ó 2005 Elsevier Ltd. All rights reserved. 33 Keywords: Clothing ventilation model; Modulated microclimate air layer; Womersley flow; Steady periodic heat transfer in clothing 34 0017-9310/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijheatmasstransfer.2005.03.001 * Corresponding author. Tel.: +961 1 350000x3594/3590; fax: +961 1 744 462/642. E-mail address: farah@aub.edu.lb (N. Ghaddar). URL: http://webfaculty.aub.edu.lb/~farah/ (N. Ghaddar). International Journal of Heat and Mass Transfer xxx (2005) xxx–xxx www.elsevier.com/locate/ijhmt HMT 4788 No. of Pages 16, DTD = 5.0.1 30 March 2005 Disk Used ARTICLE IN PRESS