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RESEARCH PAPERS: Heat and Mass Transfer

Heat and Moisture Transport Through the Microclimate Air Annulus of the Clothing-Skin System Under Periodic Motion

[+] Author and Article Information
K. Ghali

Department of Mechanical Engineering, Beirut Arab University, Beirut, Lebanon

N. Ghaddar1

Department of Mechanical Engineering, American University of Beirut, P.O. Box 11-0236, Beirut 1107-2020, Lebanonfarah@aub.edu.lb

E. Jaroudi

Department of Mechanical Engineering, American University of Beirut, P.O. Box 11-0236, Beirut 1107-2020, Lebanon

1

Corresponding author.

J. Heat Transfer 128(9), 908-918 (Feb 10, 2006) (11 pages) doi:10.1115/1.2241811 History: Received July 12, 2005; Revised February 10, 2006

The study is concerned with the heat and moisture transport in a ventilated fabric-skin system composed of a microclimate air annulus that separates an outer cylindrical fabric boundary and an inner oscillating cylinder representing human skin boundary for open and closed aperture settings at the ends of the cylindrical system. The cylinder ventilation model of Ghaddar (2005, Int. J. Heat Mass Transfer, 48(15), pp. 3151–3166) is modified to incorporate the heat and moisture transport from the skin when contact with fabric occurs at repetitive finite intervals during the motion cycle. During fabric skin contact, the heat and moisture transports are modeled based on the fabric dry and evaporative resistances at the localized touch regions at the top and bottom of points of the cylinder. Experiments were conducted to measure the mass transfer coefficient at the skin to the air annulus under periodic ventilation and to measure the sensible heat loss from the inner cylinder for the two cases of fabric-skin contact and no contact. The model predictions of time-averaged steady-periodic sensible heat loss agreed well with the experimentally measured values at different frequencies. The model results showed that the rate of heat loss increased with increased ventilation frequency at fixed (=amplitude/mean annular spacing). At amplitude factor of 1.4, the latent heat loss in the contact region increased by almost 40% compared to the loss at amplitude factor of 0.8 due to the increase in fabric temperature during contact. The sensible heat loss decreased slightly between 3% at f=60rpm and 5% at f=25rpm in the contact region due to higher air temperature and lack of heat loss by radiation when fabric and skin are in touch. The presence of an open aperture has a limited effect on increasing the total heat loss. For an open aperture system at amplitude factor of 1.4, the increase in heat loss over the closed apertures is 4.4%, 2.8%, and 2.2% at f=25, 40, and 60rpm, respectively.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the physical domain of the fabric-air layer-skin system when (a) fabric does not touch the inner cylinder and (b) fabric is in contact with the inner cylinder at θ=0deg and θ=180deg

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Figure 2

The computational grid

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Figure 3

A schematic of the experimental setup

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Figure 4

The measured space-averaged temperatures with time of the skin and air layer at 60 and 80rpm

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Figure 5

The predicted and measured time- and space-averaged skin and air layer temperature as a function of the ventilation frequency at ζ=0.8

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Figure 6

The predicted and measured time- and space-averaged skin and air layer temperature as a function of the ventilation frequency at ζ=1.4

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Figure 7

The variation of (a) the steady periodic time-averaged lumped air layer temperature and (b) steady periodic time-averaged fabric temperature as a function of the angular position θ for the ventilation frequencies of 25, 40, and 60rpm at ζ=0.8 and 1.4

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Figure 8

The variation of the steady periodic time-averaged (a) sensible and (b) latent heat loss as a function of the angular position θ for the ventilation frequencies of 25, 40, and 60rpm at ζ=0.8 and ζ=1.4

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Figure 9

The 2-D ventilation model predictions as a function of the amplitude ratio ζ of (a) the time-space-averaged total ventilation rate in the microclimate and (b) the time-space-averaged sensible and latent heat loss in W∕m2 at f=25, 40, and 60rpm

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Figure 10

A plot of (a) the total ventilation rate versus the amplitude ratio at different frequencies of motion and (b) the time- and θ-space-averaged radial flow rate variation in the axial direction at different amplitude ratios for f=25, 40, and 60rpm at ζ=0.8 and ζ=1.4

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Figure 11

The variation of the steady periodic time and angular-space-averaged (a) sensible and (b) latent heat loss as a function of the axial position x for the ventilation frequencies of 25, 40, and 60rpm at ζ=0.8 and ζ=1.4

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