Effect of moisture transport on mixed convection in vertical annulus of a heated clothed vertical wet cylinder in uniform cross wind

Abstract

Ventilation and heat and moisture transport from a vertical clothed wet and heated cylinder subject to uniform cross wind are studied by modeling and experimentation to investigate the effect of wet cylinder conditions and external wind humidity on renewal rate of the air annulus and its temperature. The coupled parabolic momentum, moisture, and heat balance equations including buoyancy are formulated and solved for uniform surface heating and uniformly wetted inner cylinder boundary to predict the air annulus vertical temperature distribution, moisture evaporation rate from the inner surface, total ventilation through the clothing and the top opening, and sensible and latent heat loss for any given environment conditions, clothing permeability and thermal properties, wind speed and annulus geometry. Experiments were performed in a low speed wind tunnel in which a uniformly heated vertical cylinder covered by a wet stretch fabric enclosed by a clothed outer cylinder is placed in uniform cross flow of known temperature and relative humidity. Good agreement was found between the model and the experimental measurements of sensible and latent heat losses, and air annulus temperature profile. A parametric study is performed to study the effect of moisture on sensible and latent heat loss and the induced mixed ventilation for constant heat flux surface condition of the heated clothed cylinder. The effect of adding wet model effect on the axial mass flow rate in vertical annulus does not exceed 3percent in comparison with dry cylinder mixed convection at the same total heat flux at ambient conditions of 10°C and 50percent relative humidity. For equal heat input to the wet cylinder in comparison to the dry cylinder at ambient conditions of 10°C and 50percent relative humidity, the air layer temperature decreased by 1.51°C and 2.62 °C in air layer temperature for permeabilities of 0.05 and 0.25 m-s when compared to air layer temperature for the dry case. © 2010 by ASME.