Numerical investigation of the effect of moisture on buoyancy-driven low turbulence flow in an enclosed cavity.

Highlights • The effect of moisture content on natural convection flow in a cavity with differentially heated vertical and conducting horizontal walls was investigated. • Natural convection flow and heat transfer are very sensitive to the level of moisture present in the air and even at low temperature gradient between the cavity vertical walls. • The presence of moisture causes changes in the energy equation, which has a significant effect on the heat transfer coefficient and influences the weak natural convection flows inside the cavity. • The vertical walls have been found to show greater sensitivity for heat transfer with changes in moisture content, while both horizontal walls are almost insensitive to moisture content variation. • The heat transfer coefficient increases proportionally with increasing moisture concentration, while the average relative humidity inside the cavity significantly reduces with increasing temperature gradients between the vertical walls of the cavity. Abstract This paper reports a numerical investigation of low turbulence buoyancy-driven flow of moist air and heat transfer inside a rectangular cavity with differentially heated vertical walls. The variations of the flow, temperature and moisture inside the cavity has been analysed together with heat transfer coefficients for a range of mass fraction of water vapour and temperature gradients between the vertical walls of the cavity. The accuracy of the numerical methodology was also scrutinised by conducting a rigorous validation study of benchmark experimental data for the average Nusselt number for similar buoyancy driven cavity flow. The results of this investigation showed that during the natural convection process, the change in moisture content in the moist air has a significant influence on the flow and temperature fields inside the enclosure and the variation of the vertical wall temperature gradients have also shown to affect the moisture concentration inside the cavity. The percentage change in the average heat transfer varied significantly depending on the mass fraction of moisture in the air and the temperature gradient between the vertical walls. The results also showed a 3.5% increase in the average heat transfer for every 0.02 kg/kg increment in the mass fraction of water vapour. The findings from the study are significance to scientists and practitioners who are responsible for moisture management in enclosed space at the design threshold and for optimisation of energy used in buildings. [ABSTRACT FROM AUTHOR]