Effect of Emissivity on the Heat and Mass Transfer of Humid Air in a Cavity Filled with Solid Obstacles

Abstract

Section 6 of the "Repository policy for OpenAIR @ RGU" (available from http://www.rgu.ac.uk/staff-and-currentstudents/library/library-policies/repository-policies) provides guidance on the criteria under which RGU will consider withdrawing material from OpenAIR. If you believe that this item is subject to any of these criteria, or for any other reason should not be held on OpenAIR, then please contact openair-help@rgu.ac.uk with the details of the item and the nature of your complaint. The work reported here is a 2D numerical study on the buoyancy-driven low-speed turbulent flow of humid air inside a rectangular cavity partially filled with solid cylindrical objects for 10 a Rayleigh number of 1.45 Â 10 9 . Variations of Nusselt number, buoyancy flux, vapor mass fraction, and turbulence viscosity ratio are presented for various emissivity values of wall surfaces. It was observed that during the natural convection process, radiation effects are very significant and the air/water vapor combination results in a small increase in heat transfer as compared with the pure natural convection of dry air. 15

Natural Convection Flow and Heat Transfer in an Enclosure Containing Staggered Arrangement of Blockages

“…For all cases, temperature data for the mid-height and mid-width displays a stable core region and hence emphasis is placed on profiles near the walls. The numerical results using the current methodology has already been thoroughly scrutinised and validated against reliable experimental data [17,18] and hence excluded from this paper.…”

“…The geometrical configurations used in these investigations are shown in Fig.1 for 12×6 blockages and are similar to the cavities used in previous investigations [15][16][17]. As can be seen, the objects are stacked as in-line and staggered.…”

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

“…The Discrete Ordinate Method (DOM) [48][49] has been used to simulate the radiative heat transfer between all wall surfaces and the fluid for both the humidified and un-humidified cases. The DOM has been chosen due to its proven superiority in predicting radiative heat transfer involving a participating medium and surface-tosurface radiation as reported by Versteeg and Malalasekera [50] and Iyi et al [51]. The humid air was treated as absorbing-emitting and non-scattering gray medium.…”

“…(13) The change in the average heat transfer coefficient as a function of the variation in the water-vapour content in moist air and the change in the vertical wall temperature gradient can be explained by the mass differential between dry air and water vapour. Since the molecular weight of water is less than that of dry air, an increase in the amount of water vapour in the moist air will increase the buoyancy force which will result in an increase in the convective current inside the cavity [51]. Hence, the species density gradient in the fluid mixture will increase with increasing water vapour content, which leads to the increase in the strength of convective current associated with natural convection flow inside the cavity.…”

Interaction of Radiation and Turbulent Natural Convection: A Pseudo-Direct Numerical Study

“…Turbulent natural convection was computed in terms of the standard kinetic energy and its dissipation rate (k−ε) model. The effect of walls emissivity on turbulent buoyancy driven flow of the humid air in a cavity with cylindrical obstacles was analyzed by Iyi et al [4]. Heat transfer via turbulent natural convection and surface thermal radiation in an enclosure partially filled with a porous medium was studied in [5].…”