Mohammed A. Antar

Effect of viscosity ratio, spin and Reynolds number on the flow characteristics about a liquid sphere in a gas stream

Boundary‐layer flow around a spinning liquid sphere moving steadily in a gas stream is investigated numerically. The shear stress exerted on the spheres surface results in surface rotation in the meridional direction in addition to the azimuthal velocity resulting from the spinning of the liquid sphere. The parameters controlling the flow around the sphere are the external flow Reynolds number (Re), the liquid‐to‐gas viscosity ratio (μ*) and the spinning parameter (Rer/Re)2. The effect of these parameters on the velocity components (namely the meridional, radial and azimuthal velocity components) and on the shear stress is shown. Moreover, their effect on the location of external flow point of separation is also demonstrated.

The effect of thermal radiation on the heat transfer characteristics of lid-driven cavity with a moving surface

Purpose – There are industrial applications for varying speed lid-driven flow and heat transfer such as the float glass process where the glass film stretches or thickens depending on the desired thickness. Hence the tin cavity underneath or the nitrogen cavity above is being driven by a variable speed. The purpose of this paper is to simulate such behavior. Design/methodology/approach – Numerical solution of variable speed lid-driven cavity is carried out with thermal radiation being considered using control volume approach and staggered grid and applying the SIMPLE algorithm. Transient simulation is used for 2D model in the present study. Second order upwind schemes were used for discretization of momentum, energy equations and time. Findings – Under laminar conditions, thermal radiation plays a significant role in the heat transfer characteristics of the lid-driven cavity. This effect is more significant for blackbody radiation and decreases as the surface emissivity decreases. Nusselt number (Nu) beha...

Carbon dioxide adsorption separation from dry and humid CO2/N2 mixture

Abstract In this study, we report the effect of water vapor on CO2 uptake using Mg-MOF-74 via adsorption breakthrough modeling and lab experiments. Carbon dioxide is the most influencing gas that significantly expedites global warming. Therefore, it is ultimately necessary to reduce the rapid increase of CO2 concentration in the atmosphere by means of Carbon Capture and Storage (CCS). CO2 separation by physical adsorption is an interesting technology to achieve CO2 capture with minimum energy penalties. Metal-organic framework (MOF) adsorbents forms a class of adsorbents with much higher specific surface areas than conventional porous materials such as activated carbons, and zeolites. However, most MOFs show notable hydro instability for CO2 separation from humid flue gas. Mg-MOF-74 is a superior adsorbent amongst other adsorbents owing to its high CO2 uptake at flue gas conditions. A model is developed using User-Defined-Function in an ANSYS Fluent program. Two and three-dimensional models are validated by comparing their results with experimental work carried out by the authors, at ambient temperature, and published experimental data for high temperature conditions. The effect of water vapor is studied at different temperatures and various relative humidity values for Mg-MOF-74. Results indicate that CO2 uptake has been significantly reduced with the existence of more than 5% water vapor when Mg-MOF-74 is used as an adsorbent.

Investigation of the Effect of the Top and the Bottom Temperatures on the Performance of Humidification Dehumidification Desalination Systems

Humidification dehumidification process is an attractive small scale water desalination technique in which desalinated water is produced by mimicking the nature’s water cycle. Various modifications to the basic HDH system can be vital in improving the productivity and reducing the production cost of the fresh water. In this study, a closed-air-open-water water-heated (CAOW-WH) cycle and a closed-air-open-water air-heated (CAOW-AH) cycle are modeled and optimized. Effects of mass flow ratio, humidifier and dehumidifier effectiveness, relative humidity, top and bottom temperatures (main concern of study) on the gain output ratio (GOR), the recovery ratio (RR), entropy generation in the system have been analyzed and presented. It has been observed that an optimal mass flow ratio exists for both the cycles, which maximizes the GOR of the system. Moreover, effectiveness of the humidifier and the dehumidifier is an important parameter, which determines the productivity of the systems. Furthermore, a higher GOR can be obtained at low Tmin and high Tmax and at high Tmin and low Tmax for systems heated by a water heater, whereas the GOR of the air heated HDH system increases with increasing both the Tmin and the Tmax for values of humidifier and dehumidifier effectiveness of 0.8. This study provide extended design charts for building an optimum HDH system to produce a pre-determined rate of desalinated water.Copyright