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A numerical investigation of entropy generation in laminar forced convection of gas flow over a recess including two inclined backward and forward facing steps in a horizontal duct under bleeding condition is presented. For calculation of entropy generation from the second law of thermodynamics in a forced convection flow, the velocity and temperature distributions are primary needed. For this purpose, the 2-D Cartesian co-ordinate system is used to solve the governing equations which are conservations of mass, momentum, and energy. These equations are solved numerically using the computational fluid dynamic techniques to obtain the temperature and velocity fields, while the blocked region method is employed to simulate the inclined surface. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. The numerical results are presented graphically and the effects of bleeding coefficient and recess length as the main parameters on the distributions of entropy generation number and Bejan number are investigated. Also, the effect of Reynolds number and bleeding coefficient on total entropy generation which shows the amount of flow irreversibilities is presented for two recess length. The use of present results in the design process of such thermal system would help the system attain the high performance during exploitation. Comparison of numerical results with the available data published in open literature shows a good consistency.

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This paper presents a numerical investigation for laminar forced convection flow of a radiating gas over an inclined backward facing step in a horizontal duct subjected to bleeding condition. The fluid is treated as a gray, absorbing, emitting, and scattering medium. The two-dimensional Cartesian coordinate system is used to simulate flow over inclined surface by considering the blocked-off region in regular grid. The governing differential equations consisting the momentum and energy are solved numerically by the computational fluid dynamics techniques to obtain the velocity and temperature fields. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. Since the gas is considered as a radiating medium, convection, conduction, and radiation heat transfer mechanisms take place simultaneously in the gas flow. For computation of the radiative term in the gas energy equation, the radiative transfer equation is solved numerically by the discrete ordinate method to find the radiative heat flux distribution inside the radiating medium. The effects of bleeding coefficient, inclination angle, optical thickness, albedo coefficient, and the radiation-conduction parameter on the flow and temperature distributions are carried out.

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The literature devoted to numerical investigation of adsorption of heavy metal ions on carbon nanotubes is scarce. In this paper molecular dynamics is used to simulate the adsorption process and to investigate the effect of the infl uencing parameters on the rate of adsorption. The predictions of the molecular dynamics simulation show that the adsorption process is improved with increasing the temperature, pH of solution, the mass of nanotubes, and surface modifi cation of CNT using hydroxyl and carboxyl functional groups. The results predicted by the model are compared with the experimental results available in the literature; the close agreement validates the accuracy of the predictions. This study reveals that the water layers around the carbon nanotubes and the interaction energies play important roles in the adsorption process. The study also shows that electrostatic force controls the attraction of zinc ions on the nanotube sidewall.

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