Mixed convection heat transport from multi-cylinders finds numerous applications in chemical, petroleum, and food industries. This study presents the mixed convection characteristics of an inline array of heated circular cylinders in non-Newtonian power-law fluids for the following governing parameters: fluid volume fractions; 0.70≤ φf ≤0.99, power-law index; 0.4≤ n ≤ 1.8, Reynolds number; 1≤ ReD ≤40, Prandtl number; 1≤ PrD ≤50 and Richardson number; 0≤ RiD ≤2. Mathematical model equations are solved using the Finite Volume Method within the framework of Boussinesq approximations. Thermal features are explored using isotherms, local and averaged Nusselt numbers. Qualitatively, isotherms display a complex relationship with the governing parameters. Local and average Nusselt numbers improve with increasing Reynolds, Prandtl and Richardson numbers, shear-thinning natures. An opposite nature is noted for shear-thickening fluids. Nusselt numbers were further improved with increased fluids volume fractions contrary to decrease in forced convections cases. At maximum Reynolds, Prandtl and Richardson numbers, Nusselt number increased by 30.53% and 13.11% for shear-thinning (n = 0.4) fluids, respectively for φf = 0.70 and 0.99. An unsteady nature was also found in shear-thinning regions at larger volume fractions. Lastly, statistical analysis is presented for the average Nusselt numbers to depict additional physical insights of the numerical outcomes.

The thermal characteristics of incompressible non-Newtonian power-law fluids across periodic array of circular cylinders have been examined using the finite volume-based numerical solver ANSYS-FLUENT for the following ranges of physical parameters: Reynolds number; 1 ≤ Re ≤ 40: Prandtl number; 1 ≤ Pr ≤ 100: power-law index; 0.40 ≤ n ≤ 1.8; and fluid volume fractions ranging from 0.70 to 0.99. The thermal features have been described via isotherm patterns, local and average Nusselt numbers and the Colburn heat transfer factor and found to be strongly dependent over the above physical parameters. It was observed that the dense isotherms with the increasing inertial and viscous diffusion suggest an improvement in the rate of heat transfer across the periodic cylinders. An increase in local Nusselt number was seen with the increasing values of Re and/or Pr across all the fluid volume fractions. Further, the different behavior of the average Nusselt number was noticed because of the shear-thinning and shear-thickening natures. An enhancement of about 97% was noticed in the shear-thinning region between the extreme fluid volume fractions for the highest value of Pr and the lowest values of Re and n . However, in many cases, the enhancement was noticed to be even more than 100%. An empirical correlation for the average Nusselt number and the Colburn heat transfer factor ( j H ) has been developed to give the additional physical insight of the results. Finally, the comparison was made with the available literature which displayed a good agreement with the present results.

Aiding buoyancy mixed convection features of Newtonian fluids across a periodic array of heated cylinders have been studied numerically using a commercial CFD solver ANSYS FLUENT. The governing equations have been solved for the following ranges of physical parameters: Reynolds (1 <= Re <= 40), Prandtl (0.70 <= Pr <= 50) and Richardson (0 <= Ri <= 2) numbers and fluid volume fractions of 0.70-0.99. Qualitatively, the dense and curved streamlines and isotherms were seen with the increasing inertial (Re), viscous diffusion (Pr) and buoyancy parameter (Ri) across all the fluid volume fractions. The drag coefficients were observed to be diminished with an upturn in Re and fluid volume fractions, whereas an opposite behavior was noticed with rising in Pr and buoyancy parameter. The Nusselt numbers were found to be enhanced with Re and Pr numbers and moreover with fluid volume fractions also as in contrast to forced convection (Ri = 0) cases. Aiding buoyancy enhances flow as well as heat transfer features and yields unsteady behavior also at the higher fluid volume fractions and Re for all the values of Pr and Ri numbers. Moreover, statistical correlations have been developed for the total drag coefficient and average Nusselt number to gain the more physical insight of the results. Lastly, the findings have been compared with the literature which displayed the good agreement within the ranges of parameters studied herein. (C) 2018 Elsevier Ltd. All rights reserved.

We have prepared a cross-linked polystyrene anion exchange composite membrane for the electrolysis of sodium chloride to produce sodium hydroxide by selective removal of chloride ions. The composite membrane is homogeneously modified by gas phase nitration, followed by amination using hydrazine hydrate, and further reaction with dichloroethane and triethylamine to introduce quaternary ammonium charges on it. We showed that the membrane is specific to the transport of chloride ions through its pores. The performance of the membrane has been evaluated in terms of current efficiency and power consumption, and the effect of various parameters like current density, initial salt concentration, and circulation rate is studied. The maximum current efficiency obtained is 96.5% and the corresponding power consumption is 0.1216 kWh/mol at 5.2 N initial salt concentration and current density of 254 A/m(2). (c) 2008 American Institute of Chemical Engineers.