On some issues in the computational modelling of spacer-filled channels for membrane distillation

Abstract

This study addresses issues which arise in the computational and experimental modelling of flow and heat / mass transfer in membrane distillation and other processes adopting spacer-filled channels the combined effects of the main parameters that characterize the process (notably spacer pitch to channel height ratio l/H, flow attack angle γ and Reynolds number Re) and the applicability of simple correlations; the influence of the spacer's thermal conductivity. In regard to the complex influence of the parameters, Re, l/H and γ were found to interact heavily, making a separate-effect analysis impossible and power-law friction or heat / mass transfer correlations of little use. Thermal conduction in the spacer, even for low-conductivity polymeric spacers (λ≈0.15 Wm -1 K -1 ), was found to be responsible for up to 10% of the total heat transfer;

Influence of the boundary conditions on heat and mass transfer in spacer-filled channels

“…CFD simulations of spacer-filled channels for membrane processes started to appear in the literature since the year 2001 and have been presented at an increasing rate since then. Hitsov et al [3], Fimbres-Wehis and Wiley [4], Karabelas et al [5] and La Cerva et al [6] have presented reviews addressing a number of issues in the modeling of such channels.…”

Coupling CFD with a one-dimensional model to predict the performance of reverse electrodialysis stacks

“…Due to the compensative sink term SC, C is independent of the specific cross section chosen. The unit cellaveraged mass transfer coefficient k on each wall is best defined[40] as is the wall concentration and {Nw} is the molar flux from the wall into the fluid, both averaged over a specific wall (solution-membrane interface) of the unit cell. Note that {cw} and {Nw} are still, in general, functions of the axial location along the channels, y.Finally, k is made dimensionless as a Sherwood number Sh=k(2H)/D.…”

Toward Incorporation of Membrane Properties Non-Uniformity in Spiral Wound Module Performance Simulators—Effect of Non-Uniform Permeability on Fouling Layer Evolution

“…The proposed approach allows the handling of high-resolution non-uniformities in membrane permeability and fouling layer thickness without a considerable increase of the computational load of the existing simulation approaches. This approach can be also extended to the modeling of other membrane processes (e.g., membrane distillation [32]) that exhibit the same non-uniformity problems. It is important to clarify that the present work refers to intrinsic non-uniformities of the membrane itself.…”