Performance Comparison of Alternative Hollow-Fiber Modules for Hemodialysis by Means of a CFD-Based Model

Abstract

Commercial hemodialyzers are hollow-fiber cylindrical modules with dimensions and inlet–outlet configurations dictated mostly by practice. However, alternative configurations are possible, and one may ask how they would behave in terms of performance. In principle, it would be possible to depart from the standard counter-flow design, while still keeping high clearance values, thanks to the increase in the shell-side Sherwood number (Sh) due to the cross-flow. To elucidate these aspects, a previously developed computational model was used in which blood and dialysate are treated as flowing through two interpenetrating porous media. Measured Darcy permeabilities and mass transfer coefficients derived from theoretical arguments and CFD simulations conducted at unit-cell scale were used. Blood and dialysate were alternately simulated via an iterative strategy, while appropriate source terms accounted for water and solute exchanges. Several module configurations sharing the same membrane area, but differing in overall geometry and inlet–outlet arrangement, were simulated, including a commercial unit. Although the shell-side Sherwood number increased in almost all the alternative configurations (from 14 to 25 in the best case), none of them outperformed in terms of clearance the commercial one, approaching the latter (257 vs. 255 mL/min) only in the best case. These findings confirmed the effectiveness of the established commercial module design for the currently available membrane properties.

Hydrophilic Modification of Dialysis Membranes Sustains Middle Molecule Removal and Filtration Characteristics

“…The core element of the dialyzer is the membrane, which may differ substantially between dialyzers used in clinical practice. Membrane features, such as material and composition, geometry, or man-ufacturing, including the sterilization method, influence the initial membrane performance and its stability during treatment time [12][13][14][15][16][17][18][19]. In contrast to the early era of hemodialysis treatments with cellulose-based or synthetic low-flux membranes, advances in dialyzer technology have led to the development of synthetic high-flux membranes [11,14,15,54,55].…”

“…To achieve the treatment targets that were shown during the CONVINCE trial to impact patient outcomes, the dialysis session must be performed with a dialyzer that enables high ultrafiltration volumes and high middle molecule removal [11]. Dialyzer performance is mainly determined by the dialyzer membrane, which may differ in material composition, geometry, or structure, including the pore size and properties of the blood-facing surface [12][13][14][15][16][17][18][19]. Different dialyzers for the treatment of dialysis patients are available on the market, consisting of synthetic (e.g., polysulfone, polyethersulfone, polyacrylonitrile (PAN), polymethylmethacrylate (PMMA), polyester polymer alloy (PEPA), or ethylene-vinyl alcohol co-polymer (EVAL)) or cellulose-based membranes, which may differ in their physical properties, such as in terms of hydrophilicity, membrane potential, or permeability [13][14][15][16][17][20][21][22][23].…”

CFD Modeling of Heat Exchanger with Small Bent Radius Coils Using Porous Media Model

“…In paper [11], several alternative geometries of hemodialysis modules were simulated by means of a computational fluid dynamics model. This is based on a porous media treatment and accounts for both diffusive and convective (ultrafiltration) fluxes.…”

Computational Fluid Dynamics Analysis of a Hollow Fiber Membrane Module for Binary Gas Mixture

“…Due to high market demand, the membranes are used for commercial applications to separate gaseous mixtures and are less economical [14,15]. Membrane gas separation has many applications such as Gases 2023, 3 hydrogen recovery in refineries, sour gas treatment, hydrogen recovery from ammonia, air separation for oxygen purification, and carbon dioxide removal from natural for large scale [16]. In heavy oil and petrochemical industries, membrane systems have integrated with other industrial units, but the scenarios for different groups are limitless.…”

“…Membrane module design is also essential for improving the efficiency of gas permeation performance through the membrane [25]. The CFD technique has been used for flow behavior in the rectangular channel with different feed spacers [16,26]. Many researchers have studied the flow characteristics of membrane modules for gas separation processes.…”