Three‐Dimensional Simulation of Mass Transfer in Artificial Kidneys

Abstract

In this work, the three-dimensional velocity and concentration fields on both the blood and dialysate sides in an artificial kidney were simulated, taking into account the effects of the flow profiles induced by the inlet and outlet geometrical structures and the interaction between the flows of blood and dialysate. First, magnetic resonance imaging experiments were performed to validate the mathematical model. Second, the effects of the flow profiles induced by the blood and dialysate inlet and outlet geometrical structures on mass transfer were theoretically investigated. Third, the clearance of toxins was compared with the clearance value calculated by a simple model that is based on the ideal flow profiles on both the blood and dialysate sides. Our results show that as the blood flow rate increases, the flow field on the blood side becomes less uniform; however, as the dialysate flow rate increases, the flow field on the dialysate side becomes more uniform. The effect of the inlet and outlet geometrical structures of the dialysate side on the velocity and concentration fields is more significant than that of the blood side. Due to the effects of the flow profiles induced by the inlet and outlet geometrical structures, the true clearance of toxins is lower than the ideal clearance, especially when the dialysate flow rate is low or the blood flow rate is high. The results from this work are significant for the structural optimization of artificial kidneys and the accurate prediction of toxin clearance.

Finite-Element Modeling of Time-Dependent Sodium Exchange across the Hollow Fiber of a Hemodialyzer by Coupling with a Blood Pool Model

“…In line with these considerations, sodium diffusion across the membrane was modeled as porous media transport, according to theoretical equations [9 and 10]. The Millington and Quirk model (28) was chosen for calculation of the effective diffusivity, as reported in (11). Islam et al (8) estimated porosity for each of the 3 layers composing the membrane of a Polyflux 210H hemodialyzer.…”

“…In 2-dimensional (2D) models, flow and/or concentration fields are computed on a bi-dimensional surface representing the axial and radial directions of the blood-membrane-dialysate interface (4–8). Three-dimensional (3D) models are also reported in the literature (9–11). Models with higher levels of abstraction describe the kinetics of body pools for substances like urea or sodium with ordinary differential equations (ODEs) (3, 12–16).…”

Artificial Organs 2015: A Year in Review

“…Weiping Ding et al of the University of Science and Technology of China, Hefei, Anhui, China simulated the three‐dimensional velocity and concentration fields on both the blood and dialysate sides in an artificial kidney. Their results showed that as the blood flow rate increases, the flow field on the blood side becomes less uniform; however, as the dialysate flow rate increases, the flow field on the dialysate side becomes more uniform.…”

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

“…In the last years, three-dimensional (3-D) models have been developed, based on the concept that the fiber bundle can be treated as two interpenetrating porous media. For example, Ding et al [22] used their model to investigate the effects on mass transfer of inlet and outlet geometrical structures and of the distribution tabs [23]. Also Cancilla et al [24] developed a model that falls into this category for studying the influence of the most relevant parameters and of the operating conditions on the dialyzer's efficiency.…”