Read the article and write a 500 word summary including the following. 1-Discuss

Question

Read the article and write a 500 word summary including the following.

1-Discuss mass transfer in the artificial kidney (hemodialysis). What are the governing equations? How is performance measured?

2-Identify three ways that you would propose to improve the efficiency of hemodialysis.

Thoughts and Progress Three-Dimensional Simulation of Mass Transfer in Artificial Kidneys this work are significant for the structural optimization of artificial kidneys and the accurate prediction of toxin clear ance. Key Words: Artificial kidney-Magnetic reso- Mass transfer-Clearance-Hollow fiber nance imaging The artificial kidney is the core of hemodialysis. It usually consists of a bundle of hollow fibers encapsu- lated in a cylindrical cartridge, and it can remove uremic toxins and excess water for patients with kidney failure using diffusion and convection. To l of Mechatronics Engineering,improve the flow field in artificial kidneys and University of Electronic Science and Technology of thereby enhance the clearance of toxins, understand- China, Chengdu, Sichuan, China Departments of ing the velocity and concentration profiles in artificial *Weiping Ding, *Weili Li, Sijie Sun, §Xiaoming Zhou, **Peter A. Hardy ,,Suhail Ahmad, and #Dayong Gao Center for Biomedical Engineering and Department of Electronic Science and Technology University of Science and Technology of China, Hefei, Anhui; SSchool Bioengineering and # Mechanical Engineering, University of Washington; Scribner Kidney Center, Seattle, WA; and **Center for Biomedical Engineering, University of Kentucky, Lexington, KY, USA kidneys has been the focus of many studies (1-3) Computed tomography (CT) and magnetic reso- nance imaging (MRI) technologies have been used to detect velocity or concentration profiles in artificial kidneys. Using these two noninvasive technologies, a as been made, for considerable amount of progress h Abstract: In this work, the three-dimensional velocity and ncentration fields on both the blood and dialysate sidesexample with the visualization of velocity and con- in an artificial kidney were simulated, taking into account centration fields for blood and dialysate (4-8), the effect of baffles on the flow uniformity of dialysate outlet geometrical structures and the interaction between 1,39), the transport of water or solute across hollow fibers (10,11), and the optimization of the flow distri- bution of dialysate and blood (2,9,12-15). The limita- the effects of the flow profiles induced by the inlet and the flows of blood and dialysate. First, magnetic resonance imaging experiments were performed to validate the math- ematical model. Second, the effects of the flow profiles induced by the blood and dialysate inlet and outlet geo- tion of these technologies is that is difficult to metrical structures on mass transfer were theoretically differentiate velocity and concentration profiles on investigated. Third, the clearance of toxins was compared both the blood and dialysate sides in the process of 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 dialysis (3,6). Consequently, the velocity and concen tration fields on both sides are generally studied inde- increases, the flow field on the blood side becomes lesspendently 9,16). That is, either the blood or the uniform; however, as the dialysate flow rate increases, the dialysate flow is static in experiments. Under this situation, one cannot clearly identify the effect of the flow profiles induced by the inlet and outlet geometri- cal structures of one side on the velocity and concen flow field on the dialysate side becomes more uniform. The effect of the inlet and outlet geometrical structures of the more significant than that of the blood side. Due to the y and concentration fields is on ve effects of the flow profiles induced by the inlet and outlet tration fields of the other side. Therefore, the effect of geometrical structures, the true clearance of toxins is lowerthe interaction between the flows of blood and than the ideal clearance, especially when the dialysate flow dialysate on mass transfer when the inlet and outlet rate is low or the blood flow rate is high. The results from geometrical structures are considered is still unclear As an alternative, three-dimensional (3D) simula tion based on the finite element method is a feasible doi:10.1111/aor.12415 way to predict the entire velocity and concentration fields on both the blood and dialysate sides. eigHowever, due to the requirements for the meshing of Received January 2014; revised July 2014. d reprint requests to Dr. Address Ding. Center for Biomedical Engineering. Department of Elec- tronic Science and Technology, University of Science and Tec nology of China, Hefei, Anhui 230027, China, or Dr. Dayong Gao, Department of Mechanical Engineering, University of Washing- ton, Seattle, WA 98195, USA. E-mail: wpdings@ustc.edu.cn (Dr Ding); dayong@u.washington.edu (Dr. Gao) an complex regions, the discretization of a large set of equations, and the tremendous computational resources, up to now, the literature has rarely pre- sented such theoretical work, let alone coupled 3D

Explanation / Answer

Mass transfer in artificial kidney as the mass transfer region with hollow fibers can be considered a doubly porous region where the blood side is regarded as one porous domain and the dialysate side is regarded as other porous domain. These two domains are independent of each other, and their interface is porous fiber membrane. The purpose of this work is to present the effects of flow profiles induced by inlet and outlet geometrical structures and the interaction of flows of blood and the dialysate with mass transfer therefore the derivation of main equation and assumption they involved are omitted. To simply problem some of the equation with following assumptions are simplified here.

1. The effect of local ultrafiltration on the viscosity and density of blood/ dialysate is negligible.

2.The density of ultrafiltrate is equal to the density of dialysate.

3. The osmotic pressure difference is negligible compared with transmembrane hydraulic pressure difference.

The governing eq is eq(6).

The performance is measured by to avoid complex boundary condition between the porous region ( hollow fiber bundle) and the non porous region(inlet and outlet geometry) the eq 1 is used to obtain velocity on both side blood and dialysate side.

Ans2. We can improve the efficiency of hemodialysis by controlling the factor affecting diffusion.

i. Heat: affects the thermodynamics of molecules so you can speed up diffusion and dialysis by increasing the temperature.

ii. Concentration: the rate of diffusion is directly proportional to the concentration of molecule. As a result, probability that the molecules will come in contact with the dialysis membrane and diffuse through the other side will be higher if there is high concentration of these molecules.

iii. Molecular weight: The rate of diffusion is inversely proportional to the molecular weight of molecule so higher the molecular weight the slower the rate of movement and lower the chance of diffusion through the membrane.

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