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In silico fluid dynamic characterization of two piston-equipped prototypes of diaphragm pump for automated peritoneal dialysis.

Stefano Castello

In silico fluid dynamic characterization of two piston-equipped prototypes of diaphragm pump for automated peritoneal dialysis.

Rel. Umberto Morbiducci, Diego Gallo, Giuseppe De Nisco, Elena Torta. Politecnico di Torino, Corso di laurea magistrale in Ingegneria Biomedica, 2021


In the last years peritoneal dialysis has established as one of the best solutions to treat end-stage renal disease patients. The possibility of performing the dialytic sessions at home, automatically and overnight has increased the spread of the therapy known as Automated Peritoneal Dialysis (APD). APD treatment is managed and controlled by the cycler. It consists of a device that actively regulates the motion of the dialysis fluid inward and outward the patient. Improvements in peritoneal dialysis are directly related to a better management of the therapy, and therefore on a continuous evolution of the pumping mechanism at its basis. This thesis focuses on the fluid dynamic characterization of two innovative prototypes of diaphragm pump for APD. The models consist of a chamber accommodating the fluid with different shape (rectangular for Prototype 3.1 or squared for Prototype 3.2), a membrane limiting the chamber on the top, and a piston moving the membrane to set the fluid in motion. For each prototype, two working conditions were modeled: (1) the diaphragm completely deformed and the chamber almost empty, and (2) the diaphragm in its resting position and the chamber full of dialysate. Each model was meshed, and the finite volume method was used to solve the Navier-Stokes equations. In detail, five different values of inflow flow rate, covering the range of device operation (50-400 ml/min) were applied, while a reference pressure value was prescribed at the outlet boundary. A total of 20 steady-state different simulations were performed: one for each value of inlet flow rate and for each pump in both deformed and non-deformed configuration. Results were analyzed in terms of pressure and wall shear stress (WSS) distributions at the membrane inner surface, and velocity streamlines in the chamber. Finally, filling and discharging phases were characterized in terms of the inlet-mid chamber-outlet differential pressures. The two investigated models showed comparable distributions of pressure and WSS at the inner surface of the diaphragm as well as velocity streamlines developing in the chamber. As expected, the maximum values of membrane pressures, WSS and fluid velocity increased with the increase of the inflow rate. Overall, the highest values of all the investigated fluid dynamic quantities resulted for Prototype 3.1. In addition, peaks of pressure and WSS clearly emerged at its membrane close to the inlet and outlet channels. As for the differential pressures involved in the diaphragm pump filling and discharging phases, it clearly emerged that Prototype 3.2 performs better than Prototype 3.1, requiring less forces to pump the fluid out of the chamber with a certain flow rate, and allowing to store a higher amount of dialysate during the filling phase.

Relators: Umberto Morbiducci, Diego Gallo, Giuseppe De Nisco, Elena Torta
Academic year: 2020/21
Publication type: Electronic
Number of Pages: 118
Additional Information: Tesi secretata. Fulltext non presente
Corso di laurea: Corso di laurea magistrale in Ingegneria Biomedica
Classe di laurea: New organization > Master science > LM-21 - BIOMEDICAL ENGINEERING
Aziende collaboratrici: Politecnico di Torino
URI: http://webthesis.biblio.polito.it/id/eprint/19668
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