Assesment of applicability of friction pumps in human circulatory system

Abstract

U ovom radu opisana je problematika i proračunavane su radne karakteristike srčanih pumpi. U uvodnom poglavlju opisana je opća problematika modernog društva vezanog za srčane bolesti i rastuća potreba za srčanim pumpama koje će pružiti potporu srcu, ili ga u potpunosti zamijeniti. U prvom poglavlju je opisana krv i njezine karakteristike, kao i problemi koji su vezani uz krv. Također su opisani mehanizmi hemolize i tromboze, temeljem koje su definirani kriteriji za rad pumpi (dopušteno područje smičnih naprezanja i indeks oštećenja crvenih krvnih zrnaca). U drugom poglavlju je opisano srce i njegov rad. Isto tako su analizirane srčane pumpe koje se koriste u praksi.U nastavku rada definiranoje radno područje srčane pumpe na temelju fizioloških podataka vezanih uz stvarno srce. Za dva tipa frikcijskih pumpi: cilindrične frikcijske pumpe i frikcijske pumpe s rotirajućim diskom su izvedeni analitički izrazi koji povezuju prirast tlaka i protok kroz pumpu, te definiraju potrebnu snagu za pogon pumpe, te minimalna i maksimalna smična naprezanja, stupanj korisnosti pumpe i indeks oštećenja crvenih krvnih stanica. Definirane su dvije vrste dijagrama: jedni koji služe za izbor pumpe (gabarita i brzine vrtnje), a drugi za analizu karakteristike odabrane pumpe (zadanih gabarita) u zadanom radnom području. Usporedbom dvaju pumpi zaključilo se da bi pumpa s rotirajućim diskom bila povoljnija, ali taj bi zaključak bilo nužno provjeriti kroz numeričko rješavanje potpunih Navier-Stokesovih jednadžbi koje opisuju strujanje kroz ove dvije pumpe, budući da je korišteno analitičko rješenje za pumpu s rotirajućim diskom vjerojatno fizikalno nerealno, zbog pretpostavki koje je bilo nužno uvesti da bi se rješenje moglo naći.This paper describes the issues and calculated the performance of the heart pumps. The introductory chapter describes the general problems of modern society related to heart disease and a growing need for cardiac pumps that will support the heart, or completely replaced it. The first chapter describes the blood and its characteristics, as well as problems related to blood. It also describes mechanisms of hemolysis and thrombosis, which are based on defined criteria for the operation of the pump (permissible area of the shear stress and damage index of red blood cells). The second chapter describes the heart and how it works. Heart pumps that are used in practice are also analyzed in this chapter. Further in this work working fieldof heart pump is defined based on physiological data related to the actual heart. For two types of friction pumps: cylindrical friction pump and friction pump with rotating disc are derived by analytical expressions that connect the growth pressure and flow through the pump, define the power required to drive the pump, the minimum and maximum shear stress, efficiency pump and damage index of red blood cells. There are two types of diagrams defined: one that is used for selection of the pump (size and speed), and the second to analyze the characteristics of the selected pump (of selected dimensions) in the default working field. Comparing the two pump types it was found that pump with a rotating disc was favorable, but it would be necessary to check this conclusion with complete numerical solution of the Navier-Stokes equations for the flow through the two pumps, since the used analytical solution of a pump with a rotating disc is probably physically unrealistic, because of the introduction of assumptions that was necessary to find a solution