Name: Renata Trevelin da Silva
Type: MSc dissertation
Publication date: 31/03/2017

Namesort descending Role
Edson Jose Soares Advisor *
Renato do Nascimento Siqueira Co-advisor *

Examining board:

Namesort descending Role
Edson Jose Soares Advisor *
Kleiber Lima de Bessa External Examiner *
LEONARDO DOS SANTOS External Examiner *
Renato do Nascimento Siqueira Co advisor *

Summary: Drag reduction by polymers has been studied over the past decades and several industrial applications can be found. Beyond industrial applications, soluble drag reducing polymers have also shown to produce beneficial effects on blood circulation and may represent a way to treat cardiovascular disorders. In the present work, we investigate the effects of different types of polymer on the drag reduction capacity of nutrient saline solutions commonly on perfusion systems. Three different polymers are tested: Polyacrylamide (PAM), Polyethylene oxide (PEO) and Xanthan Gum (XG), with concentrations of 10, 50 and 100 ppm. The first stage of the work is developed in a cylindrical double gap rheometer device. In this stage, viscosity curves were obtained, increasing the shear rate, in order to understand the rheological characterization of the fluid, and constant shear rate, to analyze the loss of efficiency over time. All the tests were conducted using both distilled water (AD) and Krebs-HEPES nutrient saline solution (SN) as solvent. Our findings suggest that the Krebs HEPES nutrient saline solution composition does not change significantly PAM and PEO behavior, showing that they can be satisfactorily diluted in this solvent without loss of efficiency as drag reducers. However, it modifies XG conformation, drastically reducing its efficiency as drag reducer. The second stage consists of experiments in tail arterial bed of rats using an organ perfusion system, with Krebs-Henseleit nutrient solution as solvent. Such experiments are performed in order to evaluate the way the drag reduction promoted by the polymers is influenced by the interactions with the solvent and the cells of the arterial tissue during the flow. The tests are conducted varying the flow rate to the tail artery for each polymer concentration, to evaluate whether the solution is capable of lowering the perfusion pressure. The results suggest that PAM is efficient to reduce the perfusion pressure but PEO and XG does not seem to be good reducers under our experimental conditions, these results are not yet conclusive and need to be better studied.

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