Toplinsko i reološko ponašanje nanofluida

undergraduate thesis

• Title (english): Thermal and rheological behavior of nanofluids
• Author: Marija Ždrakić
• Mentor: Jasna Prlić Kardum (mentor)
• Committee member: Jasna Prlić Kardum (predsjednik povjerenstva)
• Committee member: Aleksandra Sander (član povjerenstva)
• Committee member: Vanja Kosar (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2015-09-18, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering; Mechanical, Thermal and Separation Processes

Abstract

U ovom radu ispitivana je stabilnost i termo-fizikalna svojstva nanofluida sa i bez aditiva. Za pripravu suspenzija korištene su nanoĉestice Al2O3 koje su dispergirane u demineraliziranoj vodi u 0.5, 1.0, 1.5 vol %. U suspenziju koja sadrži 0.5 vol % Al2O3 dodani su razliĉiti aditivi (polivinil alkohol (PVA), polivinilpirolidon (PVP), arapska guma (AG), heksadeciltrimetilamonijev bromid (CTAB) i natrijev dodecil-sulfat (SDS)) u razliĉitim masenim omjerima.
Pripravljenim nanosuspenzijama izmjerena je gustoća, viskoznost i koeficijent toplinske vodljivosti. Da bi se definirala stabilnost nanosuspenzija, praćena je promjena pH vrijednosti i toplinske vodljivosti suspenzija s vremenom.
Poboljšanje stabilnosti postiže se povećanjem volumnog udjela Al2O3, te dodatkom aditiva (s izuzetkom SDS-a). Iako su nanofluidi s dodanim aditivima stabilniji od nanosuspenzija bez aditiva, njihovom upotrebom se smanjuje toplinska vodljivost, povećava gustoća i viskoznost. Korištenjem površinski aktivnih tvari mijenjaju se reološke karakteristike nanosuspenzija iz newtonskih u nenewtonske fluide.
Najbolja stabilizacijska svojstva pokazao je PVA ĉijom upotrebom se ne mijenja reološko ponašanje nanosuspenzije, a viskoznost i gustoća mu se neznatno povećavaju u odnosu na nanofluid iste koncentracije bez aditiva. Toplinska vodljivost nije smanjena, a stabilnost je zadovoljavajuća.

Abstract (english)

In these work stability and thermo- physical properties of nanofluids with and without additives were examined. Nanofluids were prepared by disperzion of Al2O3 nanoparticles in demineralized water in 0.5; 1.0; 1.5 vol%. In 0.5 vol% suspension different additives in different volume portions were added (Polyvinyl alcohol (PVA), Polyvinylpyrrolidone (PVP), Gum arabic (AG), Hexadecyltrimethylammonium bromide (CTAB) and Sodium dodecyl sulfate (SDS).
Density, viscosity and thermal conductivity of prepared nanosuspensions were determined. To define the stability of the nanosuspensions, the change in the pH values and thermal conductivity of the suspensions was measured within a time period.
The improvement in the stability was achieved through the increase of the mass ratio of Al203, and through the addition of the additives (not including SDS). Although the nanofluids with the additives proved more stable than the ones without the additives, the use of the additives decreased thermal conductivity, and increased the density and viscosity. The use of surfactants changed rheological characteristics of the nanosuspensions from Newtonian fluids into non-Newtonian fluids.
PVA was shown to have the best stabilising properties. It’s use didn’t change the rheological characteristics of the nanosuspension, and viscosity and density were only slightly increased in comparison to the nanofluid of the same concentration but without the additives. Thermal conductivity was not decreased, while the stability was satisfactory.

• Keywords: Al2O3; koeficijent toplinske vodljivosti; nanofluid; aditivi; termo-fizikalna svojstva nanofluida
• Keywords (english): Al2O3; coefficient of thermal conductivity; nanofluid; additives; thermo-physical properties of nanofluids
• Language: croatian
• URN:NBN: urn:nbn:hr:149:393092
• Study programme: Title: Environmental Engineering - Undergraduate study; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka ekoinženjerstva (sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka ekoinženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2016-12-02 14:05:31