Nanofluidi polietilen glikola i višestjenčanih ugljikovih nanocijevi

master's thesis

• Title (english): Polyethylene glycol based nanfluids with multiwall carbon nanotubes
• Author: Lucija Rebrović
• Mentor: Fabio Faraguna (mentor)
• Committee member: Fabio Faraguna (predsjednik povjerenstva)
• Committee member: Ante Jukić (član povjerenstva)
• Committee member: Marin Kovačić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2019-09-26, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering

Abstract

Nanofluidi su u posljednjih nekoliko desetaka godina privukli mnogo pažnje znanstvenika i industrije zbog povećane toplinske vodljivosti u usporedbi s baznim fluidima. Ugljikove nanocijevi su čestice kod kojih je primjećena izvrsna toplinska vodljivost. Iz tog razloga se često koriste kao sastavnica nanofluida. Cilj ovoga rada bio je pripremiti i istražiti svojstva nanofluida polietilen glikola prosječne molekulske mase 200 g/mol (PEG-200) i četiri vrste višestjenčanih ugljikovih nanocijevi (engl. multi-walled carbon nanotubes (MWCNT)) pri udjelima od 0,1; 0,25; 0,5; 0,75; 1; 2,5; 5 i 10 mas. % MWCNT. Istražen je utjecaj duljine i širine nanocijevi na reološka svojstva i toplinsku vodljivost nanofluida. Dodatno je ispitan utjecaj funkcionalizacije nanocijevi karboksilnom (COOH) skupinom na navedena svojstva. Osim samog utjecaja strukture, ispitana je i ovisnost navedenih svojstva nanofluida o koncentraciji MWCNT. Primijećeno je da kod nanofluida sastava 10 mas.% MWCNT u slučaju kratkih uskih oksidiranih MWCNT dolazi do povećanja toplinske vodljivosti od 133 % u odnosu na bazni fluid. Oksidirane MWCNT ostvaruju bolje interakcije s polietilen glikolom pa je tako i kod dugih uskih oksidiranih MWCNT primijećen porast od 112 % u odnosu na bazni fluid. Kod nanofluida koncentracija 0,01-1 mas.% MWCNT primjećeno je newtonsko ponašanje, dok se nanofluidi s kratkim i širokim nanocijevima viših koncentracija ponašaju dilatantno, a nanofluidi s dugačkim i uskim nanocijevima pseudoplastično. Povećanjem temperature i smanjenjem koncentracije MWCNT u nanofluidu smanjuje se viskoznost.

Abstract (english)

Nanofluids have gained a lot of attention from scientists and companies in the last few decades due to their enhanced properties such as thermal conductivity. Carbon nanotubes are nanoparticles which are recognized for their outstanding thermal conductivity. For that reason, they are often being used as nanoparticles in nanofluids. Aim of this work was to prepare and investigate nanofluids of polyethylene glycol-200 (PEG- 200) with four types of multi-walled carbon nanotubes (MWCNT) in the concentration range of 0.1; 0.25; 0.5; 0.75; 1; 2.5; 5 and 10 wt.%. Nanofluids have been prepared by ultrasonic mixing of PEG and four types of MWCNT differentiating in length and radius. Two types of MWCNTs were pristine, and two were oxidized, containing carboxyl (COOH) functionalized group. The influence of length, width, functionalization and concentration of MWCNT on thermal conductivity and rheological properties of nanofluids was studied. Thermal conductivity and rheological properties of base fluid were also investigated. It was observed that nanofluids containing 10 wt.% of short and wide nanotubes have the biggest increase of thermal conductivity (133 %) in the reference to the base fluid. Nanofluids with types of MWCNT which contain carboxyl group have better heat transfer properties compared to the pristine. In the case of nanofluids with long and narrow oxidized CNT there was an increase in thermal conductivity of 112 %. Nanofluids in the concentration range 0.01-1 wt.% of MWCNT have Newtonian behavior and those with higher concentrations have non-Newtonian behavior. For nanofluids containing short and wide nanotubes shear thickening behavior is observed, and those containing long and narrow nanotubes have shear thinning behavior. By increasing the temperature and decreasing concentration of MWCNT in nanofluids, viscosity decreases.

• Keywords: nanofluidi; višestjenčane ugljikove nanocijevi; polietilen glikol; toplinska vodljivost; reološka svojstva
• Keywords (english): nanofluids; multi-walled carbon nanotubes; polyethylene glycol; thermal conductivity; rheological properties
• Language: croatian
• URN:NBN: urn:nbn:hr:149:853825
• Study programme: Title: Chemical Engineering - Graduate study; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka kemijskog inženjerstva (magistar/magistra inženjer/inženjerka kemijskog inženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2022-02-27 14:19:35