magistrsko delo magistrskega študijskega programa II. stopnje Strojništvo
Aljaž Nemanič (Author), Iztok Golobič (Mentor), Matevž Zupančič (Co-mentor)

Abstract

V delu obravnavamo vpliv koncentracije n-butanola v vodni zmesi s samoomočljivostnimi lastnostmi na izboljšan prenos toplote pri mehurčkastem vrenju. Ta vpliv obravnavamo tako na mehansko obdelanih površinah kot tudi na jedkanih površinah. Analizo lastnosti površine vzorcev smo opravili z merjenjem kota omočenja, SEM posnetki in Ramansko spektroskopijo. Na merilni progi Laboratorija za toplotno tehniko za vrenje v bazenu pod pogojih atmosferskega tlaka smo izvedli eksperimentalno ovrednotenje prenosa toplote pri vrenju z dvakrat destilirano vodo in z zmesjo dvakrat destilirane vode in n-butanola pri več različnih koncentracijah. Pri tem smo beležili vrelne krivulje in ostale parametre za ovrednotenje prenosa toplote pri vrenju. Pri uporabi redestilirane vode smo na brušenih površinah dosegli kritične gostote toplotnega toka do 1285 kW m-2, koeficienti toplotne prestopnosti so dosegli vrednosti 54.7 kW m-2 K-1, na jedkanih površinah pa smo dosegli kritične gostote toplotnega toka do 1836 kW m-2 in koeficiente toplotne prestopnosti do 62.2 kW m-2 K-1. Z uporabo samoomočljivih fluidov smo pri vrenju na brušenih površinah uspeli dvigniti kritično gostoto toplotnega toka v primerjavi z redestilirano vodo, na jedkanih površinah pa so samoomočljivi fluidi poslabšali vrelno krivuljo zaradi spremembe površine pri intenzivnem vrenju, kar smo opazili iz posnetkov SEM analiz. Po večkratnem testiranju na enem vzorcu se je pri vrenju na brušenih površinah vrelna krivulja izboljšala, medtem ko se je na jedkanih površinah poslabšala. Na podlagi analize površin vzorcev po izpostavljenosti vrenju samoomočljivega fluida ocenjujemo, da je prišlo do kemične reakcije bakrenih spojin na površini vzorca z n-butanolom.

Keywords

magistrske naloge;mehurčkasto vrenje;izboljšan prenos toplote;vrelna krivulja;kritična gostota toplotnega toka;samoomočljivi fluidi;koeficient toplotne prestopnosti;jedkane površine;

Data

Language: Slovenian
Year of publishing:
Typology: 2.09 - Master's Thesis
Organization: UL FS - Faculty of Mechanical Engineering
Publisher: [A. Nemanič]
UDC: 536.24:66.046.7(043.2)
COBISS: 78459395 Link will open in a new window
Views: 301
Downloads: 40
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Other data

Secondary language: English
Secondary title: Influence of n-butanol concentration in aqueous solution on enhanced nucleate boiling heat transfer
Secondary abstract: The present work investigates the influence of a self-rewetting n-butanol aqueous solution on enhanced nucleate boiling heat transfer. This influence was investigated on mechanically treated surfaces and on etched surfaces. Surface characteristics were evaluated through SEM imaging, by measurement of contact angle and Raman spectroscopy. Pool boiling experimental setup constructed by the Laboratory for thermal technology was used to determine the boiling heat transfer characteristics of treated surfaces during saturated boiling of pure water and self-rewetting fluid at various concentrations. During experiments we recorded boiling curves and other relevant data to evaluate the boiling performance. Critical heat flux using pure water on mechanically treated surfaces reached up to 1285 kW m-2 and up to 1836 kW m-2 on etched surfaces, while the heat transfer coefficients reached 54.7 kW m-2 K-1 and 62.2 kW m-2 K-1, respectfully. By using self-rewetting fluids on mechanically treated surfaces we reached higher critical heat fluxes, while boiling of such fluids on etched surfaces resulted in lower critical heat fluxes than achieved with pure water. Through SEM imaging we observed changes of the surface after boiling of self-rewetting fluids on both surfaces. We estimate that a chemical reaction of copper compounds with n-butanol took place on the boiling surfaces.
Secondary keywords: master thesis;nucleate boiling;enhanced heat transfer;boiling curves;critical heat flux;self-rewetting fluid;heat transfer coefficient;etched surfaces;
Type (COBISS): Master's thesis/paper
Study programme: 0
Embargo end date (OpenAIRE): 1970-01-01
Thesis comment: Univ. Ljubljana, Fak. za strojništvo
Pages: XXIV, 70 str.
ID: 13366722