Pool boiling heat transfer characteristics of nanofluids
Name
214327112-MIT.pdf
Description
Full printable version
Size
5.5 MB
Format
Adobe PDF
Checksum (MD5)
5bc7090528042ff253ae722ff51008f5
Author(s)
Kim, Sung Joong, Ph. D. Massachusetts Institute of Technology
Advisor(s)
Jacopo Buongiorno and Lin-Wen Hu.
Date Issued
2007
Publisher
Massachusetts Institute of Technology
Abstract
Nanofluids are engineered colloidal suspensions of nanoparticles in water, and exhibit a very significant enhancement (up to 200%) of the boiling Critical Heat Flux (CHF) at modest nanoparticle concentrations (50.1% by volume). Since CHF is the upper limit of nucleate boiling, such enhancement offers the potential for major performance improvement in many practical applications that use nucleate boiling as their prevalent heat transfer mode. The nuclear applications considered are main reactor coolant for PWR, coolant for the Emergency Core Cooling System (ECCS) of both PWR and BWR, and coolant for in-vessel retention of the molten core during severe accidents in high-power-density LWR. To implement such applications it is necessary to understand the fundamental boiling heat transfer characteristics of nanofluids. The nanofluids considered in this study are dilute dispersions of alumina, zirconia, and silica nanoparticles in water. Several key parameters affecting heat transfer (i.e., boiling point, viscosity, thermal conductivity, and surface tension) were measured and, consistently with other nanofluid studies, were found to be similar to those of pure water. However, pool boiling experiments showed significant enhancements of CHF in the nanofluids. Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometry (EDS) analyses revealed that buildup of a porous layer of nanoparticles on the heater surface occurred during nucleate boiling. This layer significantly improves the surface wettability, as shown by measured changes in the static contact angle on the nanofluid-boiled surfaces compared with the pure-water-boiled surfaces. It is hypothesized that surface wettability improvement may be responsible for the CHF enhancement.
Description
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2007.
Includes bibliographical references (leaves 79-83).
Subjects
Nuclear Science and Engineering.
MIT Department
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
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