Experimental and numerical nvestigations of loop heat pipe performance with nanofluids
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Date
2016-08-01
Authors
Prem Gunnasegaran
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Abstract
Experimental and numerical investigations of heat transfer and fluid flow aspects of loop heat pipe (LHP) are presented in this thesis. The overall goal is to enhance the thermal performance of LHP charged with nanofluids as the working fluids. Thus, the SiO2-H2O, Al2O3-H2O, Fe2NiO4 and diamond-H2O served as the working fluids with nanoparticle mass concentrations ranged from 0 to 3 % in LHP was employed. This study has five distinct parts. First, experimental apparatus and procedures were designed and implemented for measurements of the surface temperature of LHP. Second, a 3D model based on the heat transfer by conducting where the LHP as a whole was modeled by assuming it as a conducting medium, without taking into account the events occurring inside the LHP. The aim of this work is to compare the temperature of solid surface of LHP with experimental results. Third, a 3D model based on the characterization of the working fluid inside the LHP to give an insight into the heat transfer and fluid flow mechanism was developed and tested in ANSYS-Fluent Software. Fourth, as an excellent tool for experiment design and optimization, Design of Experiment (DOE) was employed to optimize the nanofluid mass concentration and the heat input to get the best performance of the LHP. For the SiO2-H2O and Fe2NiO4-H2O-charged LHP, there existed an optimal concentration of 0.5% and 1%, at which reductions in the overall thermal resistance (Rth) of about 2.7oC/W (or 5.84%) and 2.6oC/W (or 7.17%), respectively, were obtained as compared with pure water. For the Al2O3-H2O and diamond-H2O-charged LHP, the Rth decreased with the increase in the mass concentration of nanoparticles. Fifth, a commercial liquid cooling kit of LHP system similar as used in experimental study was installed in real desktop PC CPU. The test results of the proposed system indicate that the average decrease of 5.75oC (14%) was achieved in core temperatures of desktop PC CPU charged with diamond-H2O as compared with pure water. The results from this study should find its use in many industrial processes in which the knowledge on the heat transfer behavior in nanofluids charged LHP is of uttermost importance.