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URN etd-0823111-121121 Statistics This thesis had been viewed 1739 times. Download 1227 times. Author Jian-Jhang Chen Author's Email Address No Public. Department Mechanical Engineering Year 2010 Semester 2 Degree Master Type of Document Master's Thesis Language zh-TW.Big5 Chinese Page Count 84 Title Optimization by Entropy Approach for the Fin Arrangement of a Heat Sink Keyword entropy effectiveness fin optimum heat sink heat sink optimum fin effectiveness entropy Abstract In this study, a theoretical analysis of a heat sink is presented to pursue the maximum thermal dissipation and the least material cost. Due to the general derivation, the longitudinal fin arrays on a heat sink can be arranged as either square, rectangular, equilaterally triangular, cylindrical, or annular cross-section. By inputting the dimensionless parameter, Biot number, shape parameter and the total mass, the heat balance equation is derived in transcendental form which can be solved by iterative method to calculate the optimum fin length. Meanwhile, the thermal resistance of a heat sink can be obtained to illustrate the cooling performance under various design conditions.
This study presents a mathematical approach to calculate the total heat loss from a heat sink by summing up the fin spacing on the assign sink surface and the surface of rectangular fins, with each of them able to have its specified thermal conductivity and heat transfer coefficient. Meanwhile, the optimum equation with maximum heat dissipation is derived and solved to find the optimum configuration of fins in a heat sink by inputting the values of dimensionless parameters, Bi,γ, and M . Several cases including fin arrangements with various thermal conductivity distributions and heat transfer coefficients will be explored for practical application.
During the computing process, in the first part, convective effect from the fin tip is not included to the impact of the heat transfer performance. In the second part, the convective effect will be included on the fin tip. The entropy generation is a unique concept that combines both the heat sink resistance and pressure drop. It can be obtained by combining a mass, force, energy, and entropy balance across a heat sink. It is a function of all system parameters considered in this study. By minimizing entropy generation with respect to each design variable, the overall thermal performance of a heat sink can be optimized. The entropy minimization is used to explore the thermal and fluid performance. In optimization process what is needed to know is the base area and the total mass. Thereafter, the optimum fin number and fin dimension can be obtained through this study. And these results can be used as reference for designer in the design of heat sink.
Advisor Committee Hong-Sen Kou - advisor
Ji-Jen Lee - advisor
Cheng-Fang Chen - co-chair
Sheam-Chyun Lin - co-chair
Files Date of Defense 2011-07-27 Date of Submission 2011-08-23