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Title page for etd-0623108-211710


URN etd-0623108-211710 Statistics This thesis had been viewed 3130 times. Download 1495 times.
Author Chih-wei Chen
Author's Email Address No Public.
Department Mechanical Engineering
Year 2007 Semester 2
Degree Ph.D. Type of Document Doctoral Dissertation
Language English Page Count 112
Title OPTIMUM THERMAL ANALYSIS OF A HEAT SINK WITH VARIOUS FIN CROSS-SECTIONS AND A MICROCHANNEL HEAT SINK
Keyword
  • Microchannel
  • Optimum
  • Heat sink
  • Simulated annealing
  • Simulated annealing
  • Heat sink
  • Optimum
  • Microchannel
  • Abstract In the first topic of this study, a theoretical analysis of a heat sink is presented to pursue the purpose of maximum thermal dissipation and the least material cost. Due to the general derivation, the longitudinal fin arrays on a heat sink can have either square, rectangular, equilaterally triangular, or cylindrical cross section. By input the Biot number, Bi*, heat transfer coefficient ratio Hb* and He*, the heat transfer 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.
      The second topic of this study presents a mathematical approach to calculate the total heat loss from a heat sink by sum up the fin spacing on the heat 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*)i, (Hb*)i , (He*)i, and number of fins, n. Finally, several examples including fin arrangements with various distributions of thermal conductivity and heat transfer coefficients have been successfully explored for practical application.
      In the last topic of this study, a three-dimensional numerical simulation of the microchannel heat sink is presented to study the heat transfer characteristics and then find the optimum configuration. Based on the theory of a fully developed flow, the pressure drop in the microchannel is analytically derived under the requirement of the flow power for a single channel. In the first part of this topic, the effects of one design variables representing the channel width, channel height, the ratio of fin width to the channel width, and the ratio of substrate thickness to the channel height on the thermal resistance of a microchannel heat sink are investigated, separately. In addition, the constraint of the same flow cross section is carried out to find the optimum dimension. Then, the minimum thermal resistance and optimal channel width with various flow powers and channel heights are obtained by using the simulated annealing method. As to the second part of the present topic, the fin width and channel width are chosen as the design variables to find their optimum sizes. For the third part, the depths of the microchannel heat sink in this study are fixed at either 1 cm and 2 cm, separately, Three design variables including channel height, fin width and channel width are individually prescribed in a suitable range to search for their optimum geometric configuration when the other specifications of the micrechannel heat sink are fixed by 24 different cases.
    Advisor Committee
  • Hong-sen Kou - advisor
  • Ji-jen Lee - advisor
  • none - co-chair
  • none - co-chair
  • none - co-chair
  • none - co-chair
  • none - co-chair
  • Files indicate access worldwide
    Date of Defense 2008-05-22 Date of Submission 2008-06-23


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