The integrated study of Experimental and Numerical Simulation on Enhancing Heat-Dissipation performance for a Heat Sink Assembly

• Main Authors: Cheng-Ju Chang, 張正儒
• Other Authors: Sheam-Chyun Lin
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/83892676987406300199

博士 === 國立臺灣科技大學 === 機械工程系 === 103 === Abstract This study combines numerical simulation and experimental technique to investigate the cooling characteristic of a bracket-type heat-sink assembly for ensuring CPU operating under the critical temperature. At first, numerical visualizations on the thermal/fluid fields are used to justify the physical mechanisms inducing an excessive temperature rise. Then, several alternatives are proposed to enhance the cooling capacity of the heat sink assembly. They are the adjustment on heat-pipe arrangement to increase its contact opportunity with cooling airstream, and the addition of holes on fin surface to generate the possible heat/flow recirculation between two adjacent fin passages for a better convective heat transfer. Furthermore, two types of vortex generators (flow down and flow up) are evaluated and installed to create a longitudinally perturbed flow to increase the heat dissipation capability of bracket-type heat assembly. As a result, with the appropriate heat-pipe arrangement, triangular holes, and location of vortex generators, the heat dissipation ability of bracket-type heat sink assembly is improved obviously. The CPU temperature is reduced from 349.2K to 346K and the thermal resistance of thermal module is improved from 0.274 to 0.252 K/W. Also, a more uniform temperature distribution is identified with the aids of longitudinal airflow generated by mounting the flow-up vortex generator. And the cooling capacity of heat sink assembly is enhanced since the fluid is guided to the heat-concentrated area when the flow-down vortex generators are adopted. Moreover, the optimum fin number (47) is found to decrease CPU temperature and thermal resistance further to 343.8K and 0.234 K/W, respectively. Thereafter, considering the limitations of fan noise, the proper fan operating at 2,500RPM is selected to produce the fan performance (3.48 mm-Aq, 86.9 CFM). Also, the calculations on CPU temperature and thermal resistance are obtained as 326.61K and 0.123 K/W, which are correlated well with the experimental results (327.4K and 0.129 oC /W) . The error percentage between numerical and experimental results on the thermal resistance is 4.65% and on the CPU temperature is 0.8 oC. In conclusion, this rigorous and systematic design scheme for bracket-type heat sink assembly is successfully established for designing the new and effective thermal module.