Numerical Simulation of Portable Electronic Cooling Using Phase Change Material

• Main Authors: Yi-HsienWang, 王譯賢
• Other Authors: Yue-Tzu Yang
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/84365009223442319291

博士 === 國立成功大學 === 機械工程學系碩博士班 === 100 === This dissertation explores transient three-dimensional heat transfer simulations of a hybrid PCM (Phase Change Material) based heat sink using numerical cooling technique. Thermal energy is transferred to the calculation domain through the base of heat sink. The N-eicosane is adapted as the role of latent heat storage with PCM to place inside heat sink cavity. The governing equations of melting model are solved by a control-volume-based finite-difference method with a power-law scheme to describe the heat transfer of the simulation system. The melting mushy zone boundary is predicted by an enthalpy-porosity like numerical approach due to the phase change of heat transfer, which is employed to transform the physical latent heat phase change domain from solid PCM to liquid mode. In addition, the PCM-air VOF (volume of fluid) model is adapted to solve PCM-air gap boundary which is caused by PCM’s volume expansion for the difference of variable density. In this study, numerical computations are conducted with various power levels (2W-4W), different orientation tests (vertical/horizontal/slanted), and various modes (charge / discharge). For further precise prediction, the calculating time step (0.03s, 0.05s, and 0.07s) size is discussed in the literature for transient accuracy as well. The developed theoretical model is validated by comparing numerical predictions with the available experimental data in the literature. The numerical results show that the transient surface temperatures are reasonably predicted with a maximum discrepancy of 10.2%. The present numerical computations also include the comparison of thermal performance and fluid fill with different amounts of fins (0, 3 and 6 fins). Through this study, it is found 1. The test of orientation shows limited effect on the thermal performance of the system (within 2℃). 2. Hybrid system using PCM (N-eicosane) can be well controlled under 320K if the melting ratio is under 0.9. 3. A maximum discrepancy of grid independence is within 10.2% between present and experimental data. 4. From Fe (Fin effect), the heat transfer performance with 6 fins provides better thermal control. The suitable fins arrangements can provide the system better heat dissipation status which help to explore new hybrid efficiently cooling system under same operation temperature. Therefore present results could provide the future exploitation based on the same geometric and heat source distribution.