| Summary: | 博士 === 國立清華大學 === 動力機械工程學系 === 92 === ABSTRACT
Both experimental and theoretical studies on heat transfer and flow friction characteristics of compact cold plates have been successfully performed. The research topics conducted in the present study include (1) heat transfer and flow friction of compact cold plate with single-sided discrete single-chip heating; (2) heat transfer and flow friction of compact cold plate with single-sided discrete multi-chip heating; and (3) heat transfer and flow friction of compact cold plate with double-sided discrete multi-chip heating. The influencing parameters such as chip heat flux, air mass flow rate, chip orientation and core structure are investigated. In the study, the comparisons between the transient-/steady-state theoretical results and experimental data for all the cases of cold plate with single-/double-sided discrete chips are made with a satisfactory agreement.
In thermal aspect, the heat transfer characteristics explored in the present study include transient-/steady-state local and average thermal behaviors of cold plate installed with single-sided and double-sided discrete single-/multi-chips. From the results, the effects of chip heat flux and air mass flow rates on the normalized transient cold-plate heat flux ratio of cold plate are insignificant for all the cases of cold plate with single-/double-sided discrete chips. The correlations of the normalized transient convective heat flux ratio of cold plate for discrete single chip and multichips are presented, respectively. Similar with a series of transient experimental results in the existing studies, the present results for compact cold plates with various heating conditions demonstrate that both transient local and average effective Nusselt numbers (or heat transfer coefficients) in purely forced convection cases may be considered as the steady-state values during transient period. The effects of chip heat flux on transient-/steady-state local and average effective heat transfer coefficients, effective Nusselt number and thermal resistance of cold plate are insignificant for all the cases with single-/double-sided discrete chips. For all the cases of cold plate with single-/double-sided discrete chips, the transient-/steady-state local and average effective heat transient performances of cold plate increase with increasing air mass flow rate; while, the transient-/steady-state local and average thermal resistance decreases with increasing air mass flow rate. Besides, as compared with the heat transfer predictions for a flat plate, a significant heat transfer enhancement can be achieved between 686% and 2530% for all the cases of cold plate with single-/double-sided discrete chips. In fluid flow aspect, the flow friction characteristics such as overall pressure drops and flow friction factor through cold plate are explored. The results manifest that the overall pressure drop of the cold plate increases with increasing air mass flow rate; while it is insignificantly affected by chip heat flux.
As for exploring the effects of cold-plate orientation and core structure, the results reveal the effect of cold-plate orientation on the heat transfer and flow friction behavior for cold plates is insignificant. The effect of core structure on the distribution of the transient normalized convective heat flux is insignificant. The transient-/steady-state local and average effective heat transfer performance of cold plate with Core II is higher than that with Core I . At a specified upstream flow rate, the overall pressure drop of cold plate with Core I is higher than that with Core II because of a smaller channel velocity for Core II. The j/f value of cold plate with Core II is greater than that of with Core I.
To investigate the feasibility of using the superposition principle for double-sided cold plate with two single-sided cold plates, the present experimental data and numerical results verify that the temperature rises of cold plate with double-sided discrete multi-chips can be superposed by those of two cold plates with single-sided discrete multi-chips during both tansient- and steady-state period. Furthermore, all thermal and flow friction characteristics are not significantly affected by cold plate with single-sided discrete single-chip or multi-chip heating condition. Accordingly, a series of new correlations of steady-state heat transfer and flow friction characteristics such as , , , and , , f, j and j/f are finally presented.
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