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曾憲中01

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鄭澤明(Tzer-Ming Jeng)、曾憲中(Sheng-Chung Tzeng)、許冠維()、黃昱翔(Yu-Xiang Huang)

Paper name：

震盪氣流通過矩形鰭柱散熱座時的流動與散熱特性研究

Fluid flow and heat transfer characteristics of the oscillating flow across the rectangular pin-fin heat dink

Name of activity：

2013年能源與冷凍空調學術暨技術研討會(2013ERAC)

2013 Energy and HVAC Academic & Technology Conference (2013ERAC)

Keywords：震盪氣流、鰭柱散熱座、熱傳、場流觀測、旁通空隙

Oscillating flow, pin-fin heat sink, heat transfer, flow visualization, bypass clearance.

Abstract：本研究以實驗方法探討鰭柱散熱座於震盪氣流下的流動與熱傳特性。傳統鰭柱散熱系統係利用固定流量之氣流通過鰭柱散熱達成強制對流冷卻的目的，本研究設計一種震盪氣流裝置，可以產生震盪式流動的冷卻氣流，由於冷卻器流的流量會震盪變化，使得氣流在鰭柱之間產生不穩定的流動，氣流撞擊在駐留鰭柱陣列間的時間也會增加，能有效提升整體散熱能力。本研究之鰭柱散熱座至於具/不具上通空隙之槽道內，完成震盪氣流的咽瘤場觀測與不對稱壁面加熱下之平均紐塞數測定，從煙流場觀測發現流線在橫向有顯著的波動，而與穩態流動比較，目前之震盪流在不具旁通的槽道約能提升20~34%的散熱能力，惟旁通空隙過大時，震盪氣流的熱交換的能力反而比穩態氣流為差，證明震盪氣流在不具旁通或特定旁通條件下能有效增強鰭柱散熱得熱傳能力。

This work experimentally investigate the fluid flow and heat transfer characteristics of the pin-fin heat sink with the oscillating fluid flow. The cooling system of finned heat sink usually employs the steady flow with fixed flow rate to complete the objective of forced convection. This work designed and manufactured a device to oscillate air flow. The air flow would be unstable in the passages among the fins due to the oscillation of flow rate, increasing time of air through the fins. Therefore, the overall heat-transfer performance would be enhanced. At the present study, the pin-fin heat sinks with various fin heights were installed in the rectangular channel, resulting in different bypass clearances between the pin fins and the shroud of the test channel. The smoke flow visualizations for the oscillating-flow system were completed. The heat-transfer tests under the asymmetrically heated condition were performed to obtain the average Nusselt numbers. The smoke lines with obvious waves in the transverse direction were found in the results of the flow visualizations. By comparing to the steady flow system, there was about 20~34% increment in the overall heat-transfer performance at the operating state without bypass clearance. However, if the bypass clearance was too big, the heat-exchange capacity of the oscillating flow was less than that of the steady flow. It demonstrates that the oscillating flow promotes the cooling performance of pin-fin heat sink at the non-bypass and specified bypass conditions.

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