探討自然對流對活塞之熱傳效益

Abstract

本文主要目的以套裝軟體STRA-CD以三維的方式模擬活塞內部加裝冷卻渠道，觀察此渠道在活塞做往復運動下以及考慮自然對流效應下，渠道內部流場和溫度場的變化，並討論冷卻流體對活塞高溫壁面的熱傳增益，而模擬結果並與同步與實驗作對照，以驗證模擬的真實性。 主要探討在往復運動下的流場和溫度場之變化，以了解這類問題的運動機制，並針對不同的流場雷諾數、進口速度與振動頻率，以及加熱壁面溫度，比較其對活塞高溫壁面的熱傳增益。綜合所獲得的結果，當活塞運動後，會在活塞高溫壁面附近產生類似的牽引和推擠流體現象，使得原本附近高溫壁面上之溫度邊界層受到擾動而被破壞和縮小，熱傳效果會普遍提升。

The aim of this simulation is to investigate the variations of flow and thermal fields in the cooling channel within the reciprocating piston, and discuss the heat transfer effect of the cooling flow on the heat surface of the piston. The STRA-CD is adopted to investigate the variations of the flow and thermal fields induced by the reciprocation of the piston. The heat transfer effects of different Reynolds numbers, and reciprocating frequency on heat transfer rate are shown and discussed. Based on the above procedures, the results show that the reciprocating piston would draw and push the cooling flow. Therefore, the heat transfer rate is enhanced remarkably.