頁籤選單縮合
題名 | Heat Transfer of Orthogonal-mode Reciprocating Turbulent Swirling Tube Flow=正交往復管渦紊流熱傳研究 |
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作者姓名(中文) | 張始偉; | 書刊名 | 海運研究學刊 |
卷期 | 7 1999.04[民88.04] |
頁次 | 頁93-112 |
分類號 | 444.73 |
關鍵詞 | Heat transfer; Orthogonal-mode reciprocating flow; Twisted-tape insert; |
語文 | 英文(English) |
中文摘要 | 本文探討一內設扭旋片管於正交往復時之熱傳實驗研究結果。研究動機為瞭解應用扭旋片於壓燃機活塞冷卻時之功效及其熱傳之物理機制。實驗測試前先進行參數分析以求出控制此類流場熱對流現象之無因次參數群,並依照此參數群設計實驗及數據分析程序。實驗檢測五種往復頻率分別為0,0.83,1.25,1.67 and 2 Hz。參數範圍為:雷諾數3,000∼12,000:往復數:0∼0.9。當測試管正交往復時,脈動力及往復浮力效應因往復運動產生而改變靜態管時之熱傳現象。於低往復數時,往復熱傳係數降低至靜態管值之75%左右。若持續增加往復數,往熱傳係數遂逐漸增加;於高往復數下,往復熱傳係數可增加至靜態管值之60%左右。 |
英文摘要 | This paper describes the results of an experimental study aimed at revealing the heat transfer physics of twist-tape insert in an uniformly heated tube for turbulent flow situations with and without system reciprocation. This study is motivated by the needs to understand the effectiveness of twist-tape insert on the heat transfer augmentation when applies to the piston cooling of a CI engine. Prior to the experimental tests, a parametric analysis was performed for which the dimensionless groups those characterized heat convection were identified and adopted to formulate the experimental program and procedures of data reduction. The parametric test matrix involves Reynolds and pulsating numbers respectively in the ranges of 3,000∼12,000 and 0∼0.9 with five different reciprocating frequencies tested, namely 0, 0.83, 1.25, 1.67 and 2 Hz. The non-reciprocating experimental data confirmed considerable heat transfer enhancement due to twisted-tape insert. When test tube reciprocated in orthogonal to the main flow direction, both pulasting and reciprocating buoyancy forces arose which modified the heat transfer from non-reciprocating situations. Initially a range of heat transfer impediments relative to the non-reciprocating results, that could reduce local Nusselt numbers to levels about 75 percent of non-reciprocating values took place when these reciprocating forces were relatively weak. Further increases of relative strengths of reciprocating forces resulted in subsequent heat transfer recovery and could lead to about 60% of heat transfer enhancements relative to non-reciprocating values. |
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