臺灣博碩士論文加值系統

本研究是設計圓形管加裝一可忽略熱阻之隔板，使之成為一組固定外壁溫度具有迴流裝置之圓柱同心套管熱交換器，此系統所推導出的數學模型是屬於共軛格拉茲問題(conjugated Graetz problem)，以分離變數法並利用正交展開方法(orthogonal expansion technique)，探討迴流效應對雙套管間的熱傳效率之影響，其結果與單行程無隔板系統作比較。結果顯示，預混效應及滯留時間效應是影響熱傳效率的兩個因素，並討論兩者對系統的影響。本系統在格拉茲數大時，其效率提昇率有明顯改善，而不同的隔板位置對系統之間的效率亦有顯著影響。 同時在本文中，迴流系統因隔板裝置及不同的迴流比值而增加的能源消耗率也將與單行程系統作比較，以探討雙套管之加熱系統在低能源消耗率時，熱傳效率改善之最佳操作設計。

A new device of counterflow heat exchangers in concentric tubes with uniform wall temperature and with external refluxes has been designed. An orthogonal expansion technique for solving such a conjugated Graetz problem is developed and applied to investigate a substantially improving the heat transfer. An expression for calculating an infinite series of both positive and negative sets of eigenvalues and eigenfunctions was set up. Theoretical results show that the recycle-effect can enhance the heat transfer rate for large Graetz numbers were comparing with that in an open tube (without an inner tube inserted and without recycle). Competition between preheating effect and residence-time effect can be used to explain the heat transfer behavior. The effect of inserter location on the enhancement of heat transfer efficiency as well as on the increment of power consumption has also been discussed.

目錄
中文摘要I
英文摘要II
目錄III
表目錄V
圖目錄XI
符號說明XX
第一章 緒論1
1.1 前言1
1.2 迴流效應對系統的影響2
1.3 研究動機3
1.4 研究架構4
第二章 文獻回顧5
2.1 文獻回顧5
2.2 格拉茲問題. 6
第三章 基本理論9
3.1 二行程無迴流模型之理論分析14
3.2 末端出口模型之理論分析21
3.3 出口迴流至末端模型之理論分析28
3.4 末端迴流至入口模型之理論分析35
3.5 內外層等體積流動模型之理論分析41
3.6 熱傳效率的改善47
3.7 能源消耗之增加率問題48
第四章 結果討論51
4.1 二行程無迴流模型之結果討論52
4.2 末端出口模型之結果討論54
4.3 出口迴流至末端模型之結果討論57
4.4 末端迴流至入口模型之結果討論61
4.5 內外等體積流動模型之結果討論65
4.6 增加的能源消耗問題68
第五章 結論與建議152
5.1 二行程無迴流模型152
5.2 末端出口模型153
5.3 出口迴流至末端模型153
5.4 末端迴流至入口模型154
5.5 內外等體積流動模型154
5.6 五種模型之比較155
5.7 未來研究方向156
參考文獻158
附錄(一)163
附錄(二)166
附錄(三)170
附錄(四)176

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