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Computer-Aided Design on Finned-Tube Air Heater and Its Heating Capability
|Authors: ||Ci-Yuan Siao|
|Contributors: ||NTOU:Department of Mechanical and Mechatronic Engineering|
Fin-tube heat exchange;LMTD;drying chamber;ventilation rate
|Issue Date: ||2013-10-07T03:03:18Z
|Abstract: ||本研究主要係探討工作流體為熱媒油之鰭管式空氣加熱器於乾燥室之加熱特性分析。分別對管側及殼側，依次計算出雷諾數、熱對流係數、總熱括係數、熱傳面積，以及需要的管數及壓降。其次根據乾燥室換氣率與熱散失量、計算出乾燥室溫度隨時間的變化關係。 結果顯示不同的乾燥室結構尺寸對於乾燥室溫度造成影響，如內框厚度不同影響了溫升率與加熱時間、保溫層厚度變化則會造成熱散失率的變化、換氣率的大小會改變最終穩態溫度之高低，因此本文將針對這些參數所造成的影響數據化，方便比較與參考。 本研究之計算程式使用Microsoft Excel撰寫，程式內含相關物理性質並具查詢功能；程式在給定條件下，首先輸入結構尺寸、操作溫度與流量、設計參數等，計算出空氣加熱器之雛型，包括傳熱管長度、排列方式、外徑、管數等資訊，其次經由數值分析之試誤法算出熱傳量及熱交換器空氣端出入口溫度，依次求出下一時間階之結果，繪出乾燥室溫度對時間變化圖，以進行設計評估熱交換器大小是否恰當。|
The objective of this study is to investigate the thermal characteristics of fin-tube air heaters powered by Dowtherm oil, and the outlet is used in heating a drying chamber. The Reynolds number, heat transfer coefficients inside and outside the tube are calculated, and hence the heat transfer area and the number of tubes are readily obtained. In addition, the layout of the tubes is studied accompanied with the pressure drop required. Secondly, according to the amount of heat loss and ventilation rate, the temporal variation of temperature in drying chamber is presented. The temperature of the drying chamber was found to change with the dimension of the drying chamber, such as thicknesses in different layer of the inner frame, insulating layer and outer frame. The rate of heat loss as well as the ventilation influences the ultimate temperature. The above mentioned parameters are studied in this thesis. The computer program was coded in Excel language which developed by Microsoft. First of all, input information includes the detailed structure size and operating conditions. The temperature dependent physical properties are inquired from the date base sheets. The preliminary structure of air heater is suggested. Coupled to the drying chamber, through a series of numerical analysis, the temperature at the exit of drying chamber can be estimated in each time step. Finally, the variation of temperature versus time is plotted in diagrams to assess whether the size of the heat exchanger design is satisfied.
|Appears in Collections:||[機械與機電工程學系] 博碩士論文|
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