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    Please use this identifier to cite or link to this item: http://ir.lib.ksu.edu.tw/handle/987654321/12410


    Title: 考慮熱輻射用於熱交換或保溫情況之各種形狀冷/熱管或容器之完整熱傳特性研究 (新制多年期第2年)
    Authors: 黃景良
    陳文立
    謝明勳
    康智發
    吳金翰
    莊曜鎔
    沈柏宏
    王懋竣
    Date: 2010-11-03
    Issue Date: 2010-12-16 11:14:50 (UTC+8)
    Abstract: 熱交換器之使用在工業和生活上之應用非常普遍,由於熱輻射公式含溫度的四次方在計算上非常麻煩,大多數熱傳專家學者在經驗上認為只要表面溫度和環境溫度相差不大時,熱輻射便可忽略不算。故此在大多數熱傳和冷凍空調教科書在熱交換器例題示範和業界在熱交換器實務設計上,幾乎一致性地忽略輻射熱傳的影響。但經我們以圓管在實際應用情況來模擬驗證,發現只要在外部熱對流係數不大和較大輻射放射率時,即使表面溫度和環境溫度相差不大情況熱輻射也不可忽略,否則造成頗大誤差,會影響熱交換器的設計品質。本計畫將進一步探討用於熱交換之各種形狀冷/熱管或容器在考慮熱輻射時之完整熱傳特性研究。冷/熱容器和管路之保溫同樣在工業和生活上之應用非常普遍,一般熱傳專家學者在經驗上認為由於保溫降低表面溫度和環境溫度的差距,因此熱輻射便可忽略不算。故此在一般熱傳和冷凍空調教科書在保溫例題示範和業界在保溫實務設計上,幾乎一致性地忽略輻射熱傳的影響。但經我們以絕熱圓管在實際應用情況來來模擬驗證,只要在外部熱對流係數不大和隔熱材包覆不太厚且隔熱材表面放射率很高時,熱輻射的影響便不可忽略,否則造成不少誤差,甚至會導致影響熱系統或冷凍空調設計的品質。本計畫主持人和共同主持人近年來共同研發出對各種形狀冷/熱管或容器在不考慮熱輻射條件下可靠一維近似模型,本計畫將在此基礎下進一步改良出可適用於考慮熱輻射之各種形狀保溫冷/熱管或容器之可靠的一維近似完整熱傳模型。本計畫另一目的是證明使用高放射率表面可提高熱交器的性能和使用低放射率絕熱表面可提高絕熱的效果。
    Heat exchangers are widely applied to the industries and our common living surroundings, because the heat radiation equation contains the 4th order exponential of temperature which is very complicate in calculations. Thus most heat transfer experts and scholars recognized from their own experiences that the heat radiation effect can be ignored while the temperature difference between outer duct surface and surrounding is not great enough. From this view point, the heat exchangers demonstrated examples shown in most heat transfer as well as air conditioning and refrigeration text books, and the practical commercial designs of heat exchangers, commonly ignore the effect of heat radiation. From our simulation practices of a circular duct in some practical situations, it is found that the heat radiation effect can not be ignored in the situations of low ambient convective heat coefficient and greater surface emissivities even in the situation of the temperature difference between outer duct surface and surrounding is not very big. In those situations, the heat radiation ignore will affect the design quality of heat exchanger. This project will study detail about the complete heat transfer characteristics of various-shape ducts and containers applying to heat exchanging with the heat radiation effect. The insulations of cold/hot containers and ducts are commonly applied in the industries and living surroundings as well. Most heat transfer experts and scholars recognized from their own experiences that the heat radiation effect can be ignored due to the small temperature difference between insulated surface and surrounding. From this view point, the insulation demonstrated examples shown in most heat transfer as well as air conditioning and refrigeration text books, and the practical commercial designs of insulations, commonly ignore the effect of heat radiation. From our simulation practices of an insulated circular duct in some practical situations, it is found that the heat radiation effect can not be ignored in the situations of thinner insulation with low ambient convective heat coefficient and greater surface emissivities. In those situations, the heat radiation ignore will affect the design quality of insulation. The host and co-host of this project have developed a series of reliable one-dimensional heat transfer models for insulated arious-shape ducts and containers without considering the heat radiation effect. This project will based on the former results to develop the suitable and reliable one-dimensional heat transfer models for insulated various-shape ducts and containers considering the heat radiation effect. The other purpose of this project is to prove that using greater surface emissivity can improve the performance of heat exchanger and using smaller insulated surface emissivity can improve the performance of insulation.
    Appears in Collections:[機械工程系所] 研究計畫

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