冷凍乾燥機熱交換器熱傳研究

Heat Exchanger Thermal Analysis of Research on Freeze-Drying Equipment

陳俊宏(Chun-Hung Chen)

指導教授 ： 鄭鴻斌

國立臺北科技大學/機電學院/能源與冷凍空調工程系碩士班/碩士(2011年)

摘要

熱交換器的效率對冷凍真空乾燥機的性能影響很大，因此本論文利用計算流體力學(CFD)分析軟體FULENT_6.3模擬殼側部份各案例變化，分析其溫度及流場分布。本模擬分析應用於冷凍真空乾燥機的方法，採質量守衡與能量守衡方程式配合 紊流模式及有線體積SIMPLE法進行數值分析。此外，藉由改變電熱管之長短、增設隔板以及隔板加熱方式，確保系統省能與增加效率。經由多樣化案例模擬，獲致下列幾項結果：電熱管總表面溫度不變下，電熱管長度越短換熱效率越差，其效率與傳熱表面積大小呈現非等比例變化；增設隔板，改變流體流向而增加擾動，提高熱交換率；加熱隔板其加熱面積與電熱管總表面積相同，僅做幾何改變以取代電熱管加熱，加熱隔板較電熱管換熱次數多，可改善熱交換效率。總之，基於冷卻及加熱同時考量下，本研究建議採用具山形隔板之熱交換器，其冷熱混合型設計在本研究案例中較傳統式設計可提升166.1%，可作為冷凍真空乾燥系統效能改善參考。

關鍵字

螺旋管 ； 電熱管 ； 熱交換器 ； 計算流體力學 ； 冷凍乾燥

並列摘要

The efficiency of heat exchanger has a great impact on the performance of freeze vacuum dryer, therefore, this study used the CFD analytical software FULENT_6.3 to simulate various changes in shell side and analyze the temperature and flow field distribution. This simulation analysis was applied to the freeze vacuum dryer. The mass conservation and energy conservation equations, turbulence model and finite volume SIMPLE method were used for numerical analysis. In addition, the system energy was saved and the efficiency was increased by changing the length of electric heating tube, adding spacer plates and spacer plate heating modes. The results showed that if the total surface temperature of electric heating tube does not change, the shorter the electric heating tube, the worse the heat exchange efficiency, the efficiency and the heat transfer surface area change in unequal ratios; adding spacer plates that changing the flow direction could increase disturbance and heat-exchange rate; the heating area of heating spacer plate is identical with total surface area of electric heating tube, there is only geometric change replacing electric heating tube to heat, the heat exchange of heating spacer plate is more frequent than that of electric heating tube, the heat exchange efficiency can be increased. To sum up, considering cooling and heating at the same time, this study suggests adopting the heat exchanger with chevron spacer plates, the cooling-heating hybrid type design can increase the efficiency by 166.1% in the cases of this study compared with traditional design. The findings can serve as references for improving the efficiency of freeze vacuum drying system.

並列關鍵字

helical tube ； electric heating tube ； heat exchanger ； CFD ； Freeze-drying

參考文獻

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