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標題: | 過熱蒸汽蒸煮澱粉類食物之熱質傳研究 Study on Heat and Mass Transfer in Superheated Steam Heating Process of Starchy Food |
作者: | Hung-Wen Chen 陳泓文 |
指導教授: | 李允中(Yeun Chung Lee) |
關鍵字: | 過熱蒸汽,熱質傳遞,數值模擬,有限元素法, Superheated steam,Heat and mass transfer,Finite element method,Mathematical modeling, |
出版年 : | 2013 |
學位: | 碩士 |
摘要: | 過熱蒸汽指是在特定壓力下其溫度高於該壓力沸點之蒸汽,利用過熱蒸汽處理食物可以讓食品品質較不易流失,且過熱蒸汽比熱空氣乾燥有更高的能源效率。雖然過熱蒸汽使用於食品加工上已經有相當長一段時間,但仍尚未完全建構出過熱蒸汽處理孔隙性澱粉過程時之熱質傳現象耦合現象。在本研究中,我們的實驗原型以商品化水波爐產生之過熱蒸汽加熱孔隙性澱粉食物--饅頭,並且以T型熱電偶及濕度感測晶片及電子天秤紀錄加熱過程中的饅頭內部溫度、濕度及重量變化。在加熱過程中,從溫度變化可觀察到水份的蒸發及凝結對於熱質傳有顯著的影響,水蒸汽在孔隙性食物中的穿透使得升溫溫度曲線與非孔隙食材明顯不同,且表面與食材內部溫度也因為水份含量的多寡有著相當大的溫差。在數學模型的建立上,本研究中以能量及質量傳遞當作統御方程式,在生成項部份放入水份的凝結項,此凝結項會造成被蒸煮食材內部產生能量、水份及水蒸汽含量之變化,而邊界條件上也將過熱蒸汽初期凝結、後期接近乾燥之現象考慮進去。我們以有限元素模擬軟體(COMSOL Multiphysics)將上述數學模型之模擬結果與實驗數據比較,以驗証本數學模型假設之正確性。模擬結果與實驗數據與模擬數值吻合,因此在本研究中建立之數學模型可提供澱粉類孔隙性食物在過熱蒸煮上的基礎研究,並在未來可應用於更複雜的食品材料上。 Superheated steam means the steam temperature is higher than the boiling point under the ambient pressure. The usage of superheated steam in food process industry provides some benefits, like high energy efficiency and f maintaining better food quality. Superheated steaming has been applied in food treatment for decades, the heat and mass transfer mechanism of superheated steaming in porous starchy food has not been fully explored. In this study, we developed the mathematical models which coupled with energy, water and vapor transport during superheated steaming process. Experiments of reheating a porous starchy food, the steamed buns in our case, was operated to observe the temperature, humidity and weight change under superheated steaming. The mathematical models involved the governing equations of heat and mass transfer with water condensation and evaporation in the porous starchy matrix and the boundary conditions was considered of superheated steaming environment. We compared the experimental data with the simulation results which solved by commercial finite element software (COMSOL Multiphysics) to verify the correctness of this models. It showed a good agreement between the experimental and simulation results in temperature and water content change during the process. The effects of water condensation and evaporation were significant during the heating process; the vapor transported through the porous media can contribute different temperature increasing profile from other non-porous material. The models constructed in this study can provide a fundamental concept of superheated steam treatment in porous starchy food for the future study in more complicated food process. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/60474 |
全文授權: | 有償授權 |
顯示於系所單位: | 生物機電工程學系 |
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