蔬果收穫後冷藏貯藏階段之熱物性質預估模式研究

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論文名稱: 蔬果收穫後冷藏貯藏階段之熱物性質預估模式研究
研究生姓名: 張曜欽
指導教授姓名: 謝欽城;劉展冏
出版年: 2002
學校名稱: 國立屏東科技大學
系所名稱: 機械工程系
關鍵字: 熱流模擬軟體;熱物性質;預估;phoenics;Thermo-physical Properties;Prediction
摘要: 本研究以紅蘿蔔、白蘿蔔、馬鈴薯、印度棗、紅龍果、番石榴及蓮霧為實驗材料,進行蔬果冷卻程序之研究。研究中提供了一個簡易及有效的預測方法,以熱流套裝模擬軟體PHOENICS結合中心線固定溫度法來預測蔬果熱傳導係數(k)及熱擴散係數(α),並配合設計一量測系統予以驗證此預測方法之可靠性。冷卻過程中,樣品溫度的變化由熱電偶測得,並繪製成降溫曲線,由此冷卻曲線與電腦模擬冷卻曲線相互比較。最後將實驗所得的熱傳參數及外界條件輸入熱流套裝模擬軟體,並以套裝軟體數值運算來求解蔬果的熱傳導方程式。比較冷卻曲線的估計值與實驗量測值之差異,結果發現此兩種冷卻曲線的趨勢相當一致,因此可利用本實驗模式來模擬蔬果冷卻時間之預估。 另以冷藏庫做蔬果貯藏鮮度實驗,以屏東地區所產蓮霧為材料,研究結果發現低溫貯藏期間不論櫥架壽命、色澤變化、質地特性方面,皆優於室溫對照組,證實以12℃貯藏不會造成蓮霧寒害,可降低總生菌數大幅延長櫥架壽命,對於色澤與質地方面有保持效果。In this research, the cooling process of carrot, radish, potato, Indian jujube, night-blooming gereus, guava, and wax-apple was studied. This thesis develops a simple but very effective method which combines the center-line-fixed-temperature method and the flow field simulation program PHOENICS to predict thermal conductivity (κ) and thermal diffusivity (α) of fruits and vegetables. A measuring system was also designed to test the developed method. The cooling curves of various specimens were established by measuring samples'' center temperatures using thermocouple and temperature recorder during the cooling process. The cooling curves from both experiment and simulation were compared with each other. Experimental parameters for heat transfer and boundary conditions of fruit and vegetable were fed to the flow field simulation program, and solved the heat conduction equation. The results showed that the differences of both aforementioned methods were minute, and the trend of cooling curves were corresponding consistent. Therefore this developed model can be utilized in predicting temperature distribution for fruit and vegetable during cooling or cold storage. Also in this study, wax-apple produced the freshness of in Ping-Tong were also studied for its low temperature, high humidity storage. The results indicated that low temperature contributed to the improvement of shelf-life, color change, and texture, comparing with room temperature storage. It proved that 12℃ would not cause the chill injury, and showed be useful in preserving the quality for fruits and vegetables.
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