臺灣博碩士論文加值系統

摘 要

本文主要探討冷凍室之物品於冷凍時之降溫效率，提供使冷凍業者對冷凍室內物品擺置作為重要參考。主要參數包括：1.冷凍室內部出風口位置與數量2.冷凍物品與地面間之距離3.分割冷凍物品為不同等份等三種。在數值求解方面，使用數值套裝軟體「I-DEAS」來模擬不同Case下之三維速度場與溫度場的分佈情形。研究過程中，藉由改變冷凍室出風口位置與數量之不同變化條件，找出能夠在較恰當時間內達到所需冷凍溫度的組合。接著再對此冷凍室內擺入冷凍物品，並調整物品與地面之間距，以及對具有同體積的物品切割成不同等份來分析。
由結果顯示冷凍室中增加出風口數量可有效提升冷凍室內溫度分佈的均勻性與冷卻速率，以及出風口位置設於冷凍室中央且風口朝下更能迅速降低冷凍室內溫度。冷凍物品若能具有適當的離地間距，則可減少冷凍室內高溫流體的聚積，並且增加氣流與物品之接觸面積，使得提升物品的冷卻速率。有效的分割冷凍物品成數個部份擺放，不僅有助於氣流的流通性，亦能減少渦流形成，增加流體與物品表面積的接觸，提高物品之冷凍速率。

ABSTRACT

In the study, the cooling of an object in a refrigerator is investigated. The main parameters include the location of inlet of air flow, the distance of frozen food away from ground, and the partition of frozen food on the bases of a same volume. In the analysis, the software of I-DEAS was applied to solve the three dimensional flow field and temperature distribution numerically. The purpose of the present study is to find an appropriate arrangement with a proper time to achieve the required cooling situation.
The results show that the increase in the number of the inlet increases the cooling rate and a more uniform temperature distribution is detected. As the loop between inlet and exit of air flow is shortened, the circulating effect is pronounced. The frozen food raised from the ground and the partition of frozen food can both promote the cooling rate as well as the improvement in uniform temperature profile inside the frozen food, Through the present study, it provides an important reference to the industrial application.

目 錄

中文摘要.................................................Ⅰ

英文摘要.................................................Ⅱ

目錄.....................................................Ⅲ

表目錄...................................................Ⅵ

圖目錄...................................................Ⅶ

符號說明.................................................ⅩⅠ

第一章 緒論..............................................1
1-1 前言..................................................1
1-2 文獻回顧..............................................3
1-3 研究目的..............................................7
第二章 數值方法..........................................8
2-1 簡介..................................................8
2-2 物理模型..............................................8
2-3 基本假設.............................................10
2-4 統御方程式...........................................11
2-5 紊流模式.............................................12
2-6 數值求解程序.........................................14
2-6-1 基本元素有限體積法簡介.............................14
2-6-2 離散方程式.........................................15
2-7 數值模擬程序.........................................17
第三章 熱傳分析.........................................24
3-1 紐塞數...............................................24
3-2 熱傳量...............................................26
第四章 結果與討論.......................................27
4-1 格點測試.............................................27
4-1-1 不同時間階誤差量討論...............................28
4-1-2 不同時間格點對CPU運算時間討論......................29
4-2 冷凍室對不同位置與數量出風口之討論...................29
4-2-1 冷凍室之熱流場分析.................................30
4-2-2 冷凍室之溫度冷卻特性...............................32
4-3 不同冷凍物品擺放位置之影響...........................34
4-3-1 冷凍物品及周圍之熱流場分析.........................34
4-3-2 冷凍室與冷凍物品之冷卻速率.........................37
4-4 冷凍物品做數個分離部份之探討.........................38
4-4-1冷凍物品及周圍之熱流場分析..........................38
4-4-2 冷凍物品與冷凍室之冷卻速率.........................40
4-5 不同冷凍物品擺置與分離對紐賽數之討論.................41
第五章 結論.............................................73
參考文獻.................................................74

參考文獻

1. Foster, A. M., Barrett, R., James, S.J. and Swain, M.J., “Measurement and Prediction of Air Movement Through Doorways in Refrigerated Rooms,” International Journal of Refrigeration, Vol. 25, pp. 1102-1109 (2002).

2. Huan, Z., Ma, Y. and He, S., “Airflow Blockage and Guide Technology on Energy Saving for Spiral Quick-Freezer, International Journal of Refrigeration, Vol. 26, pp. 644-651 (2003).

3. Wang, H. and Touber, S., “Distributed Dynamic Modeling of a Refrigerated Room,” International Journal of Refrigeration, Vol. 13, pp. 214-222 (1990).

4. Cortella, G., Manzan, M. and Comini, G., “CFD Simulation of Refrigerated Display Cabinets,” International Journal of Refrigeration, Vol. 24, pp. 250-260 (2001).

5. Tso, C. P., Yu, S. C. M., Poh, H. J. and Jolly, P. G., “Experimental Study on the Heat and Mass Transfer Characteristics in a Refrigerated Truck,” International Journal of Refrigeration, Vol. 25, pp. 340-350 (2002).

6. Huan, Z., “Performance Evaluation Indexes for Quick-Freezers,” International Journal of Refrigeration, Vol. 26, pp. 817-822 (2003).

7. Campanone, L. A., Giner, S. A. and Mascheroni, R. H., “Generalized Model for the Simulation of Food Refrigeration. Development and Validation of the Predictive Numerical Method,” International Journal of Refrigeration, Vol. 25, pp. 975-984 (2002).

8. Huan, Z., He, S. and Ma, Y., “Numerical Simulation and Analysis for Quick-Frozen Food Processing,” Journal of Food Engineering, Vol. 60, pp. 267-273 (2003).

9. Hossain, M. M., Cleland, D. J. and Cleland, A. C., “Prediction of Freezing and Thawing Time for Foods of Regular Multi-Dimensional Shape by Using an Analytically Derived Geometric Factor”, International Journal of Refrigeration, Vol. 15, pp. 227-234 (1992).

10. Hossain, M. M., Cleland, D. J. and Cleland, A. C., “Prediction of Freezing and Thawing Time for Foods of Two-Dimensional irregular Shape by Using a Semi-Analytical Geometric Factor”, International Journal of Refrigeration, Vol. 15, pp. 235-240 (1992).

11. Tocci, A. M. and Mascheroni, R. H., “Freezing Times of Meat Balls in Belt Freezers: Experimental Determination and Prediction by Different Methods,” International Journal of Refrigeration, Vol. 17, pp. 445-452 (1994).

12. Schneider, G. E. and Raw, M. J., “Control-Volume Finite Element Method for Heat Transfer and Fluid Using Co-located Variables-l Computational Procedure,” Numerical Heat Transfer, Vol. 11, pp. 363-390, (1987).

13. Thomas, M .E., Shimp, U. R., Raw, M. J., Galpin, P. F. and Raithby, G. D., “The Development of an Efficient Turbo Machinery CFD Analysis Procedure,” AIAA/ASME/SAE/ASEE/ 25th Joint Propulsion Conference, Monterey, CA, July 10-12, (1989).

14. Rhie, C. M. and Chow, W. L., “A Numerical Study of the Turbulent Flow Past and Isolated Airfoil with Trailing Edge Separation,” AIAA, Paper. 82-0998, (1982).

15. MAYA Heat Transfer Technologies Ltd., “I-DEAS ESC Reference Manual,” ESC ref9w, (2001).

16. Incropera, F. P. and Dewitt, D. P., “Introduction to Heat Transfer,”4rd ed., Appendix A, JOHN WILEY and SONS, (2002).

17. Moureh, J. and Derens, E., “Numerical Modeling of the Temperature Increase in Frozen Food Packaged in Pallets in the Distribution Chain,” International Journal of Refrigeration, Vol. 23, pp. 540-552, (2000).
18. “I-DEAS Electronic System Cooling Analysis,” from
C:\SDRC\I-DEAS9\SDRCHelp\LANG\English\vendor\maya\escref9

19. “ESC Flow Solver and Modeling Theory,” from
http//:www.mayasim.com/experse/papers/