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研究生：	洪凱納 Kelana, Nugroho Putra
論文名稱：	具有定通量的圓形管中紊流熱性能增益之研究 Study on thermal performance enhancement of turbulent flow in a circular tube with constant heat flux
指導教授：	吳鴻文 Wu, Hong Wen
學位類別：	碩士 Master
系所名稱：	工學院 - 系統及船舶機電工程學系 Department of Systems and Naval Mechatronic Engineering
論文出版年：	2020
畢業學年度：	108
語文別：	英文
論文頁數：	99
中文關鍵詞：	熱傳增益、扭旋片安裝、方形切口、等邊三角形長縫、摩擦因子增益比、熱液動性能
外文關鍵詞：	Heat transfer enhancement, twisted tape insert, square-cut, equilateral triangle slit, friction factor enhancement ratio, thermal-hydraulic performance
相關次數：	點閱：101 下載：0
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摘要
具有扭旋片插入物的圓形管中的熱傳遞具有對流熱交換器的能力，這需要提高能量利用率並減小尺寸和成本。使用水作為工作流體，數值為6.9892 Prandtl，對具有不同類型的三角形穿孔和增加的方形切口的設計扭旋片插入件進行了數值研究。扭旋片插入物有五種類型的三角形穿孔尺寸，分別為16 mm，14 mm，12 mm，10 mm和8 mm，雷諾數範圍為6000、10000和14000的三種不同值用於研究當前工作中的傳熱和流體流動特性。首先用不具插入件的光滑管驗證數值模型，並將其與從Dittus-Boelter相關性獲得的結果進行比較。並與Vashista等人單扭旋片的實驗數據加以比較，發現兩者結果一致且相近。
由連續性，能量和動量控制的方程式在管壁處施加恆定的壁溫。在入口處，指定了水的流速和溫度。在出口處，使用流出條件。邊界條件求解器的類型是基於壓力的時間穩定的，然後在k-ε模型中使用RNG。結果表明，具有三角形穿孔插入件的圓管在尺寸溫度下的熱工液壓性能因子和摩擦因子比其他更高，這被認為是性能更好的原因。雷諾數為6000的模擬溫度顯示最高溫度473.1654 K，網目號為3807824，在銅管區域的熱通量為719066.2 W / m2。開發並驗證了努塞爾特數和摩擦因數與雷諾數的函數與比率3.5扭旋片之間的關係。

Abstract
Heat transfer from a circular tube installed by twisted tape insert has the capacity of a convectional heat exchanger to increase the energy level and minimize size and cost. The design for twisted tape inserts with different types of perforated triangle and inserted square-cut is investigated numerically using water as working fluid with Prandtl number of 6.9892. The tape inserts have five sizes of 16 mm, 14 mm, 12 mm, 10 mm and 8 mm perforated triangle with three different values of the Reynolds number equal to 6000, 10000 and 14000 to explore the fluid flow and thermo-hydraulic performance in the current work. According to the results obtained from the Dittus-Boelter, the numerical simulation is first validated with a smooth pipe. Furthermore, the present results of single twisted tape insert are compared with the experimental data of Vashista et al, and the comparison results are fairly consistent.
Fluid flow and heat transfer past the tube with a constant heat flux is subject to the equations of continuity, energy and momentum. Water speed and temperature are specified at the inlet. At outlet, an outflow condition is used. The solver type is pressure based with steady and RNG in k-epsilon model. The results show that thermo-hydraulic performance of the circular tube with triangular perforated insert is higher compared to others as the reason for improving performance. Simulation temperature with H10 model and Reynolds number 6000 shown the maximum temperature 473.1654 K with mesh number 3807824 and heat flux is 719066.2 W/m2 on copper tube area. The relationship between Nusselt number and friction factor enhancement ratio is developed and validated as a function of Reynolds number with twisted tape ratio 3.5.

Content

摘要	I
誌謝	II
Abstract	III
Content	V
List of Table	VII
List of Figure	VIII
Nomenclature	XII
Chapter 1 Introduction	1
1-1 Background	1
1-2 Literature reviews	3
1-3 Objectives and motivation of present study	11
Chapter 2. Concept of CFD and geometry	13
2-1 Fundamental	13
2-2 Assumptions	13
2-3 Mathematical formulas	14
2-3-1 K-Epsilon (ϵ) Model	16
2-4 Discretization method	18
2-4-1 Finite volume method	19
2-4-2 Least Square Gradient	20
2-4-3 Discretization of momentum equation	22
2-4-4 Discretization of continuity equation	23
2-5 SIMPLE method	24
2-5-1 The SIMPLE Computational process	26
2-5-2 Under-relaxation factor	27
2-6 Geometry model and mesh	28
2-6-1 Geometry	28
2-6-2 Mesh	29
2-6-3 Numerical model	30
2-7 Boundary conditions and Parameters	31
2-7-1 Boundary layer	31
2-7-2 Boundary conditions	33
2-7-3 Convergence criterion	34
2-7-4 Parameters	34
Chapter 3 Results and discussion	38
3-1 Grid independent test	38
3-2 Validation of simulation	40
3-3 Effect of different sizes of equilateral triangle slit on flowfield and temperature variation	41
3-4 Effect of different sizes of equilateral triangle slit on thermo-hydraulic performance	46
3-5 The Mass Flow Rate (MFR)	48
Chapter 4 Conclusions and future work	50
4-1 Conclusion	50
4-2 Future work	51
References	52

List of Table
Table 1. Summary of literature review in heat exchanger tube with insertion	57
Table 2. Summary of literature review in heat exchanger tube without insertion	61
Table 3. Dimension of twisted insert	64
Table 4. Properties of water	64
Table 5. Properties of aluminum	64
Table 6. Properties of Copper	65
Table 7. Mesh for each models	65
Table 8. Results of mesh independent test	66






 
List of Figure

Figure 1. A control volume with neighbors	67
Figure 2. One dimensional domain	67
Figure 3. Configuration twisted insert tape with tube	67
Figure 4. Boundary conditions	68
Figure 5. Temperature contour of the H10 model with Re=14000, Z/L1=0 until Z/L1=1000	68
Figure 6. Validation of Nusselt Number for smooth tube with Dittus-Boelter	69
Figure 7. Validation of friction factor data for smooth tube with Blasius	69
Figure 8. Comparison result between Single Twisted insert of Vashista [16] and present study	70
Figure 9. Flowfield pattern H8 at Z/L1=250-750 for Re at (a)6000, (b)10000 and (c)14000	71
Figure 10. Flowfield pattern H10 at Z/L1=250-750 for Re at (a)6000, (b)10000 and (c)14000	72
Figure 11. Flowfield pattern H12 at Z/L1=250-750 for Re at (a)6000, (b)10000 and (c)14000	73
Figure 12. Flowfield pattern H14 at Z/L1=250-750 for Re at (a)6000, (b)10000 and (c)14000	74
Figure 13. Flowfield pattern H16 at Z/L1=250-750 for Re at (a)6000, (b)10000 and (c)14000	75
Figure 14. H8 Temperature contour and streamline at Z/L1=500 for Re at (a)6000, (b)10000 and (c)14000	76
Figure 15. H10 Temperature contour and streamline at Z/L1=500 for Re at (a)6000, (b)10000 and (c)14000	77
Figure 16. H12 Temperature contour and streamline at Z/L1=500 for Re at (a)6000, (b)10000 and (c)14000	78
Figure 17. H14 Temperature contour and streamline at Z/L1=500 for Re at (a)6000, (b)10000 and (c)14000	79
Figure 18. H16 Temperature contour and streamline at Z/L1=500 for Re at (a)6000, (b)10000 and (c)14000	80
Figure 19. Velocity Vector of H8 at Z/L1=500 for Re at (a)6000, (b)10000 and (c)14000	81
Figure 20. Velocity Vector of H10 at Z/L1=500 for Re at (a)6000, (b)10000 and (c)14000	82
Figure 21. Velocity Vector of H12 at Z/L1=500 for Re at (a)6000, (b)10000 and (c)14000	83
Figure 22. Velocity Vector of H14 at Z/L1=500 for Re at (a)6000, (b)10000 and (c)14000	84
Figure 23. Velocity Vector of H16 at Z/L1=500 for Re at (a)6000, (b)10000 and (c)14000	85
Figure 24. Isothermal lines of H8 at Z/L1=500 for Re at (a)6000, (b)10000 and (c)14000	86
Figure 25. Isothermal lines of H10 at Z/L1=500 for Re at (a)6000, (b)10000 and (c)14000	87
Figure 26. Isothermal lines of H12 at Z/L1=500 for Re at (a)6000, (b)10000 and (c)14000	88
Figure 27. Isothermal lines of H14 at Z/L1=500 for Re at (a)6000, (b)10000 and (c)14000	89
Figure 28. Isothermal lines of H16 at Z/L1=500 for Re at (a)6000, (b)10000 and (c)14000	90
Figure 29. Turbulent Intensity of H8 for Re at (a)6000, (b)10000 and (c)14000	91
Figure 30. Turbulent Intensity of H10 for Re at (a)6000, (b)10000 and (c)14000	92
Figure 31. Turbulent Intensity of H12 for Re at (a)6000, (b)10000 and (c)14000	93
Figure 32. Turbulent Intensity of H14 for Re at (a)6000, (b)10000 and (c)14000	94
Figure 33. Turbulent Intensity of H16 for Re at (a)6000, (b)10000 and (c)14000	95
Figure 34. The Nusselt number versus Re for tubes with various equilateral triangle slit lengths	96
Figure 35. Variation of Nusselt number enhancement ratio with Reynolds number for different lengths of equilateral triangle lengths	96
Figure 36. The friction factor versus Re for tubes with various equilateral triangle slit lengths	97
Figure 37. Variation of friction factor enhancement ratio with Reynolds number for different lengths of equilateral triangle slit	97
Figure 38. Thermo-hydraulic performance factor as function of Re for different types of twisted tapes	98
Figure 39. The MFR of inlet	98
Figure 40. The MFR of outlet	99
                                    

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校內：2025-02-10公開
校外：2025-02-10公開

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