臺灣博碩士論文加值系統

本文係利用有限體積法(FVM)離散Navier-Stokes方程式和能量方程式並化成代數方程組。接著運用解壓力耦合方程一致的半隱式方法(SIMPLE, Semi-Implicit Method for Pressure-Linked Equation Consistent) 迭代至收斂，獲得流場及溫度場。此模擬將三種不同斜肋間距比(為斜肋間距對風道高度比的簡稱)的鰭片: 斜肋間距比= 1.2、0.8和0.6，放置於33 mm x 33 mm x 750 mm通道內，固定放置高度(22mm)改變離入口的放置位置(230, 250 and 270 mm)和雷諾數(5000, 6500, 8000, 9500)，分析強制對流之溫度場與速度場分佈。
研究結果顯示:在雷諾數等於5000-9500，熱塊前端(0.3L)斜肋間距比= 0.6(C7)的平均紐賽數較其他兩種提高，最大增加率為7.2%。在雷諾數等於5000-9500，熱塊中段(0.33L)斜肋間距比= 0.8(C5)的平均紐賽數較其他兩種提高，最大增加率為6.0%。在雷諾數等於5000-9500，熱塊後段(0.36L)斜肋間距比= 0.6(C9)的平均紐賽數較其他兩種提高，最大增加率為10.3%，可以得知縮短間距有助於熱傳增益。從鰭片之平均紐賽數上看到，在雷諾數等於5000-9500，C2、C5和C8相較於其他擺放位置鰭片的平均紐賽數是最高的。在三種不同數量的斜肋間距比與三種不同的位置，在熱塊的中段，熱傳效益是最好的，熱性能係數隨雷諾數增加而下降，隨著鰭片移動到熱塊的中段(0.36L)，熱性能係數效益最佳，在C7得到最佳的熱性能係數。

The Navier-Stokes equations and energy equation are constructed by the Finite Volume Method (FVM) and then are discretized to a system of algebraic equations and dimensionless of mathematical formulation. They can be solved by semi-implicit method for pressure linked equations-consistent (SIMPLE). The solutions must be iterated to converge within each step to obtain the temperature and flow field.
This simulation places three different plate with slits and inclined ribs (pitch ratio= 1.2, 0.8 and 0.6) on a channel (33 mm x33 mm x750 mm) and changes the x direction (230, 250 and 270 mm) with four Re levels (5000, 6500, 8000, 9500) to investigate the temperature and flow field without gravity in forced convection.
In this study, the pitch ratio and the placed position of the plate with slits and inclined ribs are changed to study the effect of the influence on the heat transfer. At Re= 5000-9500, the (Nu)avg of pitch ratio= 0.6 (C7) in the front section of the heated blocks (0.3L) is improved compared with the other two cases (C1 and C4), and the maximum increase rate is 7.2%. At Re= 5000-9500, the (Nu) avg of pitch ratio= 0.8 (C5) in the middle section of the heated blocks (0.33L) is improved compared with the other two cases (C2 and C8), and the maximum increase rate is 6.0%. At Re= 5000-9500, pitch ratio= 0.6 (C9) in the rear section of the heated blocks (0.36L) is improved compared with the other two cases (C3 and C6), and the maximum increase rate is 10.3%, and it can be known that decreasing the pitch ratio contributes to the heat transfer. At Re= 5000-9500, the (Nu)avg of C2, C5 and C8 are higher than those of other placed positions. For three different pitch ratio and different placed positions, heat transfer benefit is best in middle section of the heated blocks, and the (Nu)avg of C5 is highest. The thermal performance factor decreases when the Re increases. When the plate with slits and inclined ribs is moved to the middle of the heated blocks, thermal performance factor increases the most. At Re= 5000-9500, thermal performance factor of C7 is highest.

摘要 I
誌謝 II
Abstract III
Content V
List of Table VII
List of Figure VIII
Nomenclature XIX
Chapter 1 Introduction 1
1-1 Background 1
1-2 Literature reviews 3
1-3 Objectives and motivation of present study 10
Chapter 2. Numerical theory and geometry 12
2-1 Principle 12
2-2 Mathematical formulation 12
2-2-1 Parameters 13
2-3 Renormalized Group (RNG) turbulence model 15
2-4 Discretization method 17
2-4-1 Finite volume method 17
2-4-2 Least Squares Cell Based 18
2-4-3 Discretization of momentum equation 19
2-4-4 Discretization of energy equation 20
2-5 SIMPLE method 20
2-5-1 Velocity-correction equation 20
2-5-2 Computational process 22
2-5-3 Under-relaxation factor 22
2-6 Geometry model and mesh 23
2-6-1 Numerical model 23
2-6-2 Geometry 23
2-6-3 Mesh 24
2-7 Boundary conditions and Parameters 25
2-7-1 Boundary conditions 25
2-7-2 Convergence criterion 25
Chapter 3 Results and discussion 26
3-1 Grid and time-step independent test 26
3-2 Accuracy of simulation 27
3-3 Influence of different pitch ratio to flow field and heat transfer performance 27
3-4 Influence of plate with slits and inclined ribs on different placement of X direction to flow field and heat transfer performance 30
Chapter 4 Conclusions and future work 33
4-1 Conclusion 33
4-2 Future work 34
References 35

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