Numerical study of three dimensional forced convection flows in wavy and divergent

مقدم أطروحة جامعية

Bashir, Anmar Muwaffaq

الجامعة

الجامعة التكنولوجية

الكلية

-

القسم الأكاديمي

قسم الهندسة الكهروميكانيكية

دولة الجامعة

العراق

الدرجة العلمية

ماجستير

تاريخ الدرجة العلمية

2008

الملخص الإنجليزي

A computational study of three-dimensional fluid flow and heat transfer through a smooth wavy and diverged-converged ducts encountered in compact heat exchanger applications were carried out.

Laminar and turbulent flows at Prandlt number equals to 0.7 (for air) and 5.85 (for water) were used in this study, The governing equations were solved using CFD technique based on a body fitted coordinate formulation.

An elliptic grid generation technique was applied to transform geometry from curvilinear grid in physical domain in terms of (x, y, z) into rectangular grid in computational domain in term (£, n, v).

The governing equations (continuity, momentum, and energy) are discredited using finite volume method.

The final discredited forms of governing equations are solved iteratively using TDM A solver, the solution used the power law scheme and SIMPLE algorithm method for pressure and velocity correction.

The k-£ turbulence model was used for the turbulence flow with wall functions concept near walls. For wavy ducts, an aspect ratio of (L / H = 4), and length ratio of (L / 2a = 10, 6.67, 5) and for the diverged-converged duct, a height ratio (Hmim / Hmax = 0.55, 0-46, 0.39 and 0.33) were adopted.

Seven Reynolds numbers (50, 100, 200, 300, 3000, 4000, and 5000) were studied for laminar and turbulent flows to both geometries. A computer program using Fortran 90 language was modified and used to solve the flow in both geometries and the results for the diverged-converged duct are compared with that present by Bahaidarah et.

al.

2005 The numerical results for laminar and turbulent flows at all the length and height ratios showed that increasing Reynolds number leads to increase in vortex flow in the wall-waviness valley region.

This will causes the effect of the dominating viscous force and the boundary layer separation, it was also found that the maximum average Nusselt number for wavy duct at Pr = 0.7 and Pr = 5,85 is at length ratio (L / 2a = 10) but it becomes minimum at length ratio (L / 2a=infinity) for laminar How.

The maximum average Nusselt number for diverged-converged ducts is at a height ratio (Hmin/Hmax=0.46) at Pr=5.85 and it becomes minimum at height ratio (Hmin / H max =1) for laminar flow, while at Pr = 0.7 the maximum average Nussclt number is at a height ratio (Hmin / Hm4K=l) but it becomes minimum at a height ratio (Hmin / Hmax= 033) for laminar flow and (Hmin / Hmax= 0.39) for turbulent flow. Finally, it can be concluded that the wavy duct performs better than the diverged-converged duct in terms of average Nusselt number for air heat exchangers.

For water heat exchangers the behavior is approximately similar in both geometries.

التخصصات الرئيسية

هندسة الميكاترونكس

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• MLA
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لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-305367