This assignment analyzes fluid flow and heat transfer in a mixing elbow using CFD. The objective is to calculate velocity distribution, temperature changes, and pressure distribution as two fluids at different temperatures and velocities mix. Hexahedral and tetrahedral meshes are used and compared. Results show uneven mixing and temperatures. Recommendations include increasing the inlet diameter and changing the inlet location to improve mixing and using external cooling to balance temperatures.

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Assignment No. 01
Mixing Elbow
21.05.2021
Shivam choubey
Student No: CFDB30321004

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Objective
• Objective of this study is to understand mixing elbow problem.
• Calculate Velocity distribution over bend pipe.
• Calculate Temperature destruction between fluids.
• Calculate and understand pressure distribution over bend
pipe.

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Problem Statement
As shown in the picture, has following boundary conditions are used during the simulation.
Image 1
Boundary Name Temperature Velocity
Inlet 1 100°C 50 m/s
Inlet 2 70°C 30 m/s
• The main object is to understand
temperature velcotiy and pressure after
mixing.
• Pressure is 1 atm.
• Working fluid is water.
• Walls are Adiabatic.
Inlet1
Inlet2
outlet

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CFD Setting
Image 2 Meshing view
Mesh 1
Hex mesh
Parameter
Nodes 41279
Skewness 0.932
Volume 4.236728e-03
Orthogonal
Prop.
0.07
Aspect ratio 34.45
Mesh 1
Tetra mesh
Parameter
Nodes 48749
Skewness 0.932
Volume 5.249490e-03
Orthogonal
Prop.
0.15
Aspect ratio 15.45

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Results
Image 4 (Setup) Image 5 (Residual)
• Used 3 procsses to solve problem.It is fast compare to serial processes.
• To see image 5, we could say residual is almsot constant.
• The residual is almost constant after 250 iteration.

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Image 6
Image 6.1
Image 7 Image 7.1

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Image 8 Image 8.1
• Image 6 and image 6.1 show,inlet2 is velocity decreases due to friction of pipe wall. When inlet1 has more
velocity than inlet2, this makes increases velocity suddenly.
• Image 7 and image 7.1 shows that,inlet2 temp are more then compare to inlet1 , it makes decreases in
temp due to mixing.
• Fluid is not fully mixed .

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Tetra Meshing
• Both of mesh are showing same result.
• Result shows tetra mesh working good
while mixing.
• Hexa mesh is really fast
convergence,compare to tetra meshing

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Design Recommendation
During this analysis there is two main problems have been seen:
•Mixing is not Proper
•To solve this we could increase the inlet1 diameter.
•We can also change the location of inlet1.
Temperature distribution is not homogenous
•To solve this problem improving mixing will also help.
•We can use external cooling to balance the temperature.

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Conclusion
• During simulation, it is clear that the velocity at the outlet (nearly 37 m/s ) is more compare to inlet2 (30
m/s) and less than inlet1 (50 m/s). This is a correct observation according to theory.
• Inlet 2 temp. is 70°C and inlet 1 temp. 100°C, after mixing temp. at an outlet is nearly 79°C. This is also a
correct observation according to theory.
• Mixing is not good inside the section.
• Temperature is high in some places that may cause stress imbalance.
• If the fluid is hot then proper insulation must be used.