To study mixing efficiency in a tee geometry
In this project we will study the mixing efficiency of hot and cold air when they are mixed in a tee shaped pipe. For this we have taken 3 cases.
In all the 3 cases the inlet of hot air is considered to be the left hand side and outlet is the right hand side. The top opening is for the cold air.
CASE I : Short Tee
Length of pipe along x-direction: 0.19 m
Inlet temperature of hot air: 25 degree celsius
Inlet temperature of cold air: 10 degree celsius
Inlet velocity of hot air = 3 m/s
Inlet velocity of cold air = 6 m/s
No of iterations = 1150
The meshing pattern along center plane is shown below:
The mesh quality graph for the above meshing is shown below:
The area weighted average temperature at the outlet of the mixing tee comes out to be around 20 degree celsius as shown below:
The standard deviation of the outlet temperature is around 1.5 as shown below:
A graph comparing the value of scaled residuals against the number of iterations is shown as below:
The velocity profile along a plane cut on the middle is shown below:
The temperature profile is as shown below:
CASE II: Long Tee
Length of pipe along x-direction: 0.26 m
Inlet temperature of hot air: 25 degree celsius
Inlet temperature of cold air: 10 degree celsius
Inlet velocity of hot air = 3 m/s
Inlet velocity of cold air = 6 m/s
No of iterations = 1150
The meshing pattern along center plane is shown below:
The mesh quality graph for the above meshing is shown below:
The area weighted average temperature at the outlet of the mixing tee comes out to be around 20 degree celsius as shown below:
The standard deviation of the outlet temperature is around 1 as shown below:
A graph comparing the value of scaled residuals against the number of iterations is shown as below:
The velocity profile along a plane cut on the middle is shown below:
The temperature profile is as shown below:
CASE III: Short tee (Momentum ratio 4)
Length of pipe along x-direction: 0.19 m
Inlet temperature of hot air: 25 degree celsius
Inlet temperature of cold air: 10 degree celsius
Inlet velocity of hot air = 3 m/s
Inlet velocity of cold air = 12 m/s
No of iterations = 1150
The meshing pattern along center plane is shown below:
The mesh quality graph for the above meshing is shown below:
The area weighted average temperature at the outlet of the mixing tee comes out to be around 17.5 degree celsius as shown below:
The standard deviation of the outlet temperature is around 1 as shown below:
A graph comparing the value of scaled residuals against the number of iterations is shown as below:
The velocity profile along a plane cut on the middle is shown below:
The temperature profile is as shown below:
A comparison table concluding the above 3 cases is shown below:
From the above study we can make the following conclusions:
- Increasing the length of the pipe and keeping other parameters same did not make much difference to the outlet temperature.
- An increase in velocity of the cold air helps in lowering the outlet temperature of the mixing gases.
- Changing the length of pipe and keeping all other parameters same affects the number of iterations required for convergence.
- Varying the momentum ratio also afffects the number of iterations required for convergence.
In all the above three cases we observe that even after convergence there is disturbance/oscillations in the graph. This might be due to coarser meshing or a few bad cells in the mesh.