Week 1- Mixing Tee

Internal flow simulation for Mixing Tee

Aim: To analyze average temperature and standerd diviation in outlet for two given cases

Case 1:

1. • Short mixing tee with a hot inlet velocity of 3m/s.
   • Momentum ratio of 2, 4.
   • hot inlet temperature is 36⁰C & the Cold inlet is at 19⁰C.

Theory :

In CFD the softwares uses the continuity momentum , mass and energy conservation equations nothing but the Navier stokes equation,

solving partial diffrential equation is possible but solveing non linier partial diffrential equations is very very tough where reynolds numers power to 6 and more will in such case Computional fluid dynamics help to solve equations ,

In present senario we are mesureing average outlet temprature while inlets from 2 diffrent temperature and velocity

here we to sutdy the effect of the change in velocity over temp we change momentum ratio and

to study the effect of length of pipe we use short and long pipes for diffrent cases

Methodology

Volume is been extracted and above thickened solid is suppresed for phsysics

After completing the Geometry setup we use Mesing module to mesh the model and create named selection and

give them like Inlet X ( hot air ) inlet and inlet Y(cold air)and and outlet Pressure is gauss pressure 0

other surfaces are given as walls

After finishing the mesh we move towards the Setup and solving by opening ansys fluent

Here we Run steady state and hybrid solvers and as thiere exis the temperature we use energy equation and

Physical model as my judgement i use the K epsilon

And we creat report to know outlet tempertature thats Surface based area wieghted avarage temperture at outlet

to know effectiviness of mixing we use the Stnadard diviation for temperature at outlet

Results

above resuiduels for 12m/s

for 12m/s

for 12m/s

Countor plots

Length of Mixing Tee	Shrot
Cell counts	12730
Average outlet temperature for Momentum ratio 2(6m/s)	300C 80iterations
Average outlet temperature for Momentum ratio 4(12m/s)	270C 137Iiterations
No of iterations to converge

Movementum ratio 2(6m/s)

Conclusion

From the above data we got know that As change in Velocity at inlet (cold inlet ) as increses the tempertature decreses

Momentum ratio incresed from 2 to 4 thats 6m/s to 12m/s velocity temperature decresed from 36degree to 30degrees for 6m/s 27degrees for 12m/s.

CASE 2: Long mixing tee

Here in this case we study the effectivness of the lenght of the pipe for the average outlet temperature

As above case 1 here we used same procedure to set geometry and solve

Tabel for comparision

Length of Mixing Tee	Shrot	Long
Cell counts	12730	15663
Average outlet temperature for Momentum ratio 2(6m/s)	300C 80iterations	29.530C 70iterations
Average outlet temperature for Momentum ratio 4(12m/s)	270C 137Iiterations	270C 80iterations
No of iterations to converge

Line plots along the pipe for long mixing tee

For case 2 Velocity at inlet is decresed to 12m/s to 6m/s

below are the results counoutor plots and line plots

Contour plots

Lines plots for Velocity and temperature

Conclusion

From the above data we can conclude that Momentum ratio is inversly proportional to temperature at out let

and as Length of the pipe increses not much changes occered in temperature at outlet from case 1 short length to long length

Lets make on Mesh indipendent study one case 12m/s long mixing tee

Basicaly mesh indipendent study means makeing the results very very less dependent on mesh that is like makeing the mesh more refined step by step and at some point results become contant then results are mesh indipendent

after makeing mesh more refinied

27.43degreee outlet temperature is which is not much change and for this case result are indipendent of the mesh .