Mixing Efficiency of TEE

Objective :-

Your job is to set up steady-state simulations to compare the mixing effectiveness when hot inlet temperature is 36⁰C & the Cold inlet is at 19⁰C.

Use the k-epsilon and k-omega SST model for the first case and based on your judgment use the more suitable model for further cases. Giving the reason for choosing a suitable model is compulsory.

• Case 1
  • Short mixing tee with a hot inlet velocity of 3m/s.
  • Momentum ratio of 2, 4.
• Case 2
  • Long mixing tee with a hot inlet velocity of 3m/s.
  • Momentum ratio of 2, 4.
• Momentum ratio = velocity at cold inlet / velocity at hot inlet

In a table, compare the following values from the 2 cases.

Introduction :-

The mixing TEE geometry of mixing fluids or in this case air is generally useed for application that requires efficient mix of two streams of fluid these type of geometry are used widely i high pressure application such as air conditioners etc

Procedure:-

• Case 1
  • Short mixing tee with a hot inlet velocity of 3m/s.
  • Momentum ratio of 2, 4.
• Case 2
  • Long mixing tee with a hot inlet velocity of 3m/s.
  • Momentum ratio of 2, 4.

Setup Details :-

• Type of solver = Pressure based
• Fluid = Air
• Turbulece Model = K-Epsilon and k-Omega
• initial condition = Hybrid initialization.
• num of iteration = 250.
• wall type = no slip.
• Time step frequency = 1.

Case = 1

SHORT MIXING TEE

Momentum 2 & Mesh Grading 5 :-

Geomentry Model :-

Mesh Model :-

K-Epsilon Model :-

Temperature Graph:-

Residuals graph:-

Standard deviation Graph :-

Velocity Graph :-

Temperature contour :-

Temperature along :-

Velocity contour :-

Velocity along :-

K-Omega Model :-

Temperature Graph:-

Residuals graph:-

Standard deviation Graph :-

Velocity Graph :-

Temperature contour :-

Temperature along :-

Velocity contour :-

Velocity along :-

Perform Mesh independent study for any one case.

Momentum 4 & Mesh Grading 2 :-

K-Epsilon Model :-

Temperature Graph:-

Residuals graph:-

Standard deviation Graph :-

Velocity Graph :-

Temperature contour :-

Temperature along :-

Temperature along closed mesh :-

Velocity contour :-

Velocity along :-

Velocity along close mesh:-

Momentum 4 & Mesh Grading 5 :-

K-Epsilon Model :-

Temperature Graph:-

Residuals graph:-

Standard deviation Graph :-

Velocity Graph :-

Temperature contour :-

Temperature along :-

Velocity contour :-

Velocity along :-

K-Omega Model :-

Temperature Graph:-

Residuals graph:-

Standard deviation Graph :-

Velocity Graph :-

Temperature contour :-

Temperature along :-

Velocity contour :-

Velocity along :-

Case-2

LONG MIXING TEE

Momentum 2 & Mesh Grading 5 :-

Geomentry Model :-

Mesh Grading:-

K-Epsilon Model :-

Temperature Graph:-

Residuals graph:-

Standard deviation Graph :-

Velocity Graph :-

Temperature contour :-

Temperature along :-

Velocity contour :-

Velocity along :-

K-Omega Model :-

Temperature Graph:-

Residuals graph:-

Standard deviation Graph :-

Velocity Graph :-

Temperature contour :-

Temperature along :-

Velocity contour :-

Velocity along :-

Momentum 4 & Mesh Grading 5 :-

K-Epsilon Model :-

Temperature Graph:-

Residuals graph:-

Standard deviation Graph :-

Velocity Graph :-

Temperature contour :-

Temperature along :-

Velocity contour :-

Velocity along :-

K-Omega Model :-

Temperature Graph:-

Residuals graph:-

Standard deviation Graph :-

Velocity Graph :-

Temperature contour :-

Temperature along :-

Velocity contour :-

Velocity along :-

From the above images

• The resultant average temperature in both K-Episilon and K-Omega is similar only.
• K-Episilon is easly converged
• The irrespective of length of the pipe the average temperature observed in both the cases is the same therefore it can be said that lenghth does not effect the mixing .
• The velocity of the cold fluid effect the average temperature and mixing the fluids if the velocity of cold air is higher than the average temperature of the fluid at outlet is lower
• using finer mesh or not the average temperature of the outlet fluid doe not differ much therefore mesh independent study can be performed.
• The outer temperature of the fluid when momentum ratio 2 or4 are 31 c and 2 c

Conclusion:-

1. K-Epsilon turbulence is preferable as the K-o=Omega gives higher deviation thus being less accurate.
2. Higher the momentum ratio greater efficirncy of the TEE pipe.
3. The length of the pipe does not efficiency therefore shorter pipe length is recommended to savwe material costs .
4. Short TEE pipe usefull.