Week 1- Mixing Tee

AIM: To simulate and study the flow and mixing effectiveness of a short and long tee for different momentum ratio.

OBJECTIVE:

• volume extraction of model through spaceclaim.
• perform defined mesh.
• setup the boundary conditions of k-epsilon and k-omega sst,different momentum ratios,velocitys and temperature.
• And finally CFD post process of contour and line plots.

INTRODUCTION:

The device is used to control flow stream. the fluid stream enters with two inlets and passed out to combined of mixture at outlet .the hot fluid stream is along with x direction,the cold flow stream along with y direction and finally the average temperature stream along with x direction set up steady-state simulations to compare the mixing effectiveness when hot inlet temperature is 36⁰C & the Cold inlet is at 19⁰C.

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

FORMULA:

Momentum ratio = velocity at cold inlet / velocity at hot inlet

PROCEDURE:

case 1: shorter mixing tee K-EPSILON

• velocity at hot inlet =3 m/s
• temperature at hot inlet=36c
• temperature at cold inlet=19c
• momentum ratio=2

geometry:

1.importing the model.

2.fluid volume extraction.

3.suppress for physics.

1.importing the model:

the first step in this case is importing the solid tee model to the space claim.

2.fluid volume extraction:

volume extraction is defined as extracting the volume phase from the solid geometry. here the fluid volume is extracted by using the volume extraction command.

3.suppress for physics:

suppress for physics is a command it is used to deactivate the solid model.in this case we only requires the fluid volume so that the solid model is suppresed.

meshing:

meshing is the process of dividing the solid model into a small individual element.here we are discretizing the solid model into a small element of size 0.003m.we obtained,

no of elements = 12686

no of nodes = 2825

after completion of meshing naming should be done. proper naming should be given for all the faces and the quality of the each element is checked.

set up:

this is the major step in analysis because here only we gave the values and conditions of the tee model.this case runs under the following condition,

general:

1.steady state

2.pressure based solver

material:

fluid-air

model:

1.k epsilon -standard k epsilon-standard wall function

cell zone condition:

volume-fluid-air

boundary condition:

1.inlet x- velocity inlet-3m/s

2.inlet y- velocity inlet-6m/s

initialization :

after intialization a plane has to be created normal to the z axis. the temperature and velocity of the tee is analysed in the plane and average temperature at the outlet is to be calculated.finally the calculation is to be runned for 600 iterations.

solution:

the calculation is converged in the 145 iterations.

result:

temperature contour :

temperature line plot :

velocity contour:

velocity line plot:

case 2: shorter mixing tee K-EPSILON

• velocity at hot inlet =3 m/s
• temperature at hot inlet=36c
• temperature at cold inlet=19c
• momentum ratio=4

meshing:

no of elements = 12686

no of nodes = 2825

solution:

the calculation is converged in the 90 iterations.

result:

temperature contour :

temperature line plot :

velocity contour:

velocity line plot:

case 2: shorter mixing tee K-OMEGA

• velocity at hot inlet =3 m/s
• temperature at hot inlet=36c
• temperature at cold inlet=19c
• momentum ratio=2

meshing:

no of elements = 12686

no of nodes = 2825

solution:

the calculation is converged in the 150 iterations.

result:

temperature contour :

temperature line plot :

velocity contour:

velocity line plot:

case 2: shorter mixing tee K-OMEGA

• velocity at hot inlet =3 m/s
• temperature at hot inlet=36c
• temperature at cold inlet=19c
• momentum ratio=4

meshing:

no of elements = 12686

no of nodes = 2825

solution:

the calculation is converged in the 130 iterations.

result:

temperature contour :

temperature line plot :

velocity contour:

velocity line plot:

case 2: long mixing tee K-EPSILON

• velocity at hot inlet =3 m/s
• temperature at hot inlet=36c
• temperature at cold inlet=19c
• momentum ratio=2

meshing:

no of elements = 15727

no of nodes = 3499

solution:

the calculation is converged in the 120 iterations.

result:

temperature contour :

temperature line plot :

velocity contour:

velocity line plot:

case 2: long mixing tee K-EPSILON

• velocity at hot inlet =3 m/s
• temperature at hot inlet=36c
• temperature at cold inlet=19c
• momentum ratio=4

meshing:

no of elements = 15727

no of nodes = 3499

solution:

the calculation is converged in the 100 iterations.

result:

temperature contour :

temperature line plot :

velocity contour:

velocity line plot:

Mesh independent study

meshing:

no of elements = 27080

no of nodes = 47439

LINK:

https://drive.google.com/file/d/15qkXkgP2mMdW_K8M2cotkc9JSC82A0tE/view?usp=share_link

conclusion:

in case 1 the momentum ratio is only 2 so that the ratio of the hot velocity and cold velocity is 1:2 due to this low velocity the fluid does not combine well so the efficiency in this case is very low.similarly in case 2 also has the same momentum ratio but here the length differs so that the efficiency is quiet high when compared to the case 1.where as in case 3 the momentum ratio is high when compared to other two cases and the velocity ratio is 1:4 so that the velocity at cold inlet is four times the velocity of the hot inlet.here the efficiency is directly proportional to the velocity at cold inlet.if the velocity at cold inlet increases the efficiency also increases.here case 3 has high efficiency when compared to other two cases.