Week 1- Mixing Tee

OBJECTIVE

To simulate the flow of air through the mixing of Tee and understand the length of pipe and momentum ratio of velocity for mixing of air by using two types of pipe i.e. short pipe and long pipe.

INPUT:

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
3. hot inlet temperature = 36 ⁰C
4. cold inlet temperature = 19⁰C

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

from the definition of momentum ratio, we calculated the velocity of the cold inlet = 7.2 m/sec.

STEP 1: PRE-PROCESSING:

1. first, we imported the CAD model as shown in figure 1 and remove the undesirable part which does not takes part in flow simulation

as shown in figure 2.

figure(1) : CAD MODEL

FIGURE(2): VOLUME EXTRACTED MODEL

• next step is to create a mathematical model i.e meshing but before messing we have to give boundary conditions to the body and then we create a mesh.

MESH GEOMETRY: MESH SIZE 0.005

FIGURE() : MESH MATRIX

SHORT LENGTH TEE:

MODEL: K-EPSILON

MOMENTUM RATIO: 2

HOT INLET VELOCITY : 3m/sec

COLD INLET VELOCITY: 6m/sec

NODES: 21331

ELEMENTS: 105879 RESIDUAL PLOT:

AREA WEIGHTED OF TEMPEATURE AND VELOCITY

STANDARD DEVIATION OF TMEPERATURE AND VELOCITY

CONTOUR PLOTS

MODEL: K-EPSILON

MOMENTUM RATIO: 4

HOT INLET VELOCITY : 3m/sec

COLD INLET VELOCITY: 12m/sec RESIDUAL:

AVERAGE WEIGHTED OF TEMPERATURE AND VELOCTY

STANDARD DEVIATION OF TEMPERATURE AND VELOCITY

CONTOUR PLOTS OF TEMPERATURE AND VELOCITY:

MODEL: K-OMEGA(SST)MODEL

MOMENTUM RATIO: 2

HOT INLET VELOCITY :3 m/sec

COLD INLET VELOCITY: 6m/sec RESIDUAL PLOT:

STANDARD DEVIATION OF TEMPERATURE AND VELOCITY

AREA WEIGHTED OF TEMPERATURE AND VELOCITY

CONTOUR PLOTS OF TEMPERATURE AND VELOCITY:

MODEL: K-OMEGA

MOMENTUM RATIO: 4

HOT INLET VELOCITY: 3m/sec

COLD INLET VELOCITY: 12m/sec RESIDUALS

AVERAGE WEIGHTED OF TEMPERATURE AND VELOCITY

STANDARD DEVIATION OF TEMPERATURE AND VELOCITY

CONTOUR PLOTS:

TEMPERATURE DISTRIBUTION

VELOCITY DISTRIBUTION

OBSERVATION:

• By comparing the above couture's, we can say that the k-epsilon model is extracting more turbulence than the K-omega(SST) model.
• converging time is more in the K-epsilon model as compared to the K-omega(SST)model.
• therefore we will be using the K-omega model for future calculations.

LONG LENTH TEE:

MODEL: K-OMEGA(SST) MODEL

MOMENTUM RATIO = 2

HOT INLET VELOCITY = 3m/sec at 36 ⁰C

COLD INLET VELOCITY = 6m/sec at 19 ⁰C

CAD MODEL FOR LONG LENGTH TEE

MESHED TEE: MESH SIZE 5mm

MESH MATRIX: The majority of mesh elements are in the range of 0.6 to 1.0 so mesh quality is acceptable.

RESIDUAL PLOT:

NODES: 28241

ELEMENTS: 139785

AVERAGE WEIGHTED OF TEMPERATURE AND VELOCITY:

STANDARD DEVIATION OF TEMPERATURE AND VELOCITY

CONTOUR PLOTS

1. TEMPERATURE DISTRIBUTION

2. VELOCITY DISTRIBUTION

CONCLUSION:

• As the length of the pipe increases, the mixing of fluid time increases, and the temperature at the end also decreases.
• In both cases (K-EPSILON and K-OMEGA), k -epsilon has better results as we can see in the residual plot, and converge faster as compared to the k-omega(SST) model.