MIXING TEE SIMULATION CFD REPORT

In the following project, the efficiency of MIXING-TEE is to be analysed for three distinct kind of cases.They are give below:

CASE 1:

• Short mixing tee with hot inlet velocity of 3m/s
• Momentum ratio of 2
• Hot air temperature: 30°C
• Cold air temperature: 10°C

CASE 2:

• Long mixing tee with hot inlet velocity of 3m/s
• Momentum ratio of 2
• Hot air temperature: 30°C
• Cold air temperature: 10°C

CASE 3:

• Short mixing tee with hot inlet velocity of 3m/s
• Momentum ratio of 4
• Hot air temperature: 30°C
• Cold air temperature: 10°C

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

CASE 1: MOMENTUM RATIO 2& HOT INLLET VELOCITY 3M/S

Temperature Plot at the outlet:

Standard-Deviation of Temperature at the Outlet Plot:

CFD ANALYSIS:

Temperature Simulation:

Velocity Diagram:

Convergence Plot:

OBSERVATION FROM CASE 1 RESULTS:

The temperature simulation diagram display us that the mixing of cold and hot air is not appropriate. It can be identified from the standard deviation of temperature at the outlet. It increases above 5°C and drops to 3°C (approx.) and it continues in that value along the process. And the average outlet temperature is around 20°C.

CASE 2:

Temperature Simulation

Velocity Diagram:

Temperature Plot at the outlet:

Standard Deviation of Temperature at outlet:

Convergence Plot:

OBSERVATION FROM CASE 2 RESULTS:

From the temperature diagram of case 2, it can be seen that the mixing of hot and cold air is slightly better than the case:1 which is a shorter pipe although all the other parameters are same. It is mathematically proved by the graph showing the standard deviation of temperature at the outlet. It is maintained below 3°C but fluctuates a bit. But there is not a notable change in outlet temperature meaning that using a longer pipe alone cannot increase the mixing efficiency of a mixing-Tee.

CASE 3:

Temperature Plot at the outlet:

Standard-Deviation of Temperature at the Outlet Plot:

Convergence Plot:

CFD ANALYSIS:

Temperature Simulation:

Velocity Diagram:

OBSERVATION FROM CASE 3 RESULTS:

In case:3, we have used the same short pipe, but the velocity of cold air is increased to 12m/s. Comparing the three cases, the mixing efficiency is better in this particular case with higher cold inlet velocity.The mixing is much proper and the standard deviation of temperature at the outlet is below 2°C which is the least of the above three analysis results which is a proof of higher mixing efficiency. Moreover, the average outlet temperature is around 17.5°C which is also lower.

COMPARISON TABLE:

	CASE-1	CASE-2	CASE-3
NO OF ELEMENTS	22149	22489	29186
AVE.OUTLET TEMPERATURE	20°C	19.8°C	17.5°C
NO.OF ITERATIONS TO CONVERGENCE	35	40	38

CONCLUSION:

From the results of the above three cases, it can be clearly seen that the mixing efficiency is higher in the 3rd case which is the shorter pipe with the cold inlet at 12 m/s. But my proposal would be using a higher velocity cold inlet along with a longer tee. This will further increase the quality of mixing and also favourable for maintaining a lower temperature.