analysis of mixing tee with different lengths and momentum ratios
Problem statement: To study the mixing efficiency in a T-pipe and the factors affecting it.
Abstract : mixing T-pipe is used in various chemical mixing process to obtain a desired mixture and it is also used in HVAC applications.
In this , analysis were made on a mixing T-pipe by varying length and momentum ratios and the obtained results were
compared to select a pipe from which mixing efficiency is more
Geometry
1.short mixing tee
2.long mixing tee
i had the volume extracted from each of the pipes using volume extract tool in ansys spaceclaim and then moved on to mesh the volume.
and then moving on to setup, i had used double precision and set processing options to parallel and started ansys fluent
a steady state simulation was performed on the T-pipe
- model- made use of energy equation as the temperatures are involved and as the viscous flow is turbulent,i\'ve made use of k-epsilon model in this case
case1(momentum ratio-2)
- boundary conditions - 1.at hot air inlet - air with a velocity of 3mt/s and at a temperature of 36ºC
2.at cold air inlet- air with a velocity of 6mt/s and at a temperature of 19ºC
k-epsilon model
short pipe long pipe
k-omega model -
short pipe long pipe
after observing both the cases and comparing it with a reference the temperature contour plot obtained in k-omega model is similar to that
of the reference one and velocity profiles of both the models remain same. so, a conclusion is made that k-omega (SST) turbulent model holds
good for flow models that involves temperature. So k-omega model is used in remaining cases
case1(momentum ratio-2):
- Boundary conditions-1.at hot air inlet- air with a velocity of 3mt/s and is at a temperature of 36ºC
2.at cold air inlet- air with a velocity of 6mt/s and is at a temperature of 19ºC
residuals plot
short pipe long pipe
line plots of temperature and velocity
Area Average of Temperature on outlet
long pipe - 30.582 [C]
short pipe - 30.604 [C]
case2(momentum ratio-4):
- boundary conditions - 1.at hot air inlet - air with a velocity of 3mt/s and at a temperature of 36ºC
2.at cold air inlet- air with a velocity of 12mt/s and at a temperature of 19ºC
short pipe long pipe
contour plots of temperature and velocity
countour plots of temperature and velocity
residuals plot
temperature line plot along the length
velocity line plot along the length
standard deviation plot
the results obtained for a refining mesh are as follows
Area Average of Temperature on outlet
long pipe - 27.845 [C]
short pipe - 28.021 [C]
the case (long pipe,momentum ratio-4 ) is subjected to different mesh size and a mesh independent study is made and the obtained results are tabulated as follows
conclusion
from the results we can conclude that the mixing efficiency is increased when the velocity of the cold fluid is increased and also we can conclude that more the length higher the mixing efficiency and lower the temperature at the outlet