simulation of Mixing tee
Project name: simulation of Mixing tee
Description: in air conditioner mixing tee is used to mix cold and hot air.
Fluid domain: For the simulation of mixing of the air we required fluid domain of air. from the right side of x-axis hot air enter, form y-axis cold air enter, from the left side of x-axis mixture of cold and hot air leaving the fluid domain.
fig 1 fluid domain
Meshing: fluid domain is divided into many small cells. this process called meshing.
governing equations are solved on each of the mesh cells.
fig 2 meshing of the fluid domain
Boundary conditions: to solve the PDE governing equations we need boundary conditions.
boundary conditions for case 1 (Short pipe)
hot air inlet temperature = 36 Celcius
cold inlet temperature = 19 Celcius
hot air velocity = 3 m/s
cold air velocity = 6m/s
momentum ratio = 2, 4
Momentum ratio = velocity at cold inlet / velocity at hot inlet
Use the k-epsilon and k-omega SST model for the first case
boundary conditions for case 2 (long pipe)
hot air inlet temperature = 36 Celcius
cold inlet temperature = 19 Celcius
hot air velocity = 3 m/s
cold air velocity = 6m/s
momentum ratio = 2, 4
solution:
case 1: a short pipe with momentum ratio 2,4
meshing
fig 3 meshing of short pipe
turbulence model: K omega SST model is used
The SST - model includes all the refinements of the BSL - model, and in addition, accounts for the transport of the turbulence shear stress in the definition of the turbulent viscosity.
Convergence:
fig 4 Residuals of case 1 momentum ratio 2
convergence occurs around 250 iterations.
fig 5 Residuals of case 1 with momentum ratio 4
convergence occurs around 400 iterations.
plot:
Temperature
fig 6 temperature contour momentum ratio 2
fig 7 temperature contour momentum ratio 4
velocity
fig 8 velocity contour momentum ratio 2
fig 9 velocity contour momentum ratio 4
Line Plot:
Temperature
fig 10 temperature line plot
Velocity
fig 11 velocity line plot
Parametric study:
input parameter: 1 mesh element size
2 cold inlet velocity
output parameters: 1 Avg outlet temp
2 Ave outlet velocity
3 Mesh element count
fig 12 Parametric Study of short pipe
case 2: a long pipe with momentum ratio 2,4
meshing
fig 13 meshing of long pipe
turbulence model: K epsilon Realizable Enhanced Wall Treatment model is used
The realizable - model contains an alternative formulation for the turbulent viscosity.
A modified transport equation for the dissipation rate, , has been derived from an exact equation for the transport of the mean-square vorticity fluctuation.
Convergence:
fig 14 Residuals of case 1 momentum ratio 2
convergence occurs around 80 iterations.
fig 15 Residuals of case 1 with momentum ratio 4
convergence occurs around 400 iterations.
Contour Plot:
Temperature
fig 16 temperature contour momentum ratio 2
fig 17 temperature contour momentum ratio 4
velocity
fig 18 velocity contour momentum ratio 2
fig 19 velocity contour momentum ratio 4
Line Plot:
Temperature
fig 20 temperature line plot
Velocity
fig 21 velocity line plot
Parametric study:
input parameter: 1 mesh element size
2 cold inlet velocity
output parameters: 1 Avg outlet temp
2 Ave outlet velocity
3 Mesh element count
Fig 22 Parametric Study of long pipe
Effect of length and momentum ratio on the result
As the length of pipe increase, the effective temperature of mix air reduces.
As the momentum ratio increase, the effective temperature of mix air reduces.