MIXING EFFECTIVENESS OF TWO DIFFERENT TEMPERATURES AND FLUID FLOW IN A MIXING TEE
The main emphasis of performing this simulation is :
- To observe the mixing effectiveness of two different temperatures of air entering through different inlets at different velocities in a tee shaped geometry
- To study the mixing effectiveness by calculating the standard deviation and area weighted average of temperature at the outlet
- To observe the effect of the grid size on the intensity of interaction
- To increase hands on the ANSYS fluent CFD modelling software.
Mixing in a tee junction:
- Fluid mixing is represented in the form of mixing two jet flows with good mixing efficiency.
- Due to its perpendicular jet injection, it have better efficiency than parallel or coaxial jet injection devices.And also rapid mixing is possible in a distance of few tube diameters from the injection point.
- The interaction intensity determines the quality of mixing and also the pressure drop.The total pressure drop includes the pressure drops of momentum and pressure drops of friction.
- Pressure drop due to momentum flux and achieved steady state)
- Pressure drop due to heat exchange and phase transitions to steady state)
Models:
Two different solid models constructed using solid works are extracted into space claim and fluid volume required for simulation is prepared in this branch of ansys CFD(fluent)
Series of operations(Explained heuristically) :
Geometry extraction and preparation using SPACECLAIM:
Geometry is extracted into spaceclaim and prepared by supressing the not needed geometry to perform the simulation
Activate or supress for physics:
Hiding the geometry will not effect the object's inclusion in the simulation.To avoid the hidden geometry to be involved in the simulation using the supress physics option for the solid geometry will avoid the simulation to be performed at those surafces which in turn helps in simulating the fluid volume.
Setting up the mesh parameters suitable for simulation using Mesher tool:
Here, the element size for the geometry and the zones of cells, boundaries are ID'd
Setup using cfd fluent:
In this tool, we have the options to control the output data and manipulate the essential data(initial conditions,boundary conditions) to start and perform a simulation and generate the reports related to the variables of flow.
Double precision is chosen to aid the achievment of convergence/divergnce faster compared with single precision.And also to see more accurate results.
Solution:
We can see our results that are generated in this section.
- Display results in CFD post:
Contour plots of flow variables , face rendering with different flow variables etc can be done in using this tool.
Case with default element size
Geometry:
- SHORT MIXING TEE(fluid volume with meshing)
- Momentum ratio = 2
- element size = default(0.010219)
Scaled residuals:
Average outlet temperature:
Standard deviation at outlet:
Velocity profile:
Temperature profile:
Standard deviation and area weighted average of temperature:
Case 1
Geometry:
SHORT TEE
Momentum ratio : 2
element size: 2e-3
Scaled residuals:
Standard deviation of temperature at outlet:
Area weighted average of temperature at outlet:
Standard deviation and area weighted average of temperature:
Velocity profile:
Temperature profile:
CASE 2
Geometry:
Long tee
Momentum ratio : 2
element size: 2e-3
Scaled residuals:
Area weighted average of temperature at outlet:
Standard deviation of temperature at outlet:
Velocity profile:
Temperature profile:
Computed values of area weighted average and standard deviation of temperature:
Case 3
Geometry:
SHORT MIXING TEE
Momentum ratio = 4
element size = 0.002
Scaled residuals:
Standard deviation of temperature on outlet surface:
Area weighted average of temperature on outlet boundary:
Computation of Standard deviation and Average temperature at outlet:
Velocity profile:
Temperature profile:
Tabulated analysis for both the models and different momentum ratios: