Week 1- Mixing Tee

AIM

To perform steady-state simulations to compare the mixing effectiveness of Tee joint of different lengths using Ansys Fluent.

OBJECTIVE

To study about the various mixing properties of fluid in a basic tee mixing to annalyse the temperature and velocity variation in the fluid matter flowing through it.This has a great application in industries like hvac systems ,cooling units in hospitals and many more .They also show their role in boilers and in heat exchangers .

PROCEDURE

CASE 1-short mixing tree of momentum ratio 2

• first open the design in space claim and load the design
• then annalyse the design in space claim as we are concerned only with the volume which is involved with the fluid we will remove all other body parts
• for this we have to create the volume
• we can create volume by going to prepare and selecting the volume extract
• we will then slect the edges and click and complete
• we will be able to hide the body under structures and veiw only the volume
• we will save ethe model and open workbench
• We will select the fluid flow(fluent) and drag it to design schematic
• we willl the select the mesh
• when the mesh opens we will import the design which was saved before in the space claim
• After this we will hide the body under the geometrics and we will only veiw the volume
• we will assign different sections name by slecting the faces and typing N in keyborad
• we will assign names like input y,input x,output x,body
• After asssigning the sections we will click the mesh and give the mesh element size as 4mm for a good meshing and then right click mesh and then generate the mesh
• after generating the mesh we will see the mesh quality under which wwe will select the mesh metrics and see the mesh quality
• after that we will close the mesh and go back to workbench and slect the setup
• we will slect double precision and use four processor and start fluent
• after starting the fluent we will first check the meshing by clicking perform the mesh checks
• After the mesh selection we will go to physics
• under this we will select pressure,absolute,steady system and select viscous as K epsilon
• after that we will create edit material to creat and edit the fluid for the study
• after selecting the terms we will go to assigning conditions to cell zones
• here we select the volume and edit its properties for air as fluid
• after this we will assign conditions to diffrent boundaries based on the user input
• we will give input parameter for inlet x as velocity 3m/s and temperature as 36 degree celecius
• we will give input parameters for inlet y as 6m/s as we hvae momentum ratio as 2 and the temperature as 19 degree celsius.
• we will keep outlet at zero gauge pressure condition
• we will then go the selection where we will select the definitions or reults which are all required for the solutions
• after selecting we will click initialize and give the no of iterations as 50
• we will annalyse the reports by generating the graphs
• From above graph we can see that std dev temp plot starts converge from 70^th iteration and std.dev temp=1.575 c.
• After this we will close fluent and go back to workbench
• we will select results
• we will click the sections we want to visualize from the cases and wew ill click contact region
• Then we will click insert
• we will add a plane in xy plane
• After generating the plane we will go to the contact region and under render we will increase the transparancy and change its colour
• Then in plane we will slect the temperature under variable and click apply
• under the default legend window we can change the units of the legend
• we then creat a line which will be of closed in nature
• we will generate the chart using chart create,
• we will generate task by changing the variables in different x and y coordinates and we can find the graph

We will then generate the calculations for the given formulae and find temperature

CASE 2-with Mr=4

• we will start from setup as the previous processors are same
• after starting the fluent we will first check the meshing by clicking perform the mesh checks
• After the mesh selection we will go to physics
• under this we will select pressure,absolute,steady system and select viscous as K epsilon
• after that we will create edit material to creat and edit the fluid for the study
• after slecting the terms we will go to assigning conditions to cell zones
• here we select the volume and edit its properties for air as fluid
• after this we will assign conditions to diffrent boundaries based on the user input
• we will give input parameter for inlet x as velocity 3m/s and temperature as 36 degree celecius
• we will give input parameters for inlet y as 12m/s as we have momentum ratio as 4 and the temperature as 19 degree celsius.
• we will keep outlet at zero gauge pressure condition
• we will then go the selection where we will select the definitions or reults which are all required for the solutions
• after selecting we will click initialize and give the no of iterations as 100
• we will annalyse the reports by generating the graphs
• we will close it and go to results
• we will now annalyse the chart

we will move to next case

CASE3-Long mixing tree of Mr=4

• we will start from setup as the previous processors are same as that for short mixing tree .
• after starting the fluent we will first check the meshing by clicking perform the mesh checks
• After the mesh selection we will go to physics
• under this we will select pressure,absolute,steady system and select viscous as K epsilon
• after that we will create edit material to creat and edit the fluid for the study
• after slecting the terms we will go to assigning conditions to cell zones
• here we select the volume and edit its properties for air as fluid
• after this we will assign conditions to diffrent boundaries based on the user input
• we will give input parameter for inlet x as velocity 3m/s and temperature as 36 degree celecius
• we will give input parameters for inlet y as 12m/s as we have momentum ratio as 4 and the temperature as 19 degree
• we will create the results and then the chart and find the relations

CASE 4-Long mixing tree of Mr=2

• after starting the fluent we will first check the meshing by clicking perform the mesh checks
• After the mesh selection we will go to physics
• under this we will select pressure,absolute,steady system and select viscous as K epsilon
• after that we will create edit material to creat and edit the fluid for the study
• after slecting the terms we will go to assigning conditions to cell zones
• here we select the volume and edit its properties for air as fluid
• after this we will assign conditions to diffrent boundaries based on the user input
• we will give input parameter for inlet x as velocity 3m/s and temperature as 36 degree celecius
• we will give input parameters for inlet y as 6m/s as we have momentum ratio as 4 and the temperature as 19 degree
• we will create the results and then the chart and find the relations

Conclusion-

1. As the cell size decreases, cell count increases which increases the mesh accuracy
2. Also, with increase in cell count, simulation time get increased quadratically.
3. It is observed that as the cell count increases, solver needs more number for iterations to converge a particular value, while for lower cell count, solver converges fast.
4. the curves shows a inverse relations of velocity and temperature with length at the the interface where hot and cold liquid mix
5. the smaller the mesh element size the more the iteration converge to the actual value