Conjugate Heat Transfer Simulation
objective
In this project simulation is done on tick tube of aluminium is externally heated at 10000-watt per meter square with inflow air is travelling with 700 Reynolds number that in laminar flow condition of air, and also analysing the solution of simulation is on three different grids. In conjugate heat transfer, problem convection is at the interaction of fluid and wall, and conduction in a solid tube which is externally heated, so to simulate these type of problem converge uses super cycling concept.
Super cycling in converge
to solve conjugate heat transfer case converge uses supercycle concept in which In an engine, the time-scale necessary to resolve solid heat transfer is usually much greater
than that for fluid heat transfer. It takes many engine cycles for the solid temperature to
reach steady-state. Super-cycling in CONVERGE is an acceleration method that solves
time-dependent CHT problems to a steady-state in a solid with fewer engine cycles.
`Re = (rho*V*D)/(Dynamic viscosity)`
re =700 that is laminar flow conditions
`rho = 1.177`
D=0.03m
Dynamic viscosity = 0.00001856
velocity = 0.37 meter per sec
case setup -
- geometry preparation and validation
- boundary flagging
- application
- materials
- simulation parameters
- boundary conditions
- initial parameters and conditions
- grid control
- post-processing
1.1 geometry preparation and transforming normal to the fluid domain
make geometry using converge
transform all normal to the fluid domain.(use geometry dock-transform-normal)
2.1 boundary flagging
To assign boundaries geometry dock - boundary -flag
Important boundaries in this case setup are inflow, outflow, solid outer wall
, solid inner wall, solid thick wall respectively
3.1 application
- This case comes under general flow
4.1 materials
The predefined mixture is air and gas simulation should be marked up.
4.1.1 gas simulation
Use suggested by the software.
4.1.2 solid simulation
choose aluminium
4.1.3 global transport parameters
Use as same as suggested by the software.
4.1.3 species
gas as n2 and o2
solid as aluminium
5.1 simulation parameter
5.1.1 run parameter
Use transient solver, full hydrodynamic and compressible solver.
5.1.2 simulation time parameter
Set cycle from 0-0.5s min-max time step as 1e-6.
5.1.3 solver parameter
Use suggested by the software.
6.1 boundary condition and initial condition and event
goto initial condition make 2 region id first as a fluid region and second is a solid region
set fluid region species as air and 0.37 meter per second in the z-direction( according to geometric direction)
set solid region as aluminium
For inflow region-name fluid region
pressure BC as Neumann
velocity BC ie. Dirichlet as 0.37 in the z-direction
temperature Bc Dirichlet as 300k
species bc as air
For outflow region-name fluid region
Pressure BC as 101325 pascals
velocity bc as Neumann
specified value as 300k temperature in backflow
species as air
for solid thick wall region-name solid region
slip wall stationary Boundary with velocity Neumann
solid outer wall region-name solid region
stationary slip boundary with a flux of -10000 watt per meter square
The solid inner wall (observe normal )
boundary type interface
slip boundary
region fluid region
velocity BC as law of wall
temperature BC as law of wall
turbulence K.E as Neumann
turbulence dissipation eps BC as law model
for solid region
temperature bc as specified
velocity Bc as slip
7.1 physical model
1.1.1
select turbulence and super cycling
supercycle setting
output point as outflow cylindrical curve here z coordinate must be inside the region for better supercycle.
8.1 grid control
simulation base gid test 1 as 0.004 { figure 1}
9.1 post-processing
- Goto post section variable -turbulence and marked y+
- Use output file to control over post-processing file.
post-processing using ParaView
the velocity profile in an externally heated tube of grid size0.004 m and sup cycle of 0.05sec
the temperature profile in an externally heated tube of grid size0.004 m and sup cycle of 0.05sec
change of Y+ data
plotting in converge
1.1 plot of meantime vs simulation time for solid region
the mean temperature is the average of minimum and maximum temperature in solid region
From the above chart, it\'s clearly visible how a change in grid size and supercycle time is changing in mean temperature with respect to time the value of grid size 0.004 meters and 0.0035 meters with supercycle temperature is 1516.25k,1490.25k respectively here in order to reached converge values simulation time has to increase.
2.1 plot of meantime vs simulation time for the fluid region
the mean temperature is the average of minimum and maximum temperature in the fluid region. Above graph shows mean temperature change in the fluid region for different grid size and different supercycle time setup , Heare no values of mean temperature reached to converge because the value of fluid flow is very low so convection is very low.
3.1 plot of average temperature at inlet and outlet vs time
note: In the above plot, the legend from 1st to 6 are from grid size of 0.004m
From the above chart, it\'s clearly visible how a change in grid size and supercycle time is changing in mean temperature with respect to time the value of grid size 0.004 meters and 0.0035 meters with supercycle of 0.01s; temperature is 1133.68k,1139.16k respectively, here in order to reached converge values simulation time has to increase.
Time for simulation
1.1 externally heated aluminium tube with grid size 0.004m and super-cycle 0.05s
total time 595s
2.1 externally heated aluminium tube with grid size 0.004m and super-cycle 0.02s
total time 613.51
3.1 externally heated aluminium tube with grid size 0.004m and super-cycle 0.01s
total time 755.48s
4.1 externally heated aluminium tube with grid size 0.0035m and super-cycle 0.05s
total time 910.95s
5.1 externally heated aluminium tube with grid size 0.0035m and super-cycle 0.01s
total time 1120.04s
6.1 externally heated aluminium tube with grid size 0.005m and super-cycle 0.05s
total time 316.4s
7.1 externally heated aluminium tube with grid size 0.005m and super-cycle 0.01s
total time 380.91s
Conclusion
Thus we have simulated conjugate heat transfer simulation on an externally heated aluminium tube with airflow in a tube with different grid size and for different super cycling time, It is observed that as super cycling time decreases (for 0.004 gride size) from 0.05 sec to 0.01sec, A total time to solve an equation is increased And As grid size decreases(from grid size of 0.005m to 0.0035m) total time to solve navies stroke equation is increases because of increment in cell count.
If we have to achieve converge results we have to simulate this solution for more time or we have to increase the Reynold number so the mean temperature converges in this given 0.5 seconds of time.
Use of Conjugate Heat Transfer Simulation in Internal combustion engine as to design appropriate size of fins and water jacket volume.
References
1-converge studio manual