Week 6: Conjugate Heat Transfer Simulation
Objective :- Setup the baseline simulation flow through the pipe ,check the grid dependence test by varying grid size according to the given reynolds number 7000. Also compare the result of supercyle stage interval to 0.01,0.02 and 0.03 with baseline simulation.
Introduction
The term conjugate heat transfer (CHT) is used to describe processes which involve variations of temperature within solids and fluids, due to thermal interaction between the solids and fluids. The exchange of thermal energy between the two physical bodies is called study of Heat Transfer, the rate of transferred heat is directly proportional to the temperature difference between the bodies. A typical example is the heating or cooling of a solid object by the flow of air in which it is immersed and some other example includes conduction through solids, free and forced convection in the gases/fluids and thermal radiation.
Super cycling in converge
1. Super cycling is used by converge studio in conjugate heat transfer problem.
2. Converge studio solves the fluid and solid region together with the trensient solver during initial time step.
3. Stores the instantaneous heat transfer coefficient and temperature of the interface boundary .
4. There after freezes the fluid solver and time averege of htc and apply them at B.C at the interface.
5. Then solves for solid region temperature until it reaches steady state using steady state solver.
6. Upates the solid region temperature field and unfreezes the flui solver and repeat this process until solid temperature converge.
Inlet velocity
Given reynolds number:- 7000
Radius= 0.015
`rho=`1.184 kg/m^3
`mu= 1.849*10^-5 (kg)/(m-s)`
`Re=(rho *v* d)/(mu)`
`7000= (1.184.v.0.03)/`1.849*10^-5`
v = 3.643 m/s
Import the given geometery in converge studio
Geometry of cylinder was created in converge studio 3 using create option, with inner radius 0.015m and outer 0.02m the length of the cylinder is 0.2m in z direction.
Case setup
Application Type- Time based
Material type- Gas simulation , Solid simulation
Species-O2 N2 Aluminium.
Solver-
Simulation Time Parameter
Solver
Boundary Conditions
Outer wall
Solid state
Inlet
Outlet
Region and initialization
Physical Model-
Turbulence- K-Epsilon
Super cycling modeling
Base grid-0.004m, 0.003m, 0.002m
Output
Post variable selection- Additional selection Y+ used
Result
Baseline
Grid size -0.004m
Inlet velocity in z direction-5m/s
Total number of cell is constant after 0.5 sec
Mean temperature
When time increases solution get stable
Post process result for base line simulation
Temperature Contour
From the above contour we absorve that temperature is high near the wall and decreases from wall to centre of the pipe.
Velocity contour
Velocity is maximum near the center of the pipe when radial distance increases from the center velocity decreases.
Pressure contour
Presure is constant each and every where in the fluid region.
Glif
Glif is used to shows direction of fluid.
Grid Depedence Test
Plot of the total cell element for different grit size
Plot for fluid and solid region for all three grids
Mean temperature plot for all three solid and fluid region are seperately , they are each converging at slightly different values. Fluid profile is competely transient in nature. Grid is temperature dependent further refinement give high refined value .
Effect of super cycle stage interval
Effect of super cycle interval is checked for three storing super cycle data ie 0.03 , 0.02, 0.01 sec for the same grid size 0.003 meter element size . Super cycle effect is the time to solve the equation and reach the convergence.
Super cycling total simulation time
super cycle stage interval-0.01s
simulation time- 1141.099s
super cycle stage interval-0.02s
simulation time- 1178.14s
super cycle stage interval-0.03s
simulation time- 1344.31s
Velocity and temperature contour for three different grid size
For 0.004 grid size
For 0.003 grid size
For 0.002 grid size
From the above velocity contour we can say that when the grid size refined velocity increases and from temperature contour temperature of fluid region near wall decreases for refined mesh.
Conclusion
The difference in temperature between solid and fluid reduces with reduction in grid size.
Value of Y plus increases with increases in grid size
Simulation time is higher for higher super cycle stage interval