Exhaust Port Challenge
CONJUGATE HEAT TRANSFER ANALYSIS
AIM-To simulate a Conjugate heat transfer analysis
INTRODUCTION
Conjugate heat transfer corresponds with the combination of heat transfer in solids and heat transfer in fluids. In solids, conduction often dominates whereas in fluids, convection usually dominates. Conjugate heat transfer is observed in many situations. For example, heat sinks are optimized to combine heat transfer by conduction in the heat sink with the convection in the surrounding fluid.
PROCEDURE
1.Preparing the geometry
For the simulation an exhaust port of a 4 cylinder engine is taken. The CAD file of the exhaust port is uploaded to spaceclaim."Extract volume" command is used to create the flow path of the exhaust gases. The flow path of the exhaust gases was named fluid_vol. The walls of the exhaust port is named as solid_vol.Then the topology of both the components was set to shared.And in the end interference was checked.
2.Meshing
After preparing the geomety the mesh were generated.First an Inflaltion layer was added between the flow path and the wall of exhaust.Total thickness of 5 layers was set to 5 mm with a growth rate of 1.2.The mesh size for the wall is set to 10mm. the image of the final mesh is given below.
3. Simulation
After the meshing, Fluent was opened and the simulation was done.A steady state simulation was done using k-epsillon model. The velocity at the inlet was set to 5 m/s at 700K. The heat transfer coefficiet of the wall of the exhaust port (except the flanges at the inlets and outlets) is set to 20 W/m^2 k. The subject fluid is taken as Air and material for exhaust port is taken as aluminium. The simulation was done for 300 iteration.The result for velocity the temperature are given below.
4.Conclusion
The Heat transfer Coefficient are the wall of the exhaust port was calculated. The theoritical way to find the HTC is by using the formula
Nu=hD/k
Where
H is the HTC of the material
D is the characteristic length
k is thermal conductivity of material
Nu is Nusselt Number
The formula for Nusselt number for turbulant flow is
Nu=0.023Re^0.8 Pr^n
Where
Re is Reynold number
Pr is prandtl number of air
n=0.3