Week 4 - CHT Analysis on Exhaust port
Objectives:
- Give a brief description of why and where a CHT analysis is used.
- Maintain the y+ value according to the turbulence model and justify the results.
- Calculate the wall/surface heat transfer coefficient on the internal solid surface & show the velocity & temperature contours in appropriate areas.
- How would you verify if the HTC predictions from the simulations are right? On what factors does the accuracy of the prediction depend on?
A1) The Conjugate Heat Transfer (CHT) analysis type allows for the simulation of heat transfer between solid and fluid domains by exchanging thermal energy at the interfaces between them. Typical applications of this analysis type exist as, the simulation of heat exchangers, cooling of electronic equipment, and general-purpose cooling and heating systems. The internal combustion engine industry is moving toward simulating the entire system rather than independent components. The accuracy of the predicted combustion in the cylinder is dependent on the temperature boundary conditions in the cylinder. By considering heat transfer in the metal components (e.g., the cylinder head, liner, piston, exhaust, etc.), the cylinder wall no longer has a user-specified temperature, but instead has temperatures predicted as part of the complete-system simulation. This makes the overall simulation results more predictive by reducing the dependence on assumed boundary conditions.
Baseline Simulation:
Refined Mesh Simulation:
(In 2021R1 ansys academic software, there is no option to obtain the Heat Transfer Co-eff graph but we can theoretically calculate the value. )
Simulation Verification:
As you can see the theoretical value is very closer to the recorded values from the simulation report. The error is only 14%. The other way we can prove that the simulation accuracy is by comparing the average outlet velocity which comes out to be 25.24m/s (theoretical value is 25m/s).
By this two metrics we can verify that our simulation is correct.