Week 4 - CHT Analysis on Exhaust port

THEORY

Computational Fluid Dynamics(CFD) and more specifically conjugate heat transfer (CHT) analysis can accurately predict heat transfer by simultaneously solving all the relevant solid and flow field heat transfer processes, for example: conduction through solids, free and forced convection in the gases/fluids and thermal radiation.

The CHT approach has an advantage over FE Thermal Analyses in that wall heat transfer coefficients and their local variations on surfaces are directly calculated within the model rather than based on simplified empirical calculations. The CHT approach therefore has benefits for those applications where heat transfer is either non-uniform or difficult to calculate empirically.

Here we are conducting an analysis on the exhaust port of an engine. The Geometry of the exhaust port is in the image below. With this analysis

we can find out the Heat transfer coefficient.

The heat transfer coefficient or film coefficient, or film effectiveness, in thermodynamics and in mechanics is the proportionality constant between the heat flux and the thermodynamic driving force for the flow of heat (i.e., the temperature difference, ΔT):

The overall heat transfer rate for combined modes is usually expressed in terms of an overall conductance or heat transfer coefficient, U. In that case, the heat transfer rate is:

It is used in calculating the heat transfer, typically by convection or phase transition between a fluid and a solid. The heat transfer coefficient has SI units in watts per squared meter kelvin: W/(m²K).

The geometry represents an exhaust port with 4 inlets and 1 outlet. which are shown below. The idea is so simulate the flow of hot gasses(in this case air) and see how the temperature and the velocity vary. It is made of aluminium and passes hot air in this simulation.