CHT analysis on Exhaust Port Manifold

Why- 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.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.So, to capture this phenomena of heat transfer between solid and liquids , CHT analysis is performed.

Where-heating or cooling of a solid object by the flow of air in which it is immersed,conduction through solids, free and forced convection in the gases/fluids and thermal radiation,coolers, heaters, or heat exchangers.

Mesh Model (refined mesh with inflation layers in the solid region):

Velocity Contours:

Baseline Mesh Velocity Contour:

Refined Mesh Velocity Contour:

as we can see from above contour the Maximum velocity is increased to 40.8 m/s from 37.2 m/s as the mesh is refined

Temperature Plot:

Baseline Mesh Temperature Plot:

Refined Mesh Temperature Plot:

From above contours, there is no change in the max temperature, but as you can see the variation of temperature near inlet for mesh (around 550 deg c) is quite different from the baseline mesh (464.4 deg c).

Heat Transfer Coefficient Plot:

Baseline mesh HTC plot:

Refined mesh HTC plot:

from the above plots, the max htc is increased to 215.7 W/m^2 K from 105.9 W/m^2 K as the mesh is refined. And inflation layers capture smooth variation of htc as compared to baseline mesh.

refined mesh produced changes in results of temperature, velocity and HTC as mention above for each contour respectively.

Verification of HTC predictions:

1) check with experiment results.

2) check where Max velocity is, since Max velocity gives max reynolds number and max reynolds number signifies max HTC (because of forced convection), in this case we can see from the htc and velocity plots, in the max velocity region, we get Max HTC.

factors that affect accuracy of result:

1) mesh quality and no of elements in mesh and proper capturing of near wall regions (inflation layers) (check y+ value) where heat transfer takes place.

2) type of element used-quad or tetra.

3) boundary conditions imposed.

4) type of solver used.

5) proper cad geometry without any dangling edges.