Week 4 - CHT Analysis on Exhaust port

Conclusion

Wall heat transfer coefficient can be calculate by using

Where Nu = Nusselt number, h = heat transfer coefficient,

d = diameter of pipe,

k = thermal conductivity of fluid W/mK

Nu = 0.023 Re ^0.8 Pr ^0.4

Pr = Prandtl Number, Pr = , where = dynamic viscosity, kg/ms; j/kg k;

Re = Reynolds Number and can be calculated by

Re= , where; = velocity of fluid;; = dynamic viscosity of fluid.

Observation table

S No		Baseline simulation	Refine mesh
1.	No of elements	141404 elements & 28122 nodes	· 1005193 elements & 366727 nodes
2.	Heat transfer coefficient	10.24 w/m2K	22 w/m2K
3.	Max velocity	3.7 m/s	4.07 m/s`
4.	Max temperature	693 K	693 k

In the baseline mesh the wall heat transfer coefficient shows 10.24 w/m2K, whereas in refined mesh the heat transfer coefficient has increased showing a value of 22 w/m2k. Further enhancing the Y+ value shows the heat transfer coefficient of wall increased from 5 mm to 3mm and changing the total layer thickness to first layer thickness have shown that the there is a decrease in heat transfer coefficient which is 18.24 w/m2k.

The value of heat transfer coefficient using k-omega sst model has been used to investigate the effect of different methods on wall heat transfer coefficient, in k-omega sst model the wall heat transfer coefficient value have higher value of 24 w/m2K in comparison to k-e standardised model, this is due to k-omega sst model captures the near boundary conditions better compare to k-e standardised model which captures far away boundary conditions better.

The temperature, pressure and velocity contours plots for both baseline mesh and refined mesh using k-epsilon standardised model are plotted above, the figures shows that there is a better temperature, pressure and velocity distribution in refined mesh model when compare to baseline mesh.

Therefore refining the mesh model provides better results in comparison to baseline mesh.