Week 4 - CHT Analysis on Exhaust port

Give a brief description of why and where a CHT analysis is used.

Conjugate Heat Transfer (CHT) analysis is used for the simulation of heat transfer between solid and fluid domains by exchanging thermal energy at the interfaces between them.

Some examples are: the simulation of heat exchangers, cooling of electronic equipment, and general-purpose cooling and heating systems.

AIM: Perform CFD analysis for an exhaust port and plot temperature, velocity and heat transfer contours.

Solver settings:

Inlet boundary conditions:

Outer wall convection:

Reference values:

Characteristic length: Inlet pipe diameter

Area: Inlet area

Temperature:Ambient temperature

Velocity: 5m/s

Y+ value:

Geometry:

Residuals:

Area weighted average of heat transfer coefficient:

Streamlines:

Average of wall Y+:

Wall heat transfer coefficient:

The Dittus-Boelter equation (for turbulent flow) is an equation used for calculating the Nusselt number. It is easy to solve but is not recommended to use when there is a large temperature difference across the fluid. This equation is generally used for smooth tubes, so while using for rough tubes (most commercial applications) is cautioned.

To validate our simulations results we need to hand calculate the heat tranfer coefficient.

Nusselt number Nu=hl/k where h is heat transfer coefficient, l be the length and K the thermal conductivity of the material.

To find heat transfer coefficient (h) we need to find nusselt number.

Dittus-Boelter Equation helps us to find Nusselt number.

Nu=0.023*(Reynolds number^(4/5))*(pr^n)

Here n is 0.4 if the fluid is heated or 0.3 when the fluid is cooled off

Using these two equations we can find the heat transfer coeficient and validate our CFD analysis.