Surface Heat Transfer Coefficient on a heated cylinder
 

Hello everybody!

I am looking for answers regarding the heat transfer coefficient utility heatTransferCoeff in OpenFoam (v2106).


The case runs with chtMultiRegionSimpleFoam with radiation.

• It is a hollow cylinder immersed in water, heated from the inside by a heating element (1000W) which radiates. The cylinder warms up and heats the external water surrounding it. The simulation runs fine.

• I am looking to approximate the heat transfer coefficient between the cylinder and the water so I can get rid of the simulated water and shorten computation time.

Currently, I compute the HTC using the utility heatTransferCoeff and the mode Tref, and I compare it with the following formula in paraview:

htc = wallHeatFlux/(Twall - Tref)

with wallHeatFlux computed with the utility, Twall the local temperature and Tref = 333K (60°C) the water temperature far from the cylinder.


The results between these two are similar, but they both give values betweend 5000 and 10000 W/m²/K which seems huge for a htc in free convection, considering that the outer cylinder reaches a maximum temperature of 64°C (4 degree difference with the reference temperature).

I ran the same simulation with Fluent. I get similar temperatures, but the "Surface Heat Transfer Coefficient" estimated by Fluent is around 70 W/m²/K and the "Wall Adjacent Heat Transfer Coefficient" is similar to what OpenFoam gets, so 5000-10000 W/m²/K.


So after all that:

• What is the difference between the Surface Heat Transfer Coefficient of Fluent and the OpenFoam utility?

• Does someone know how the Surface Heat Transfer Coefficient of Fluent is calculated? I could not find the answer online. Is it possible to obtain the same computation with OpenFoam?

Any hint is appreciated, and thanks to everybody who read the whole thing, I will provide any missing details!