Learning Forum

[Alwan Hibatullah]

I have two models as seen in this picture. The first model is a helical coil covered by a solid jacket, and the second model is a helical coil covered by a helical channel (solid). in both models, a constant heat flux is applied to the solid domain, and adjusted so that the helical coil in both models will receive the same amount of flux. The inlet velocity and temperature on both models are the same, and the size of the helical coil is more or less the same.

However, when the simulation results come out, why do the helical coils in the two models have different Nusselt values? in the second model which is coated with a helical channel, the Nusselt value is in accordance with the correlation, and in the first model which is coated with a solid jacket, the Nusselt value is wrong and far from the correlation

How can this happen when both fluids have the same size, receive the same heat, and are covered by the same solid material, but have different wall temperatures. can anyone give me a suggestion to fix the first model?

[Federico Alzamora Previtali]

Hello, 

Is the mesh at the walls of the coil the same for both models? The boundary mesh and inflation layers are important to capture the heat transfer accurately and could potentially affect Nu if too coarse.

[Alwan Hibatullah]

hi

yes, the mesh and inflation layer on both models are the same. for the jacket cooling model, regardless of the inflation layer I use, be it thin or thick, it has the same Nu value (wrong result), but for the helical channel model, the inflation layer affects the Nu value

[Federico Alzamora Previtali]

Are your results sufficiently converged?

You could compare the resulting convective and conductive heat transfer results between models to see if this provides any guidance on the difference in Nu