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Convergence issues for laminar flow and heat transfer

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Hi,

I briefly explain the problem I'm trying to solve: I want to evaluate the transient heat transfer between a finned tube (with water flowing inside it) covered by a layer of PCM. I perform the study using a 2D axisymmetric geometry. First of all I need to evaluate the mesh that allows to describe appropriately this phenomena. The path followed: 1- convergence study limited to the laminar region (stationary) -> PROBLEM: varying the maximum and minimum dimensions of the cell (triangular) I don't get a "smooth" path (see attached image). Since the tube has a inner diameter of 18 mm but a length of 1.3 m, could it be the problem due to the high difference between the two dimensions? 2- After having found the right mesh (but now it is not like that) I would use the results for the laminar flow to investigate the transient heat transfer. In this way I can divide the two studies and reduce the computational time (IS THAT RIGHT?). For the PCM region, I encoutered another problem: the length is still 1.3 m, but the fins are 10 x 0.4 mm and the step between two fins is 2.42 mm. This time too I don't know how to manage the mesh.

Thank you for the help.

Daniele



0 Replies Last Post Jul 5, 2019, 4:37 a.m. EDT
COMSOL Moderator

Hello Daniele Marocco

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