Problems with the temperature module

I’m modeling a reservoir with the temperature module activated, but when i see the results i realize that it has a problem when the grid increases the number of rows, particulary in this model i observed that my temperature loses nearly 3 degrees, could it be caused by heat transfer coefficient problems, if it is not, what causes this problem?

10^-3 to 10^-6 are typical ranges of values. However, these are just background, minimum values. If you have a single layer model then this is not used. If you have multiple layers then the vertical eddy viscosity default calculation method is Galerpin to which this background number is added. You should check you have this set correctly, Turbulent Intensity > Turbulent Intensity Advection Scheme > should be set to 1.