Heat transfer coefficient for convection

Hello

I want to test different nozzles and se which one has the best heat transfer coefficient.

The nozzle are blowing on a Surface the static pressure of air is 1000Pa and the air temp is 20degrees.

The Surface is set to 300degrees constant.

I run the test and get very differen values on the heat transfer coefficient with the same nozzle.

but with different meshes.

So my question is what mesh should i use ?

Best Regards

Per

SolidworksSimulation