It seems that this is a convective heat transfer analysis - but indeed you are correct that the y+ field is not available. Maybe @anon62721193 can comment further on this.
Regarding your inlet velocity, it appears that you are using a volumetric flow rate so .15 m3/s (or were you intending this to be an inlet velocity of .15 m/s?) :
When you download the result from SimScale, you need to open the case.foam file in ParaView and click Apply - then you should be able to see the preliminary results.
This image is done using the clip filter. The 340 m/s speeds are misleading - once I rescaled the magnitude it’s more in the range of 60 - 70 m/s which still seems to fast but this could be stemming from the inlet condition .
Have you seen this tutorial from our “Air-Conditioning and Ventilation Workshop”? Think it might be helpful for your application