" The influence of the boundary
layer, that has also been noted, is probably also not that important, and
in any case only applies to convective heat transfer."

The boundary layer and its heat transfer coefficient have nothing at all to do with convective heat transfer.  All heat passing thru the boundary layer passes by conduction.  It is why the insulation in the wall of your house works, presuming your house is not so leaky thru the siding and inner surface that the insulation is a waste of money.  It is also why a cluster of bees can maintain a high temp in the body of the cluster while those on the outside of the cluster are exposed to temps close to the temp outside the hive.  The thickness of the boundary layer is impacted by air movement and as it thins due to air movement the coefficient will drop as you have a thinner layer to conduct heat thru.  It is vitally important as without that boundary layer effect bees would have zero chance of surviving freezing temps much less the much lower temps many of us have every winter.  You can easy have a temp difference across the boundary layer around a cluster of bees of 40 or 50 deg F or even more if it is really cold outside.  Just like you can have that kind of temp difference across the boundary layer on a single pane window.

You do not need to take my word for this.  Go get any entry level college text book on physics and read the chapter on heat.

Dick

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