If we concentrate only in temperature I like to see things the following way

1.- Naturally EHB prefer to nest in a cavity. (I have seen at Australia them
hanging from trees, but never in colder climates)

2.- Air - with no convection - is the best insulation.  The distance between
the heat source and the heat sink must be a trade-off between convection and
diffusive (or conductive) transfer of heat for air to be a good insulation.

If I take the two aboves as true, then, this ratios of volume of the cavity
compared to the population of the cluster, simply means that the available
"empty" space should not allow convection and minimize diffusion. For a heat
source of around 37°C and a sink of under 10°C this size should not be
bigger (wider?) than 45 milimitres. The above based on a rough calculation I
did long time ago using a standard langstroth hive as the cavity X,Y
dimentions.

-- 
Juanse Barros J. -- who btw have a MSc in energy and environment UK Reading
1994.
APIZUR S.A.
Carrera 695
Gorbea - CHILE
+56-45-271693
08-3613310
http://apiaraucania.blogspot.com/
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