I think you are making this too complicated.
The bees cluster, forming a more or less solid mass in between combs, and in the cells of those combs...the bees are able to regulate the flow of air in and out (and within) the cluster.
When the temperature is cold, the bees do what they can to retain heat within the cluster....tighten up, limit air flow.
As soon as it is getting too warm in the cluster, the bees start to shed heat.
If you want to do an experiment, you can take a 5 frame nuc, screen the bottom and the top, and put it in the refregerator (or outside in the winter...somewhere around 30-40 degrees). They make very little sound, very little heat is coming up through the screen, and very little smell is coming up through the screen.
As you warm them up, there is a "switch", where they go from holding the heat in to shedding it. It is obvious from the sound, the heat, and the smell.
The size of the cluster determines their ability to keep the cluster warm. If the cluster is too small or does not have "fuel", they will not be able to maintain their temperature.
Remember that the bees can be removing moisture from one cell to ripen honey, and increasing moisture in the next cell to keep the brood healthy.
If you want to talk about thermal flows within the hive, you have to take the comb, and the tens of thousands of little fans and heaters placed strategically throughout the combs. It isn't as simple as a swimming pool, but it need not be complicated.
More bees can maintain their temperature better than less bees.
Don't let condensation fall on the cluster...either with top cover design, absorbant material, or ventilation.