I was embarrassed to ask about this originally, but it seems I am not alone with questions.  having viewed several flying cooling system flow designs at the rotary round-up, perhaps it isn't that critical.

  one aspect I trying to understand is the expansion tank.  there shouldn't a big flow thru there, right?  if the pressure is greatest at this far rotor housing top port, then it must be lower in the expansion tank, and a slow flow will take place towards the expansion tank, right?  the small diameter line will tend to push bubbles thru and they will separate in the expansion tank. so, if they enter the tank above water level, this line will suck air from the expansion tank as the cooling fluid cools and has a lesser volume, right? not good.   if the expansion tank feeds the cooling circulation system by T'ing into the water pump output, then it is all on the higher pressure side of the system, and the air in the expansion tank won't have a tendency to be sucked into the circulation?  is the design intention to keep the expansion tank under pressure, rather than have it part of the flow [circulation]?    if the expansion tank was plumbed into the water pump inlet port, then a second circulation route is created, which doesn't involved the radiator [rear rotor port to tank to water pump, thru engine block to rear port....], right?

as far as the bubble line for the radiator it seems that it would work by allowing trapped bubbles in the higher end of the radiator to travel uphill to the expansion tank.  is the pressure at the radiator also higher, as with the rear port?

enough questions.  clear as mud, right?   kevin