Well I am back at home and will try to get the swissflow flowmeter up and running over the next couple of days. It seems to me that there are 2 possible exmplanations for the increase of C/W at low temperatures: (a) losses from the chilled wb not being insulated that become more and more important as temperature drops and (b) lowered flow rates due to increased viscosity/resistance to flow.
It looks like you can model (b) reasonably well, and I do know that I was having problems with the coolant freezing and had to increase glycol levels as I was first setting things up. That would indicate to me that the fluid indeed is getting pretty viscous even now. Hopefully there will be no surprises with the swissflow and I can post some definitive test results and sort this out.
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