Al.
What I am after is trying to determine what the minimum required
flow is for the horsepower generated. More than anything else, I do not
want to be BELOW that amount, and consider it a minimum. Understandably, trying
to place twice or nearly 3 times the flow through the same circuit will result
in higher pressures and perhaps some pump cavitation. I will deal with that as
I have to.. more than anything else I want to make sure I am not starting off
with a DEFICIT of water flow ability.
I don’t know what water pump you have (stock), but as a general comment, I would say that the stock pump would provide adequate flow rate. The main issues with cooling are usually with other aspects, and generally related to the ‘air-side’ – heat exchanger sizing, scoop and duct design, pressure drop, etc.
I am considering 2 smaller radiators, and originally I intended to plumb them in series to get the best cumulative Delta-T across them, but if I have "pressure" problems due to the pump's flow, I may go to a parralel arrangement
Cumulative coolant side delta-T (determined by the flow rate) is, by itself, not the issue; but rather average radiator temp. The higher that is (for a given flow rate), the more effective the heat transfer to the air. Parallel flow will give you a higher average rad temp.
Designing heat rejection is always a tradeoff of cooling capacity and drag, and if you don’t have air flow control you have to design for takeoff and climb, and have excess capacity for cruise. For the Velocity SE, 180-200 hp is plenty for takeoff, even if you have more available. So on the warmest days you may throttle back shortly after the wheels are off. About 65 sq. in. ‘effective’ scoop intake area (for coolant) should give you adequate airflow on a hot day. Figuring a radiator core thickness of about 2 ˝”, and a core face area of about 250 - 275 sq. in. should do it.
With a pusher, there is always another aspect, cooling on the ground. This may require auxiliary fan(s); however, I have found that with the cooling air exiting the cowl, the negative pressure created by the prop at taxi rpm is sufficient to allow running 15-20 minutes at low power with air temp of about 80F, or lower. Your results may vary.
Just one man’s analysis for similar power (NA 20B), John and Steve also have data for their Cozys.
Al