I feel water cooling deserves it's own thread. It is a topic almost everyone has wondered about at one time or another.
I want to start it all out with an accomplished result...Almost everyone has seen my motor.
My theory was to perform motor cooling by induction with the water cooled tubes.
It used Propylene-glycol/water 50%-50% mix. The pump was about 2 gallons/minute. It used a large aluminum heat exchanger and lots of air.
Today I drove half way home with no water circulation, maintaining 60 Deg. C. (9 miles and 105-F. AMB.), I stopped, plugged in the pump and drove home. It was sitting on 55 Deg. C......
5 Degrees measured at the stator windings........
My Thoughts: 5 degrees is disappointing. I believe it was because of lack of contact surface. It was not worth doing.
Conclusion: Unless your motor is operating within the last 30% region, this cooling method is not effective. The only way it would be effective is if you were really marginal and it kept the motor from over temping.
I am in the first 30% region. I really do not need any type of extra cooling.
It just adds extra cost, weight, complexity and ultimately draws from the pack (mileage).