water cooling efficiency

[Ramtornado]

but the motor stays cool after 5 minutes of full trotle run
i do not see any flow out of the exit
i tried to do fast runs close to shore

what else can i do to see the flow
maybe with on Bord camera on the exit ??

[ReddyWatts]

Yes or just video it as it passes and transfer video to your computer for a better look.

Can you blow air through the tubing?

[rearwheelin]

well i am not shore that there is any flow in the tubing's

You can put a catch can inside the boat , take the tubing that is (the exhaust) and stuff it into a plastic coke bottle threw the cap of it(drill hole in the cap ) and tape it in the boat, after that poke a couple really small holes at the top side of your catch can so your can wont build pressure as the water comes in, take a lap or two around the lake and the can should be atleast half full..

[Ramtornado]

WOW that's the simplest way to do that
thanks a lot i had in mined more complex setup of a camera LOL :)
i think there is no other way to do that i can measure it precisely the amount of water flowing it the tubs

its possible even to calculate the flow rate ...

i will do that soon:)

[Fluid]

but the motor stays cool after 5 minutes of full trotle run
i do not see any flow out of the exit

Then regardless of the flow rate your system is working. Don't worry about it.

...since the heat exchange works best with the greatest temperature differential, longer “stay time” is counter-productive.

While it is true that a high temperature differential helps, the above ignores the specific heat capacity of water which insures that fast moving water will not heat up! It takes time for the heat to transfer, this is the reason that auto engine cooling systems work best with a restriction in the flow - race cars which run without the thermostat use a restrictor plate instead to improve cooling by slowing the flow rate.

Water in turbulent flow picks up heat more slowly as well, and turbulent flow is easy to achieve in water lines and ESC tubing at a relatively low velocity. I've done the experiment and it verifies the science. But some will ignore science and do what they want anyway. Fortunately, even inefficient cooling is better than none.




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[ReddyWatts]

That is the myth. The reason why an auto cooling system works better with a restriction of water flow where it leaves the block is because it raises the water pressure in the block to raise the boiling point of water and reducing the creation of air bubbles that reduce heat transfer effeciency.

[rearwheelin]

WOW that's the simplest way to do that
thanks a lot i had in mined more complex setup of a camera LOL :)
i think there is no other way to do that i can measure it precisely the amount of water flowing it the tubs

its possible even to calculate the flow rate ...

i will do that soon:)

Also , dont completly seal your hatch because that could effect your flow rate , dont flip it over and you will be alright

[detox]

The engine temperature is primarily controlled by a wax-pellet type of thermostat, a valve which opens once the engine has reached its optimum operating temperature. Allowing too much flow of coolant to the radiator would result in the engine being over cooled and operating at lower than optimum temperature.

http://en.wikipedia.org/wiki/Radiator_(engine_cooling)


...

[Ramtornado]

Also , dont completly seal your hatch because that could effect your flow rate , dont flip it over and you will be alright

well its easy to say don't flip over its impossible to predict in full speed the hatch is not playing any roll in the water cooling system

you mean wen i do the water test
its sound more likely to not close the hatch completely to allow the air out from the inside of the coke bottle
:)

[FE Wannabe]

Ramtornado,
You could always vent the Coke bottle to the water exit in the hull to prevent any pressure build up.
That way you could still tape up the hatch good.

[rearwheelin]

well its easy to say don't flip over its impossible to predict in full speed the hatch is not playing any roll in the water cooling system

you mean wen i do the water test
its sound more likely to not close the hatch completely to allow the air out from the inside of the coke bottle
:)

Yes

[BakedMopar]

Yes, air will not transfer heat as good as water. The water pickup needs to be directly in the water and not coming from prop wash.

What about prop wash pickups. I use these on a couple boats and they cool just as good.

[ReddyWatts]

I personally do not like or recommend prop wash pickups for maximum heat transfer effeciency.

We are not dealing with temps close to the boiling point and do not need to restrict the water flow that creates back pressure for elevating the boiling point. (Five pounds of pressure will raise the boiling point by 10 degrees F etc......) For our boat applications we only need to get the heat out quickly with the largest temp differential possible, therefore do not restrict the flow and try to keep air pockets out of the cooling system.

[Ramtornado]

When i built my first boat i thought to put prop wash pickups, its seems to be the perfect spot to put them there but still you have some times the effect of the water cavitation behind the prop.

The prop pushes water in to the tube so you have faster flowing cooling system in theory
maybe i am wrong but i put them in front of the prop, then the boat have some bad effect on the prop
Expert II

[ReddyWatts]

Try moving the pickups or changing the angle for better water flow.

Also cut the end of the pickup tube at a 30 degree angle to help funnel the water into the tube from the prop wash.