larger id water tubing ,does it really help?

[boredom.is.me]

The flow rate argument pops up way too often. Ask yourself this: are you trying to cool your motor, or are you trying to heat your water? If you are trying to heat your water, then having the water sit on the heat source will do that (slow rate). We're not trying to do that though. We are cooling the motor. All we care about is the delta. We want the lowest possible water temperature at all times. This is done by replacing the water that is being heated as soon as possible. With that said, we want a fast flow rate. If the water comes out of the boat warm, then it's sitting there way too long. This is an open loop system. Unlike in a car's cooling system (closed loop) we don't care about what happens after the water takes on heat. We just want it gone.

As for the tubing size, it doesn't really matter at the lengths that we work with. It's a similar concept for our electrical wiring. As long as it isn't the smallest (most restrictive) portion, there shouldn't be a single cause for concern. Now if we wanted distance, as in several meters/yards, then you start to look at the increasing boundary layer growing on the tubing walls. That's why all of our infrastructure uses giant piping in comparison to what we use, even if we are at the same flow rate or current draw (amps).

[fweasel]

yay for thermo and fluid dynamics.

[NativePaul]

Bigger pipes/tubes are better, but there is only so much you can do with water cooling the outside of the motor can, or the surface or legs of a FET on however good the flow is. Even if you could to refrigerate the areas we can water cool and keep them at freezing point while running, they are still making heat internally and if you run too big a load for too long you overheat them and will let the magic smoke out.

The size of your prop will have a much bigger effect on the temperature of your motor and ESC than the size of your water pipes does.

[kfxguy]

Mike W.
MadProps. Thermostats in internal combustion engines are there to keep water in the block until the engine warms up (around 200'F). At that time the thermostat opens and allows water to enter the radiator to have heat removed.

Guys ask yourself, Am I trying to cool components or heat water to make coffee?
If you're making coffee I suggest you leave that water in the system as long as you can. If not...……..

30 years in the commercial refrigeration business and I assure you that in a water cooled condensing unit you will NOT reduce the head pressure and liquid line temperature by reducing the water flow. Slow that flow down and the water temperature will increase, but so will the temperature of the heat exchanger.

This. And let me add something. In a car’s cooling system, air is cooling the water. Which takes time. If it flows through the radiator faster than the heat can be transferred into the air, then yea, you’ll have a problem with it overheating. I’ve heard of people “thinking” a thermostat is there to slow the flow down, but that’s not true.

Now. We are taking about cooling something with a constant supply of cool water. Of course more flow is going to cool better.