Watercooling and flow: is there such a thing as too much flow??

[Shooter]

This has me worried about using a "Y" fitting inside the boat. One leg goes through the ESC and its exit fitting. The other leg goes through the cooling jacket and its exit fitting. The cooling jacket seems to have much reduced flow. So, is all the water going to exit through the ESC path, leaving the motor to overheat. If so, should I use a restricted size exit on the ESC line to force water through the cooling jacket line?

Good question. I think the answer is that you will get flow to both, but less to the higher restriction.....not zero flow.

As for air, I agree, it doesn't matter which way you point the nipple, but the height location is very important. The exit must be at the the highest point. See example.... I'm pumping 10cc/s through this clear container. The exit is at the side. Check out the huge air bubble. It is not present if I put the exit at the top.

[Shooter]

This has me worried about using a "Y" fitting inside the boat. One leg goes through the ESC and its exit fitting. The other leg goes through the cooling jacket and its exit fitting. The cooling jacket seems to have much reduced flow. So, is all the water going to exit through the ESC path, leaving the motor to overheat. If so, should I use a restricted size exit on the ESC line to force water through the cooling jacket line?

Still pondering this one, as it's such a good question. If you are not 'choked' for flow (in electrical terms....your power supply can provide enough current), then your pressure head at both inlets (ESC and motor), created by the rudder running through the water, would not drop. If this is the case, then the restriction you add to the ESC would certainly reduce flow to the ESC, but it would not affect flow to the motor. There's only so much potential (delta pressure) to provide flow and both the ESC and motor are subjected to the same potential.

[nata2run]

Wow! every time I try to be scientific about subjects like these it spins me out. What is calculated is not always the right approach. Sometimes we have to make compromises for many reasons. Could be the way we want to place hardware to compensate for CG or looks or whatever it may be. If after the install you blow through the cooling lines, and you suffer from RITFS (Red In The Face Syndrome) there may be a problem. If you can't easily blow through it, chances are that water won't either.

By using the shortest way of cooling you are more likely to have a setup with minimal resistance. As for myself, I try to use silicone tubes that are 4-4.5mm ID and 7.5-8mm OD (thick walled and can handle pressure). That insures that there is minimal water restriction over the 1.5 feet of cooling lines commonly used. If the whole system is fitted within those inner dimensions, then chances are that water will pass through evenly without generating high and low pressure points. Of cause it's not always the case. Some ESC's have 2.5-3mm nipples and a combined water travel path of 200 feet before the exit nipple, making it a long travel for the cooling water to reach the final exit nipple.

There are other factors involved as well. What's your pickup like? can it actually pick up water and generate pressure? if the pickup is located on the sponson of a cat, is it even in contact with water? But over all, if you can easily blow through the system, then chances are you will have efficient cooling. my 2 cents anyway.

By shortest possible I mean.
part of cooling 2.jpg

By 200 feet I mean
200 feet.jpg

[lt130th]

This has me worried about using a "Y" fitting inside the boat. One leg goes through the ESC and its exit fitting. The other leg goes through the cooling jacket and its exit fitting. The cooling jacket seems to have much reduced flow. So, is all the water going to exit through the ESC path, leaving the motor to overheat. If so, should I use a restricted size exit on the ESC line to force water through the cooling jacket line?

Like electric current, water will take the path of least resistance through your cooling system. Maybe reduce the ID of the tubing after your ESC to equalize the flow rate between its path & the motor's. Just make sure the water still moves through at a good rate & isn't lingering very long. It needs to carry the heat away at a good pace to do its job.

[lt130th]

Still pondering this one, as it's such a good question. If you are not 'choked' for flow (in electrical terms....your power supply can provide enough current), then your pressure head at both inlets (ESC and motor), created by the rudder running through the water, would not drop. If this is the case, then the restriction you add to the ESC would certainly reduce flow to the ESC, but it would not affect flow to the motor. There's only so much potential (delta pressure) to provide flow and both the ESC and motor are subjected to the same potential.

This goes along with the conservation of mass. Lets say you have only a y-adapter inletting a constant volume of water at a constant velocity & pressure. One outlet has a smaller ID than the other. More water volume will pass through the outlet with the larger ID until you reduce that cross-sectional area to match the smaller ID outlet. Your pressures will be constant throughout the system, which can be confirmed by the Bernoulli equation. There's something important to include here, that I was hinting at in one of my previous posts about conservation of mass and the continuity equation. if the two outlets have the same cross-sectional area, in order for the exit velocity to be the same as the inlet velocity, the total cross-sectional area of the two outlets has to be equal to the inlet cross-sectional area. that means ID's half that of the inlet, on each outlet, if we're talking about cylindrical tubing.

[lt130th]

See example.... I'm pumping 10cc/s through this clear container. The exit is at the side. Check out the huge air bubble. It is not present if I put the exit at the top.

While, I predict a similar result, there are two variables missing from this experiment that must be considered. You are pumping water into a large cavity, but inside a water jacket exists a motor can which changes the type of flow & introduces friction effects due to the size & shape of the path the water is being forced through.

[zooma]

Thanks for the replies. I understand Shooter's explanation of equal head pressure in each line. I am the third owner of this boat, and I have been running it without overheating for a year. I guess that I just noticed it recently. I have another boat plumbed this way, so I will have to pay more attention to what it's doing, too.

[lt130th]

Food for thought: Ultimately, heat is lost energy in your FE powertrain. The best way to cool the components is to make the electrical and mechanical system more efficient. Then, you won't have to worry about optimizing the cooling system to carry away/transport all of that lost energy.

[gearhd48]

you could do that or increase the line size to the motor (path of least resistance) and increase the motor output fitting. I personally don't like the smaller size fitting on the ESC. So here we go again with a persons perspective on cooling, more psi or more volume.

[properchopper]

Food for thought: Ultimately, heat is lost energy in your FE powertrain. The best way to cool the components is to make the electrical and mechanical system more efficient. Then, you won't have to worry about optimizing the cooling system to carry away/transport all of that lost energy.

Common Sense ; What a Concept !

[zooma]

you could do that or increase the line size to the motor (path of least resistance) and increase the motor output fitting. I personally don't like the smaller size fitting on the ESC. So here we go again with a persons perspective on cooling, more psi or more volume.

Already at 4 mm Kintec lines and largest OSE outlets. Nothing larger that I know of.

[dmitry100]

So then is it best to keep the shortest path possible for the least resistance when hooking up your lines? Like in style #1

But if I was to have both ESC's make use of both inlets -- that would possibly guarantee that I will have more cooling overall since both sponson water inlets probably don't have 100% water flow and pressure due to air pockets and what not.

What do you guys think is the best way to setup the cooling lines for twin SF or T180 type Esc's? I always figured keeping the shortest path is the way to go then I was thinking it might be a good idea to have both ESC's use both lines equally (like style #3) for the reason above.

Have any of you guys tested any of these and checked data logs...

-- Dual cooling lines --
Style #1 (Keeping both inlet/outlets completely separate to each side) which is what I have right now:
(Inlet 1) --> ESC 1 --> Motor 1
(Inlet 2) --> ESC 2 --> Motor 2

Style #2 (I see these on some T180 setups):
(Inlet 1) --> ESC 1 --> ESC 2 --> Motor 1
(Inlet 2) --> ESC 1 --> ESC 2 --> Motor 2

Style 3 (Benefits of each ESC having both inlets equally):
(Inlet 1) --> ESC 1 --> ESC 2 --> Motor 1
(Inlet 2) --> ESC 2 --> ESC 1 --> Motor 2

[gearhd48]

Common sense, Hey ain't that what I got in my pocket?? LOL

[T.S.Davis]

Still pondering this one, as it's such a good question. If you are not 'choked' for flow (in electrical terms....your power supply can provide enough current), then your pressure head at both inlets (ESC and motor), created by the rudder running through the water, would not drop. If this is the case, then the restriction you add to the ESC would certainly reduce flow to the ESC, but it would not affect flow to the motor. There's only so much potential (delta pressure) to provide flow and both the ESC and motor are subjected to the same potential.

Pete, you have to balance the two legs to get the same flow at each.

I do this for a living. This is an oversimplification and a bit backwards to the way I design systems but I'll try to get your brain around it. Imagine a piece of pipe with three sprinklers on it and a second piece of pipe with one sprinkler on it. Both are supplied from the same source. Now picture a fire where all 4 heads fuse. The pipe with a single outlet can't flow at the same rate as the three outlet pipe. If I want both branches to flow the same I have to increase the friction loss to the three outlets. I could do this by decreasing the pipe size to the three heads, by increasing the friction loss to those outlets (longer distance, more fittings, a pinch point), or by simply using a smaller orifice. Actually for sprinklers I can't use a mixed orifice. Code issue. I think you see what I mean though.

In our case the water after the wye will flow at a higher volume through the easier route and less through the higher friction route. At some point you could have no flow. Think 2" dia line going one way and 1/16" going other other. Not much traveling through the 1/16 line"

It's funny how often the thermodynamic talk comes up. Back in the early 2000's we were cooling our end bells and we had coils instead of cool cans. I asked if at some point the friction loss would render flow impossible. Consensus was then that if the water was still moving then yahoo. I used to think slow it down a bit but not so much any more.

As for the cooling properties of water maybe we need to take a page from NFPA. To fight high challenge fires they have us throw massive quantities of water on them. I just finished a design that lays down 1.2 gpm per sq.ft. over a 1200 sq.ft. area for 90 minutes. After balancing it plops down 1457 gallons per minute.

More is better where cooling is concerned.

Oh, I tried the cooling coil/canister thing in 2005. Should have worked but me being a hack then I just made a mess. I always wanted to mount a PC radiator in the turbine on my scale. Thought maybe pre-cooling the water on it's way to the electronics would help. Never got around to it. Batteries are the week link in my scale.

[lt130th]

Common Sense ; What a Concept !

You would think, right? Not everyone thinks of heat in terms of performance they're losing that they could try to get back. Instead, the water cooling threads seem to outweigh threads about proper gauge & length of wire between specific circuit elements, or measuring output shaft-work & power required...or simply rotor-shaft bearing upgrades, pro's/con's of thrust bearings, best flex shaft grease, illiminating runout & balancing shafts, strut bushings, etc.