Water cooling

[Old School]

Just after information as regards improving water cooling flow. Obviously, one would need to limit the available length of hose internally plus increase the I.D. of the hose, however, would adding additional outlets improve flow, please. A hull I am currently building I have substituted the stock single outlet rudder to one with a dual outlet with four pickup holes on the blade.

I am thinking to individually feed both the motor and ESC and then on the outlet from the motor and ESC, split the flow with a Y splitter to two outlets for each. I am thinking that making an additional outlet may improve the flow given the additional pickup holes on the rudder blade.

Obviously internal resistance of both the hose and the ESC and motor jacket will limit flow, but I am thinking as if it is traffic restricted to one lane and then another lane opens up encouraging flow through the whole system.

[fweasel]

keep it simple. are you currently having cooling problems with this setup? While I'm all for feeding the motor and ESC with independent water feeds, splitting the outlets seems unnecessary and in practical application, will likely introduce more potential points of failure (leaks) with negligible improvement on cooling. Thermodynamics also comes into play with the amount of time the coolant is in contact with the heated surfaces and the opportunity to remove heat from the system.

[Old School]

Many thanks. The boat is currently under construction so I am just seeing what needs to be done.

[785boats]

I generally run 4mm ID lines throughout the boat & use some 5mm brass tube as an outlet through the hull with the 4mm tube stretched on to that.
Of course the nipples on the coolers, rudder, & ESC have to be the largest possible for the water flow to be as large as possible too.

Separate lines for ESC & Motor can work well, but so can just a single line through both.
As fweasel said, I don't think that splitting the outlets will gain much. Just make the outlet size as large as possible for the fastest flow.

[Old School]

Many thanks. I generally try to solve problems before they occur but perhaps too much in the way of bits and pieces will be more a problem than just optimising the setup that I already have.

[Shooter]

Thermodynamics also comes into play with the amount of time the coolant is in contact with the heated surfaces and the opportunity to remove heat from the system.

Oh no, not this again!

[properchopper]

[boredom.is.me]

keep it simple. are you currently having cooling problems with this setup? While I'm all for feeding the motor and ESC with independent water feeds, splitting the outlets seems unnecessary and in practical application, will likely introduce more potential points of failure (leaks) with negligible improvement on cooling. Thermodynamics also comes into play with the amount of time the coolant is in contact with the heated surfaces and the opportunity to remove heat from the system.

Oh no, not this again!

I know right. It's something that will never end... just like the white and gold dress.

It is indeed thermodynamics. If you understand how the specific heat of a substance works, you would know that pushing more water through the system is more beneficial than letting it sit. We're not trying to heat up the water.

I haven't been around in ages. Feels good to be back.

[CraigP]

This seems to be a hot point of discussion. People that want to move the water slower so it gains more heat are confusing the water’s ability the conduct heat with an inefficient heat exchanger. This is usually related to the area ratio of the heated structure and the area of water contact.

It’s pretty simple, if you are seeing very little temp differential between inlet and outlet water and your heated surfaces are running fairly cool, then you’re cooling system is at its best. If the temp diff is low and you’re running hot, then the heat exchanger is not right. Slowing the water down will only raise the temp of the heated surfaces of interest. Not the right direction.

Only if you are running a high temp differential and the heated surfaces are too hot can the conclusion be made that the flow rate is too low. This can only be verified by data logging inlet water temp, outlet temp and temp of the heated surface, or the electronic side of the heat exchanger. I’ve never seen this body of evidence posted, so it comes down to opinions, and you know what they say about opinions!

I do run dual water lines, because there’s more volume of water in the boat at any given time. As to leaks, I use a pressure/vacuum pump and test the integrity of the system before I run. My text spec is holding 18psi for 15 seconds. I also use OSE water clamps at all joints. There’s a few of them, for sure! I’ve had to swap out small ID fittings with larger, especially on front motor mount plates. I do use large diameter water hose, 9/32” I believe. I’m not even close to temp problems, running 108-112 on motor and ESC. If you have a problem, then you might need to gather some facts on your particular implementation.

[rol243]

we all must remember that don,t just think because you have a water cooled motor and a water cooled esc that you going to be able to run your boat safely at speed and duration cause you can see water is exiting the outlet. no matter how good the cooling is there is still your motor / esc / battery / prop etc etc set up to take into consideration, example an over sized prop will load the motor / esc and cause excessive heat being water cooled or not.

[CraigP]

That is right on the mark! The biggest problem in high current hulls is the heat exchanger design. The motor cooler needs as close to 100% water fill as you can get, and there has been plenty of good suggestions posted on this site to get good motor cooling. The ESC is unfortunately, more a product of the ESC manufacturer. Again, lots of info on what ESC’s cool better over others. But it you run the ESC at rated current, it’s going to run hot! A good solution is to use prudent de-rates, and not run stuff at 100%. As mosfets get hotter, they get a larger voltage drop when ON. This can cause a thermal runaway situation that no amount of water cooling can remedy. This volt drop/thermal curve is logarithmic. So it will be fine to a point, then the heat will take off like a rocket! You just have to keep away from that threshold. Under these conditions, you’re not getting the good volts to the motor, so I would think that there’s a point of diminished returns, where less hot setups can actually be faster, since the motor gets more volts. I think most of us has experienced this...