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Thread: larger id water tubing ,does it really help?

  1. #1
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    Default larger id water tubing ,does it really help?

    as asked ,does a larger id diameter tubing in fact lower temps on your motor and esc vs standard size tubing ?

    has anyone documented a before and after temp test? i am curious .
    volantex vector pro ,proboat veles 29 , traxxas spartan, hobbyking/tfl pursuit ,ft009 with rescue rigging

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    Water can only flow at a rate the smallest orifice will allow. ESC and motor jacket 90’s are b the biggest offenders here. Running a larger dia tube will lower parasitic losses in flow. Whether this translates into a better cooling system I am not sure. No test has been done that I know of.

  3. #3
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    i am a big fan of real world tests . i cant see wasting the money if no real result will occur .theres always that "i feel like it helped" factor but thats just not enough for me .hopefully someone who done a real test will chime in .
    volantex vector pro ,proboat veles 29 , traxxas spartan, hobbyking/tfl pursuit ,ft009 with rescue rigging

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    srislash is correct.
    it does not matter if the tubing ID is 4 or 8 mm if its connected to a fitting with a 2 mm ID. Flow will always be limited by the smallest ID.
    Also, limiting the tubing length will also help with flow.
    Typically, I have replaced the fittings on my ESC and water jacket, and cooling exit. All will have a 4 mm ID.
    Cheetah, Super Rio, (Mod) Starship (Mod and sold),

  5. #5
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    Quote Originally Posted by larryrose11 View Post
    srislash is correct.
    it does not matter if the tubing ID is 4 or 8 mm if its connected to a fitting with a 2 mm ID. Flow will always be limited by the smallest ID.
    Also, limiting the tubing length will also help with flow.
    Typically, I have replaced the fittings on my ESC and water jacket, and cooling exit. All will have a 4 mm ID.
    makes good sense .do they make 4mm fittings? i usually drill open the top of the rudder fitting a little to increase flow but never gave thought to the rest of the fittings ...duh
    volantex vector pro ,proboat veles 29 , traxxas spartan, hobbyking/tfl pursuit ,ft009 with rescue rigging

  6. #6
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    Larger diameter, higher quality silicone tubing also reduces kinking and does not deform when bent as easily as the thinner, smaller diameter tubing can. Wall thickness helps flow and reduces restrictions just as much as internal diameter does. I spend most of my effort boring out or replacing restrictive barbs. I replace the cooling lines mostly for cosmetic reasons to keep my installs looking clean and organized.
    Vac-U-Tug Jr (13mph)

  7. #7
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    Higher flow rate does not mean better cooling. It has everything to do with the rate of heat transfer from the motor/esc to the cooling water. I helped my son with a science project years ago to test this. A lower flow rate cooled better, but it is about finding the best flow rate whether higher or lower for the application. The more surface area to transfer heat to the water the better. Hence IME bigger can motors and longer water jackets cool better.
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    i seen some larger diameter water line tests done on watercooled pc`s and the results were very similar no matter how large or small the tubing was .i guess the best scenario is to run separate lines to each motor and esc but again this theory has no real world test results that i can find either .
    volantex vector pro ,proboat veles 29 , traxxas spartan, hobbyking/tfl pursuit ,ft009 with rescue rigging

  9. #9
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    Peter A typed a good answer with lower flow rate stayed long to grab more heat and I tried it and Peter A was spot on. Also Jan of Netherlands chimed in a long time ago by using pipe in long straight lines flowed better than rubber hose. Makes sense! I made exit pipe a hair smaller which helped a lot. I do have a ? for the above, what is the space between motor and cooling jacket.?
    Last edited by Norwest; 01-08-2020 at 04:32 PM. Reason: info

  10. #10
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    Back to the same old question, does size matter? Most of the ladies say no! (Sorry jest couldn't help it lol) Question, Inlet size, one tiny little opening vs 2 tiny little holes in a rudder vs large brass tube prop wash inlet = volume = flow rate = size? How effective is our water cooling any how? Is the water passing thru the system in our boats really there long enough to do a great job cooling things down any how? Get the electrics wrong , over stress, over prop, all the cooling in the world wont stop the magic smoke from exiting your electrics. That said I would still rather have some than none. All sounds like a nice science project, now where to get Gov. funding for research?
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  11. #11
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    I struggle with grasping how a lower flow rate or less volume of flow could possible cool better. So I researched this and found the following info on the Overclockers forum:

    There is an elementary equation from basic thermodynamics that states that the rate of heat transfer (Q) equals the mass flow rate (M) times a constant (the specific heat of water) times the delta T (fluid temp out minus fluid temp in).

    Q=M x c x Delta T

    In other words, the rate of heat transfer is directly proportional to mass flow rate. You increase the flow rate, you will then increase the rate of heat transfer. Since you cannot mess with mother nature it is very naive to think it works any other way.

    Assume the CPU inserts a constant rate of energy (Q) into the cooling system. Then, from the relationship above, increasing the mass flow rate must result in a smaller delta T because Q remains constant. This smaller Delta T (fluid out - fluid in) also means that the average fluid temperature in the water block is somewhat lower even though the rate of heat transfer has not changed.

    Now lets look at the heat transfer from the CPU to the water. The rate of heat transfer between two points is proportional to the temperature difference between those points. In our case this Delta T (not to be confused with the one above) is the temperature of the CPU minus the average water temperature in the water block. Lowering the average water temperature, as we did above by increasing the flow rate, means we have a little better heat transfer from the CPU to the now somewhat cooler water. The result is that the CPU runs a little cooler.

    This all says that if you increase the flow rate, and everything else remains constant, you will decrease the CPU temperature.

  12. #12
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    EG: thermostats are in our automotive vehicles to slow down/hold water in the radiator " longer " to to A cool off the heated water BEFORE it is sent to the block to absorb more heat.....and B allow the cooler water in the block absorb the heat in the motor BEFORE it is sent to be cooled again

    EG: take a cup of coffee, touch the surface with an ice cube....the ice certainly started to melt but did you lower the temp with that split second cooling?....now drop the ice cube in the cup for a minute....yes NOW you lowered the temp & enough to actually calculate the drop in temps....the "longer" the cold ice sat there the more the temps dropped

    install the tiniest water cooler on your motor you can, to a point of being ridiculous, and tell me your motor doesnt get hotter!
    it gets hotter because the lower volume of water is equivalent to faster flow rate .....it takes less time for the water to enter and exit the cooling system and consequently absorbs less heat

    more volume is most advantageous when the flow is slower
    Last edited by MadProps; 01-10-2020 at 01:19 PM.

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    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.
    Last edited by Doug Smock; 01-10-2020 at 09:51 PM. Reason: typo
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  14. #14
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    Ultimately it is about finding the best flow rate for your system. As a rule of thumb, use the longest/biggest cooler you can fit which will give more surface area and water volume for the water to transfer heat. If heat is an issue, work on tuning your cooling system by testing and measuring temps until you get the best cooling for what you are doing, whether it be fun running, zoom zoom or ovals. Heck everyone spends plenty of time testing props, adjusting struts/stingers/tabs etc, do the same with your cooling. Ultimately electrics run better cooler.
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  15. #15
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    I see no need for tuning. Run the largest and shortest lines you are able to through the largest possible nipples and outlets and your cooling system will be optimized.

  16. #16
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    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).

  17. #17
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    yay for thermo and fluid dynamics.
    Vac-U-Tug Jr (13mph)

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    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.
    Paul "tug Killer" Upton-Taylor, Cat lover.
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  19. #19
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    Quote Originally Posted by Doug Smock View Post
    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.
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