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Water cooling methods and effectiveness.

75K views 149 replies 40 participants last post by  dtbaker 
#1 ·
I feel water cooling deserves it's own thread. It is a topic almost everyone has wondered about at one time or another.

I want to start it all out with an accomplished result...Almost everyone has seen my motor.

My theory was to perform motor cooling by induction with the water cooled tubes.
It used Propylene-glycol/water 50%-50% mix. The pump was about 2 gallons/minute. It used a large aluminum heat exchanger and lots of air.

Busted: Today I drove half way home with no water circulation, maintaining 60 Deg. C. (9 miles and 105-F. AMB.), I stopped, plugged in the pump and drove home. It was sitting on 55 Deg. C......

5 Degrees measured at the stator windings........

My Thoughts: 5 degrees is disappointing. I believe it was because of lack of contact surface. It was not worth doing.

Conclusion: Unless your motor is operating within the last 30% region, this cooling method is not effective. The only way it would be effective is if you were really marginal and it kept the motor from over temping.

I am in the first 30% region. I really do not need any type of extra cooling.
It just adds extra cost, weight, complexity and ultimately draws from the pack (mileage).

Miz
 
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#3 ·
AC50's have a built-in fan on the drive end that pulls air through the motor and exhausts radially out the end cap through 4 slots.

I also have a ducted fan inside the intake tube. It was mostly to compensate for the air filter element restriction.

I was in low gear, about 5,100 RPM, 1.72:1 with a 6.14:1 axle ratio and a 32" tall tire. I was cruising at 100-110 amps @45 MPH.


I hope this helps.

Miz
 
#5 ·
I feel water cooling deserves it's own thread. It is a topic almost everyone has wondered about at one time or another.

I want to start it all out with an accomplished result...Almost everyone has seen my motor.

My theory was to perform motor cooling by induction with the water cooled tubes.
It used Propylene-glycol/water 50%-50% mix. The pump was about 2 gallons/minute. It used a large aluminum heat exchanger and lots of air.

Busted: Today I drove half way home with no water circulation, maintaining 60 Deg. C. (9 miles and 105-F. AMB.), I stopped, plugged in the pump and drove home. It was sitting on 55 Deg. C......

5 Degrees measured at the stator windings........

My Thoughts: 5 degrees is disappointing. I believe it was because of lack of contact surface. It was not worth doing.

Conclusion: Unless your motor is operating within the last 30% region, this cooling method is not effective. The only way it would be effective is if you were really marginal and it kept the motor from over temping.

I am in the first 30% region. I really do not need any type of extra cooling.
It just adds extra cost, weight, complexity and ultimately draws from the pack (mileage).

Miz
I did the same thing to one of my motors and now I am doing air cooling on my dc motor.
 
#6 ·
Busted: Today I drove half way home with no water circulation, maintaining 60 Deg. C. (9 miles and 105-F. AMB.), I stopped, plugged in the pump and drove home. It was sitting on 55 Deg. C......

5 Degrees measured at the stator windings........

My Thoughts: 5 degrees is disappointing. I believe it was because of lack of contact surface. It was not worth doing.
Hi Miz,

I wouldn't throw it out yet. It might show only 5º but that is with a fairly cool motor. 60ºC on the stator winding is hardly taxing the motor. Get it up to 150ºC and try your experiment.

The amount of heat removed and resulting reduction in winding temperature is dependent on the temperature differential. So there was little difference between the coolant and ambient and little difference between the coolant and the motor frame. So you saw a small difference w & w/o coolant circulation.

Jacket liquid cooling works best on totally enclosed motors running continuously. Every little bit helps when you're pressing the machine to the limits. Limit on your motor is 180ºC, but use around 150 on the measurement.

I think you need to run that rod harder ;)

major
 
#8 ·
Thermal compound (paste) might help some. I doubt the motor surface or the tubing surface is perfectly smooth, the compound could help fill the gaps

I was thinking the same thing as major, heat flow is proportional to temperature difference. It should move much more heat at higher temperatures.


I had been thinking of trying the same thing for a while now, I'm glad you posted this.
 
#9 ·
Thermal compound (paste) might help some. I doubt the motor surface or the tubing surface is perfectly smooth, the compound could help fill the gaps

I was thinking the same thing as major, heat flow is proportional to temperature difference. It should move much more heat at higher temperatures.


I had been thinking of trying the same thing for a while now, I'm glad you posted this.
Using air cooling with water cooling will help keep the motor cooler.
 
#11 ·
Conclusion: Unless your motor is operating within the last 30% region, this cooling method is not effective. The only way it would be effective is if you were really marginal and it kept the motor from over temping.
I wouldn't throw it out yet. It might show only 5º but that is with a fairly cool motor. 60ºC on the stator winding is hardly taxing the motor. Get it up to 150ºC and try your experiment.
I was thinking the same thing as major, heat flow is proportional to temperature difference. It should move much more heat at higher temperatures
Yah, I think we all are in agreement on this point. So Maybe we could adopt a rule. Like your motor temp needs to be above 50% of it's maximum rating before water cooling even becomes viable.


Miz
 
#13 ·
I'm planning on experimenting with Open Revolt controllers and want to build chill plates for them, instead of finned heat sinks. Also, the motor going in my e-bike, for the first stage is a little ProTech permanent magnet, totally enclosed, deal. Even though it's not slated to be in the bike long, and will really only be used around the aisles of the shop, or at events (if we still don't have the actual Mars motor), I am planning to build a little cooler for it. It is actually the motor I bought for the big cooling blower unit on the Model E, so this motor cooler might have a purpose beyond the fist stage of the bike.

I thought about wrapping it with copper tubing, ala Miz, but had two concerns with that. One, the contact surface of the round section tubing is so small, against the motor frame - kind of like a motorcycle tire. Two, the coolant has to travel through the entire length of the tubing to get the heat away from the motor. I believe you said you used 75ft of copper tubing Miz? That seems like an awfully long time to carry heat, and if it works well the coolant is at motor temp for a lot of that journey, and unable to collect more heat from the motor. It would be interesting to shoot the tubing at different points with an infrared to see if it's cooler at the inlet side than the outlet...

One of my Team members and I came up with the idea to make two aluminum pieces that cup around the frame tightly and are clamped together. Holes will be drilled through the cooling plates, threaded, tapped, and fitted with compression nipples, on the ends; then fitted to a little hand fabricated tank on each end - like a radiator. I haven't modeled the tanks yet, and this model is just a rough sketch, but try to imagine a little half-round, miniature, tank with eleven little short flanged sections of tubing soldered or welded to it, with compression nuts on them.


I admit, it's a helluva lot of fabrication, but we're prone to this type of excess. Someone may be able to simplify this basic concept and implement it. The main point is all the water comes in cool, makes an equal path across the motor frame, and exits (hopefully) full of waste heat.


As I said, this is just a rough sketch to communicate the idea, and help me think it through. To fit in the mock-up case I made to go over this little motor, I can't have those big clamping bolts. I did those for here to illustrate the concept.
 
#15 ·
I'm planning on experimenting with Open Revolt controllers and want to build chill plates for them, instead of finned heat sinks. Also, the motor going in my e-bike, for the first stage is a little ProTech permanent magnet, totally enclosed, deal. Even though it's not slated to be in the bike long, and will really only be used around the aisles of the shop, or at events (if we still don't have the actual Mars motor), I am planning to build a little cooler for it. It is actually the motor I bought for the big cooling blower unit on the Model E, so this motor cooler might have a purpose beyond the fist stage of the bike.

I thought about wrapping it with copper tubing, ala Miz, but had two concerns with that. One, the contact surface of the round section tubing is so small, against the motor frame - kind of like a motorcycle tire. Two, the coolant has to travel through the entire length of the tubing to get the heat away from the motor. I believe you said you used 75ft of copper tubing Miz? That seems like an awfully long time to carry heat, and if it works well the coolant is at motor temp for a lot of that journey, and unable to collect more heat from the motor. It would be interesting to shoot the tubing at different points with an infrared to see if it's cooler at the inlet side than the outlet...

One of my Team members and I came up with the idea to make two aluminum pieces that cup around the frame tightly and are clamped together. Holes will be drilled through the cooling plates, threaded, tapped, and fitted with compression nipples, on the ends; then fitted to a little hand fabricated tank on each end - like a radiator. I haven't modeled the tanks yet, and this model is just a rough sketch, but try to imagine a little half-round, miniature, tank with eleven little short flanged sections of tubing soldered or welded to it, with compression nuts on them.


I admit, it's a helluva lot of fabrication, but we're prone to this type of excess. Someone may be able to simplify this basic concept and implement it. The main point is all the water comes in cool, makes an equal path across the motor frame, and exits (hopefully) full of waste heat.

As I said, this is just a rough sketch to communicate the idea, and help me think it through. To fit in the mock-up case I made to go over this little motor, I can't have those big clamping bolts. I did those for here to illustrate the concept.
You will have the same issue as miz, small surface contact area. A gap of only tens of microinches will reduce cooling greatly, as then heat transfer is by convection rather than conduction. There is no way you will get the surfaces of two rigid parts so perfectly matched that they have more than a couple percent contact area. Even if you could, the contact area would then be limited to a few percent anyway due to surface roughness for say a 40 micro-inch surface finish. Heat sink compound will help considerably, but it won't compensate poor machining. Need to minimize that gap, maximize contact area. Turbulent fluid flow also helps, as it breaks up the boundary layer in the fluid, increasing heat transfer from the metal to the fluid. But that is a much smaller effect than reducing the heat transfer coefficient between the jacket and motor. I agree with the need to shorten the tubing length to maximize the delta T between fluid and motor over the entire length.
 
#14 ·
My impression was that miz understands heat flow is proportional to heat transfer coefficient and temperature differential. Seems his point was that the former is low due to small contact area, so the coil only provides a small amount of additional cooling, and for his normal driving conditions it isn't required.

Conclusion: Unless your motor is operating within the last 30% region, this cooling method is not effective. The only way it would be effective is if you were really marginal and it kept the motor from over temping.

I am in the first 30% region. I really do not need any type of extra cooling.
It just adds extra cost, weight, complexity and ultimately draws from the pack (mileage).Miz
Heat is more of an issue with my controller than my motor, but it typically doesn't get over about 55-57 C with ambient in upper 90's. What temperature was your controller miz,and how are you cooling it?
 
#24 ·
Copper is worse than most metals when cold worked. It gets "Work hardened" and must be annealed before it can be bent again. Cold working (either compression or stretching) produces a system of uneven stresses in the matrix and the material loses what elasticity it had. (The next time you bend it, it fractures).

I would use a common sheet metal bead roller to flatten copper tubing and then reheat it with a propane torch to anneal.

The wrapping could be done by hand as I did, or in a lathe.

If you want to go all out, I would sand the motor case and "Tin" the surface. That way you could heat and solder it as you wound it on the case. Of coarse, that would mean Stator removal.But it would conduct heat nicely.

A point was brought up that the water would heat soak in the first section and leave the last half of the motor hot. My air flow is encoder end to drive end. So, my water flow is drive end to encoder. (An attempt to even out the temperature slope in the motor).

Now we are to the point of a LOT of work and added weight.

Better to just machine yourself an aluminum motor case like Ivansgarage did.

In retrospect, My AC50 has a 120C maximum temperature. Water boils at 100C. My temps are running 60C area.

I am thinking that unless my temps reach 100C, I dont need water cooling.

At that point it would not cool the motor down, but it would slow or stop any further rise in temperature.

Miz
 
#25 ·
I would like to throw another water cooling subject on the table.

My controller.

Curtis 1238R with a custom cold plate made by Ivansgarage.

It is of the "Bath tub" design.

It uses the thermo-siphon principal. Cold liquid in at the bottom, warm liquid out the top in a natural convection manner.

Some say it is inefficient because there are "dead" spots with no flow.
Some say it makes the upper controller run hotter than the lower.
Some say it will corrode and ruin the controller.

All are valid points.

My thoughts:

it is inefficient because there are "dead" spots with no flow.
When a liquid is in a dynamic environment, it will react most at the point of greatest energy absorption. So while the complaint is correct, the liquid never really stands still.

it makes the upper controller run hotter than the lower.
This is partly true, but greater water volume is a good "Band-aid" to this glitch.

it will corrode and ruin the controller.
The heat and pressures in a conventional ICE cooling system does not exist here. Even then it takes years to do any real damage. But, careful addition of anti-corrosives will slow this down further. I am a proponent of the "direct contact" method of heat transfer.(Water contact) It is magnitudes more efficient than conduction alone.

So far, it is working really well. No leaks even when held by the 4 corner bolts alone. (Use a good anaerobic gasket compound-keep the surfaces flat)

I have about 2 GPM flow and am using a 50-50 solution of Propelyene Glycol.
It is cheapest from the Pet store. It is nice to work with and is environment friendly.

Miz
 
#28 · (Edited)
My controller is running 48C with an ambient of 109F. Motor was 55C /water and 60C /air.

Remember- flatland, stoplights a mile apart, light weight vehicle.

The max temp rating is low for class H. (120C)

It should be able to run as high as 180C before suffering damage. Unless there is another reason besides insulation rating.....

Miz
 
#29 ·
I haven't seen it mentioned yet, so I just want to point out that copper pipes with an aluminum radiator is a recipe for galvanic corrosion. Use only one metal for the entire coolant loop, or expect to replace things sooner or later.

Also, if the coolant doesn't see high enough temperature it won't kill bacteria. I'm not sure how much of a concern this is in reality, but Tritium's controller manual points it out. There are biocides that can be added to the coolant.
 
#30 ·
Last time I looked under the hood of my F150, I had aluminum, brass, copper, stainless steel and cast iron, all in the cooling system. I guess that is why the coolant is so exotic...That or FORD does not read forums.

Seriously, My degree is in Metallurgy. In a pure chemical form, you are correct, but we all must replace things eventually. I just think of it as a standard maintenance deal. No liquid cooling system lasts forever. I try to not
"over think" the problem and accept 4 years between flushing and some parts replaced as normal, here in the alkaline South West, USA. (Other places get 5-10 years on theirs)

Miz
 
#31 ·
I smile anytime I see someone posting about using different metals or conductive materials together on the internet, because I know the galvanic FUD is coming! :D

I also love, love, love, getting new engineering interns in my shop so I can teach them how we effortlessly do so many of the things in hot rodding that the books (or inexperienced teachers) say cannot be done. ;):cool: Some are freshman engineering students - I know their professors are going to love me! :D
 
#33 ·
I just like being sarcastic. When someone says something like that about certain metals in certain conditions, people with a lot of experience know that it's someone who doesn't have much, or has been indoctrinated into an unreasonable fear by someone who doesn't.

In all fairness to engineers (I really love them, almost went to school to be one), engineers are the reason I know I don't have to be afraid of galvanic reaction in most of these cases. The cars I dissect and put back together (a little differently), and that they originally designed, are full of these combinations of metals. Aluminum engine blocks full of steel sleeves, bolts, bearings, etc, are the example that come to mind first, when the subject comes up.

If one does the homework, they'll likely find (as Miz suggested) that by the time galvanic reaction/corrosion becomes an issue the part or vehicle will have exceeded its intended service life. The ones they're wrong on, have replacements at the local parts stores ready for human consumption; still no major issue, as it's usually just a slow, discernible, wear issue, not catastrophic failure.
 
#34 ·
I would think that the aluminum would pull heat away faster than the water pool. I would opt for an aluminum cooling plate where there are tubes running through the aluminum to pull away the heat from the aluminum and the aluminum pulls heat away from the controller. Being that you now have a huge open hole filled with coolant I suspect that the flow is not so good as to pull heat away fast enough. Kinda like just using a huge block of aluminum to pull heat away from the controller with not fins or fan. Thinking that the huge block of aluminum would suffice. Boy was I wrong. That sucker heated that block up quick and then the heat had no where to go. The controller went into limp mode again. Once I put on a heat sink with fins and a fan I was able to pull the heat away fast enough to never allow the controller to over heat even in 110 degree weather doing stop and go in town with high currents. The coolant tubes within a heat sink will allow the moving water to suck out the heat fast when pushed through a good radiator. A pond will absorb heat but I bet not fast enough. When the water from your tubes hit that pond it all slows down builds pressure then gets pushed once again through a small opening. Odd that there is no track for the coolant to flow.

Try it and see since you have it already but it does not seem to be a sound way to build a coolant heat sink.
 
#35 ·
Todd in response to your post about galvanic reactions in this case why not use mineral oil. We have been using it to cool our computers for quite some time and don't get any kind of bio growth in our system and once it reaches temp it tends to stabilize temperature after it runs for a while. As well it is not poisonous to the environment. And also it tends to lower operating temps better than any other type of coolant we have tried. Also a few years back I was running mineral oil in my VF1000 F Honda while club racing here in Indiana plus I did not have to remove it in the winter. I just had to wait for a little while for it to warm up before I turned on the pump.And if my memory doesn't fail me it is inert with almost all materials like aluminum, copper, brass and with steel it tends to be a rust inhibiter. As well it has no problem with teflon, rubber or silicone tubing as far as I know. Just a little bit of homegrown technology from an old hot rodder.
 
#37 ·
Todd in response to your post about galvanic reactions...
Me?! I'm just a jerk being sarcastic when I see comments about galvanic reaction/corrosion. I have never even considered the issue of biological growth in a cooling system, until it was posted here. I would just add something to it, like a couple shots of moonshine (being sarcastic again). :D


...And not to put too fine of a point on my theory, but the water jacket in every liquid cooled engine ever made is just a water tank and they cool just fine. Yes they have air pockets and dead spots, but they work and deal with many, many magnitudes of heat more than a controller can produce.

Miz
I don't think I can agree with you there Miz. The water jackets inside, at least modern, engines are more passages than tanks, IMO. The ratio of inlet/outlet volume to internal capacity is what I would look at, if I were concerned about this. If it would take the outlet too long to clear the room, and the inlet is constantly funneling in more, at the same rate, there's more of a chance for some fully heated coolant to wear out its welcome.

That being said, your bathtub plate is obviously doing the job, so I would file this whole concern in the same folder with galvanic so and so: got it, considered it, deemed it not critically relevant - more important things to focus on.
 
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