Cooling Fan Tech

[Isdtbower]

I used to think they were simple

They are if you might have a 57 Chevy and talk about how much HP, RPMs, Water pumps, and etc. They know the installation size, but they can mess with depth, tube size, # of tubes, # of fins/inch, thickness, one or two pass, Alum or ?', Tanks, add trans cooling, add engine oil cooling, add transfer case cooling, Brazing, etc.etc. Some radiators at KOH have been known to reach the $5-10k mark. (And some only survive a day of pre-running.) You need to understand how to install it without it vibrating or ripping apart because you know cages don't/shouldn't flex. And, of course, fans and relief flappers that open when speeds are faster than a fan can suck....

 

[HYDRODYNAMIC]

Flappers are a bandaid for shallow shrouds were the air doesn’t have room to get to the blade. Usually in the corners. If your fan ever becomes a restriction throw it away. The fan should always be pulling air even at high vehicle forced air speeds.

 

[Rockwood]

Flappers are a bandaid for shallow shrouds were the air doesn’t have room to get to the blade. Usually in the corners. If your fan ever becomes a restriction throw it away. The fan should always be pulling air even at high vehicle forced air speeds.

I assume there's a speed where the fan isn't physically turning fast enough to "outrun" incoming air, no?

 

[HYDRODYNAMIC]

I assume there's a speed where the fan isn't physically turning fast enough to "outrun" incoming air, no?

Yes, 30mph the fan should start unloading and 50mph the fan should free wheel. Before comparing radiator wind speed velocity to vehicle speed think about radiator location, core thickness, angle, grill or any other restriction. OHV’s do not have giant front mounted radiators running at high sustained speeds or ducted air intakes, well some have added roof ducts to bring air down and into the radiator, which helps show that even fast cars need more forced air flow.
If the fan becomes a restriction it will also be flowing at its max output. You should not have to drive fast to have adequate cooling at least in go fast rock crawler realm.

 

[CarterKraft]

Check my maths...

This skid steer has a 23"x13" engine cooler core 4.25" thick the other half of the radiator is hydraulic oil cooler of similar size at 23"x9"x4.25"
The engine is 73 horse power.
It has a 18" ish fan spinning a max of 2900 RPM. I don't have any specs of the fan blade but I have a picture.
The fan motor is 14.53 cc per rev with a max pressure of 2600 psi
The pump to drive it is for the sake of easy maths 10 GPM (21cc per rev)
Using online calculators for hydraulic horsepower I am getting 15 horse power, converted to watts is 10,000+ watts....
Are we really that under powered in electric fan cooling with 850w fans?

 

[CarterKraft]

To further my questioning...
This cooling system is from a 273 horse power excavator.
This radiator arrangement has stacked 4750 RPM brushless fans around 32 amps draw each X2 for 3 fans.
The machine has a total of 11 of these 14" brushless 24v SPAL fans for a total of 9350 watts.
I am guessing the electric watts are more efficent in this application?

These 3 stacked fans, whats the deal with that? Higher pressure capability or higher flow? I feel like its just higher pressure.

 

[HYDRODYNAMIC]

Check my maths...

This skid steer has a 23"x13" engine cooler core 4.25" thick the other half of the radiator is hydraulic oil cooler of similar size at 23"x9"x4.25"
The engine is 73 horse power.
It has a 18" ish fan spinning a max of 2900 RPM. I don't have any specs of the fan blade but I have a picture.
The fan motor is 14.53 cc per rev with a max pressure of 2600 psi
The pump to drive it is for the sake of easy maths 10 GPM (21cc per rev)
Using online calculators for hydraulic horsepower I am getting 15 horse power, converted to watts is 10,000+ watts....
Are we really that under powered in electric fan cooling with 850w fans?

Be careful of calculating max psi and flow with actual. It looks like the motor has a PWM flow control for variable output.
The fan might only pull half the psi or be supplied half the oil so 10,000 watts turns into 5,000. That blade looks like it can pull a lot of pressure through a thick core which is wasteful as far as efficiency goes, so maybe it takes twice the power due to the thick core. Doesn’t mean it’s designed wrong, just uses alot of power to cool.
My core is around 30”x16”x2.25” and has 1,200 watts available which is probably more watts than reasonable for the core. Surface area between the CAT and mine are close enough but the CAT core is twice the thickness and fan power ramps way up as the restriction goes up and CFM goes down needing even bigger fans and more power.

 

[CarterKraft]

Be careful of calculating max psi and flow with actual. It looks like the motor has a PWM flow control for variable output.
The fan might only pull half the psi or be supplied half the oil so 10,000 watts turns into 5,000. That blade looks like it can pull a lot of pressure through a thick core which is wasteful as far as efficiency goes, so maybe it takes twice the power due to the thick core. Doesn’t mean it’s designed wrong, just uses alot of power to cool.
My core is around 30”x16”x2.25” and has 1,200 watts available which is probably more watts than reasonable for the core. Surface area between the CAT and mine are close enough but the CAT core is twice the thickness and fan power ramps way up as the restriction goes up and CFM goes down needing even bigger fans and more power.

You are right its demand fan but with it disconnected it's full flow.
BUT I have not fully tested pressure at each part of the circuit, just know it develops 2600 psi during the fan calibration of 2900 RPM.
There isn't any load on this circuit other than the fan, the charge pressure is under 500 psi as well as the pilot pressure so the increase in pressure is to drive the fan. I'll do some more testing when I get a chance.

I noticed the fan details after looking at all these electric fans and there is not much in the way of sound suppression features it seems, at WFO it is loud as hell.

 

[Bebop]

This cooling system is from a 273 horse power excavator.
This radiator arrangement has stacked 4750 RPM brushless fans around 32 amps draw each X2 for 3 fans.
The machine has a total of 11 of these 14" brushless 24v SPAL fans for a total of 9350 watts.

As an FYI, the 1400hp Hoonitruck has 2 of these 14" brushless fans.

 

[CarterKraft]

As an FYI, the 1400hp Hoonitruck has 2 of these 14" brushless fans.

Do you know any details on that radiator?
I'm sure it's 30-40% bigger than the OE unit.

 

[Bebop]

Do you know any details on that radiator?
I'm sure it's 30-40% bigger than the OE unit.

31" x 16" overall.

I'm just saying heavy equipments have cooling needs you can't compare to a vehicle.

 

[CarterKraft]

31" x 16" overall.

I'm just saying heavy equipments have cooling needs you can't compare to a vehicle.

The hydraulic one is out of line for sure but the electric might not be too far out of line.
The stacked fans is really interesting, I've read that that is really hard to practically use because there is so much turbulence off the first fan the second fan has to be reversed rotation, although I have no idea if they are or not.

 

[Isdtbower]

Well. This has widened the conversation. Neat.

IN the early days of KOH, Brad Falin (Fallon, NV) built a IFS/IRS buggy with hummer portals and a hydraulic fan. It was bigger and hauled azz. That fan would blow your hat off. It was on the back of the car flatish with a front motor. It could have had a BBC. He had his thoughts together. Definitely not a follower. Too bad he stopped race'in.

 

[HYDRODYNAMIC]

Did some testing on my fans and core. Got an average of 25MPH across the front of the core. Velocity behind the fans is not laminar. Its directed out in a cone shape with high and low spots. That was with both of the 600W fans at 100%.
Next I want to force air on the front of the core and measure velocity after the core.

 

[CarterKraft]

Did some testing on my fans and core. Got an average of 25MPH across the front of the core. Velocity behind the fans is not laminar. Its directed out in a cone shape with high and low spots. That was with both of the 600W fans at 100%.
Next I want to force air on the front of the core and measure velocity after the core.

I could get some mph readings of one of those skid steer radiators I showed pretty easily.
I didn't say it in that post but that fan is a pusher not puller.

 

[Satan's_Minion]

Lots of factors that account for the amount of fan performance you need. Skid steer is a tough application as the core face area is smaller than you would like for the power level, so you need to use more fan power to make up for that. Fan power is linear with restriction, but the air side resistance of the core will be exponential.

When you move from direct drive or other fan types to electric you will need to better utilize the fan power as it is now a limited quantity. The packaging flexibility gained can give you more space than traditional geometry. The end result is a more efficient cooling package as you are not wasting fan power on the pressure.

You also gain efficiency with decoupled control from the engine speed and loads. In a traditional system if you didn't have variable control your fans are usual over driven at peak HP as they have to be sized for lower rpm peak torque. When you change the package to running coolers in parallel vs series you can again increase the efficiency by individually controlling the zones. When your fans in a zone only run against the restriction of the specific zone vs working to push through the entire stack you save power.



Machinery has to be able to cool at 100% power continuously in all conditions. Has zero ram air. And maximum allowable engine/fluid temps are lower. Probably some of the driving factors to why you see so much more fan power vs race vehicles.

 

[Thatg9659]

 

[HYDRODYNAMIC]

The noise from that thing will get rocks and beer cans thrown at you for sure. Smaller the blade, higher the speed, higher the frequency, more annoying.

 

[CarterKraft]

I have been operating on a newly learned principle for fan blade direction/pitch.
In the case of the skid steer I posted above the "Cup" of the blade was supposed to be in the direction of the air flow or CUP IS UP.

After learning about that rule of thumb I wondered if my somewhat poor cooling fan on my pro-street car had a backwards fan blade.
I did some fuckery with a couple old fans to get it switched to puller from pusher and it's possible the blade is not on correctly for the direction of rotation.

Any thoughts? This is the rear (engine side) of a front mounted radiator in my '82 Elco.
It appears to me to be backwards based on "CUP" but the curved blades are a wildcard.
At the moment I am not sure which direction the fan turns.

 

[HYDRODYNAMIC]

I have been operating on a newly learned principle for fan blade direction/pitch.
In the case of the skid steer I posted above the "Cup" of the blade was supposed to be in the direction of the air flow or CUP IS UP.

After learning about that rule of thumb I wondered if my somewhat poor cooling fan on my pro-street car had a backwards fan blade.
I did some fuckery with a couple old fans to get it switched to puller from pusher and it's possible the blade is not on correctly for the direction of rotation.

Any thoughts? This is the rear (engine side) of a front mounted radiator in my '82 Elco.
It appears to me to be backwards based on "CUP" but the curved blades are a wildcard.
At the moment I am not sure which direction the fan turns.

That looks correct from what I can see. The A of the blade leads like a bird wing and the scoop/cup is on the high pressure side.
I have 3 Spal brushless fans and one is leads A and two lead V. Both have the scoop/cup on the high pressure side.
There is alot of mechanical design that can be copied from nature.

 

[arse_sidewards]

The noise from that thing will get rocks and beer cans thrown at you for sure. Smaller the blade, higher the speed, higher the frequency, more annoying.

Won't be any worse than room full of server racks. Nobody will hear it over the V8s and open headers anyway.

 

[CarterKraft]

That looks correct from what I can see. The A of the blade leads like a bird wing and the scoop/cup is on the high pressure side.
I have 3 Spal brushless fans and one is leads A and two lead V. Both have the scoop/cup on the high pressure side.
There is alot of mechanical design that can be copied from nature.

Holy cow never put the bird wing together with the propeller blade...

But from my point of view it looks like the high pressure side is on the vacuum side of the fan? I know it's hard to see.

Am I still confused?

 

[CarterKraft]

Here's a shot of the whole package, it's all admittedly shitty components...

 

[Rockwood]

Did some testing on my fans and core. Got an average of 25MPH across the front of the core. Velocity behind the fans is not laminar. Its directed out in a cone shape with high and low spots. That was with both of the 600W fans at 100%.
Next I want to force air on the front of the core and measure velocity after the core.

Speed UTVs have been having issues keeping cool with the windshield on. I saw this:

As their beauty cover/shroud (it wraps around the front), and it appears they're recycling air from the fans (you can see the top of the radiator in the second pic, but I can't see anything sealing it from air behind the shroud).

Anyway, it's a case-study in what not to do on the back side of the fan IMO.

 

[CarterKraft]

Speed UTVs have been having issues keeping cool with the windshield on. I saw this:

As their beauty cover/shroud (it wraps around the front), and it appears they're recycling air from the fans (you can see the top of the radiator in the second pic, but I can't see anything sealing it from air behind the shroud).

Anyway, it's a case-study in what not to do on the back side of the fan IMO.

Yeah the air coming off fans is not in a cylinder directly behind the fan

 

[HYDRODYNAMIC]

Speed UTVs have been having issues keeping cool with the windshield on. I saw this:

As their beauty cover/shroud (it wraps around the front), and it appears they're recycling air from the fans (you can see the top of the radiator in the second pic, but I can't see anything sealing it from air behind the shroud).

Anyway, it's a case-study in what not to do on the back side of the fan IMO.

It sure looks like a heat trap, the fan exhaust is most likely catching the edge of the shroud and recycling internally.
Looking cool and being cool are not the same thing. Those fans look like cheap import knockoffs.
3 of the 10” brushless Spals would probably fit and be a ton of air flow
The vortex from the windshield might be pushing hot air back into the cab and recycling the hot air plus heating up the occupants.
Wonder how loud those fans right behind your head would be? I’ve always been worried about leaks that close without solid shields.

 

[HYDRODYNAMIC]

Holy cow never put the bird wing together with the propeller blade...

But from my point of view it looks like the high pressure side is on the vacuum side of the fan? I know it's hard to see.

Am I still confused?

That blade might not have a curve in relation to pressure side so you can run it as a pusher or puller.

 

[CarterKraft]

That blade might not have a curve in relation to pressure side so you can run it as a pusher or puller.

I'll do more measured testing next time I get it off the lift.

 

[Rockwood]

It sure looks like a heat trap, the fan exhaust is most likely catching the edge of the shroud and recycling internally.
Looking cool and being cool are not the same thing. Those fans look like cheap import knockoffs.
3 of the 10” brushless Spals would probably fit and be a ton of air flow
The vortex from the windshield might be pushing hot air back into the cab and recycling the hot air plus heating up the occupants.
Wonder how loud those fans right behind your head would be? I’ve always been worried about leaks that close without solid shields.

The entire thing is built in China (or Vietnam) with the finest of Chinese-sourced products.

The windshield certainly isn't helping, but people have been running windshields in desert vehicles and SxSs for years now without issue. I think the myriad of design problems are stacking heavily against that motor staying cool. Sucks to have a desert vehicle that can't run a factory optioned windshield when it's above 80*.

 

[CarterKraft]

connector ideas?

BMW "Brose" fan with triangle connector
I am thinking a 120amp Anderson connector...
If I could find a pigtail or new housing I would just use that, I don't have the fan yet otherwise I'd have more info on the existing connector.