Soarer Central: Archive through December 04, 2006

Soarer Central Mechanical - Common Thermals Archive through December 04, 2006

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Mark Paddick
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ACT
UZZ31 V8 Soarer , JZZ30 TT Soarer

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Monday, December 04, 2006 - 09:42 am, by: Mark Paddick (Sparks)

Anybody else wanna argue the point?

But please don't quote advertising bullshit at me.
I'm sick of pointing out that advertising and sales people generally have no technical expertise whatever in the field and are only sprouting whatever crap they can think of that sounds good in order to sell their product which is what they are paid to do cos they can't find a real job 'cos they haven't got any real qualifications anyway and nobody likes them and they're useless.

No offence intended to any of the decent sales reps out there. I know there are some.
Any offence taken by advertising executives was fully intended and there's a lot more where that came from!

Graham Dollisson
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Monday, December 04, 2006 - 09:50 am, by: Graham Dollisson (Alloyvee)

Love your work Mark and I couldn't agree more!!

Peter Nitschke
JunkFilterer
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Monday, December 04, 2006 - 10:02 am, by: Peter Nitschke (Pen)

There is also a big difference between the amount of air a fan can move in ideal free air conditions and how much it can move when it is under load, eg having to pull/push it through a radiator core.

The clutch and hydraulic fans both have bigger blades and a lot more power at their disposal to ensure they can actually do the job when it counts.

Have a listen to most 240volt kitchen/bathroom exhaust fans these days, you can hear the speed varying all the time as the outside wind varies the pressure in the roof. The load is dictating how well the fan can work.

Peter Nitschke
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Monday, December 04, 2006 - 10:12 am, by: Peter Nitschke (Pen)

As to load, I used to have a hand crank generator out of those really old phones where they had to wind the handle to get the operators attention.

Unconnected, it was really easy to turn, but put a load on it, eg short the terminals, and it became very hard to turn as it was trying to generate power, and you need to do work to achieve that.

Same thing with the alternator having to make the power for the fans.

Keep in mind too, that it takes around 20 minutes of driving for the alternator to replace the power used to crank start the engine. So when you need the fans the most, idling in city traffic, that is exactly when the alternator isn't making much power due to the low engine speed, so then it has to use more of your engine power to recharge the battery if/when you do get moving.

However, with all that has been said above, electric fans can work, but it's very hard to argue that it's a better solution for a Soarer.

Mark Paddick
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Monday, December 04, 2006 - 10:51 am, by: Mark Paddick (Sparks)

I didn't even want to start on load effects for electric motors and how the current can triple and the heat multiply nine times in a motor supposedly not being overstressed. Heats up the airflow it's trying to cool too.

The electric factory fan setup in the Camry works very well and uses bugger all power from the engine but as I said it's radiator is bigger than a Soarer one for an engine making less than half the power and heat. It's one of the most efficient cooling systems ever but won't work for getting rid of more heat when the system is confined to the same space.

Now if it were a Ferrari of an earlier vintage the cooling system theory for them is rather nice and goes like this;
Stick a dirty great V12 engine up front.
Now work out what the radiator size needs to be to cool it unassisted by fans or pumps.
Build a bigger better radiator than that and stick it in front of the V12. Stretch the nose of the car to make it fit if you have to and tell PininFarina to shove it if he objects to you altering his design; it looks better anyway and cooling is the priority.

Confirm that it will all work by convection only, idling in traffic on a hot day. And then add a water pump.

Decide that the car's going to have A/C and rip it all out again and build a bigger one.

Get it all working and then stick a couple of electric fans in front of the whole show just in case.

Now do the whole lot again with engine and gearbox oil coolers and confirm that neither will overheat dangerously if the water cooling system is totally disabled and driven in the worst possible conditions with the A/C flat-out all the time.
Stick a thermostat controlled bypass in line so you don't blow the oil coolers and filters off on a cold morning.

Go back and check and modify the water cooling system 'cos you've stuck oil coolers all over the place now and altered the airlow.

Funny but they don't ever seem to overheat.

These old engines may have a problem or two but it's never cooling related.

Mark Paddick
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Monday, December 04, 2006 - 12:01 pm, by: Mark Paddick (Sparks)

You can just see where the top of the radiator is in this pic.
It is as wide as the car nearly and as tall as possible.
It is also about 18 inches thick which you can't see.
This is a very good design using electric fans for an engine with an optimistic 370 HP. Close to a good TT with a few mods (TT'll never have the torque down low but)
There's no way it'd fit in a Soarer. That Ferrari is 9 feet wide.
Also note the louvered bonnet to create good airflow through the radiator.

Nathan Siy
Tinkerer
BC
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Monday, December 04, 2006 - 01:26 pm, by: Nathan Siy (Natesiy)

Lets take things point by point here:

So your saying adding 2 e-fans will overload and kill your factory alternator...no, it won't.

I've drawn close to 600 amps of my factory alternator so far. I've rebuilt countless alternators, rewound them, and yes at full load you will draw 2-4 crank HP from it....When it's at full load. Your factory battery can hold a few hundre cranking amps and can supply your entire vehicle electrical system for an hour or so. The draw of 20...30...even 40 amps while the vehicle is running is only going to lower your alternators charge time but WILL NOT "kill" your alternator.

"E-fan" radiators are different, because electric fans are so different from clutch fans or hydraulic fans....Fans are fans. Your taking 1 example, a Toyota Corolla as your main basis point. Now why don't you take every high performance car and tally up how many are using clutch/hydraulic crank powered fans...They're using thicker radiators with e-fans...hmmmm. blows your "thinner radiators is required for e-fans" theory.

Why would Toyota use a thinner radiator with e-fans. Hmmm. because the e-fans take up room. The e-fans add a few inches to the thickness of the radiator core. They're mounted directly to the core to maximize air flow.

Your magical shroud increases efficiency of the clutch fan over 20%...? Like your basic science class, increasing distance from the 1 point source to another (rad core to fan) decreases the efficiency by.....anyone remember.....a factor of 4. Measuring a light source from 1M away is 4 x as bright as measuring that same light source from 2 M away.

Your clutch fan 7" away from the radiator with a shroud VS 2 electric fans 0.05" away from the radiator core. I haven't measure anything and i don't intend to, but do the math yourself.

Let me know if there any any other points I missed that is of relevence to the topic and i'll be happy to find a viable explanation on why electric fans ARE better in every way to a crank driven, hydraulic or clutch controlled fan.

Just ask anyone is motorsports.

Dan McColl
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Monday, December 04, 2006 - 02:45 pm, by: Dan McColl (Hoon)

Simple. A clutch fan with a shroud, doesn't matter how far away from the radiator it is, still effectively pulls airflow through 100% of the radiator core. You could put the fan 100 meters away, and with a 100 meter long shroud it would still be as effective as it is 7 inches away or 1 mm away.

The clutch fan also has 200 KW on tap if it needs it to pull extra air if necessary, but will run with basically zero load when not needed.

Thermal's, however, unless they also cover the whole core and are shrouded, can't even come close to covering the full core. Simple area of a circle maths (since you want to bring maths into this). Then you have the in-efficiencies of the electrical system, 50% loss in the alternator turning HP into electricity and then 50% in-efficiency in the electric fan motors turning the electricity into hp again there are some big losses there.

Then there's the problem that on a hot day, stuck in traffic, if your temp starts going up the thermal's can do diddly squat about it where'as the clutch fan can tighten up and tighten up till it's drawing the necessary airflow to maintain temp. (remember the clutch fan has the full engine power behind it wheras the thermals have two piddly in-efficient electric motors.)

Peter Nitschke
JunkFilterer
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Monday, December 04, 2006 - 03:03 pm, by: Peter Nitschke (Pen)

Nathan Siy wrote on Monday, December 04, 2006 - 01:26 pm:
Just ask anyone is motorsports.

They don't spend much time idling in traffic.

In fact most race cars will overheat if they aren't kept moving. Heck, they overheat just from tailgating.

Perhaps you just made our point for us?

Mark Paddick
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ACT
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Monday, December 04, 2006 - 03:17 pm, by: Mark Paddick (Sparks)

Most serious motor sport engines have no fan at all. Just have a look at any Formula one or Champ car. There's not a fan on or in the car anywhere.
They don't get any more serious than that.

The rest I will dissect later so if you're squeamish tune another channel.

Peter Nitschke
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Monday, December 04, 2006 - 03:25 pm, by: Peter Nitschke (Pen)

Anyone bring the popcorn?

Mark Paddick
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ACT
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Monday, December 04, 2006 - 03:53 pm, by: Mark Paddick (Sparks)

At least now we've decided that the load is on the alternator and not the battery; sort of almost. I'll straighten that one out a bit too.

I'd go and patent your install methods though real quick before someone else steals them.
Free power is damn hard to come by!
Like physically impossible even.

Nathan Evans
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Monday, December 04, 2006 - 04:00 pm, by: Nathan Evans (Soarer7)

So... how bout that weather hey? Plenty of it....

Nathan Evans
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Monday, December 04, 2006 - 04:01 pm, by: Nathan Evans (Soarer7)

Im starting to regret asking the question if it going to start bullshit

Mark Paddick
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Monday, December 04, 2006 - 04:21 pm, by: Mark Paddick (Sparks)

As I shall explain later, the fan shroud is one of THE most important parts of any radiator design with or without fans of any type,
The Formula One and Champ cars don't have fans but every radiator and oil cooler is fully shrouded and ducted as well.
Never mind 20% the magic of fan shrouds can make as much as 80% or more difference to the efficiency of ANY cooling system. Whether it be in a car or not. Passive or forced convection systems. Heat pumps. All honour the magic of the shroud.

I would get a fan shroud for your TT Nathan if it were mine.
In fact come to think of it the white one outside IS mine and I've been looking to replace the shroud for a while but haven't got to it because it is still working and I don't drive that car much. It is fixable but I want a better or even new one.

It will be cheaper or at least around the same price as Electric fans and WILL work heaps better unless you go to the trouble of fabricating a custom shroud for them among a lot of other things.
You have a system that was very carefully designed by the factory to work in that car with that engine and a huge safety margin which is why you haven't killed it running without the shroud.
It would take a lot of effort to replace that with a system that worked as well let alone any better.

Oh, and I'll choose to believe that the other statement doesn't apply to me.
You won't see any bullshit from me as far as this subject matter is concerned.

Ben Socratous
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Monday, December 04, 2006 - 05:22 pm, by: Ben Socratous (Socrates)

Mark with all the crap that has flown on this thread, just want to be sure that you got that I wasn't having a dig at you or anything, someone asked a question and I just replied with what I have done.

Only reason I went the thermo route is that when my clutchy died, wreckers in Adelaide wanted nearly $600 for a 2nd hand one!

If it is any consolation to the questions being asked here, I am actually currently sourcing the requiered parts to put the original equipment back on my car. I've got the clutch, now I just need to find a fan. Think I'll be better off making my own shroud (more carbon, WOOT!) than trying to find one in decent knick.

Nathan Siy
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Monday, December 04, 2006 - 06:41 pm, by: Nathan Siy (Natesiy)

We'll just leave it at different strokes for different folks.

I'll post up some before and after engine temps after the e-fans are in for everyones reference.

Just had e-fans on my previous 2 drift cars and 3 domestics and all have seen substatial gains in whp. Some had OEM shrouds, some did not. All gained on the dyno, none lost an alternator or battery.

Mark Paddick
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Monday, December 04, 2006 - 06:46 pm, by: Mark Paddick (Sparks)

No probs Ben.

I would probably have done the same given the costs.
I would make sure that the plastic in front of the radiator is in place.
The fans mounted on the radiator won't benefit from a shroud there but the stuff in front of the radiator is needed at highway speeds or the fans will have to run for much longer periods.
This is often removed when a large intercooler is fitted (as on my car).
I put a colder thermostat in and temporarily fixed the shroud and around town it's fine but it does creep up a bit on the highway.
I can't fit the original on my car but I have made up a few test pieces and the improvement is dramatic.
At a constant 100kph it runs a about 20deg C cooler at the radiator outlet hose with the new ducting temporarily fitted.
I confirmed this on four separate runs, either adding the new duct or removing it.
As soon as the car got up to speed the radiator temp dropped almost instantly after the duct was fitted when the car was already hot.
Adding something similar if your original is no longer there will help the fans enormously.

As you may have inferred it turns out that a shroud has no effect if the fans are in close proximity to the radiator.
This is because the effect of a shroud is to move the radiator surface, in total as it's all shrouded, out to the end of the shroud. This effectively makes the distance of the hydraulic or clutch factory fans from the radiator zero as would be shown in the relevant mathematical equations covering this sort of stuff.

So in the following statement just substitute zero for the clutch fan distance and alter the conclusion to reflect the outcome and the statement is absolutely correct;

" Your magical shroud increases efficiency of the clutch fan over 20%...? Like your basic science class, increasing distance from the 1 point source to another (rad core to fan) decreases the efficiency by.....anyone remember.....a factor of 4. Measuring a light source from 1M away is 4 x as bright as measuring that same light source from 2 M away. "

So if you follow the math which I don't feel like explaining as it would take at least an associate Diploma of Engineering course to do so you will have to beleive me...or not. I don't care.
But it says basically that a fan with a shroud is infinitely better than one that is not in complete and total contact with the radiator which I assume you will agree is impossible. There will always be a gap.

And don't start me on quantum physical effects of light which has absolutely no relevance to this subject at all. Don't know how that got in there at all.

Nathan Evans
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Monday, December 04, 2006 - 07:08 pm, by: Nathan Evans (Soarer7)

Cheers for all your advice mark, do you think if you had an aluminium radiator or something liek that, that thermals would be just as good, also just wondering, but dont thermals come with shrouds and it just bolts up to the radiator or something?

P.S. Not meaning to offend anyone by my previous message, (Hard to type the tone in my voice) hahaha

David Vaughan
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Monday, December 04, 2006 - 07:47 pm, by: David Vaughan (Davidv)

Nathan, this is not a matter of "different strokes for different folks". If your fan drive is from an alternator which is driven by the engine then I am very interested in what particular variation of the first law of thermodynamics enables this setup to be more efficient than hydraulic or clutch-based drive from the engine. Can you identify the greater inefficiencies in the latter setups which might allow an electric fan to be more efficient?

Thirty years ago I was delighted to buy a car with an electric fan because the alternative at the time was a fan whose drive was a simple proportion of engine speed; i.e.inversely proportional to need. Technology of non-electric fans has advanced more than somewhat and the old advertising slogans are a sham; if you think about it.

Rehan Bandara
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Monday, December 04, 2006 - 08:17 pm, by: Rehan Bandara (Parsec)

oh dear.... "Like your basic science class, increasing distance from the 1 point source to another (rad core to fan) decreases the efficiency by.....anyone remember.....a factor of 4. Measuring a light source from 1M away is 4 x as bright as measuring that same light source from 2 M away."

this makes no sense whatsoever. I don't know where you got this from, but it is completely wrong and does not apply to flow phenomena at all.

I can explain the purpose of the shroud. Its purpose is twofold, and very important. The first reason is so that the fan sucks air through the entire radiator core. Forcing the fan to suck air through the entire width of the radiator core actually increases the flow rate through the fan, as the pressure drop across the core is lower for a given aggregate flow rate through the fan (think parallel resistances).

Now, the distance between the fan and radiator does make a difference, but it's very little. The fan is an air pump, and it moves air by virtue of the pressure difference it creates across itself. There is a small pressure drop across the walls of the shroud, and so there is a very slight loss in efficiency due to frictional losses, but it is more than made up for by the second reason for the shroud existing:

The shroud makes the fan more efficient by harnessing the tangential outward velocity imparted on the air and directing it backward towards the engine. Normally this centrifugally flung air is wasted in any propeller design, and a shroud can help to abate this (a lot of aircraft props use contra rotating fans to help here as shrouds can be impractical for some prop designs).

By directing the tangential air backward, the fan creates a larger pressure difference across the radiator, and thus increases the flow rate through the radiator.

now, on the other side of the coin, there's no way alternators and motors are 50% efficient. They are more like 90%+ efficient at converting shaft power to electricity, or vice versa.

All things considered, i don't think you can blanketly say one is better than the other either way. You would need to test both systems extensively to come to a quantitative conclusion. Flow rates without the radiator present are meaningless as the pressure that the fan can produce across the radiator is nonlinear and heavily dependant on the flow rate (like any pump).

Even once presented with flow rates, unless the same amount of radiator area is covered uniformly, then you will need to delve into thermofluid system theory to come to any meaningful conclusions about the convective heat transfer attained by each of the systems. Keep in mind a bigger temperature difference makes a heat exchanger more efficient, so more is gained by flowing the air through the hotter parts of the radiator than the cooler parts (nearer the outlet of the radiator).

The amount of convective heat transfer attained is a nonlinear function of the square of the air velocity (usually some empirical function of reynold's number and a few other dimensionless parameters). It's possible for instance, to make the cooling system more efficient by blocking off the radiator's airflow near the cooler outlet section and increasing the flow rate through the hot parts of the radiator substantially.

It's a complicated system.

Ben Socratous
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Monday, December 04, 2006 - 08:26 pm, by: Ben Socratous (Socrates)

Mark Paddick wrote on Monday, December 04, 2006 - 06:46 pm:
I would make sure that the plastic in front of the radiator is in place.
The fans mounted on the radiator won't benefit from a shroud there but the stuff in front of the radiator is needed at highway speeds or the fans will have to run for much longer periods.
This is often removed when a large intercooler is fitted (as on my car).

Yep, same here! My core is that bloody huge there is no way that I'll ever be able to utilise that plastic bit again (plus I think I threw it out). I want to get a smaller core (say 600x300x75) as mine scrapes all the time (mid entry tank aren't helpin either). Though I have never had the issue of the temp rising because of the plastic front shroud missing. I'd be very interested in your little developments on this though, maybe I can f/glass some form of kit?

Mark Paddick wrote on Monday, December 04, 2006 - 06:46 pm:
And don't start me on quantum physical effects of light which has absolutely no relevance to this subject at all

You're right, it doeesn't. And I don't want to hear anyone bringing that up anymore, I'll ramble on about physics 'till the cows come home, but that stuff is pure EVIL

WAYYYYY to many numbers for my likings