Radiators.... trying to gather information

[naughtika]

Hi everyone, just curious to know more about radiator upgrades..

I know that we often use a thicker radiator like 42mm or 50mm.. I've been on that boat and want something different..

I wanna buy a half width rather but instead of a single pass, i want it to be either twin pass or triple pass.

Simon (Jungle) gave me this idea and it does makes sense to me.. image below is shown after googling it

single pass vs twin pass

and triple pass

I know there'll be alot less volume compared to the factory setup, but I think with this, we can use a half width 40mm or 50mm thick radiator and match it with a high CFM pull type fan

so what do you guys think? yes I know Im nuts

 

[battery]

Don't know your history but im assuming your having issues with the stock stuff?

How hot does it get?

 

[Interloper]

Double pass radiators require 16x more pressure to flow the same volume of coolant through them, as compared to a single pass radiator. Triple pass radiators require 64x more pressure to maintain the same volume. Automotive water pumps are a centrifugal design, not positive displacement, so with a double pass radiator, the pressure is doubled and flow is reduced by approximately 33%. Modern radiator designs, using wide/thin cross sections tubes, seldom benefit from multiple pass configurations. The decrease in flow caused by multiple passes offsets any benefits of a high-flow water pump.

http://www.stewartcomponents.com/tech_tips/Tech_Tips_5.htm

 

[uzz320]

The two pass and three pass pictures above are the same thing, but rotated 90 degrees - they are both 3 pass.

Multi-pass helps by increasing coolant velocity, which helps with turbulence and therefore heat transfer. This is at the expense of average temperature differential between coolant and airflow - energy transferred is proportional to the temperature differential. Multi pass radiators tend to have a larger temperature difference between inlet and outlet, for obvious reasons, but can't flow as much coolant. I would think that with how most cars cooling systems are set up the coolant flow rate is not all that high anyway, meaning that the multi pass may not restrict flow a great deal and would just increase the velocity of the coolant in the radiator - hence the benefits. The decreased temperature differential between air and coolant would be less of an impact than the benefits from the extra coolant turbulence.

As for the half width idea, I forget the formula - but I reckon to have it half the frontal surface area you would need it to be more than three times as thick to do the same job (without taking multi pass benefits into account) or about double as thick with 50% higher fin density. I don't think that a radiator could be made to be more efficient than OEM, and the size that you want for less than $1000 (would probably have to be custom).

 

[uzz320]

Double pass radiators require 16x more pressure to flow the same volume of coolant through them, as compared to a single pass radiator. Triple pass radiators require 64x more pressure to maintain the same volume. Automotive water pumps are a centrifugal design, not positive displacement, so with a double pass radiator, the pressure is doubled and flow is reduced by approximately 33%. Modern radiator designs, using wide/thin cross sections tubes, seldom benefit from multiple pass configurations. The decrease in flow caused by multiple passes offsets any benefits of a high-flow water pump.

http://www.stewartcomponents.com/tech_tips/Tech_Tips_5.htm

It would depend on the particular radiators in question, but I would tend to agree that it is not worth the hassle if it isn't available off the shelf. I would be interested to see what requiring 16 and 64x the pressure actually did to the flow rate of the system - I wouldn't imagine that it would be 16 and 64x worse as pressure v flow rate is an exponential relationship, it could be that introducing the restriction decreases flow rate by 10% but to increase it back up to the original takes 1600% (16x) the pressure...

 

[VOLK]

I see big power Evos running half width rads due to needing space for massive huffers. If it works for them surely it can work for us.

 

[jungle]

I completely disagree with the 16x etc more pressure story for a dual pass. In the Legnum, The hot water arrives at the radiators top tank then, flows vertically down to the bottom. There is zero extra work required to make it do this this if you make the tanks on sides rather than top like oem. You can make the physical size of the radiator smaller because a dual pass is more efficient. The air charge gets 2 "goes" at cooling the water with a dual pass and the water must flow through the entire path.
With oem radiators, often the inlet and outlet are in line with each other-in other words the water will take the easiest path and in my above example following the precisely. There is no physical barrier making the water on the edges of the radiator actually move, so it won't and often stagnates, resulting in less than optimum cooling.


The dual pass is more efficient and despite the above links won't require any extra pump pressure flow whatever for it to work when using tanks on the side of the radiator, rather than oem top and bottom setup.


How do I know, because my track car that always got hot with the oem tank was swapped out for the dual pass I've just described and the water never got hot again.


How good was it, try solid 90C on track cooling a 500hp engine with a core size no bigger than a 300x600 intercooler.
How quickly did temps recover, by turn 2 at Queensland Raceway after rolling offmthe throttle, the temp was back to 78 degrees.


Who made it, Richard from A.R.E www.are.com.au

 

[uzz320]

I think the 16x figure is correct, but the important thing is that flow might actually only be reduced by a few % - it might just need 16x the original pressure to reach the original flow as I said above - exponential.

There is much more to it than size, design is far more important - which is why Simon's radiator performs so well for its size, but stock ones do not. I would love to see a pic Simon, I am interested in the thickness and fin density + number of tubes

 

[naughtika]

thanks for the constructive replies fellas.. keep it coming.. im no expert with how this stuff is calculated..

I only look at it with the simplest ways.. longer path with same (if not better) air flow = better cooling..

 

[Rabit]

My 1938 Chev with a 350 chev V/8 had a Commodore 6 cylinder cross flow radiator mounted vertically. At speeds above about 60mph the temp rose quite a bit. We tried restricting the flow of coolant by partially blocking the flow and it made no difference. What did work was removing the tanks and fitting plates to convert to a triple flow set up. The problem was, the water wasn't spending enough time in the radiator to effectively cool. This was all with a radiator that had brass tanks and a copper core. They are more efficient than alloy radiators and also easier to modify but are more expensive. You are correct Christian, the longer the coolant is exposed in the radiator the better as long as the flow remains the same.

 

[TME_Steve]

I have dealt with coils a lot in life, not just in cars, in fact predominantly not in cars but anyway, half the size for flow as in a dual pass, is 4x the pressure drop, but if the radiator us the same size and the water flows 2x further then it will 4x the pressure drop for 2x the distance therefore the pressure drop will be 8x normal, make it twice as thick or just get the tube volume up and your pursue drop will go back down, but then you lose the gains if increased turbulence.... 16x the power required though to move the same flowrate through the dual pass.... That all said the pressure drop over a radiator is bugger all compared with the pressure drop through the pipework and the engine and as Martin eluded a car water pump has what I would call a steep curve so increase the pressure and you won't see much dip in water flow, the flow rate is arbitrary anyway as it varies so much with engine speed

In summary you will gain cooling with a correctly setup dual pass radiator, maybe not as good as std at half the size but better, my question is why are you so bothered, or is it to make room for a bigger snail on the front?

There are other factors too like fin type and density (have a look how many fins there are on the back of an AC condenser for example.... And then there are multi row coils to give multiple passes too....

 

[jungle]

I gathered is was just an interest question Steve, I'm wouldn't think Kristian has any cooling issues, especially if its going to run on E85 too!

Only pic i could find Martin!

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[naughtika]

only cooling issues i have is how I've positioned my oil cooler and the radiator fans.. once those 2 have been re-arranged.. everything should be sweet..

the above question was just merely for information only and what if an individual would like this option, simply for more space at the front as Steve mentioned..

 

[jungle]

Ah so you heeded my warning from ages ago about the oil cooler

 

[naughtika]

no I didn't

but yes, in all seriousness.. I was thinking about it..

so my current setup is this.. say you're standing above it and looking down.. you'll see the following..

Intercooler
PS cooler (LH) and a Push type 10" fan (RH)
a/c evaporator
radiator
14" pull type fan



here's a thought.. what if I was to try and use a twin pass single layer radiator (which will be around 32mm thick I think).. inlet and outlet on the passenger side flowing horizontally and matched with an electric water pump to keep the flow up.. then for the fan, use pull type 16" with proper shrouds that covers the entire radiator fins to direct seal air flow.. of course there'll also be that 10" push type fan to assist which will be mounted on the right hand side/part of the a/c evaporator.