two radiators

[jejuu]

what are the pros n cons of using to radiators and how to install two radiators?how to connect them to the engine?tq~

[jejuu]

what are the pros n cons of using to radiators and how to install two radiators?how to connect them to the engine?tq~

[Peter7307]

Welcome to the place , jejuu.

The quick and dirty answer to your question;

CONS:
Extra weight and costs for the same volume of coolant (more brackets , intake and exit ducting , hoses , clamps etc)
More places for potential leaks
More places for air entrapment.


PROS:
Some possible design flexibilty (two smaller packages may be easier to site than one large one)
Possible lowering of CG
Easier and lower cost repairs if only one damaged

I am sure others will add to this.

Pete.

[jejuu]

but how to connect the inlet and outlet hose of the two radiators with the thermostat and the water pump?like can it be done by just connecting the two-outlet-hose for the two radiators?

[abinley]

Connect the radiators in series. The coolant comes out of the cylinder head, into rad1, out of rad1, into rad2, out of rad2, into water pump, out of water pump, back into engine.

[Maverik]

What's the benefit of going series? Heat exchangers work better with a higher temperature and higher deltaT... you should get better heat dissipation from parallel if my theory serves me right. Downside is possibly extra plumbing and you have to make sure each radiator is getting flow within reason of each other.

[Biggy72]

all of the water will pass through the path of least resistance making most of the water go through one radiator and not through the other. I don't think there is a way to make both radiators and plumbing flow equally.

[Superfast Matt McCoy]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Biggy72:
all of the water will pass through the path of least resistance making most of the water go through one radiator and not through the other. I don't think there is a way to make both radiators and plumbing flow equally. </div></BLOCKQUOTE>

If you have two of the same radiator with the same size hose going to and from, they will flow about equally. If you encounter a situation where your parallel flow system has substantially more water going through one radiator, you need to take apart the system and remove the dead mouse from the other radiator.

in response to the original question, the only major pro for 2 radiators is packaging. and if you do that, flow them in parallel for the reasons mentioned by Maverik.

[Brian Evans]

A friend of mine has an F3000 car. It's cooling system (V-6 engine) has the water outlet from one cylinder bank going to one quite small rad, the other bank going to one larger rad, and the radiator outputs combined at the input to the water pump. Combining the inputs averages the cooling ability of the two different sized rads. Making one rad smaller presumably was done to match total cooling to the system requirement. Kind of interesting, I thought.

Brian

[murpia]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Brian Evans:
Making one rad smaller presumably was done to match total cooling to the system requirement. </div></BLOCKQUOTE>
Maybe also packaging a single oil cooler on one side only?

Regards, Ian

[Maverik]

Agreed with Matt, I've thought about dual radiators for several years and the only real good argument I can come up with is packaging which could also help CG if you get tricky. Maybe, maybe not worth the effort needed to properly make it. I want to see some 50 psi cooling systems with little tiny radiators in the near future!!

[Chris Allbee]

50 psi does no good when most of these motorcycles plain bearings and cylinder wall clearances become somewhat worthless by the time the water temp registers 280 degF. Oil temps are generally a fair sight higher than the water temp...and there is a nice you tube video of the OU car in california running a 30psi cap...

[Wesley]

Though if you spent a couple hundred K then you might be able to get some coatings applied that could take it. Maybe.

[Maverik]

Hey, I never said it was possible ;-) Just that I wanted to see it... I'm sure some teams can afford those coatings...

[adrial]

With all the time spent trying to lower CG height, I am surprised to see the number of teams running giant single radiators above the engine or rear subframe. Even one single radiator hanging off the side of the car hardly seems like a good idea...

I think dual radiators is WAY cleaner and if you use a pair of rads & fans from a 1000cc bike with reasonable ducting, you will be fine. Aluminum cooling lines is another great way to increase cooling capacity...

[ad]

Im suprised everyone is dictating that packaging is the main reason for dual radiators,

there are many more pros to a twin / dual setup, along with several cons.. some are;

- larger core frontal area of equivalent total heat transfer area as compared to a single
- less flow restriction from thinner cores
- improved static vehicle balance (no need to offset say a fuel tank and begin chasing your tail)
- longer water flow path increasing convection (series dual pass configuration)
- Pain in the arse to manufacture (more leaks!)
- Check for rocks!

etc
etc

Given the experience i have had with dual setups in the past, i think packaging can be a huge pain in the ass! Try packaging efficiently (for weight and maintanence) a twin core series setup with dual electric water pumps!

I think packaging a twin is a nightmare compared to a single!

As far as a parallel setup working consistantly, i find it hard to believe, even if you can adjust the pressure drop across each radiator system, regardless of your pump configuration, over time due to scaling and the like it will constantly change! Anyone for adding feedback control to your cooling to PWM your pumps??

[Maverik]

ad... couple of things I disagree with about your pros and cons...
1. larger core frontal area... if you did your heats analysis correctly and figured out the area you NEED, then I think it would be pretty hard to choose a radiator with less than the desired amount of frontal surface area. And if you still think more is better for two radiators, you are just plain adding weight at that point. Sure you'll have the capacity to overcool, but pounds (kgs) are pounds.
2. Less restriction from thinner cores? What? You realize flow losses are greater trying to pump fluid through a smaller tube right? I could see you meaning something other than what I interpret here, but that's basic fluids.
3. Agree on vehicle balance (and cg considerations)
4. Any increase you'll see in the higher convection (assuming AL lines) will be offset by the decrease in efficiency of the second radiator from the lower deltaT. Keep in mind you are convecting heat to a relatively constant air temperature, the higher the difference between the two fluids, the more heat can be transferred. Not worth it in my opinion, but it will also make you need more frontal surface area as per your argument number one.
5. The biggest challenge to manufacturing I think would be making flow even across the cores. Packaging normally isn't too bad unless the system is an afterthought.
6. Scaling, are you kidding? I've run radiators for two years, with a drop of dawn soap or specific corrosion inhibitor (in the concentration allowed by the rules) and have never seen scaling or fouling. Unless you are testing for a year straight and never change the water, scaling and fouling shouldn't be a significant factor.

I don't mean to sound like I'm coming down on you, but some of things you said are just plain wrong in the engineering sense. Which gets me back to the only real reason I see to go to dual radiators is packaging. Maybe you can't fit the required core area in one package so it mandates another core on the other side of the car (or underneath if you like suckercars.) You also just might like the looks of big wig pro formula car...

[Pete M]

We run two radiators and the main reason we do it is packaging. It is just very cumbersome to package the core area we need with one radiator.

[Drew Price]

Maverik,

I think what Ad was trying to say about thinner cores, was that there would be less air resistance. I would be willing to bet that two small, thin, single row cores could weigh the same as one larger, possibly multiple row core.

Which comes back to it being a packaging and CG improvement, since two smaller cores on either side of the car would have a lower CG than a larger one, even if their combined weight were slightly more than a larger single.

Depending on the placement of the single, the shielding/mounting structure, firewall, sidepod, ducting, and fan would all have to be bigger.

Best,
Drew

[ad]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Drew Price:
Maverik,

I think what Ad was trying to say about thinner cores, was that there would be less air resistance. I would be willing to bet that two small, thin, single row cores could weigh the same as one larger, possibly multiple row core.

Which comes back to it being a packaging and CG improvement, since two smaller cores on either side of the car would have a lower CG than a larger one, even if their combined weight were slightly more than a larger single.

Depending on the placement of the single, the shielding/mounting structure, firewall, sidepod, ducting, and fan would all have to be bigger.

Best,
Drew </div></BLOCKQUOTE>

I'll reply more later, but thats fairly close to the point i was trying to make. Thanks Drew.

[ad]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Maverik:
ad... couple of things I disagree with about your pros and cons...
1. larger core frontal area... if you did your heats analysis correctly and figured out the area you NEED, then I think it would be pretty hard to choose a radiator with less than the desired amount of frontal surface area. And if you still think more is better for two radiators, you are just plain adding weight at that point. Sure you'll have the capacity to overcool, but pounds (kgs) are pounds.
2. Less restriction from thinner cores? What? You realize flow losses are greater trying to pump fluid through a smaller tube right? I could see you meaning something other than what I interpret here, but that's basic fluids.
3. Agree on vehicle balance (and cg considerations)
4. Any increase you'll see in the higher convection (assuming AL lines) will be offset by the decrease in efficiency of the second radiator from the lower deltaT. Keep in mind you are convecting heat to a relatively constant air temperature, the higher the difference between the two fluids, the more heat can be transferred. Not worth it in my opinion, but it will also make you need more frontal surface area as per your argument number one.
5. The biggest challenge to manufacturing I think would be making flow even across the cores. Packaging normally isn't too bad unless the system is an afterthought.
6. Scaling, are you kidding? I've run radiators for two years, with a drop of dawn soap or specific corrosion inhibitor (in the concentration allowed by the rules) and have never seen scaling or fouling. Unless you are testing for a year straight and never change the water, scaling and fouling shouldn't be a significant factor.

I don't mean to sound like I'm coming down on you, but some of things you said are just plain wrong in the engineering sense. Which gets me back to the only real reason I see to go to dual radiators is packaging. Maybe you can't fit the required core area in one package so it mandates another core on the other side of the car (or underneath if you like suckercars.) You also just might like the looks of big wig pro formula car... </div></BLOCKQUOTE>

Maverik,
Thankyou for your input, some good points, my response;
1. Obviously the sizing of the system is an iterative approach, however, once you have determined your cooling requirement in terms of heat to be dissipated for the given criteria (over a range of rpms and loads, note that this is vastly different for each of the dynamic events) you can figure out your mass flowrate for water and air, and then figure out a required heat transfer surface area. This is not the same as the frontal surface area. This varies with core geometry properties.

2. Obviously now since the heat transfer surface area is related to the volume of your core you know the volume of the core(s) depending on the water flow arrangement (ie. single, double, triple pass etc). Now assuming that you make each core of the twin radiators with a frontal area of about 75% that of the single you can now afford to reduce the thickness of the heat exchangers to bring the total heat transfer surface area to spec. Pressure drop across each core is dependant upon core thickness (among other things)

3. You may even be able to reduce fin pitch and possibly tube pitch (assuming hot side allowance) and further reduce core pressure drop.

4. Remember that twin radiators connected in series is the same as a double pass single core arrangement.

5. As far as the scaling goes, i hav always found (especially when modifying leaking cores) that the scaling inside the radiators was up to .5mm in thickness, remember most tube annulus widths are only 3-4mm! The water used was local tap water with no inhibitors.


Hope that helps some.

PS no offence taken :P

[PatClarke]

Quote AD "Remember that twin radiators connected in series is the same as a double pass single core arrangement".

No it's not Andrew! In a double pass radiator the air is preheated before the second pass. With dual radiators, cool air would flow through both cores. =]
Cheers
Pat

[VFR750R]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PatClarke:
Quote AD "Remember that twin radiators connected in series is the same as a double pass single core arrangement".

No it's not Andrew! In a double pass radiator the air is preheated before the second pass. With dual radiators, cool air would flow through both cores. =]
Cheers
Pat </div></BLOCKQUOTE>

No it's NOT Pat, dual pass radiators typically don't run the second pass behind the first, they run side by side. Each pass uses the full core thickness.

[ad]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by VFR750R:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PatClarke:
Quote AD "Remember that twin radiators connected in series is the same as a double pass single core arrangement".

No it's not Andrew! In a double pass radiator the air is preheated before the second pass. With dual radiators, cool air would flow through both cores. =]
Cheers
Pat </div></BLOCKQUOTE>

No it's NOT Pat, dual pass radiators typically don't run the second pass behind the first, they run side by side. Each pass uses the full core thickness. </div></BLOCKQUOTE>

Cheers VFR

Pat were you considering a double pass on the air side? I was actually refering to the water side double pass configuration.

[PatClarke]

Hi all,
Actually it doesn't matter. The prime objective of the post was to let you guys know (especially the Aussies and Germans) that I am hiding back here in the shadows with a pointy stick, ready to give you a jab in the ass whenever I feel cranky enough :-)
Pat

[ad]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PatClarke:
Hi all,
Actually it doesn't matter. The prime objective of the post was to let you guys know (especially the Aussies and Germans) that I am hiding back here in the shadows with a pointy stick, ready to give you a jab in the ass whenever I feel cranky enough :-)
Pat </div></BLOCKQUOTE>

Glad im not trying to argue rod ends in bending are a good thing...

Btw its amazing how many top motorsport classes that run those!

[Brian Evans]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Glad im not trying to argue rod ends in bending are a good thing...

Btw its amazing how many top motorsport classes that run those! </div></BLOCKQUOTE>

That's because rod ends in bending get less important when your car is getting judged by it's performance on track, it's maintainability, it's actual cost rather than a fictitious cost report, and isn't being built to extreme limits of weightlessness...

Rod ends in bending can be a reasonable solution IF you make them big enough and you use them with some discretion. They don't spontaneously combust...

Brian

[PatClarke]

Prod, poke, jab, jab, prod
Pat =]

[ad]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Brian Evans:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Glad im not trying to argue rod ends in bending are a good thing...

Btw its amazing how many top motorsport classes that run those! </div></BLOCKQUOTE>

Rod ends in bending can be a reasonable solution IF you make them big enough and you use them with some discretion. They don't spontaneously combust...

Brian </div></BLOCKQUOTE>

Hey ive seen that exact quote before! But wait, it was the exact reasoning that design judges hated!

I would say that it is like you have said for cost and maintanence reasons they are selected instead of encapsulated sphericals and shim packs, however aside from the ease of adjustability here i think i would rather prefer the extra security provided by an encapsulated spherical.

Getting offtopic now however.