Difference between a heat exchanger and Oil cooler

[Joel K]

Hi,

I’m in the planning stages of my LT4 SLC build and looking to install one or two small supercharger heat exchangers behind the rear side vents similar to Bob’s LSA Build.

Looks like Bob had two heat exchangers custom made by C&R Racing, my question is can you use an oil cooler as a supercharger heat exchanger? The size of the oil coolers are easy to find, but have not found smaller similar sized heat exchangers for sale. I’d prefer not to have to have them custom made assuming that is the more expensive option. I was also thinking of using twin aluminum heater cores as well. They look like they would fit in nicely. Obviously I have no idea if this is way off base but figured I’d ask. Any input is appreciated.

Here are some pic’s of Bob’s Setup..

 

[Bill Kearley]

Have a look at Piper and Lycoming oil coolers. or Google images of that nature.

 

[Howard Jones]

Talk to C&R about total cooling requirements of your engine. They really helped me with my radiator and oil cooler selection resulting in perfect coolant and oil temps on track.

The one thing that can be a challenge for race or very high power SLC's is available air inlet area. The radiator inlet is plenty big enough for the radiator and a AC condenser but I have not seen a oil cooler stacked in the same location but that would be a lot of heat especially in a high power track car. One side of the rear side scoops is big enough for a oil radiator leaving the other side for everything else. I planned my car to increase the side scoops sizes and added air scoops to the top of the car to increase ambient air flow into the engine bay to help cool the power train.

If I repaint the nose I am going to add 2 additional or increase the size the brake duct inlets and divide them. If you did that you could place the boosted air coolers in the nose. Something to think about. I am thinking of using one side to cool my transaxle with a small cooler and the other for driver cooling.

This is something to plan for now so that body mods can be done easily. Look at SLC race car pictures for air inlet ideas.

 

[Rich]

This is what I have made for either side of the LSA which equals the same surface area as the single cooler on the Holden Commodore HSV built in Aust. Given that I live in Queensland, which has a hot climate, it was just a matter of building the biggest coolers I could fit in the space. I also intend on increasing the size of the side vents as well.

 

[Joel K]

This is what I have made for either side of the LSA which equals the same surface area as the single cooler on the Holden Commodore HSV built in Aust. Given that I live in Queensland, which has a hot climate, it was just a matter of building the biggest coolers I could fit in the space. I also intend on increasing the size of the side vents as well.

Thanks Rich, I like the way you mounted them and those are pretty sizable coolers given the space.

 

[Cam]

Joel - so that I understand what you're asking - are you asking whether an oil cooler can be used to cool a supercharger's oiling system? Or are you asking whether an oil cooler can be used to cool the boosted air coming from the supercharger, aka intercooler?

 

[Joel K]

Joel - so that I understand what you're asking - are you asking whether an oil cooler can be used to cool a supercharger's oiling system? Or are you asking whether an oil cooler can be used to cool the boosted air coming from the supercharger, aka intercooler?

Hi Cam,

The LT4 has water to air cooling bricks in the supercharger unit itself. That cools the air going in to engine. The supercharger bricks are cooled by an external radiator called a heat exchanger and water is circulated by an electric water pump through th system. That heat exchanger then cools the bricks in the supercharger so they can continue to do their job of cooling the air that enters the engine.

So the question is, can I use an “oil cooler” rather than a “heat exchanger” since Oil coolers seem to be available in smaller sizes. I would use two oil coolers vs. one heat exchanger. Another way to ask the question, is there any difference in what is called a heat exchanger or oil cooler. To me, a heat exchanger implies that it will be used to cool anti-freeze and Oil cooler implies it will be used to cool Oil or transmission fluid. They are similar in construction so I am thinking they are interchangeable. I just need to make sure there is enough cooling capacity for the intended purpose. So just looking to get feedback if using oil coolers for this purpose is ok or something to avoid.

 

[Cam]

Ah, a heat exchanger is just that, a device used to transfer heat from one fluid to another. A radiator and an oil cooler are two types of heat exchangers, and the bricks you refer to are called charge air coolers, also a type of heat exchanger.

Generally heat exchangers are designed to cool specific types of fluids (oil, air, water) as the densities of each are very different.

I’m not well versed in oil cooler design but I would contact a manufacturer to get their take on whether their oil coolers would be compatible with coolant. There’s a lot of science that goes into channel sizing and optimizing between heat transfer and restriction. Since coolant is a lot less viscous than oil I’d be concerned about dwell time differences - whether the coolant would have enough time to transfer enough heat before exiting the oil cooler. I’m sure it would physically work, but not sure if it would be optimized, especially if you’re going to just do a 1:1 surface area comparison with a standard LT4 heat exchanger.

 

[Bob from Cleveland]

To all guys with intercoolers !! One issue I had was air trapped in the coolers. Water temps were wacky ... After trying MANY ways to bleed it out ... I ended up installing small bleed valves on top of each cooler.

 

[Bob from Cleveland]

The LSA "brick" that draws the heat from the intake charge is small (heater core size) I am using 3X the surface area to reject the heat across the two exchangers. I am also using a 1 gallon tank for a thermal "cushion" FYI.

 

[Joel K]

The LSA "brick" that draws the heat from the intake charge is small (heater core size) I am using 3X the surface area to reject the heat across the two exchangers. I am also using a 1 gallon tank for a thermal "cushion" FYI.

Bob, did you consider a front mounted heat exchanger(in front of the A/C condenser) before you decided on the twin rear heat exchangers? Wondering why you chose twin heat exchangers in the rear.

At some point I will need to make a decision so just curious,

 

[Roger Reid]

This is what I'm using. https://fiinterchillers.com/products/
This replaces the heat exchanger by placing a T in the A/C line. You still need a reservoir for chilled fluid.

 

[Joel K]

This is what I'm using. https://fiinterchillers.com/products/
This replaces the heat exchanger by placing a T in the A/C line. You still need a reservoir for chilled fluid.

No pun intended, that is pretty cool. I think the Demon uses a similar approach.

 

[Bob from Cleveland]

I wasn't sure if the engine itself would have heat issues, so I was worried about putting one up front.
I also thought about the "chillers" but overall cost was the issue for me.

 

[Joel K]

I wasn't sure if the engine itself would have heat issues, so I was worried about putting one up front.
I also thought about the "chillers" but overall cost was the issue for me.

Thanks Bob

 

[Scott]

Cam, I agree that a heat exchanger designed for oil is likely different than one designed for coolant due to the difference in viscosity, etc. However, the “not enough dwell time” argument is an old wife’s tale that was recently discussed here. The primary factors driving heat transfer is temperature difference (delta t) between the fluid and the heat exchanger’s wall and having enough turbulence to force the hotter fluid in the middle of the flow to wall. It’s my understanding that as delta-T decreases heat transfer efficiently exponentially decreases.

If your car was overheating, you wouldn’t drive slower or reduce fan speed to allow the air to have a higher dwell time as it passes over the radiator. Another example is when red-hot steel is quenched in a bucket of water. It cools almost instantaneously, but you would have to leave it I the water for a very long time to reach room temperature.

Joel, I’ve been on the fence for a long time about where to put my heat exchanger. It’s either going to go in the left rear side vent or in the nose. The rear requires less plumbing, but the opening is relatively small and the air flow through it isn't great even when you open it up. In addition, the right side is filled with the cold air intake which doesn't make it easy to find a place to put the oil and transaxle coolers.

While some cars place the heat exchanger in front of the condenser, SL-Cs with AC are likely on the fringe of keeping cool on a hot day in traffic. The heat exchanger heats the air resulting in a lower delta T for the condenser and radiator. Since efficiently drops off exponentially as delta T decreases you don't want to tax a system that's likely close to its limit. Also, there's not a whole lot room in front of the condenser.

However, there is a fair amount of room to the left and right of the radiator and you can easily open up the brake ducts to increase air flow. The 1,500 hp (or whatever it was) twin-turbo car built by Superlite had an intercooler mounted to the left and the right sides of the diffuser (see picture below). The angle is required to clear the headlights.

If I put the intercooling in the nose, I’ve been wondering if I do one or two intercoolers. Two obviously nearly doubles the weight, but it doubles air flow and surface area. I’m not sure how much of an impact there is to car balance… maybe I should put one on the right side to offset the driver's weight -- I'm pretty heavy these days LOL

If I go with two should they be plumbed in series or in parallel? Series is double the flow of parallel which increases turbulence (which is what you want when rejecting heat). However, the second radiator will have a lower delta T because the first radiator cooled the fluid. Parallel halves the flow, but the delta T in the second radiator is the same as the first. To my understanding delta T has an exponential effect on efficiency so parallel would seem to be the better choice.

In any event, I’d love to hear from anyone with thoughts on:
(1) one vs. two in the nose
(2) if one, should it go on the left or right
(3) if two, serial or parallel plumbing.

 

[Cam]

Scott - there are some fundamental thermodynamics issues with what you’ve written. This isn’t the place to get into it and I’m not sure I want to - it’s clear you’ve done your research and it would take a lot of data and math to convince you otherwise.

On dwell time ... how well would water cool if it were moved through a radiator at a rate of 1000 gallons/sec? Probably wouldn’t have enough time to do much heat transfer before it was pushed out the radiator and back into the engine. There’s a balance and dwell time is a factor, maybe not an issue for a properly designed heat exchanger. But pumping air through something designed to cool oil throws out all design assumptions.

Regarding the photo you’ve posted - am I correct in interpreting what you’re writing is that this car actually plumbed their high pressure discharge air and piped it via a ~1” line from the back of the car, all the way up to the nose, then back via a similar 1” line, before going into the intake or throttle body?the term “intercooler” is usually used for charge air coolers, or heat exchangers used to cool pressurized air after it’s been through some type of compressor (turbo, supercharger). Just want to be clear ... and if my interpretation is correct ... wow.

Here’s an eBay kit for a 350hp civic. The inlet diameter on this included intercooler is 2.5”, about a factor of 10x in flow area difference to the intercooler shown in your pic.

http://vi.raptor.ebaydesc.com/ws/eB...2&pm=1&ds=0&t=1522311150000&ver=0&cspheader=1

I’m guessing I’ve misinterpreted what you’re saying and that cooler photo you’re showing is for oil. End caps suggest it was designed for an incompressible fluid and not air.

 

[Joel K]

Here is a pic of the 2017 Camaro ZL1 cooling system. Looks like they use two heat exchangers for the LT4 as well as two radiators.

The Intercooler/heat exchanger is in front of the condenser and the auxiliary heat exchanger is in front of the left front wheel.

The radiator is behind the condenser and the auxiliary radiator is in front of the passenger wheel,

That’s a lot of plumbing for sure.

 

[Cam]

Thanks Joel - that pic makes a lot more sense when you’re using water as the cooling medium for the charge air cooler!

Scott - I should add what you write makes a lot more sense with that usage in mind - an air to water intercooler as opposed to air to air.

 

[Roger Reid]

Twin screw superchargers have an air to water intercooler with a reservoir serving chilled water to the heat exchanger or "brick" either above or below the rotors. Air to water intercoolers can be mounted in front or in the back connected using 1" hose and of course a pump such as https://www.summitracing.com/parts/emp-e2512a
Turbochargers can use air to air or Water to air intercoolers. Here is a good article. http://www.enginebasics.com/Advanced Engine Tuning/Water vs Air Intercooler.html
I believe Lingenfelter and some others make an intercooled manifold for turbo applications which would allow an air to water intercooler mounted front or rear. https://www.montmotorsports.com/lingenfelter-intercooled-intake-manifold-87-102-mm-ls3-lsa-ls9/