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Old 06-17-2020, 11:54 AM
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Aluminum does not dissipate heat better than copper .. aluminum changes temperature faster because of it's lower density. Since copper is denser it takes longer to heat up, and longer to cool down as the metal itself is capable of containing more heat energy. Surface heat dissipation is dependent on surface finish, air volume, air flow characteristics, and differential temperature. The amount of heat moved from source to the surface of the sink is determined by the heat transfer capability of the material.

It's a common misconception that aluminum dissipates heat faster because it cools to the touch quicker .... that is only because it contains less heat to begin with.

Aluminum does have one advantage, since it is less dense and holds less heat, an engine that is shut down will cool slightly faster because the total mass of the heat source (engine and cooling system) is less than with copper. ie ... 500 lbs mass at 200 degrees will cool down slightly faster than 510 lbs mass at 200 degrees.

A common mistake is using human touch to determine thermal properties. When aluminum engine parts became more common in the 70's people thought they got hotter because they felt hotter ... when in reality the aluminum was simply transferring it's heat to your fingers much faster than iron can.

Heat dissipation depends wholly on the ability of the material to transfer energy from the source to a sink, and copper does than almost twice as efficiently as aluminum. Yes the aluminum will heat up faster, that does not mean more energy is being removed from the coolant, it means the aluminum, as a material, is capable of holding less heat because of it's lower mass and thus equalizes it's temperature with the coolant faster.

A simple test would be to drop a 2" x 2" block of aluminum in boiling water, it will stop the water from boiling until it equalizes it's temp with the water and stops removing heat. Do the same with the same size block of copper and it will prevent the water from boiling for a longer period of time because it has more mass for the same size.

To the touch it's same effect as metal versus wood on a cold winter day. A piece of smooth wood will feel warmer to the touch than a piece of metal, despite the fact they are both the exact same temp because the metal is capable of transferring heat much faster than wood (from your finger to the metal) and is capable of holding much more heat than wood .. so it removes MORE heat from your finger. (ignoring surface finish characteristics that can greatly effect the rate of heat transfer)

Another thing aluminum is good at is reaching a stable temperature faster, and returning to ambient faster .. both due to it's reduced mass. That is why it's thermodynamically better for engines, the engine reaches operating temperature faster because of reduced mass rather than expending energy just heating up a heavy iron block. And conversely when the engine is shut down there is less residual heat because of the reduced mass.

On a modern vehicle .... when you include cost and weight, I give aluminum the advantage, and definitely on high performance applications where weight is even more of a consideration. But when it comes down to pure thermodynamic performance, copper wins.

I had this stuff pounded into my head during "Materials" classes and "Heat Transfer and Fluid Flow" classes when I was schooling for a career in the Nuclear Navy.

One rule they constantly reminded us of to prevent GMEs (Gross Misconceptual Errors), is that .... "There is no such thing as cold, there is only heat" Which is making the point that cold is not a "thing" ... it is merely the absence of heat energy. There is no system that produces "cold" there are only systems that remove heat. There is no measurement to quantify the amount of "cold", only the amount of heat. A bit off topic but it can help ground a person when they are mulling over some thermodynamic system.


Last edited by dataway; 06-17-2020 at 12:01 PM.
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  #22  
Old 06-17-2020, 04:58 PM
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Originally Posted by lust4speed View Post
My Bounder motorhome with the Ford chassis came with plastic end tanks. The motorhome was 4 years old when the first radiator started leaking at the crimped seam. Replaced it with the same model Ford radiator and that one lasted three years. Looked back a few years in the parts book and found a copper radiator. It was still doing fine when I sold the motorhome sixteen years later. So my experience with the plastic tanks wasn't good. The expansion and contraction of the aluminum on the lesser expanding plastic tanks caused both of the failures. I'll take tanks and cores made of the same material.
Yep, and that's not surprising from a big RV. The heavier the use, the faster that type of radiator fails for exactly the reason you point out.

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Old 06-17-2020, 11:07 PM
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I replace a fair number of radiators a year and 95% of them are aluminum with plastic tanks. Keeping correct coolant in the radiator and keeping it clean will extend it's life. The more compressed the radiator is under the hood and the more under hood heat, the shorter the life in my experience. Average life of the ones I see is about 10 years or the life of the extended life coolants. Fortunately, most are easy to replace and pretty cheap. But not always. Changing a radiator in a late model Ford Transit 350 HD for example is a 5 hour job for an experienced technician. In your GTO, if the $120.00 aluminum/plastic radiator is working great today and has fresh coolant in the system, I would not expect it to have an issue under normal circumstances for 5+ years at a minimum. I don't know what brand you bought, but NAPA, Oreily's, Autozone and Car Quest all sell Spectra Premium as one of their lines. They are Chinese and low cost. But I have to admit I have installed over 100 of them without a "radiator" related problem. Fitment hasn't been perfect on all of them, and adapter fittings were required on some of the coolers. But overall, pretty decent.

  #24  
Old 06-18-2020, 03:32 PM
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Quote:
Originally Posted by dataway View Post
Aluminum does not dissipate heat better than copper .. aluminum changes temperature faster because of it's lower density. Since copper is denser it takes longer to heat up, and longer to cool down as the metal itself is capable of containing more heat energy. Surface heat dissipation is dependent on surface finish, air volume, air flow characteristics, and differential temperature. The amount of heat moved from source to the surface of the sink is determined by the heat transfer capability of the material.

It's a common misconception that aluminum dissipates heat faster because it cools to the touch quicker .... that is only because it contains less heat to begin with.

Aluminum does have one advantage, since it is less dense and holds less heat, an engine that is shut down will cool slightly faster because the total mass of the heat source (engine and cooling system) is less than with copper. ie ... 500 lbs mass at 200 degrees will cool down slightly faster than 510 lbs mass at 200 degrees.

A common mistake is using human touch to determine thermal properties. When aluminum engine parts became more common in the 70's people thought they got hotter because they felt hotter ... when in reality the aluminum was simply transferring it's heat to your fingers much faster than iron can.

Heat dissipation depends wholly on the ability of the material to transfer energy from the source to a sink, and copper does than almost twice as efficiently as aluminum. Yes the aluminum will heat up faster, that does not mean more energy is being removed from the coolant, it means the aluminum, as a material, is capable of holding less heat because of it's lower mass and thus equalizes it's temperature with the coolant faster.

A simple test would be to drop a 2" x 2" block of aluminum in boiling water, it will stop the water from boiling until it equalizes it's temp with the water and stops removing heat. Do the same with the same size block of copper and it will prevent the water from boiling for a longer period of time because it has more mass for the same size.

To the touch it's same effect as metal versus wood on a cold winter day. A piece of smooth wood will feel warmer to the touch than a piece of metal, despite the fact they are both the exact same temp because the metal is capable of transferring heat much faster than wood (from your finger to the metal) and is capable of holding much more heat than wood .. so it removes MORE heat from your finger. (ignoring surface finish characteristics that can greatly effect the rate of heat transfer)

Another thing aluminum is good at is reaching a stable temperature faster, and returning to ambient faster .. both due to it's reduced mass. That is why it's thermodynamically better for engines, the engine reaches operating temperature faster because of reduced mass rather than expending energy just heating up a heavy iron block. And conversely when the engine is shut down there is less residual heat because of the reduced mass.

On a modern vehicle .... when you include cost and weight, I give aluminum the advantage, and definitely on high performance applications where weight is even more of a consideration. But when it comes down to pure thermodynamic performance, copper wins.

I had this stuff pounded into my head during "Materials" classes and "Heat Transfer and Fluid Flow" classes when I was schooling for a career in the Nuclear Navy.

One rule they constantly reminded us of to prevent GMEs (Gross Misconceptual Errors), is that .... "There is no such thing as cold, there is only heat" Which is making the point that cold is not a "thing" ... it is merely the absence of heat energy. There is no system that produces "cold" there are only systems that remove heat. There is no measurement to quantify the amount of "cold", only the amount of heat. A bit off topic but it can help ground a person when they are mulling over some thermodynamic system.
Hey, then stick with Brass. Whatever blows your skirt up. I like aluminum, it sheds heat more rapidly than brass.

  #25  
Old 06-18-2020, 03:34 PM
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Originally Posted by LATECH View Post
Hey, then stick with Brass. Whatever blows your skirt up. I like aluminum, it sheds heat more rapidly than brass.
I agree...

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  #26  
Old 06-18-2020, 03:36 PM
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Originally Posted by lust4speed View Post
My Bounder motorhome with the Ford chassis came with plastic end tanks. The motorhome was 4 years old when the first radiator started leaking at the crimped seam.
I have seen a lot of late model ford radiators fail. Mostly in the f 250 with 6.7

It is likely related to a flaw in the manufacturing process , or a less than quality end seal for the tanks. Its possible the aluminum used is too low in alloy to be strong enough to withstand the pressure , and is allowing the crimp /fingers to move and not hold tight. At any rate I have seen this in Fords lately.

  #27  
Old 06-18-2020, 03:41 PM
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Aluminum/plastic radiators are cheap to make and will make it through the warranty period.

All aluminum radiators are very affordable, why replace with Aluminum/plastic? This thread really went a long way. lol

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  #28  
Old 06-18-2020, 04:53 PM
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I tries 2 oem plastic tank rads from a wrecking yard in my car. I thought at $20 this was a way to almost steal a light weight rad with oem quality. Both pressure tested fine and cooled great but developed leaks at the tank crimps within about 6 weeks of use. They were used of unknown milage but I assumed they would be bullet proof. Wrong...
Coughed up for a good all aluminum unit and all has been good for more than 10 yrs now.

  #29  
Old 06-18-2020, 07:14 PM
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Actually core design typically has a greater impact heat transfer efficiency than the material used (assuming you are using a reasonably conductive metal) ... so in that respect a modern aluminum radiator might perform better than a 50 year old design in copper.

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