radiators-Aluminum vs. copper
radiators-Aluminum vs. copper
(OP)
What are the pros and cons of Aluminum ratiators versus brass radiators?
Jay Maechtlen
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radiators-Aluminum vs. copper
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radiators-Aluminum vs. copperradiators-Aluminum vs. copper(OP)
What are the pros and cons of Aluminum ratiators versus brass radiators?
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RE: radiators-Aluminum vs. copper
RE: radiators-Aluminum vs. copper
RE: radiators-Aluminum vs. copper
What about the thermal conductivity of Aluminum vs. Brass?
Can the Al unit be the same dimensions, or are the size and/or proportions changed?
Jay Maechtlen
RE: radiators-Aluminum vs. copper
RE: radiators-Aluminum vs. copper
precipitate aluminum phosphates and silicates out on the
inner surface of the tubes if common commercial coolants
(like Prestone green) are used in combination with hard
water.
The precipitates come from the hotter heat rejecting
surfaces like aluminum cylinder heads and are more
soluble at higher temperatures. They tend to form
inside the radiator especially as the corrosion
protection package in the coolant weakens. The thermal
efficiency of the radiator is reduced significantly as
the process progresses.
Many European auto manufacturers specify phosphate,
nitrate, and amine free coolants for that, and, a few
other reasons.
Chumley
RE: radiators-Aluminum vs. copper
RE: radiators-Aluminum vs. copper
Whilst brass radiators can be recycled the solder content is difficult to recover and recycle responsibly.
The aluminium / plastic radiator can also be welded ultrasonically or using some form of plastic welder which must be more energy efficient not to mention cheaper.
Cheers, Pete.
RE: radiators-Aluminum vs. copper
“CuproBraze is the name of a new manufacturing process for copper-and-brass automotive radiators. The process uses fluxless lead-free brazing, anneal resistant alloys and laser welding among other innovations to produce new thin-walled radiators that perform better than thicker-walled aluminum products.
The new radiator was developed by the International Copper Association and produced initially by the Universal Auto Radiator Manufacturing Company. They are typically 30% to 40% lighter than traditional copper and brass models, can be made smaller than their aluminum counterparts, and can provide up to 30% less air-side pressure drop. The CuproBraze process also shortens manufacturing time and reduces production costs.”
from http://www.copper.org/general/cfacts/copper-facts.html
“Cost-Efficient CuproBraze® Radiators Show Superior Durability in Road Tests
…In addition, CuproBraze radiators can be made smaller in size, or with significantly higher heat transfer efficiency than aluminum models. The CuproBraze process offers further advantages over standard aluminum radiators, such as greater fuel economy, lower air side pressure drop, lower cooling module costs and weight, and less parasitic engine losses….”
from http://automotive.copper.org/cuprobraze/cuprobraze-summer-1999.html
“Commercial Production of CuproBraze® Radiators Begins
Over 90 different models to be offered in 2000
The CuproBraze® revolution in automotive radiators has begun. Universal Auto Radiator Manufacturing Co. in Pittsburgh, Pennsylvania, USA, became the first company in the world to begin full production of the new CuproBraze radiator. The successful commercialization of the CuproBraze process, a break-through technology developed by the International Copper Association, will allow radiator manufacturers to build durable, high-performance radiators with cost, design and performance advantages over aluminum radiators….The CuproBraze ® radiator has three to four times the life of a soldered copper radiator."
from http://automotive.copper.org/cuprobraze/cuprobraze-10.html
Also, the CuproBraze® alloy can be HF (high frequency) welded; ultrasonic weldability had been mentioned as an advantage for Al by Peter7307. See
“Berry Radiateurs Adopts CuproBraze Process and Begins Production”
http://www.theautochannel.com/news/2002/10/21/149297.html
It appears that CuproBraze® has given Cu the competitive edge over Al in the radiator & HXer market.
Ken
RE: radiators-Aluminum vs. copper
http://automotive.copper.org/no-flux.html
RE: radiators-Aluminum vs. copper
My 2 cents worth, not the full $10.95 version.
RE: radiators-Aluminum vs. copper
I have access to any and all technology in heat exchangers for my race cars. Currently I am using the most efficient radiator I have ever used, a furnace brazed TWO core copper/brass. Keep in mind that it is a tiny bit heavier than the two core aluminium it replaces but, it is a bit more efficient at heat dissapation. Also costs a lot more, unfortunately.
I have stayed out of this discussion up till now because I rely mostly on published info and keeping an eye out for anything that is "better" as thermodynamics is not my strong suit. I DO however, have a lot of experience in using what DOES NOT work!
Rod
RE: radiators-Aluminum vs. copper
The merits of CuproBraze vs Aluminum products will be debated for many years to come.
I have personally had the privilege of being involved with the development & implementation of both Aluminum Brazing ('Composite Deposition' & Nocolok) & CuproBraze.
At the end of the day, when all marketing waffle is pushed aside, what is of most importance is the $/W = ($/kg)/(W/kg) = (Material+Production cost per mass)/(heat-transfer per unit mass).
The end-user is paying $/W of useful duty. Either at time of purchase, or during the lifetime of using the product.
Copper-Brass brazed products CAN be designed to have BETTER (W/kg) - but only if the designer designs
($/W) for CuproBraze products, from experience, has typically allowed a potential product price REDUCTION. Obviously, in the early days of a new technology, unit costs are higher than at volume pricing.
My personal opinion is the following:
CuproBraze has huge potential to fill certain market niches. I do not believe that it will ever completely replace Aluminum products. Each technology will find its place - dependant on cost & auto-manufacturer's technical requirements.
RE: radiators-Aluminum vs. copper
This message is to let you know that there are a few new papers available for download on www.adtherm.com regarding new studies performed on "Heat-Transfer per Unit Mass [W/kg]" for Copper & Aluminium radiator fins.
The results are very interesting. Copper fins can indeed be optimised to edge ahead of Aluminium, but with some interesting new design rules.
The old adage of "sure you can get more heat-transfer from copper, but it will be heavier" is not neccesarily correct.
But, the new designers need to very rather skillful, and the optimised designs tend to be rather refined. This now explains why the "Splitter-fin" fin designs were so efficient. Thin gauge, short fin height, fine louvers, centre-strip... are all good starting points...
Actually, the new technology we have developed can also be used to compare different Aluminium-Aluminium configurations, Aluminium- Stainless-Steel, anything-anything - for multi-louver automotive corrugated fins.
Regards,
Des Aubery
(adTherm Technology - www.adtherm.com - des@adtherm.com )
RE: radiators-Aluminum vs. copper
Updates:
1. "Heat-Transfer per Unit Mass [W/kg]" studies for Copper & Aluminium radiator fins - this term is known as "Specific Power". It is critical to the succesful designing of Next Generation Copper-Brass Brazed heat-transfer devices.
2. "Clad vs Particle Brazing Technology". A FAQ is being compiled by 'adTherm Technology' which will compare the two fundamental Automotive Heat-Device Brazing Technologies. This FAQ will be posted on www.adtherm.com during the next few days - it will seek to dispel many of the myths & current marketing hype regarding Aluminium & Copper-Brass brazing. Comments will be made on Nocolok, CuproBraze, Composite-Deposition technologies. This FAQ will be updated at regular intervals & comments would be welcomed.
Regards,
Des Aubery
(adTherm Technology - www.adtherm.com - des@adtherm.com )
RE: radiators-Aluminum vs. copper
If you compare the heat-transfer coefs. of NEW tubing, the brasses look great. But take a look at what happens after months/years of service in typical power plants-the brass gets fouled with sulfate/oxides, while Ti and SS stay fairly clean, and end up with better coefs.!
RE: radiators-Aluminum vs. copper
In Automotive Heat-Transfer Devices, the Copper-Brass units have to be protected externally (painted), otherwise the green/black products of corrosion make the product totally unsightly in service. The thinner the fin gauges have to be protected from corrosion.
For Aluminium, the products of corrosion are generally white & do not appear as unsightly.
For internal corrosion, Brass tubing has to rely on additives in the water-glycol coolant to protect it. Unclad Aluminium is also vulnerable to internal attack - & also depends on additives. Internally-clad aluminium tubes withstand corrosion well. Although, in general, it appears that Brass tubes have superior corrosion resistance to conventional Aluminium tubes. Long-life Aluminium tubes offer advantages, at a cost...
The cost implications of the additional painting process is not often accounted for by the new Copper-Brass Brazing technologies. It is a significant cost factor.
Des Aubery
(adTherm Technology - www.adtherm.com - des@adtherm.com )
RE: radiators-Aluminum vs. copper
RE: radiators-Aluminum vs. copper
RE: radiators-Aluminum vs. copper
Black paint will cause additional problems:
1. Acts as a small additional resistance to conductive heat-transfer ie. lowers heat-transfer performance;
2. Paint can clog the micro-louvers in the multi-louver fins, & will limit the designer's ability to create high-performance louvers... ie. lowers heat-transfer performance.
3. Paint never completely coats the centre sections of the core, leading to areas of higher corrosion potential for copper-brass radiators. (In fact unpainted copper-brass radiators last 30% longer than painted copper-brass units... interesting...)
This is where unpainted aluminium automotive heat-transfer devices are able to gain additional small performance increases...
Now, if only copper-brass radiators did not need to be coated...
Regards,
Des Aubery...
RE: radiators-Aluminum vs. copper
I appreciate your many contributions, but don’t fully agree on the painting:
1) Corrosion of Al can be worse than Cu in northern climes where salt is used to de-ice roads. Many Al radiators are painted.
2) Rather than the thick, gloppy paint that you describe, manufacturers use thin gloss [prettier & stays cleaner than flat black] black lacquer or polyurethane on radiators. E.g., GM Satin Black (SP139), a polyurethane. “Most engine paints are too thick for radiator use because they can interfere with the heat transfer and block airflow between the cooling fins. This factory-finish aerosol withstands high heat and is just the right gloss and thickness to match most OEM finishes, and is ideal for radiator applications. It is 550ºF (287ºC) chemical resistant.”
3) To avoid the incomplete coverage: “Electrophoretic coating, which is already widely used for auto components, enhances external corrosion protection by providing an even distribution of paint throughout the entire radiator, including all the innermost parts…Electrophoretic coating strengthens the radiator even further by providing maximum corrosion protection in every nook and cranny of the core with little or no addition to the overall weight of the radiator and negligible effect on heat transfer.” http://automotive.copper.org/no-flux.html
4) Maybe unscientific, but here “The [Al] radiator core was painted with a thin coat of flat black paint, the better to radiate some of the heat.” http://www.sandsmuseum.com/cars/seven/myseven/radiator/...
5) For balance: a totally pro-Al radiator site. Even they paint as part of detailing [to match OEM Corvette]: “Every replacement aluminum radiator sold today comes bare aluminum. To keep our product on the same level, we offer a lower cost 941 with a base price and option to detail the radiator for high level shows. All other models include detailing in the price. Detailing includes, painting the radiator a black semi-gloss epoxy base paint, stamping the GM part number and date code, Harrison label, ink stamp, and the correct aluminum drain valve assembly.” http://www.corvettepartsman.com/dewitt-faq.htm
RE: radiators-Aluminum vs. copper
Thanks for your reply... I will respond point-per-point below:
1) Salt-corrosion is certainly an enemy of any radiator - aluminium, or copper, no question...in USA, Russia, you name it...
Aluminium radiator manufacturers can use superior fins, which control the mode of corrosion a little better... The issue with paint, unless the part is completely dipped, is that some parts are not completely covered... these become preferentially-corroded...
Bare copper suffers the same fate... Salt is terrible stuff...
2)I am not refering to any specific paint at all... goop, or gloss, will ALL be subject to selective-coating, hence induced selective corrosion potential...
3) "Electrophoretic coating" - nice idea (works wonderfully), but WAY, WAY TOO EXPENSIVE... This idea was mooted by the ICA many years back, & still is, but the 'cost-penalty', in practice, proved to be way too prohibitive.
4) Radiation heat-transfer really only 'kicks in' at reasonably high temperatures - do the sums, if you don't believe me. For radiators, it has negligible effect & is not even considered by most serious designers of Automotive Heat-Transfer Devices... (I will do some basic calculations & post them to the board for your information...)
Regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com )
RE: radiators-Aluminum vs. copper
I would also like to update & an earlier posting you made regarding the CuproBraze Process & correct a number of your statements. (Please don't take offence, but I would like to set the record straight on a number of technical issues).
1. >>Quote: “CuproBraze is the name of a new manufacturing process for copper-and-brass automotive radiators. The process uses fluxless lead-free brazing..."
Answer: The CuproBraze Process is NOT a fluxless process, as a small amount of flux additives have to be included in the tube-to-header slurry/paste to prevent the 'de-wetting' phenomenon, & porous joints. In addition, the binders which burn off during the brazing process contribute to environmental load.
--------------
2. >>Quote: "to produce new thin-walled radiators that perform better than thicker-walled aluminum products."
Answer: In general, the CuproBraze radiator can only perform better than a 'poorly designed' Aluminium Radiator... despite all the marketing hype to the contrary...
--------------
3. >>Quote: "The new radiator was developed by the International Copper Association and produced initially by the Universal Auto Radiator Manufacturing Company. They are typically 30% to 40% lighter than traditional copper and brass models, can be made smaller than their aluminum counterparts, and can provide up to 30% less air-side pressure drop. The CuproBraze process also shortens manufacturing time and reduces production costs.”
Answer: Most of this information is from ICA marketing literature from a few years ago (1998/1999)... In practice, these original claims were never upheld in the real world. 'Universal Auto Radiator' is now bankrupt & no longer operates.
----------
4. Quote: “Cost-Efficient CuproBraze® Radiators Show Superior Durability in Road Tests..."
Answer: This claim is, in general, unsubstantiated in practice...
---------
5. Quote: "…In addition, CuproBraze radiators can be made smaller in size, or with significantly higher heat transfer efficiency than aluminum models. The CuproBraze process offers further advantages over standard aluminum radiators, such as greater fuel economy, lower air side pressure drop, lower cooling module costs and weight, and less parasitic engine losses….”
Answer: Again, these claims are, in general, unsubstantiated in practice...
----------------------
6. Quote: “Commercial Production of CuproBraze® Radiators Begins Over 90 different models to be offered in 2000
The CuproBraze® revolution in automotive radiators has begun. Universal Auto Radiator Manufacturing Co. in Pittsburgh, Pennsylvania, USA, became the first company in the world to begin full production of the new CuproBraze radiator."
Answer: Again, UAR is out of buiness (for almost 1 year, now)
--------------
6. Quote: "...the CuproBraze® alloy can be HF (high frequency) welded; ultrasonic weldability had been mentioned as an advantage for Al by Peter7307. See
“Berry Radiateurs Adopts CuproBraze Process and Begins Production”
Answer: HF welding of 85/15 CuproBraze Brass has a lower thickness of around 0.110mm. In many cases, this is not thin enough to save cost over an equivalent Aluminium tube.
--------------
7. Quote: "It appears that CuproBraze® has given Cu the competitive edge over Al in the radiator & HXer market."
Answer: This was the marketing hype we (me included) used to market CuproBraze in the early days. In practice, the expected results have, unfortunately not been achieved...
Regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - des@adtherm.com )
Best regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
>>Quote: I had heard something about adding a small elctrical charge to an aluminum radiator to prevent corrosion. I know that boat endines and gear often have a zinc plare bolted to them for a similar reason. How does this work?
DA: The zinc plate/block in a marine HX acts as a sacrificial anode which corrodes before the brass components are attacked. This is generally to stop de-zincification of the brass HX components... I have seen the effects of missing blocks & stray electrical currents in marine HX's - the brass tubes are destroyed in a few weeks... On a marine HX, the corrosion effect is more of an overall 'global effect' because the side of the HX subject to the most corrosion, is fully emersed in the sea water.
The small electrical charge to the aluminium radiator would be an attempt to try & prevent galvanic corrosion occurring... but, since, on a radiator, the galvanic corrosion occurs 'in local corrosion cells' it would be difficult to expect a 'globally applied' electrical current to sort this out. This is because the air-side of the radiator (most subject to corrosion) is NOT fully emersed in a liquid media - forcing the corrosion cells to be 'local cells'...
I hope that this explanation helps...
Best regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
So for now, just keep your cooling system full of 50/50 demin. water and a low-phos. silicate-free (and whatever else is new) antifreeze mix, and change it every 2-3 years or so.
RE: radiators-Aluminum vs. copper
I was refering to the air-side corrosion in my previous posting...
One must never forget that there are always two sides to protect.
Best regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
RE: radiators-Aluminum vs. copper
>>Qupte: Am I correct in thinking that the radiator should be electrically isolated to avoid corrosion? A manufacturer of racing radiators suggested to me that the radiator be grounded, but this doesn't seem right.
DA: I beleive that grounding could prevent 'stray current' passing through the radiator & causing additional electrical effects, over-&-above the galvanic effects already present due to the differing 'galvanic potentials' of the different metals used. Perhaps, it would also ensure that all parts of the coolant loop are at similar ground voltage...
The 'corrosion micro-cells' I was refering to occur due to local 'galvanic differences' between materials - eg. fin/braze/tube joint - all different. The differences will determine which material is preferentially corroded - on the airside of the radiator.
Best regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
On the other hand, if the radiator was well insulated from ground, it simply wouldn't be part of the circuit.
RE: radiators-Aluminum vs. copper
>>Quote: ...the source for stray current would be the block, with the coolant itself acting as an electrolyte.
DA: The block acts as a source of Zinc & is preferentially corroded. This prevents de-zincification of the INSIDE of Brass tubes of the radiator. The effect of this zinc block on the whole radiator/pump/head circuit - I haven't thought about...
As I said before, the zinc block idea works with great success in marine HX's - eg. oil coolers - with oil on the outside of the tubes - sea water inside the tubes... The velocity of flow in the entry section of the tube causes eddies which tend to erode this section of the tube... If the tubes are not protected, this activity seems to leach out the zinc very rapidly - hence the additional protective source of zinc block.
--------------
>>Quote: Current would end up finding ground through radiator if it was grounded. Any spot in the radiator that was slightly more anodic would tend to become the grounding point. I would expect the result to be one or multiple pinhole leaks.
On the other hand, if the radiator was well insulated from ground, it simply wouldn't be part of the circuit.
DA: In my experience with Aluminium radiator tubes, the vast majority of problems occur on the airside of the HX. (In Japan, some radiators are manufactured with double-clad tubes, for additional pitting protection of the tube internals. This is said to be because of the poor quality of Japan's water.)
For airside corrosion of radiators, with large grain sizes in the tubes, if pitting corrosion does begin, there is quick pin-holing of the tube... Thus, the fin material is selected to be sacrificial to the tube - preferably with a 'onion-peeling effect' of the fin (controlled corrosion), in such a way as to protect the tube. Hence the use of Zinc-rich aluminium fins.
On Aluminium condensers, the galvanics become crazy after brazing & the extruded tubes & manifolds can be quickly corroded, if suitable zinc-rich fins are not selected (at least this is my experience).
Best regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
Yes, as you said, I was only referring to the inside of the rad. I wrote my response when you were writing yours, but you hit the "send" button first. <g>
I wasn't aware of airside corrosion, but I can see why it could rapidly pit tubing. While driving along, the rad. is fairly hot, and in wet conditions there must be a lot of wetting and drying cycles. Such cycles concentrate all the harmful impurities like Cl, and corrosion rates can double for every 10 deg C (18 F) rise-if some other mechanism doesn't change things. So, at a rad. outside temp. of 80C the corr. rate *can be* 64 times faster than at 20C!
Also, for non-salt water internal use, Mg anodes are better than Zn for protecting Al. They will also protect Zn.
But if I were buying a RR or $$$ equiv., I'd want a nice Ti unit (and bigger is better!).
RE: radiators-Aluminum vs. copper
Thanks for your posting...
Wow... That corrosion rate is frightening - but it definitely occurs in practice. I have seen pictures of Russian uncoated Aluminium radiators after 1 season of operation in the Russian Winter - you can push your hand right through them... A total disaster - no wonder they began coating them...
Best regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
1) I had mentioned earlier the nasty effect of salt on Al radiators, a major factor in OEM’s having them painted. The effect of salt on copper and copper alloys is much less – saltwater evaporators often use Cu alloys rather than stainless steel.
2) Radiator mounts and straps include rubber for electrical isolation, to prevent galvanic corrosion with the steel frame.
3) An applied electrical charge to the outside of a radiator does no good (except when wet).
4) Neither a sacrificial anode (Mg or Zn) nor an applied cathodic electrical charge to the inside of a radiator will give much protection beyond a very limited area. The protection will not extend done the tubes (unless you can connect and run a network of anode wires down the tubes without shorting!). Perhaps you guys should do some electroplating and anodizing to learn how the current density drops off with distance inside holes.
5) Aluminum brazing actually comes closer to welding in terms of composition and temperature than other metals. There shouldn’t be much galvanic corrosion. CuproBraze® achieves something similar for Cu alloy – gets rid of the solder, which is both a mechanical and corrosion weak point (as I had also mentioned previously).
6) For protection of Al radiators exteriors, an alternative to painting is anodizing. Thinner and protective. Navy submarines use anodized radiators for liquid-to-seawater cooling. The anodize develops pits after about 1.5 years, then is ‘slow-stripped’ and re-anodized.
An automotive radiator given reasonable care should last the lifetime of the vehicle in normal usage. Additional washings will help where salt is used on the roads in winter.
RE: radiators-Aluminum vs. copper
Our units had been tested by many of the OEM's and the M.O.D. for performance, mechanical strength and corrosion without a problem.
It maybe that the Cupro-Braze suppliers saw a diminishing busines with the Copper/Brass/Lead materials both on cost and environmental issues and needed something to reinstate themselves into the market due to the defection to Aluminium by the majority of radiator producers.
Alot of the claims made for Cupro-Braze are ambiguous or generalisations which are little more than sales B.S. but I still believe that CB has a place in the market.
RE: radiators-Aluminum vs. copper
>>Quote:During my time running a Nocolock Brazing plant, non of our units were painted, all were supplied in the natural condition. The Nocolock flux provides a good anti corrosion barrier after the braze process. This coupled with the use of a layer of non corrosive aluminium on the inside of the tubes and headers ment we didn't suffer any major problems.
Our units had been tested by many of the OEM's and the M.O.D. for performance, mechanical strength and corrosion without a problem.
DA: This has been my typical experiences with both Nocolok & Composite Deposition (CD) Technology... The Nocolok wasn't perfect, but generally good enough for most applications. I believe that the painting is really only for the 'extreme' corrosion applications.
------------
>>>Quote:It maybe that the Cupro-Braze suppliers saw a diminishing busines with the Copper/Brass/Lead materials both on cost and environmental issues and needed something to reinstate themselves into the market due to the defection to Aluminium by the majority of radiator producers.
DA: Aluminium brazing entered that Automotive Heat-Transfer market with a superior product in terms of 'Specific Power' & advanced lightweight radiator designs. It was soon killing the sale of Copper & Brass radiator strip. The Copper producers & Strip Manufacturers (no names mentioned) felt that they had to counter this threat to their business... At that time it was basically considered that Aluminium would eventually 'kill' copper-brass radiators & that a 'brazing technology' for Copper-Brass had to be developed. The 'CuproBraze Technology' was originally developed in the USA by the ICA, in parallel with research being performed by the largest copper/brass radiator strip supplier in the world - in Sweden (again, no names). This process limped along for some 8 years, before I joined began assisting the Swedes as an Executive Technical Consultant... My brief was to build a team & to assist the comercialisation of the CuproBraze Process.
I travelled the world; built the team; generated Technology Vision; Technology Marketing Strategies; & then helped the Swedes to implement them - Asia was the main thrust of my endeavours. We had great success in interesting the Asian auto market.
In parallel with the marketing I pressed for rapid Technical Development in order to leapfrog the new technology ahead of Nocolok... We began to have success & then the internal politics & petty jealousies within the Swedish group became too much for me... I resigned, & we back to assisting them on a part-time consulting basis.
---------------------
>>>Quote:Alot of the claims made for Cupro-Braze are ambiguous or generalisations which are little more than sales B.S. but I still believe that CB has a place in the market.
DA: Absolutely true - they are ambiguous & always will be, because the real intrinsic Technical Capability behind the CuproBraze Technology is NOT WELL ENOUGH DEVELOPED... I had set forward clear Technology Roadmaps & Strategies that would pull it ahead of Nocolok - but the internal politics have basically slowed all USEFUL new developments to a grinding halt...
----------
This is why I started my new 'hi-tech' company - 'adTherm Technology' to serve as a technical sprinboard & to answer at a fundamental level if CuproBraze could ever seriously compete with Nocolok... My answer lies in my discoveries with the 'Specific Power' of the fins... See my earlier posts... Copper-Brass is not viable, unless 'radical' fin designs are used... it becomes far too complex...
IMHO opinion, CuproBraze does not have sufficient knowledgable technical resources to be able to adequately support the high-volume production of Copper-Brass HTD's - other than for a small number of factories - it is also beginning to lose ground to Aluminium again as far as costs are concerned...
Best regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
Your post made me think back a little harder to that corr. conf. You're correct, of course. What was being presented wasn't a CP system, but an electronic corrosion-potential *monitoring* system. Sorry for the brain-fade, hope it ain't perman--er, what's the subject again?
RE: radiators-Aluminum vs. copper
It seems that we have alot in common! I have been frustrated for years by the lack of research companies put into fin design, I'm convinced that the humble fin is the key to significant improvements. I can appreciate the concept of Fin Specific Power although not an academic myself I would be hard pushed to determine the figures. I have always been the man who makes fins "The Finman" and my motto has always been if you can dream it, I can make it.....
RE: radiators-Aluminum vs. copper
>>Quote: Hi Des
It seems that we have alot in common! I have been frustrated for years by the lack of research companies put into fin design, I'm convinced that the humble fin is the key to significant improvements. I can appreciate the concept of Fin Specific Power although not an academic myself I would be hard pushed to determine the figures. I have always been the man who makes fins "The Finman" and my motto has always been if you can dream it, I can make it.....
DA: The multi-louver fin design has the highest impact on the heat-transfer of Automotive Heat-Transfer Devices (HTD's). Current technology is essentially refined versions of a technology that was originally introduced around 50 years ago.
There all types of speculation about how these fin work - what factors are important - louver angle, louver pitch, fin thickness, fin height, louver length, fin pitch... you name it... How to link these all toghether to provide optimum designs - most folks have absolutely no clue...
The reason - it is impossible to find small-enough temp sensors to insert into these tiny spaces, to accurately profile the air temperatures within the fins.
This is the reason I have developed the 'Virtual Wind-Tunnel Concept' at adTherm Technology... It is to allow designers to test proposed fin designs, & to predict the performance... It entails a combination of CFD & proprietary software to map the flow regime within the fins themselves... Take a look at the adTherm website (www.adtherm.com) for a sneak preview of the next generation of design tools...
Best regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
Here is what I found:
3 core copper/brass cooled well at speed, not well at idle
4 core copper/brass cooled better at idle, but worse at speed than the 3 core
Single (1.25") core aluminum, cooled OK at speed and not well at idle
2 core (1.25"X 2) aluminum cooled extremely well at speed, and a bit better at idle than the single core.
I would rate them this way:
At speed from best to worst 1. two core aluminum 2. 3 core copper/brass 3. tie between single core aluminum and 4 core copper/brass
At idle from best to worst 1. 4 core copper/brass 2. tie between 2 core aluminum and 3 core copper/brass 3. Single core aluminum
The results lead me to believe that how the tubes and fins are laid out, and how dense they are, make more difference than what they are made of. The radiators that had the lesser resistance to airflow, because of less fins and/or thickness, did better at speed because they allowed more airflow through the radiator. The radiators that did best at idle, had more fins and/or thickness, that could dissipate the heat better at the low airflow rates at idle.
The aluminum radiators use big tubes and wider spacings of tubes and fins, so they can allow a lot of air through. If you can supply the air, they will cool extremely well. The copper brass use smaller tubes (burst strength issues) and high density finning, so they perform better at lower airflow rates, but you can't put enough air through them to get bigtime cooling.
My final solution was to use the 2 core aluminum radiator, which gave outstanding cooling at speed. To address the idle heat up issue, I made a pulley that would spin the fan at 1.3 times the speed I had, and added a viscous clutch to get rid of the added drag at speed. The extra airflow made the aluminum 2 core out perform all the others at idle.
If radiator manufacturers start telling you they cool "X" amount better than the competition, be sure to ask them what they are running for airflow velocity and static pressure drop though the radiator, and at what heat dissipation rate they are operating (to simulate idle, cruise, full power etc). Most either don't know, won't tell, or don't care because the numbers they are giving are bogus.
RE: radiators-Aluminum vs. copper
turbododge, ‘shoehorning’ in an oversized engine created a greater cooling demand while simultaneously reducing airflow. In any event, your considerable industriousness shows that the engine and radiator have to be integrated into the overall vehicle design. A bigger radiator won’t help without increased air and coolant flow (presume your water pump speeds up with the fan). Two questions: 1) Have you done any sheetmetal work to direct air toward the radiator and out of the engine compartment? 2) Were your copper+brass radiators the conventional soldered type?
Maybe radiator salesmen don’t have much technical info, but I am certain that the radiator and vehicle mfrs. do have the ‘real numbers,’ e.g., per SAE J819 Engine Cooling System Field Test (Air-to-Boil), J1393 On-Highway Truck Cooling Test Code, J1994 Laboratory Testing of Vehicle and Industrial Heat Exchangers for Heat Transfer Performance, J1542 J1994 Laboratory Testing of Vehicle and Industrial Heat Exchangers for Thermal Cycle Durability, J2082 Cooling Flow Measurement Techniques, etc.
An interesting thread.
RE: radiators-Aluminum vs. copper
The grill inlets are pretty good as stock, no big bypasses, etc, and a big chin spoiler pushes the air in very well when moving. I do have a full fan shroud on it, and did a lot of experimenting with fan position in the shroud to maximum flow through the radiator without any backflow, which was initially a big problem. (ended with only 3/8" of the fan inside the shroud).
When I sped up the fan, yes, the waterpump also sped up. To prevent the pump from cavitating, I was able to find a pump with a smaller impeller that was designed to run at the speed I went to, while moving the same amount of water as I had with the old setup. I had guessed that I was moving plenty of water, and that proved to be true.
The copper/brass radiators were the standard soldered construction with high density fin count.
We now can idle in traffic all day in 100*F temperatures with never going over 190* coolant temperature.
RE: radiators-Aluminum vs. copper
>>Quote:The results lead me to believe that how the tubes and fins are laid out, and how dense they are, make more difference than what they are made of. The radiators that had the lesser resistance to airflow, because of less fins and/or thickness, did better at speed because they allowed more airflow through the radiator. The radiators that did best at idle, had more fins and/or thickness, that could dissipate the heat better at the low airflow rates at idle.
>>Quote:The aluminum radiators use big tubes and wider spacings of tubes and fins, so they can allow a lot of air through. If you can supply the air, they will cool extremely well. The copper brass use smaller tubes (burst strength issues) and high density finning, so they perform better at lower airflow rates, but you can't put enough air through them to get bigtime cooling.
--------
DA: The thermal performance of a radiator Heat-transfer & pressure-drop with increasing airflow is TOTALLY determined by the design of the multi-louver fins... One can design either aluminium or copper-brass to perform in very similar ways ie. performance curves.
The main issue is that very, very few radiator designers really know how to properly optimise the units.
A lot of what you get from aftermarket suppliers is really - 'suck-&-see' - leaving the testing up to the user. The large Automotive First Tier Suppliers will generally design a radiator to suit a particular performance - based on 1 or more 'performance points', or an 'index'.
Issue about 3 vs 4 row radiators:
In general, you can expect to see very little, if any, performance gain under vehicle operating conditions by adding the 4th row. The reason is that the cooling air has already almost reached its maximum temperature by the end of row 3, & there is then very little 'temp driving force' left for row 4...
------------
>>Quote:If radiator manufacturers start telling you they cool "X" amount better than the competition, be sure to ask them what they are running for airflow velocity and static pressure drop though the radiator, and at what heat dissipation rate they are operating (to simulate idle, cruise, full power etc). Most either don't know, won't tell, or don't care because the numbers they are giving are bogus.
DA: Try & obtain heat-transfer/pressure-drop performance curves against air-flow & water-flow... These will come from the manufacturer's wind-tunnel tests... If they can't produce these curves for you, be suspicious of claimed performance...
Best regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
RE: radiators-Aluminum vs. copper
I guess costs start to escalate when you look at the conveyor types of furnace and the sealing systems to hold in the nitrogen. also, the recirc fans in our furnace seemed an extortionate price when we had to buy replacements.
Another one for the sharp intake of breath is, Our furnace line cost a £1000 ($1500) the second you hit the "Go" button and needed 3 hours to heat up from it's idling temp.
Its an expensive game to get into but the rewards, if you can keep feeding the furnace, are incredible.
RE: radiators-Aluminum vs. copper
>>A question, if I may. What makes a cuprobraze furnace so special that one
>>needs to pay half a million dollars for one?
>>finman:
>>I have no idea, although I paid £400k ($550-600K) for a Nocolock furnace
>>>for brazing aluminium rads.
adTherm:
To braze either Copper-Brass (CuproBraze), or Aluminium (Nocolok), a CAB-type inert atmosphere furnace is required.
In order to maintain a low Oxygen value, & so prevent oxidation during the brazing process, very pure Nitrogen has to be 'stuffed' into the furnace at various points. The oxidation can occur both during the 'heat up phase' where the product temperature is raised from ambient, to brazing temperature, & during the 'brazing phase'.
For Aluminium (Nocolok), oxidation during the 'heat up phase' is not really a major consideration. Before the brazing temp is reached, the flux melts & prepares the surfaces for melt-alloy flow - removes material oxides & wets the material surfaces to enhance melt-alloy flow. After brazing, the flux solidifies & provides a protective layer against oxidation.
For Copper-Brass (CuproBraze), oxidation during the 'heat up phase' is a real problem. If too much oxygen is present with simultaneous application of heat, then a black oxide is formed. This leaves the fins looking dirty. Prior to reaching brazing temp, the binders in the 'paste' essentially form a 'fluxing gas' & partially shield the joint during brazing. If too much oxygen is present during the brazing process, then the powder oxidises & will not melt - it becomes inactive.
The net effect of the above-mentioned oxidation sensitivities is that Nocolok products can be brazed with an oxygen content of >50 ppm, in the brazing atmosphere, whereas CuproBraze needs to be kept closer to 20 ppm, otherwise major problems can occur.
To achieve these low oxygen values, experience has shown that CuproBraze now requires far more Nitrogen than an equivalent Nocolok furnace, for the same throughput. (We did not expect this at the beginning of the project.)
Thus, the ongoing running costs of a CuproBraze Furnace will be higher than for Nocolok - in terms of Nitrogen consumption.
-------------------
>>finman:
>>I guess costs start to escalate when you look at the conveyor types of
>>furnace and the sealing systems to hold in the nitrogen. also, the
>>recirc fans in our furnace seemed an extortionate price when we had
>>to buy replacements.
adTherm:
Cuprobraze lends itself to using simpler furnaces than Nocolok, since Nocolok temperatures have to be very accurately controlled as brazing temperature is approached. CuproBraze is less sensitive due to the larger gap between melting temp of braze powder (589-600'C) & brass melting temp (~980'C) - whereas for Nocolok the cladding melts at 577'C, & base aluminium at ~ 660'C... a much narrower 'brazing window'.
In this case, CuproBraze can use 'muffle-less furnaces' hence reducing manufacturing costs somewhat. But, most manufacturers have opted for 'Nocolok-style' furnaces, just in case they have to switch back to Nocolok Production if their Cuprobraze products are not accepted in the marketplace.
---------
adTherm:
The issue of the 'style' of furnace - Convection vs Radiation - will play more of a part in the initial costing of a furnace. The choice will depend on the types of product the fabricator chooses to manufacture.
--------
>>finman:
>>Another one for the sharp intake of breath is, Our furnace line cost
>>a £1000 ($1500) the second you hit the "Go" button and needed 3 hours
>>to heat up from it's idling temp.
>>Its an expensive game to get into but the rewards, if you can keep
>>feeding the furnace, are incredible.
adTherm:
You obviously have a large furnace to feed. A smaller, batch-type, or semi-continuous-type furnace is more flexible in terms of load-scheduling. The main cost is then to keep the furnace hot - with the part heat-up load only coming when you actually braze parts. These furnaces are designed to 'feed & braze' as required.
Regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
In the early days of starting our Brazing plant we could assemble for a week and braze the whole lot during 1 day! Our assemblers were not slow but the furnace, once upto operating temp was hungry.
Our Furnace included Thermal degrease, Airblast cooling section Fluxing, Pre-heat/nitrogen purge, The Furnace, Controlled quench and final airblast cooling section all in a single line. Excellent piece of kit if you had the work for it.
Load scheduling was not a major problem but we had to be mindful that we started on the heavier components first always followed by lighter and lighter components
RE: radiators-Aluminum vs. copper
Your furnace sounds like the classic case of a system oversized for large-scale production volumes. These huge beasts cost so much money just to heat up... frightening...
Companies have been developing more flexible furnace systems eg. Seco-Warwick's 'Active Only' furnace which takes parts as they are fed in - large/small up to you... the control system takes care of the load variations...
Your work-around by loading heavy components first allowed the furnace to settle in on these large, heavy loads - incrementally backing off to smaller, lighter loads helps to maintain furnace stability...
(I have been working on a 4-zone radiation furnace simulator - with very interesting results... explains a lot of things about the system dynamics).
Regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
Most of our work was for Off-road and Static applications all big cores.
Furnace line worked well whilst controlled by lucid types, not so well under the Production dept.
RE: radiators-Aluminum vs. copper
These Furnaces are very sensitive systems (a definite feminine side exists) & have to be pampered by very smart Technologists - especially for large cores.
Once the Production Dept get hold of the Furnace, then things always start to drift... I wonder why?
Regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
Apart from not having the proverbial few hundred thousand clams in my pocket, I am curious whether a different brazing compound/alloy can be employed to create a similar output.
Is there any other way to "cuprobraze" cores without the need for an atmosphere controlled furnace?
RE: radiators-Aluminum vs. copper
>>Is there any other way to "cuprobraze" cores without the need for an atmosphere controlled furnace?
adTherm:
Not a chance, I'm afraid... Without a modified atmosphere & low Oxygen, you will never braze... you will have a dirty, oxidised core + oxidised brazing powder.
In terms of other alloys - none really can be used at temps low enough to prevent the black oxide formation I mentioned in my previous post - without atmosphere control.
You can make a small batch furnace - but it must be 'back-filled' with Nitrogen.
I performed some previous trials using an addition of Hydrogen, & hydrogen/nitrogen mixtures - good stuff... but you need the correct binder pack. Current CuproBraze Technology does not support that option - unfortunately.
Regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
I'm wondering why you wouldn't wish to use CAB to braze, if you're genuinely going to build your own furnace why not go with a tried and trusted concept? that way you will have something to go on.
Mr Adtherm may be able to offer something different??????
RE: radiators-Aluminum vs. copper
>>Mr Adtherm may be able to offer something different??????
adTherm:
If you only want to do a few prototypes, then there are simple 'Development Boxes' - if you are seriously looking into a small 'batch type furnace', then I would be more than happy to advise you - it is definitely possible... just email me... we can talk 'off-forum'
The trick lies in the oxygen control. Ironically, Aluminium has turned out to be less sensitive than CuproBraze in what oxidation it can tolerate - we can use a few tricks
Regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
RE: radiators-Aluminum vs. copper
>>How about having a decontamination bath post baking?
You won't be able to remove the black oxide that way - it will be ghastly. You have to see it to believe it. As a test, put your radiator through a friend's furnace without the Nitrogen turned on - you will be shocked...
In addition, your radiator WON'T be brazed... the powder oxidises & does not melt... it just falls off...
Regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
I wonder why a friendlier brazing alloy wasn't made. I've been corresponding with some people who say that they may be able to develop a brazing compound that does not require fluxing nor an atmosphere controlled furnace. Lost their email when my system crashed.
You got mail adTherm.
RE: radiators-Aluminum vs. copper
Messrs Adtherm & TNT2bluz, I would appreciate being kept "In the Loop" if you do not have a problem with this.
I'll drop my e-mail over to Adtherm, you never know I may be able to assist!.
RE: radiators-Aluminum vs. copper
We actually are a notch above that by converting a bakery used for making salted breakfast buns oven into a furnace. :P
RE: radiators-Aluminum vs. copper
Beware that the materials used in the oven are capable of the higher temps used for brazing, (the recirc fans on our furnace where made from inconel!)
When doing trial runs at another company we used Nitrogen supplied in a road tanker that was equiped with a small regenerator, I must admit to being sceptical when I saw the set up but it all worked fine for the trial period.
RE: radiators-Aluminum vs. copper
RE: radiators-Aluminum vs. copper
Regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
RE: radiators-Aluminum vs. copper
( standard 2.5 ltr non turbo diesel) with a Holden/Buick 3.8 ltr v6 petrol in doing so we retained the original radiator( recored as new of course)fitted a 14 in Thermo fan
( standard Transit was engine driven standard Holden is electric) the problem we have is that the Holden Parameters are 82deg C open thermostat 102deg C fan starts and whilst gentle highway running will see the engine sit at 96-98 deg C heavy use or towing bring it up to 110C straight away with little recovery on lite throttle periods. my next option is a thermostat controlled electric water pump allthough my thoughts are that this will not give a final solution. could any of you give me some advice or a site where I might be able to work out the thermal effectiveness of the standard Holden/Buick unit compared to the Transit one.
Thanks
Ric
RE: radiators-Aluminum vs. copper
Can you supply further details of the rad you've got fitted? ie face dimensions and number of tube rows.
Also before you go spending a small fotune on cooling the beast further have you tried either moving the rad? possibly downward ( a couple of inches can make a big difference!) or trying to duct the airflow into the rad a little more efficiently than good ol' Henry.
You don't say which Mk of Transit you're modifying but I know from experience that one of the models had cooling problems from lack of air flow due to bodywork.
I'm assuming that Buick/Holden means Rover for us UK bods so I'd start checking your motor before going too far as they're not mega hot runners.
RE: radiators-Aluminum vs. copper
Regards
Ric
RE: radiators-Aluminum vs. copper
Rule of thumb says it should all work fine but obviously doesn't......
Have you tried looking for air locks in the coolant side? usually up around the heater core.
If you havn't already done it, try "back flushing" the block, it may be worth popping a core plug to make sure the the motor hasn't got full of old dirt in the coolant passages.
I'm not the academic expert with the slide rule so I can't help with that side but, I used to work for a big UK aftermarket rad company so I've come across this sort of problem before.
RE: radiators-Aluminum vs. copper
How does the fuel consumption compare?
Do you usually accelerate more quickly with the new engine? Or drive at higher speeds?
Cheers
Greg Locock
RE: radiators-Aluminum vs. copper
Improving airflow will improve cooling.
Agree with finman's suggestions re ducting, etc.
A fan shroud will help.
Also, try to improve flow out of engine compartment at rear of hood/base of windshield.
Remove the thermostat (re-install for winter season).
Another idea (for belt driven fan/water pump): Reduce the driven pulley size to speed up the fan and pump (or increase the drive pulley diameter).
RE: radiators-Aluminum vs. copper
The bigger/wider engine may restrict airflow out of the engine compartment.
Another thing I didn't see mentioned is: make sure that cooling air can't recirculate from the hot side of the radiator to the cool side. (many vehicles have a baffle or 'spoiler' along the lower edge of the radiator.)
Depending on the electric fan installation arrangement and diameter, you may not be pulling air through the entire core- most engine-driven fans are fitted with a shroud to pull through the entire area of the radiator. Many front-wheel-drive cars mount the fan right against the radiator and only the circle described by the fan sees the airflow.
Greg's comments regarding engine size and efficiency were good, but I expect that a cooling system that will handle the original engine at full power should at least recover the V6 (from high temp down to normal) under light load!
Jay Maechtlen
RE: radiators-Aluminum vs. copper
I have taken all your thoughts on board and may now proceed to fit some "full sick" vents in the bonnet if all else fails or maybe a few large washers under the hinges at the back like the weelly fast race cars had in the sixties. In all seriousness I`ll look at the baffle idea, I can`t see that changeing the pump speed will help but I might try it out or even use the electric pump as a test as it is speed/flow variable. I have all but commited myself to the larger core idea and with some judicious placement of ally tape I`ll make sure every scrap of available wind passes through the core as well as mounting a second thermo fan. Don`t you just love those "yeah mate it bolts straight in" jobs especially when they include the "don`t change the rad its plenty big enough just get it recored" so of course you do that so its ready when you fire up the new engine and proceed to p.... a couple of hundred up against the wall.
I`ll let you know the results
Ric
RE: radiators-Aluminum vs. copper
Not all re-cores are the same... The difference in performance between 'good fins' & 'bad fins', for the same-sized core geometry, is significant.
Regards,
Des Aubery...
(adTherm Technology - www.adtherm.com - info@adtherm.com)
RE: radiators-Aluminum vs. copper
The idea of proper ducting both in and out is GOOD (mandatory in most cases). Sealing up the area around the rad to correct any reverse flow tendencies is GOOD. Electric fans can SOMETIMES help but they "suck" better than they "blow" (a properly ducted mechanical fan is usually more efficient but uses more hp to do it). Taking the T-stat out without using some sort of flow restriction is BAD (can increase cavitation due to loss of pressure build up and decrease dwell time in the rad). Jacking up the back of the bonnet without proper consideration for the HUGE stagnant area at the base of the windscreen is BAD.
Speeding up the fan/waterpump can cause excessive cavitation and result in a worsening condition---BAD.
Often slowing the pump down will give improved cooling via reduced cavitation and increased dwell (dubious as I have had mixed results from "dwell time" experiments, but I had to put it in) time in the rad. I have often found that multiple core rads are worse than single or double core/large tube rads mostly due to airflow restrictions in the four or five core units that were the hot setup in the 50's and 60's. Any good core mfgr can give you the heat rejection/hp capability of their products. Pull up some of their sites, especially the mfgrs in the SouthEast U.S. that do stock car (NASCAR) rads as they are pretty much cutting edge these days. Like I said last year, I have a LOT of experience in what does NOT work!!!
Rod
RE: radiators-Aluminum vs. copper
RE: radiators-Aluminum vs. copper
I have a 1983 Mercedes 240D Manual Transmission. Cooling is not much of an issue, even here in New Orleans. Neither is salt :)
The radiator is saved the thermal load of an automatic transmission oil cooler.
The prior owner abused the radiator (not OEM) and I have the choice between a Behr/Valeo plastic tank w/Al or a Nissens plastic tank w/Cu radiator.
I am careful with maintenance. Which one will last the longest in my application. (I want at LEAST another dozen years). I am leaning towards the Danes.
BTW: I run a mix of 55% ethlyene glycol, 15% propylene glycol and 30% distilled water. Very close to optimum for heat transfer/volume. Also low corrision potential.
Alan
RE: radiators-Aluminum vs. copper
are you sure it is plastic with Al?
mine is plastic with tin plated copper.
two things to throw into the discussion.
1. many people see shiny silver radiators and assume they are Al, many of these are tinned copper. tin plating eliminates the need to paint radiators, gives near perfect corrosion resistance, and is very thermaly conductive.
2. a lot of people seem to compare current high tech Al radiators to oem units from the 60's and 70's and assume that Al must be better than copper.