radiators-Aluminum vs. copper 6

[JayMaechtlen]

What are the pros and cons of Aluminum ratiators versus brass radiators?



Jay Maechtlen

 

[Metalguy]

Obviously Al rads are much lighter for the same heat transfer, but corrosion can be a problem. Al rads are harder to repair.

 

[shabba]

...corrosion and also I beleive aluminium is more prone to fatigue?

 

[JayMaechtlen]

Thanks-
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

 

[dbur7]

The effectiveness of the radiator is complicated and dependent on many parameters. Basically heat must transfer from the coolant to the pipes to the fins to the air. I think that you will find that the conductivity of the solder between the pipes and fins in a brass -copper radiator is much less than in an al radiator. This is why Al radiators are more effective; and not the relative thermal conductivities of the two materials. thermal conductivity of copper > al > brass

 

[Chumley]

Aluminum radiators, especially with plastic tanks, tend to
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

 

[romke]

the pro's of al radiators lie in lower weight and nowadays lower production costs when produced in large quantities. another consideration might be that when you have an al-engine you don't have a potential between radiator and engine that could promote corrosion due to different materials. these pro's are mainly of concern to the carbuilder. as chumley remarked: they are somewhat more critical to the use of the correct coolant. modern low-silicate coolants are preferred nowadays. these coolants are actually corrosive themselves - the idea is that they coat all aluminum parts with a thin layer of aluminiumoxide and so create a stable environment where no further corrosion takes place - and so a lifetime coolant is born that does not create a waste problem as long as the car is onthe road.

 

[Peter7307]

One other point not mentioned thus far is the obligation incurred by the makers to have as many easily recyclable components as possible in the cars.

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.

 

[kenvlach]

The competition of aluminum radiators has spurred the development of a more efficient (both thermally and production-wise) and more durable copper radiatior. Note that CuproBraze® eliminates the use of solder, which is both a corrosion weak point and an efficiency limiter as mentioned by dbur7. Solder is also deleterious for recyclability, as mentioned by Peter7307. Plenty of Internet info, search for CuproBraze.

“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

 

[kenvlach]

A summary of the technical advantages of CuproBraze® vs. Al radiators, with data and graphs, is at

http://automotive.copper.org/no-flux.html

 

[zipfast]

To answer your second question a 1 core Aluminum rad will cool as good as a 3 core copper/brass.
My 2 cents worth, not the full $10.95 version.

 

[evelrod]

zipfast, that is a pretty broad statement. Got any FACTS to back it up?
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

 

[daubery]

Hi all,

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 very cunningly

($/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.

 

[daubery]

Hi all,

This message is to let you know that there are a few new papers available for download on

http://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 -

http://www.adtherm.com

- des@adtherm.com )

 

[daubery]

Hi all,

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

http://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 -

http://www.adtherm.com

- des@adtherm.com )

 

[Metalguy]

There is one other factor that can completely blow away many arguments-one that the Cu/brass merchants used against the Ti industry for "very large" shell and tube condensers.

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.!

 

[daubery]

Hi 'Metalguy',

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 -

http://www.adtherm.com

- des@adtherm.com )

 

[Metalguy]

Interesting. Just for the record, in the mid-1960's at least small-block Vettes had lightweight Al rads., while the big-blocks got bigger and heavier brass/copper ones.

 

[ZoRG]

Another spin on the whole thing is that painting the copper black gives it even better cooling abilities, as black is the color that dissapates heat best. I don't know if it will make a noticable difference though.

 

[daubery]

Black paint will really only benefit 'radiative heat-transfer' by providing a better suface emmissivity... In automotive heat-transfer devices, the conduction & convection dominate the heat-transfer (radiative HT is essentially neglected).

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...