CuproBraze radiators were shown to be fully competitive with the brazed aluminum. These data are shown in the table below.
|Radiator Core:||Brazed Aluminum||CuproBraze I*||CuproBraze II*||CuproBraze III*|
|Header Width, mm||432||432||432||395|
|Tube Length, mm||550||550||485||505|
|Fin thickness, mm||0.114||0.038||0.038||0.038|
|Tube Wall Thickness, mm||0.381||0.127||0.127||0.102|
|Dry Core Weight, kg||1.67||1.9||1.79||1.56|
|Wet Core Weight, kg||2.04||2.33||2.17||1.89|
|Coolant Pressure Drop, kPa||4.75||3.31||2.89||4.75|
|Air Pressure Drop, kPa||0.307||0.216||0.307||0.307|
|*CuproBraze I – Lower air pressure drop, same size, heavier.|
*CuproBraze II – Same air pressure drop, smaller, slightly heavier.
*CuproBraze III – Same air pressure & coolant drop, smaller & lighter.
CuproBrazeI, designed to have the same frontal area as the aluminum radiator, has 30% lower air pressure drop but is slightly heavier. CuproBrazeII has the same air pressure as the brazed aluminum model, but is smaller in size. CuproBrazeIII combines a smaller frontal area and thinner tube walls to achieve distinct advantages in both size and weight. All four of these radiator cores have the same cooling capacity (168,000 BTU/hr) and fin depth. Their weights include fin and tube material only. This work has shown conclusively that a much lighter copper/brass radiator is possible. In addition to replacing the lead solder by a brazed joining system, tube touching design and compact core designs were among a number of innovations that reduced the weight of the copper/brass system.
It has only been in the last ten years, long after the aluminum system had its foothold on the market, that any serious thought was given to improving the joining system used in the manufacture of the copper/brass system; after all, the lead-tin solder is heavy, it tended to fail by creep at the tube-to-header joints causing leaks, and it was vulnerable to corrosion on the coolant side. This was known as “blooming” corrosion because of the voluminous lead corrosion product that often resulted in tube blockage. Environmental concerns about lead in the air in manufacturing plants and radiator repair shops also posed problems. And corrosion of the copper fins in industrial environments was another problem that required attention if the system were to be competitive.
The cost issue is nowhere near as large as the difference in copper cathode and aluminum ingot prices would suggest, because radiators are made from strip materials, not from cathode or ingot. The aluminum tube strip is a complex composite of two or three layers; these provide structural support, a brazing alloy layer and often a sacrificial inner layer to control coolant-side corrosion. The brass tube and copper fin materials are simple homogenous materials.
Consequently, the copper/brass radiator strip materials have actually been less costly than the aluminum strip, as shown below.
That left the joining and corrosion issues. In 1988, the International Copper Association launched an effort to develop an entirely new copper/brass radiator system that substituted brazed construction for the lead-tin solder. An electrophoretic coating system for external corrosion protection familiar to the auto industry, cost effective, and having negligible impact on heat transfer, was developed and proved effective in on-the-road tests. A laser welding system for production of brass tube was developed. The brazing alloy is a self-fluxing Cu-Ni-Sn-P alloy not relying on silver or other expensive materials. Brazing is done on this copper system using no flux and at the same temperature the aluminum radiator is brazed allowing brazing furnaces now used for aluminum radiators to be used for the new brazed copper/brass radiator. New anneal-resistant brass and copper fin alloys were developed.
Original equipment and aftermarket radiator manufacturers all over the world are involved in testing this new system. At long last the copper industry is addressing this market with the hard work and creative thinking required for success. Assuming the industry has the patience and capacity for follow through required, the picture some ten years from now could be that the new copper/brass system has recaptured some of the lost market share and has established an equilibrium with its aluminum competition in original equipment automobile radiators. This would further assure that copper/brass radiators would continue to be a component of the scrap stream. But this new radiator, showing up in the scrap stream possibly 15 or so years from now, will be a different product. It will be lead-free and will thus be a more versatile scrap product not limited to use in copper alloy castings as is the present copper/brass radiator.