CuproBraze is a copper-alloy heat exchanger technology for high-temperature and pressure environments such as those in modern diesel engines.Vehicle radiators: Can CuproBraze turn copper into a bona fide contender?; American Metal Market September 2008; http://dl.dropbox.com/u/46572847/Perspectives-radiators.pdfPartanen, Juho (2011). Hot property: Heat exchangers that optimize product reliability, decrease lifecycle costs and improve profitability are just the ticket for increasing the lifespan and performance of off-highway machinery; Industrial Vehicle Technology; March 2011; http://viewer.zmags.com/services/DownloadPDF The technology, developed by the International Copper Association (ICA), is licensed for free to heat exchanger manufacturers around the world.
Applications for CuproBraze include charge air coolers, radiators, oil coolers, climate control systems, and heat transfer cores.Duensing, Lauren (2006) Develop efficient heat-transfer systems, Modern Metals, March 2006. CuproBraze is suited for charge air coolers and radiators in heavy industry where machinery must operate for long periods of time under harsh conditions without failures. The technology is intended for off-road vehicles, trucks, buses, industrial engines, generators, locomotives, and military equipment. It is also used for light trucks, SUVs and passenger cars with special needs.Asia Hot on New Cooling Technology: Cooling Systems: New engine requirements mean manufacturers are changing to copper and brass for cooling systems; Automotive Engineering International, February 2005CuproBraze: Advanced heat-exchanger technology "With special needs" makes passenger cars sound like they're children or people.
Compared with previous heat exchanger models CuproBraze creates new materials for heat exchanger parts that have previously been made of soldered copper/brass plate fin, soldered copper brass serpentine fin, and brazed aluminum serpentine fin to suit more demanding applications. Aluminum heat exchangers are viable and economical for cars, light trucks, and other light-duty applications. However, they are not amenable for environments characterized by high operating temperatures, humidity, vibration, salty corrosive air, and air pollution. In these environments, the additional tensile strength, durability, and corrosion resistance that CuproBraze technology provides are useful.
The CuproBraze technology uses brazing instead of soldering to join copper and brass radiator components. The heat exchangers are made with anneal-resistant copper and brass alloys. The tubes are fabricated from brass strip and coated with a brazing filler material in form of a powder-based paste or an amorphous brazing foil is laid between the tube and fin. There is another method of coating the tube in-line on the tube mill. This is done using the twin wire-arc spray process where the wire is the braze alloy, deposited on the tube as it is being manufactured at 200-400 fpm. This saves one process step of coating the tube later. The coated tubes, along with copper fins, headers and side supports made of brass, are fitted together into a core assembly which is brazed in a furnace.Cuprobraze overview:
The technology enables brazed serpentine fins to be used in copper-brass heat exchanger designs. The benefits include tougher joints.
Performance properties CuproBraze has better than other materials in several aspects, as shown in the table below.
Property Unit Cu fin Brass tube Al fin Al tube Stainless Steel Density g/cm3 8.95 8.53 2.75 2.75 7.8 – 8 Thermal conductivity W/m °C 377 (120) 222 (160) 3 – 24 Tensile strength, room Temp MPa 330 435 40 145 > 485 Tensile strength, 260 °C MPa 270 290 31 69 > 475 Thermal expansion μm/m °C 16.5 19.9 23.6 23.6 11 – 19 Specific heat J/kg K 377 377 963 963 500 Melting temperature °C 1083 915 643 643 > 1400 Safety margin in brazing (against core melting) °C 300 300 30 30 350
Thermal performance The ability to withstand elevated temperatures is essential in high-heat applications. Aluminum alloys are challenged at higher temperatures due to their lower melting points. The yield strength of aluminum is compromised above 200 °C. Problems with fatigue cracking are exacerbated at elevated temperatures.Elevated temperature operation - Meeting the high temperature challenges of new generations of charge intercoolers (design criteria series): http://www.cuprobraze.com/pdf/temperature.pdfCuproBraze: Thermal performance (Technology Series): http://www.cuprobraze.com/documents/2Thermalperformance.pdf CuproBraze heat exchangers can operate correctly under temperatures of 290°C and above. Anneal-resistant copper and brass strip ensure that radiator cores maintain their strength without softening, despite exposures to high brazing temperatures.
Heat transfer efficiency Cooling efficiency is a measure of heat rejection from a given space by a heat exchanger.CuproBraze Efficiency (Design Criteria Series): http://www.cuprobraze.com/pdf/Efficiency.pdf The overall thermal efficiency of a heat exchanger core depends on many factors, such as thermal conductivity of fins and tubes; strength and weight of the fins and tubes; spacing, size, thickness and shape of fins and tubes; velocity of the air passing through the core; and other factors.
The main performance criterion for heat exchangers is cooling efficiency. Heat exchanger cores made from copper and brass can reject more heat per unit volume than any other material. This is why copper-brass heat exchangers generally have a greater cooling efficiency than alternate materials. Brazed copper-brass heat exchangers are also more rugged than soldered copper-brass and alternate materials, including brazed aluminum serpentine.
Air pressure drop is a factor of heat exchanger design. A heat exchanger core with a smaller air pressure drops from the front to the back of the core (i.e., from the windward to the leeward side in a wind tunnel test) is more efficient. Air pressure drops typically are 24% less for CuproBraze versus aluminum heat exchangers. This advantage, responsible for a 6% increase in heat rejection, contributes to CuproBraze's overall greater efficiency.CuproBraze: Size - When the advantage in efficiency is equivalent to a smaller-sized core (design criteria series): http://www.cuprobraze.com/pdf/Size.pdfCuproBraze: Efficient, durable, sustainable, CuproBraze heat exchanger (brochure): http://www.cuprobraze.com/documents/EfficientdurablesustainableCuproBrazeheatexchanger.pdf
Since copper's thermal conductivity is higher than aluminum, copper has a higher capacity to dissipate heat. By using thinner material gauges in combination with higher fin density, heat dissipation capacity with CuproBraze can be increased with air pressure drops still at reasonable levels.
Size Due to its high heat transfer efficiency, CuproBraze has an efficient heating effect. This is because the same heat rejection level can be achieved with a smaller-sized core. Hence, a significant reduction in frontal area and volume is achievable with CuproBraze versus other materials.
Strength and durability Three new alloys were developed to enhance the strength and durability of CuproBraze heat exchangers: 1) an anneal-resistant fin material that maintains its strength after brazing; 2) an anneal-resistant tube alloy that retains its fine grain structure after brazing and provides ductility and fatigue strength in the brazed heat exchanger core; and 3) the brazing alloy.CuproBraze: Durability and reliability (Technology Series); http://www.cuprobraze.com/documents/3Durabilityandreliability.pdf Brazing at 650 °C creates a joint that is stronger than a soldered joint and comparable in strength to a welded joint.Jean M. Hoffman, Runnin' light and cool, Machine-Design.com; March 3, 2005, http://machinedesign.com/article/runnin-light-and-cool-0303 Unlike welding, brazing does not melt the base metals. Therefore, brazing is better for joining dissimilar alloys.
CuproBraze has more strength at elevated temperatures than soldered copper-brass or aluminum. Due to the lower thermal expansion of copper versus aluminum, there is less thermal stress during the manufacturing of CuproBraze and in its use as a heat exchanger. CuproBraze heat exchangers have stronger tube-to-header joints than other materials. These braze joints are the very important in heat exchangers and must be leak-free. CuproBraze also has higher tolerances to internal pressures because its thin-gauge high strength materials provide stronger support for the tubes. The material is also less sensitive to bad coolants than aluminum heat exchangers.Finnradiator; http://www.finnradiator.com/solutions-and-technology/the-right-solution-for-you/advantages-of-the-cuprobraze-technology/excellent-durability-even-in-the-most-demanding-conditions/
Test results demonstrate a much longer fatigue life for CuproBraze joints compared to similar soldered copper-brass or brazed aluminum joints.CuproBraze Durability (design criteria series): http://www.cuprobraze.com/pdf/Durability.pdf Stronger joints allow for the use of thinner fins and new radiator and cooler designs.Coming Toward CuproBraze: Brazed copper brass technology beginning to flourish across a growing range of heat transfer applications, Nigel Cotton, Diesel Progress, North American Edition, Diesel & Gas Turbine Publications, August 2008; Diesel Progress, August 2008
The copper fins are not easily bent when dirty radiators are washed with high pressure water. Anticorrosive coatings further improve strength and resistance against humidity, sand erosion, and stone impingement on copper fins.
For further information, see: CuproBraze: Durability and reliability (Technology Series): and CupropBraze durability (design criteria series).
Emissions New legislation in Europe, Japan and the U.S. call for strong reductions in NOX and particulate emissions from diesel engines used in trucks, buses, power plants, and other heavy equipment.Bo Svensson, 2006. Cool technology to help meet emissions targets: Diesel Progress International Edition; July–August 2006, http://www.cuprobraze.com/pdf/inthenews_diesel.pdf These goals can in part be accomplished by using cleaner-performing turbocharged diesel engines and charge air coolers. Turbocharging enables better power outputs, and charge air coolers allow power to be produced with more efficiency by reducing the temperature of the air charge entering the engine, thereby increasing its density.Heat exchangers: Meeting the challenges of the future: Trucks and buses; CuproBrazeAlliance; http://www.cuprobraze.com/pdf/trucks.pdf
The charge air cooler, located between the turbocharger and the engine air inlet manifold, is an air-to-air heat exchanger. It reduces the inlet air temperatures of turbocharged diesel engines from 200 °C to 45 °C while increasing inlet air densities to increase engine efficiencies. Even higher inlet temperatures (246 °C or higher) and boost pressures may be necessary to comply with the emissions standards in the future.