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CuproBraze is a copper-alloy heat exchanger technology for high-temperature and pressure environments such as those in modern .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, , , climate control systems, and heat transfer cores.Duensing, Lauren (2006) Develop efficient heat-transfer systems, Modern Metals, March 2006. [1] 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 , , , industrial , generators, , and military equipment. It is also used for , 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 [2]"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 , light , and other light-duty applications. However, they are not amenable for environments characterized by high operating , humidity, vibration, 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.
| 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 point | °C | 1083 | 915 | 643 | 643 | > 1400 |
| Safety margin in brazing (against core melting) | °C | 300 | 300 | 30 | 30 | 350 |
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.
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).
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.
Present-day charge air cooler systems, based on aluminum alloys, experience durability problems at temperatures and pressures necessary to meet the U.S. Tier 4i standards for stationary and mobile engines.Brazed Copper-Brass Technology Flourishes in Diverse Applications; Automotive Exports; September 2009; Page 26-30Nonroad diesel engines; Emission control for stationary and mobile engines; DieselNet; http://www.dieselnet.com/standards/us/nonroad.php Published reports estimate that the average life of an aluminum charge air cooler is currently about 3,500 hours.Heat Exchangers: Meeting the challenges of the future; Market Update Series; CuproBraze Alliance; 2004; http://www.cuprobraze.com/pdf/engine.pdf Aluminum is near its upper technological limit to accommodate higher temperatures and thermal stress levels because the tensile strength of the metal declines rapidly at 150 °C and repetitive thermal cycling between 150 °C and 200 °C substantially weakens it. Thermal cycling creates weak spots in aluminum tubes, which in turn causes charge air coolers to fail. A potential option is to install stainless steel precoolers in aluminum charge air coolers, but limited space and the complexity of this solution is a tampering factor for this option.
A CuproBraze charge air cooler can operate at temperatures as high as 290 °C without creep, fatigue, or other metallurgical problems.CuproBraze: Emissions standard (Technology Series); http://www.cuprobraze.com/documents/1Emissionstandards.pdf
In accelerated corrosion tests, such as SWAAT for salt spray and marine conditions, CuproBraze performed better than aluminum.
The corrosion resistance of CuproBraze is generally better than soft heat exchangers. This is because the materials in CuproBraze heat exchangers are of equal nobility, so galvanic differences are minimized. On soft soldered heat exchangers, the solder is less noble than fin and tube materials and can suffer from galvanic attack in corrosive environments.
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