CuproBraze® 42 EXECUTIVEReport

New Designs of Charge Air Coolers Increase Performance and Durability Part II: Laboratory Testing Aids in Design Improvements

Editors Note: A brief overview o say that the Västerås tests could be performed to simulate various aspects of the standard tests per- Center is a hotbed of activity is an of service. CACs could be subjected to a variety of formed at the Brazing Center understatement. Presently,eleven static and dynamic forces, including pressure pulses was presented in Part I, which manufacturers around the globe are inside the CAC, bending forces on the inlet and out- can be found in the previous issue of the CuproBraze making , charge-air coolers let tubes, vibrations from the vehicle frame, and vari- Executive Report (i.e., Issue and other products on their own ous conditions of thermal stresses. No. 41). We continue our dedicated CuproBraze lines; and Bengt and his group have determined several fac- review of the activities at the twelve more have decided to open CuproBraze pro- tors that influence both the burst pressure and the Brazing Center with a discus- T duction facilities. The CuproBraze Alliance recently pressure cycling lifetimes. Based on testing experi- sion of how testing can be announced that eighty more companies are evaluat- ences, he offers these tips to designers of brazed cop- used in the development of superior charge air cooler ing CuproBraze heat exchangers. per- CACs. For many parts manufacturers and OEMs, the deci- designs. ■ Control over the fin height is important. In a CAC, sion to produce CuproBraze heat exchangers begins the sandwich construction of the tubes and fins with a trip to Västerås and, subsequently, they avail does not allow for variations in fin height. Exact themselves of the Brazing Center to verify specifica- part dimensions are required to form good brazed tions before committing to full-scale production. As joints between the fins and tubes. a result, the Brazing Center is a breeding ground for new heat exchanger designs. ■ If wide headers and thin gauge tanks are used As described in Part I,the testing of heat exchang- then these parts will deform at relatively low pres- ers for performance and durability is a critical func- sures; therefore, he advises, “Headers should be as tion of the Brazing Center. Durability testing is espe- narrow as possible to limit stresses in the tube to cially important in the development of CACs made of header joint and in the header close to the joint.” brazed -brass. Until very recently,nearly all ■ If thin gauge brass tanks are used, they should be CACs were made from aluminum. In the last few well designed for internal pressure, to minimize years,however,thanks in a large part to the work per- stresses in the header.“Well rounded shapes are formed at the Brazing Center,a large number of prac- necessary,”he cautions. tical copper-brass CAC designs have been developed. A benchmark CAC design was developed by the Informed CAC Design Brazing Center.(See Figures.) This CAC has also been According to Bengt Gustafsson,Technical Manager subject to wind tunnel testing to determine its perfor- for the Brazing Team at the Brazing Center,many mance,including its cooling efficiency and air pres-

A new prototypical CAC design was developed at the Brazing Center using design principles derived from testing. sure drops on the charge-air side (internal pres- The International Copper sure drop) and the cooling-air side (external Association, Ltd. (ICA) air-pressure drop). is the leading organization for the promotion Design for Manufacturing of the use of copper worldwide. The Association’s The CuproBraze process is essentially the same twenty-nine members represent about 80 for radiators and CACs, except for two impor- percent of the world’s refined copper output, tant differences: the fin heights must be more and its six associate members are among tightly controlled, as mentioned previously; the world’s largest copper and copper alloy and CACs typically have internal fins, whereas radiators do not. fabricators. ICA is responsible for guiding According to Bengt,full brazing contact policy, strategy and funding of international between the fin tips and the tube walls can be initiatives and promotional activities. facilitated by the design.“There are at least two A CuproBraze CAC- package is installed With headquarters in New York City, ICA ways to go. One is to use fins with a relatively into a at URAL truck assembly plant. operates in 28 worldwide locations through large tip radius that can flex during core com- a network of regional offices and copper pression and then flex back during the brazing,” it has also performed testing and development associations. he explains. “Another way to go is to use a rela- wind tunnel tests. tively rigid inner fin that withstands the compres- As the industry gains experience with sion pressure during core assembly and does CuproBraze, most manufacturers will seek a For general mailing information about not deform when heated during the brazing competitive edge through proprietary designs. the CuproBraze process or ICA’s cycle. This latter approach appears to work well According to Bengt, the six factors governing CuproBraze consulting services, and has the important additional benefit of CAC design are the heat transfer specification; improving pressure resistance.” please contact International Copper the type of environment, or vehicle type; Also, brazing foil can be used instead of strength and durability specifications; the Association at [email protected]. brazing paste for the internal fins. “Because weight of finished product; manufacturing con- For technical information contact the foil is thinner than the paste, the pre-braz- siderations; and the projected overall cost. [email protected]. For European ing core dimension is less and the core shrinks “The Brazing Center is ready to assist in the inquiries contact [email protected]. less during brazing,”he explains. The foil has early stages of design and manufacturing,”says no organic binder to evaporate, so there are no Bengt. “However,once a company develops its fumes that could adversely affect the internal own production capabilities, it tends to brazing. The even supply of brazing filler mate- become more independent, driving its own Contact Information rial assures uniform brazing. designs. SHAAZ is a good example. It works The Brazing Center with its OEM customers to develop new Outokumpu Copper Strip The Power to Choose designs and it performs its own testing, Sintervägen 14 The Västerås Brazing Center has cooperated P.O. Box 550 although we collaborate on some projects.” SE-721 10 Västerås,Sweden with many prospective manufacturers on pre- Bengt speculates that, although heat- Contact: Bengt Gustafsson, liminary research and development of exchanger manufacturers will always want to Technical Manager, CuproBraze CACs. The result is a benchmark know about new technologies, they eventually [email protected], CAC design. Besides mechanical testing of Telephone: +46 21-198 000 will perform their own testing of proprietary burst pressures and pressure cycling lifetimes, products, since the superior test results give SHAAZ them an advantage in the marketplace. 1, Sverdlov Street Shadrinsk 641876 Kurgan Region, Russia “The purpose of the Brazing Center is tech- www.SHAAZ.ru nology transfer,”says Bengt. “There is no inten- [email protected], [email protected] tion of establishing a design firm or testing lab- Tel/fax +7 (35253) 32-0-93, Tel +7 (35253) 3-29-39 oratory here in Västerås. At this stage, at least until the industry matures, it’s better if diverse See www.cuprobraze.com for additional designs are available.” materials suppliers, equipment makers and heat exchanger manufacturers. A CuproBraze CAC and CuproBraze radiator can be packaged in one unit. This package was designed by SHAAZ for URAL .

International Copper Association, Ltd. 260 Madison Avenue, 16th Floor,New York, NY 10016-2401 Tel:212.251.7240, Fax: 212.251.7245