Wednesday, July 8, 2009

vacuum brazed aluminium heat exhangers for aero space applications

Aeronautical Development Agency gave R&D of BHPV a development contract for the design of compact heat exchangers for the supersonic air craft which they were designing.The heat exchangers were to be fitted in an envelope volume specified by ADA. The smallest aluminium heat exchanger had dimensions of 130mm x 30mm x 55mm and the largest heat exchanger had dimensions of 250mm x 140mm x 370mm.
The smallest stainless steel heat exchanger had dimensions of 175mm x 118mm x 200mm and the largest heat exchanger had dimensions of 250mm x 140m x 282 mm.
The challenge was to optimise the design with in the space provided so that the heat exchangers meet the heat dissipating requirements. Our design engineers developed computer programmes to optimise the heat exchangers. It took us over an year to fit all the heat exchangers in the given envelope. Our work was finished.
Brazing of the heat exchangers was the responsibility of another metallurgical laboratory in the defence sector. ADA financed procuring a vacuum furnace for aluminum brazing. Even after several trials over a period of one year they were no where near achieving the brazing. The scientists in the laboratory were so secretive that they did not want us to see the brazing furnace. After much pursuation we were allowed to visit the laboratory where brazing was being carried out. Our visit convinced us that the brazing furnace is defective which was the cause for their failure in brazing. Even after several attempts the laboratory was not successful in brazing. At that time we made a proposal to ADA. We proposed that the brazing also should be a part of our design contract. ADA's scope was to import the components for brazing and supply to us.Once we acheved brazing the technology was the property of BHPV. ADA agreed to our proposal. Imported vacuum brazing furnaces are very expensive and hence we decided to manufacture a brazing furnace designed by us. The next blog describes how we went about the design of the vacuum brazing furnace.

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