Center (formerly the U. S. Army Engineer Research and Development 

 Laboratories) at Ft „ Belvoir, VA. This laboratory pursued a test and 

 evaluation program between FY55 and FY73, concentrating on lightweight, 

 all aluminum plate-fin type (as contrasted to fin-tube type) coils for 

 mobile equipment . Initial laboratory salt-fog tests per ASTM B-117-49T 

 were made on condenser coils with various combinations of conventional 

 materials and on all aluminum coils, both coated and uncoated. Successful 

 laboratory performance of aluminum coils was followed by a field test 

 at Fto Sherman, Panama Canal Zone, of twelve 3/4-ton air conditioning 

 units in which condensing coils were fabricated of different aluminum 

 alloys, some being coated with paint and/or selected chemical conversion 

 coatings o References 5 and 6 report on this work,, Performance of the 

 all-aluminum coils in the Panama air condenser field test led to an inves- 

 tigation of the effects of brazing for fin attachment which is reported 

 in references 7 and 8. Pressurized coils subjected to fan-circulated 

 marine air were exposed at Ft. Sherman to evaluate coatings for brazed 

 coils and for coils with mechanically bonded fins, which were just being 

 introduced to remedy corrosion from residual brazing salts „ These tests 

 determined the leakage failure from pitting of six plate-fin type and 

 two fin-tube type, all aluminum coils. Heat transfer was not measured . 

 The final report abstract states: 



"The results of the test program indicates that all-aluminum 

 condensers may be substituted for the copper tube/aluminum 

 fin construction currently used in military environmental 

 control units in the interest of cost savings However, care 

 should be exercised at the tube joint with any dissimilar 

 metals, which should be protected with a moistureproof , 

 external seal," 



The Fto Belvoir Laboratory advises that no changes to equipment resulted 

 from these experiments, nor was a "tropicalization" specification 

 preparedo 



It is believed that the Army test results spurred industry to develop 

 mechanical bonding techniques for all -aluminum, plate-fin condensers 

 and ultrasonic brazing which eliminates conventional aluminum brazing 

 fluxes for tubing joints. These are now accepted industry practices „ 

 Another interesting result was the conclusion that laboratory salt-fog 

 testing was of little value as an accelerated test due to the alternate 

 wetting and drying conditions existing in the field. Residual brazing 

 salts and atmospheric salt crystals were able to lodge at a fixed point 

 where continuous reaction with the aluminum could occur. In laboratory 

 salt-fog testing a continuous washing action occurred over the surfaces 

 which tends to dilute or weaken concentrated reactive points so that 

 penetration is less rapid than in high-salt natural environments. 



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