Over the period FY69 through FY72 CEL conducted the field test of 

 fourteen air conditioning units at Guam referred to previously,, Twelve 

 modified and two unmodified units were tested to evaluate the corrosion 

 control value of various metals and coatings for condensers, valves and 

 fittings in air conditioners „ Mechanical failures terminated the test 

 before corrosion effects became evident. Between FY75 and FY78 CEL 

 undertook to determine, by laboratory experiment, the long-term effect 

 of protective coating on the thermal performance and material deterioration 

 of fin-tube air-cooled heat exchangers „ The total cost of CEL work since 

 1969 was slightly over $100,000. 



The completed coating research was successful within its authorized scope, 

 It indicated a possible long-term beneficial effect of protective coatings 

 on the thermal performance of fin-tube type air-cooled heat exchangers of 

 various materials of construction. Thus, it provides the technical 

 basis for a decision whether or not more extensive research on coatings for 

 air-cooled refrigeration condensers should be conductedo Contrary to 

 the expectations of a number of practicing engineers, findings indicated 

 that substantial benefit, i e., over 50% improvement compared to an uncoated 

 coil, might be realized for a representative coating under laboratory 

 simulated conditions „ Specifically, the following conclusions can be 

 drawn from the draft report of reference 4 : 



a. Reported results show that favorable effects on heat transfer 

 can be expected for organic coatings, based on two years' exposure under 

 laboratory conditions . 



bo Test results do not permit the condenser materials/coatings to be 

 classified as "high performance" or "improved" refrigeration condensers, 

 nor to make recommendations to NAVFAC on design criteria or specifications 

 for refrigeration equipment. 



c Q Performance of the three organic (paint) coatings tested do not 

 provide a basis for selecting among the many other types of available 

 commercial and MIL-SPEC coatings tested by CEL and/or developed for 

 automotive, ordnance, and aerospace equipment, 



do Test results do not provide a basis directly for predicting the 

 condenser life expectancy or the cooling unit power consumption under 

 various conditions of operation and exposure 



Factors other than condenser material selection and coating, such as 

 the method of condenser fabrication, condenser size, and the frequency 

 of condenser washing, have an equal or greater effect on condenser life 

 and cooling unit power consumption Therefore, items (b) , (c) , and 

 (d) are appropriate subjects for continuing research. 



Army Research and Development 



Civil Engineering Laboratory work to improve the performance of air- 

 cooled refrigeration condensers in marine environments was based, in part, 

 on previous work by the Army Mobility Equipment Research and Development 



44 



