Additionally, he will be guided by reference 2 which also addresses 

 the economical selection of air-cooled condensers. This NAVFAC manual 

 establishes limits on maximum design condensing temperature and minimum 

 temperature difference between the condensing refrigerant and entering 

 air. No reference is made to power cost or other factors affecting 

 life-cycle performance, from which the inference may be drawn that 

 condenser selection economics deals primarily with initial cost. An 

 experienced designer realizes, however, that in selecting his entering 

 air and condensing temperatures he is indirectly prescribing a fouling 

 factor for the condenser he is sizingo This is necessary because 

 references 2 and 3 give no guidance in this area, as they do for water 

 cooled condensers, nor do they address the subject or provide information 

 to make allowance for corrosion effects on condenser life and efficiency 

 Thus, the design trade-off among factors which affect life-cycle system 

 cost is largely left to the experience of an equipment manufacturer/ 

 supplier. It is well-known that the technical output of an equipment 

 supplier is very difficult, if not impossible, to control under current 

 procurement regulations The complexity of the resulting design problem 

 of economic condenser selection can be illustrated most simply by a 

 listing of the design-economic variables involved, as is done in the 

 following tabulation,, 



Site Variables 



Corrosion/fouling conditions 



Labor cost/skills/avail- 

 ability 



Construction/maintenance 

 cost index 



Power costs 



Design Variables 



Condenser size 



Materials for tubes/ 

 fins 



Coated/uncoated 

 Coating material 



Oper. Variables 

 Load factor 

 Operating factor 



Level of preventive 

 maintenance 



Washed/not washed 



Washing frequency 



The Corrosion Problem 



Industry recognizes that the performance of its standard designs can 

 become deficient because of atmospheric corrosion in marine environments „ 

 Less efficient condenser heat transfer due to corrosion increases the 

 condensing temperature and pressure with a reduction in cooling capacity, 

 an increase in motor load/power consumption, and more rapid compressor 

 deterioration It is not unusual for aluminum condenser fins to corrode 

 away completely in two years or less,, Several air conditioning manufacturers 

 report a two year maximum coil lifetime expectancy in certain Texas 

 Gulfcoast and Southern California coastal locations. The Army Mobility 

 Equipment Research and Development Center considers that a one and one-half 

 year condenser lifetime is acceptable performance at Ft„ Sherman in the 

 Panama Canal Zone. A 1969 CEL report to NAVFAC on materials for air 

 conditioners states: 



"The lifetime of an air conditioner condenser with aluminum fins 

 on copper tubes at Kwajalein is about one year. Corrosion is 



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