which is coated with a thermally efficient, corrosion-resistant material 

 could be smaller in size. This would reduce costs and save additional 

 energy by reducing pumping power requirements. In addition, the longer 

 life expectancy would reduce maintenance costs, perhaps by one-half. 



The only realistic costs for coated versus uncoated heat exchangers 

 used in this study were for the all copper units. Current (1978) prices 

 range from $43.00 to $53.80 each, depending on the quantity purchased. 

 Costs of cleaning and coating are $0.01 per perimeter inch, or $25.75. 

 Thus, coating increases the price by 48% to 60%. This should be justified 

 on the basis of increased life expectancy alone. As stated previously, 

 additional savings would accrue from lower initial costs (smaller units) 

 and higher thermal and electrical (pumping) efficiencies. An excerpt 

 from a cost-effectiveness study conducted at CEL is presented in the 

 Appendix. 



CONCLUSIONS 



Based on a 2-year operation in a temperate marine environment, it 

 is concluded that for application in this environment: 



1. Copper tube/copper fin heat exchangers coated with an electro- 

 static polyester material (0.6 mil), a specification alkyd system (10.4 

 mils total), or a zinc inorganic silicate material (2.0 mils) are more 

 thermally efficient (56%, 45%, and 63%, respectively) than an uncoated 

 exchanger of this type after a 2-year operation in a temperate marine 

 environment. 



2. The three coating systems used had mostly a negative effect on 

 thermal efficiency when applied to aluminum tube/aluminum fin and copper 

 tube/aluminum fin exchangers. 



3. Uncoated aluminum tube/aluminum fin heat exchangers are more 

 thermally efficient than either the uncoated copper tube/copper fin or 

 copper tube/ aluminum fin heat exchangers after a 2-year operation in a 

 temperate marine environment. 



ACKNOWLEDGMENTS 



The authors wish to thank Mr. Joseph B. Crilly for his early work 

 in this area, Mr. James Thayer for designing the test unit, Mr. Theodore 

 Tree for assembling the test unit, Messrs. Albert F. Curry and Theodore 

 Tree for assisting in the heat exchanger coating applications at CEL, 

 Mr. Joseph C. Quigley for installation of the temperature recording 

 equipment, Mr. Charles W. Mathews for assistance in data reduction, and 

 Mr. Eddy S. Matsui for computer graphics. 



