was 1600 hours (4:00 p.m.), although this time could vary by ±30 minutes. 

 The heat transfer rate H, in Btu/hr-°F/ft length" of the heat exchanger, 

 was determined by the following equation: 



m C /T. - T \ 



where m = fluid through the exchanger, lb/hr 



C = specific heat of the liquid, Btu/lb-°F 



L = length of the heat exchanger, ft 



T. = inlet fluid temperature, °F 



T = outlet fluid temperature, °F 

 o 



T = ambient temperature, °F 



The ratios of the heat transfer rates of coated versus uncoated exchangers 

 for each coating type and exchanger material type were calculated on a 

 monthly basis for two years, and linear regression curves were computer- 

 plotted so that performance comparisons of uncoated and uncoated versus 

 coated exchangers could be made. This report includes data selected at 

 approximately 1-week intervals between 29 Jun 1976 and 11 Aug 1978. A 

 time extension beyond the planned 29 Jun 1978 completion of a 2-year 

 operation was necessary because the equipment was shut down from 8 Jul 

 to 19 Sep 1977 when the test area was paved. 



Heat transfer ratios are shown in Figures 7 and 8, and data points 

 and regression curves for coated versus uncoated copper tube/copper fin 

 heat exchangers are shown in Figures 9, 10, and 11. 



Concurrent with the operation described above, the exchangers were 

 examined for evidence of corrosion. After the Apr 1978 inspection 

 (Table 3), it was decided to attempt accelerating the rate of corrosion. 

 A small cordless electric yard and garden sprayer was used to spray 

 approximately 1 quart (0.95 liter) of seawater on the heat exchangers 

 every morning of each working day, weather permitting. After the com- 

 pletion of 2 years of operation the exchangers were inspected and the 

 results are shown in Table 4. 



FINDINGS 



The test data obtained during this investigation are shown in 

 graphical form in Figures 7 through 11. Figures 7a and 7c show the 

 negative effect of coatings on the heat transfer performance of aluminum 

 tube/aluminum fin and copper tube/aluminum fin exchangers. Figure 7b 

 shows that all three coatings improved the heat transfer performance of 

 copper tube/copper fin exchangers over that of an uncoated unit during 



"Btu/sq ft not applicable to finned tubing. 



