PRINCIPLES OF NAVAL ENGINEERING 



REAR OF BOILER 



SUPPORT CHANNELS 



PLAN VIEW 



\ VERTICAL CENTERLINE 

 OF WATER DRUM 



ELEVATION 



38.27 



Figure 10-8.— Arrangement of W-tube walk-in superheater. 



Economizer tubes may be of various shapes. 

 Most commonly, perhaps, they are a continuous 

 loop of U-shaped elements from inlet to outlet 

 header. Almost all economizer tubes have some 

 sort of metal projections from the outer tube 

 surface. These projections, which are of alumi- 

 num, steel, or other metal, are shaped in various 

 ways. Figure 10-9 shows a U-bend economizer 

 tube with aluminum gill rings that are circular 

 in cross section. Other types of projections in 

 use include rectangular fins and star-shaped 

 disks. In all cases, the projections serve to ex- 

 tend the heat transfer surface of the economizer 

 tubes on which they are installed. 



38.28 

 Figure 10-9.— U-bend economizer tube 

 with aluminum gill rings. 



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