PRINCIPLES OF NAVAL ENGINEERING 



AIR OFFTAKE CROSSOVER PIPES 

 (IN EXHAUST OPENING STRUTS) 



STEAM LANE 



TUBE SUPPORT PLATE 



CONDENSER TUBES 



CONDENSER SHELL 



AIR OFFTAKE 



SUPPORTING 

 FLANGE 



AIR COOLING 

 SECTION 



HOT WELL 

 CAGE GLASS 



TUBE PLATE 

 STAYS 



CONDENSER 



SIDEWALL 

 STIFFENERS 



AIR BAFFLE 



SUPPORTING 

 FLANGE 



AIR COOLING 

 SECTION 



CONDENSATE OUTLET 



Figure 13-3. — Cross-sectional view of main condenser. 



98.33 



sometimes used to support part of the weight of 

 the condenser so that it will not have to be en- 

 tirely supported by the turbine. 



Condenser performance may be evaluated by 

 a simple energy balance which takes account of 

 all energy entering and leaving the condenser. 

 In theory, the entering side of the balance should 

 include (1) the mechanical kinetic energy of the 

 entering steam, (2) the thermalenergy of the en- 

 tering steam, (3) the mechanical kinetic energy 

 of the entering sea water, and (4) the thermal 

 energy of the entering sea water. In theory, again, 

 the leaving side of the balance should include (1) 

 the mechanical kinetic energy of the leaving con- 

 densate, (2) the thermal energy of the leaving 

 condensate, (3) the mechanical kinetic energy of 

 the leaving sea water, and (4) the thermal energy 

 of the leaving sea water. In considering real con- 

 densers, however, the entering and leaving me- 

 chanical kinetic energies of the sea water tend 

 to be small and tend to cancel each other out, the 

 mechanical kinetic energy of the entering steam 

 is so small as to be negligible, and the mechan- 

 ical kinetic energy of the leaving condensate is 

 small enough to disregard. With all of these rel- 

 atively insignificant quantities omitted, the en- 

 tering side of the balance includes only the ther- 

 mal energy of the entering steam and the thermal 

 energy of the entering sea water, and the leaving 

 side includes only the thermal energy of the 



leaving condensate and the thermalenergy of the 

 leaving sea water. 



AIR EJECTOR ASSEMBLIES 



The function of air ejectors is to remove air 

 and other noncondensable gases from the con- 

 denser. An air ejector is a type of jet pump, 

 having no moving parts. The flow through the air 

 ejector is maintained by a jet of high velocity 

 steam passing through a nozzle. The steam is 

 taken from the 150-psi auxiliary steam system 

 on most ships. 



The air ejector assembly (fig. 13-4) used to 

 remove air from the main condenser usually con- 

 sists of a first-stage air ejector, an inter con- 

 denser, a second-stage air ejector, and an after 

 condenser. The two air ejectors operate in se- 

 ries. The first-stageair ejector raises the pres- 

 sure from about 1.5 inches of mercury absolute 

 (condenser pressure) to about 7 inches of mer- 

 cury absolute; the second-stage air ejector 

 raises the pressure from 7 inches of mercury 

 absolute to about 32 inches of mercury absolute 

 (about 1 psig). 



The first-stage air ejector takes suction on 

 the main condenser and discharges the steam-air 

 mixture to the inter condenser, where the steam 

 content of the mixture is condensed. The result- 

 ing condensate drops to the bottom of the inter 



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