Chapter 13-CONDENSERS AND OTHER HEAT EXCHANGERS 



FIRST STAGE 

 AIR EJECTOR 



SECOND STAGE 

 AIR EJECTOR 



AFTER 

 CONDENSER 



VENT TO 

 ATMOSPHERE 



(VIA 

 EXHAUST FAN) 



AUX. STEAM ^ C 

 EXHAUST 



TO 

 4 DEAERATINQ 

 TANK 



GLAND 



EXHAUST 



CONDENSER 



CONDENSATE 

 PUMP 



%-^ 



INTER 

 CONDENSER 



47.77X 



Figure 13-4.— Two-stage air ejector assembly. 



condenser shell, and from there it drains to the 

 condenser through a U-shaped loop seal line. The 

 air passes to the suction of the second-stage air 

 ejector, where another jet of steam entrains the 

 air and carries it to the after condenser. In the 

 after condenser, the steam is condensed and re- 

 turned to the condensate system by way of the 

 fresh water drain collecting tank, and the air is 

 vented to atmosphere. 



Note that the air ejectors remove air only 

 from the condenser, not from the condensate 

 which passes through the tubes of the inter and 

 after condensers. The condensate merely serves 

 as the cooling medium in these condensers, just 

 as it next serves this purpose in the gland exhaust 

 condenser and in the vent condenser. 



GLAND EXHAUST CONDENSER 



The gland exhaust condenser receives a 

 steam-air mixture from the propulsion turbine 

 glands. The steam is condensed and returned to 

 the condensate system by way of the fresh water 

 drain collecting tank, and the air is discharged 

 to atmosphere. The atmospheric vent is usually 

 connected to the suction of a small motor-driven 

 fan (gland exhauster), which provides a positive 



discharge through piping to the atmosphere above 

 decks. This is necessary to avoid filling the 

 engineroom with steam should the air ejector 

 cooling water supply fail, thereby allowing the 

 steam to pass through the inter condenser and 

 after condenser without being condensed. The 

 cooling medium in the gland exhaust condenser, 

 as in the air ejector condensers, is condensate 

 from the main condenser, on its way to the de- 

 aerating feed tank. 



In most installations, the gland exhaust con- 

 denser appears to be part of the air ejector as- 

 sembly, since it is attached to the after con- 

 denser. However, the gland exhaust condenser 

 is functionally a separate unit even though it is 

 physically attached to the air ejector after con- 

 denser. 



In serving as the cooling medium in the air 

 ejector condensers and in the gland exhaust con- 

 denser, the condensate picks up a certain amount 

 of heat. To some extent this is desirable, since 

 it saves heat which would otherwise be wasted 

 and it reduces the amount of steam required to 

 heat the condensate in the deaerating feed tank. 

 However, overheating of the condensate could 

 result in inefficient operation of the air ejectors 

 and consequent loss of vacuum in the main 



353 



