20 



CIRCULAR 740, U. S. DEPARTMENT OF AGRICULTURE 



deposits on them. If such deposits are allowed to accumulate over 

 long periods they interfere seriously with the exchange of heat. 



TYPES OF CONDENSERS 



While all condensers have as their purpose the cooling of the hot 

 ammonia gas, thereby changing it to a liquid, there are several different 

 general types. In each the hot gas is circulated through or around 

 pipes that are exposed to a cooling fluid, usually water. In a double- 

 pipe condenser the ammonia is passed through a bank of pipes. A 

 smaller pipe carrying cooling water extends full length inside each 

 section of ammonia pipe. Several banks of double-pipe condensers 



are usually mounted to- 

 gether to give the re- 

 quired capacity. In a ver- 

 tical shell-and-tube con- 

 denser the ammonia gas 

 enters the top of a large 

 vertical cylinder and the 

 condensed liquid drains 

 off at the lower end. Nu- 

 merous vertical pipes in- 

 side the cylinder are 

 mounted so that a film of 

 cooling water runs down 

 the inside of each pipe. 

 As the ammonia con- 

 denses on the outside of 

 the pipes it flows to the 

 bottom of the cylinder, 

 where it is drained off to 

 the receiver. 



The horizontal shell- 

 and-tube condenser is sim- 

 ilar to the vertical, except 

 that the shell is in a hori- 

 zontal position and the 

 water pipes carry cooling 

 water under pressure. The water is usually passed back and forth 

 through several tubes in series before being discharged. In this way 

 its velocity is increased to give more rapid cooling without having to 

 discharge large quantities. 



An evaporating condenser has the ammonia gas pass through coils 

 that are exposed to a spray or drip of water. At the same time air is 

 blown through the water spray past the pipes and causes some of the 

 water to evaporate. This evaporation keeps the water cool, so that it 

 can be recirculated, and the only waste is the water that is evaporated 

 or carried away in the air blast. This is particularly suited to condi- 

 tions where cooling water is limited or expensive and where the atmos- 

 phere is relatively dry during the time large loads are expected on the 

 refrigeration machinery. 



.5 



to 



4Q 160 



1 



— 140 



to 

 en 



S \Z<> 



8 

 ■8 



100 



80 



/ 





/ 



/ 



1 



1/ 



1/ 



/ 



// 



I / 



Co/ 



7 



// 



1 j 





/ 



1 <*y 



#/ 



7 



7 





/ / 



/ 





u 



y 





/ 



// 



1 



7 



15 



20 



25 



30 



35 



Suction pressure (pounds per sq. in.) 



Figure 3. — Effect of condensing and suction 

 pressures upon the capacity of a typical am- 

 monia compressor. 



