EVAPORATION 



359 



drawn off by a dry-air pump through the pipe b ; at c is shown a separator 

 to prevent water passing into the air pump. The condensed steam and 

 injection water flow down the fall pipe d, terminating in the sealing tank e, 

 whence they flow away by gravity. This type of condenser is first mentioned 

 in British patents 5635,' 1828, and 5785, 1829, taken out by John Davis 

 for an unnamed inventor. 



The most important distinction in condensers is the sense in which the 

 water and steam pass in relation to each other. 'When they travel in the 

 same direction the term " parallel current " is employed, " counter-current " 

 being used when the flows are opposed. In both cases, however, the flows 

 are parallel, and the terms " co-current " and 

 " counter-current " will be used in preference. 



In order to break up the water in its passage 

 through the condenser, and thus to expose a 



FIG. 214 



FIG. 215 



FIG. 216 



large surface for the better condensation of the steam, many devices and 

 arrangements are employed. 



As indicated in Fig. 213, steam enters at a, water being introduced by 

 the pipe b, and discharged as a rain through the perforated plate c ; the air 

 passes away to the air pump by the pipe d, the connection to the fall pipe 

 whence the water passes away being at e. Alternatively in this arrangement 

 the pipe b may be perforated throughout its length, the water thus leaving 

 the pipe horizontally and at right angles to the flow of the steam, thus forming 

 a cross-current system. Fig. 214 shows a co-current type of condenser, 

 and Fig. 215 a counter-current type, lettered as in Fig. 213. 



A more complex type in occasional use on the continent of Europe is 

 indicated in Fig. 216, the water being projected from the plates c, which are 

 caused to rotate at a high speed ; the lettering is otherwise as above. 



Convention has developed the injection condenser as a vertical cylinder. 



