Sec. 73.25 



FIXED-APPENDAGE DESIGN 



703 



boundary layer and accelerate it inside the scoop. 

 The after guide vanes should pick up a smaller 

 quantity of water in the more rapidly moving 

 intermediate layers and slow it down inside the 

 scoop. The aim is that at the entrance to the 

 diffuser the water shall be moving regularly at 

 more-or-less uniform velocity, indicated by the 

 four velocity vectors of Fig. 73. R. 



On high-speed vessels, and probably on medium- 

 speed craft as well, the roll-resisting keels along 

 the bilge corners act to collect the air bubbles 

 passing under the ship and to shoot them out 

 in two streams from the after inboard sides of 

 the bilge keels. This phenomenon is particularly 

 noticeable in a circulating-water channel when air 

 bubbles are circulating with the water. The 

 regions in the vicinity of the flowlines emanating 

 from the trailing edges of the bilge keels should 

 therefore be kept clear of injection or inlet 

 openings through the shell, to prevent accumula- 

 tions of air in the water sides or cooling jackets of 

 heat-exchanger systems. 



The position shown in the left diagram of 

 Fig. 73.R for the circulating-water inlet to the 

 main condenser of the ABC ship is well clear of 

 this air-collecting region on the port side. 



Openings in the hull for the discharge of water 

 from internal machinery may be located with 

 relative freedom to suit the internal arrangements. 

 In fact, they need not even be below the water 

 surface under all conditions of operation. It is 

 logical to lead water out through the hull in the 

 same manner as it was brought in, by inverting 

 the scoop section and directing it into the bound- 

 ary layer at a small angle to the flow there. To be 

 sure, if structural, mechanical, or space considera- 

 tions demand it, water can be discharged into 

 the boundary layer at any angle up to 90 deg 

 with the flow, diagrammed in Figs. 8.G and 8.H. 

 Rarely, however, is there not sufficient room to 

 provide a short elbow with multiple turning 

 vanes for changing the flow direction mechanically 

 instead of producing a hydrodynamic disturb- 

 ance in the boundary layer. If the elbow is con- 

 sidered too elaborate, and involves too large a 

 hole in the shell, fairing pieces can always be 

 fitted, corresponding to those in the referenced 

 sketches. 



73.25 Partial Bibliography on Condenser 

 Scoops. Research on inlets of the scoop type, 

 for taking water into condensers and other large 

 heat exchangers, has continued steadily if not 

 rapidly for the past half-century or more. Ap- 



pended is a Hst of references giving partial 

 coverage for the reader who wishes to pursue 

 this subject further: 



(1) Schmidt, H. F., "Theoretical and Experimental 



Study of Condenser Scoops," ASNE, Feb. 1930, 

 Vol. XLII, pp. 1-38. Comprises a basic treatment, 

 beginning with hydrodynamic fundamentals. 



(2) Hanzlik, H. J., "Condenser Scoops in Marine In- 



stallations," ASNE, May 1931, pp. 250-264 



(3) Schmidt, H. F., and Cox, O. L., "Test on a One- 



Quarter Scale Model Scoop on the U.S.S. Welborn 

 C. Wood and Preparatory Laboratory Experi- 

 ments," ASNE, Aug 1931, Vol. XLIII, pp. 435-466. 

 Fig. 5 opposite p. 437 shows the inlet flow in the 

 plane of the shell. Fig. 13 on p. 445 gives variations 

 in pressure and velocity, as measured on the 

 U.S.S. Raleigh (CL 7), for the first 14 inches out 

 from the shell, in way of the inlet-scoop position. 



(4) Weske, J. R., "Investigation of the Action of Con- 



denser Scoops Based upon Model Tests," ASNE, 

 May 1939, Vol. 51, pp. 191-213. Discusses dis- 

 charge as well as inlet performance. 



The arguments and explanations in the six 

 references which follow afford a useful insight into 

 the practical features of the flow into inlet 

 scoops for internal heat exchangers: 



(5) Schmidt, H. F., "Some Notes on E.H.P. Calculations 



and Propeller Characteristics," ASNE, Nov 1933, 

 Vol. XLV, pp. 528-533. This brief paper discusses 

 the influence, on the effective power required to 

 drive the ship, of taking in cooling water for con- 

 densers through inlet scoops, utilizing the forward 

 motion of the ship. The author points out that this 

 increment has to be added to the power pre- 

 dicted by tests of a self-propelled model. 



(6) Schade, H. A., "Discussion of Notes on E.H.P. 



Calculations," ASNE, Nov 1933, Vol. XLV, pp. 

 534-535. This is a discussion of the preceding 

 reference (5). 



(7) Schmidt, H. F., "Further Discussions on Notes on 



EHP Calculations," ASNE, Feb 1934, Vol. XL VI, 

 pp. 107-109. This is in turn a reply to reference (6). 



(8) Schade, H. A., "Discussion of Mr. Schmidt's Reply," 



ASNE, Feb 1934, Vol. XL VI, pp. 110-111 



(9) Schmidt, H. F., "Reply to Discussion by Lt. H. A. 



Schade," ASNE, May 1934, Vol. XL VI, pp. 251- 

 253. This article contains a photograph showing 

 flowlines into an inclined inlet without lip. 



(10) Schmidt, H. F., "A Criterion for Scoop Cavitation," 



ASNE, Aug 1934, Vol. XLVI, pp. 352-356. 

 Facing p. 353 of this reference there is a photograph 

 showing the lines of flow into the model of a lipless 

 inlet scoop of the Schmidt type. 



(11) "Comparative Tests of Condenser Scoops," EMB 



Rep. 384, Jul 1934. Describes tests run on EMB 

 model 3293, representing the DD 364-379 class of 

 destroyers of the U.S. Navy. 



(12) Rabbeno, G., "Appunti Prelimineari sulle Variazioni 



per Reciprooa Influenza nelle Potenze Assorbita 

 dalla Circolazione Refrigerante e dalla Propulsione 



