Principles of naval engineering - Historic Naval Ships Association

IChapter 19. -REFRIGERATION AND AIR CONDITIONING PLANTSBoth types of chilled water circulating systemsoperate on the same general principle.The secondary refrigerant (chilled water) iscirculated to the various cooling coils. Heatfrom the spaces being cooled is absorbed bythe chilled water and is removed from thewater by the primary refrigerant in a waterchiller.Figure 19-16 illustrates the flow of primaryrefrigerant, secondary refrigerant, and condenserwater in an R-11 chilled water circulatingsystem which has a single-stage centrifugalcompressor. The primary refrigerant vaporgoes from the evaporator to the compressor,where it is compressed. It is then dischargedto the condenser. In the condenser, the primaryrefrigerant vapor condenses, giving up itssuperheat, its latent heat of vaporization, andits heat of compression to the cooling waterthat flows through the condenser tubes. Theliquid primary refrigerant then passes througha high pressure float valve to the cooler.The secondary refrigerant picks up heat inthe coils of the air conditioned space and carriesthis heat to the cooler. The function of thecooler is to transfer the heat from the secondaryrefrigerant to the primary refrigerant whichsurrounds the tubes of the cooler. As this heatis transferred, the liquid primary refrigerantabsorbs its latent heat of vaporization, boils,and vaporizes. The quantity of liquid refrigerantthus evaporated varies directly with theamount of heat picked up by the secondaryrefrigerant. The vaporized primary refrigerantgoes to the compressor, and the same sequenceof events is repeated in a cyclical manner.Figure 19-17 illustrates an R-11 chilledwater circulating system with a two-state centrifugalcompressor. The refrigerant vaporcoming from the cooler goes into an openingaround the hub of the first wheel of the centrifugalcompressor. The blades in the rapidlyrotating wheel impart velocity to the vapor. Thevapor is then directed to the hub of the second-AIR CONDITIONING SYSTEMCOOLING COILSS REFRIGERANTSECONDARY REFRIGERANTCONDENSER WATERCOMPRESSOR(WFigure 19-16.— Flow diagram, chilled water circulating system withsingle-stage centrifugal compressor.147.120489