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Basic  absorption  cycle
CLASSIFICATION OF AIR COMPRESSORS

Fireman - Navy Firefighter, Fireman training manual
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The maintenance of the high vacuum within the shell is important to the proper operation of the plant. Fan-Coil  Assemblies Fan-coil assemblies (fig. 10-22) use chilled water to air-condition spaces. These assemblies are known as spot coolers. The chilled water is piped through the cooling coils of the units, and a fan forces air over the coils. Note the chilled water connections, the vent cock at the top, and the condensate collection tray at the bottom  of  the  unit. The  condensate  collection  tray  collects  the  moisture condensed out of the air. The condensate is generally piped to the bilge or a waste water drain system. It is important that the drain for the collection tray be kept clear. If the condensate cannot drain out of the tray, it collects and evaporates, leaving impurities that can rapidly  cause  the  tray  to  corrode. SELF-CONTAINED  AIR  CONDITIONERS Ships without central air conditioning may use self-contained  air-conditioning  units.  Naval  Sea Systems Command (NAVSEASYSCOM) approval is required.  A  self-contained  air-conditioning  unit  is simply  the  type  of  air  conditioner  you  see  installed  in the windows of many homes. All that is required for installation is to mount the proper brackets for the unit case and provide electrical power. These  units  use  nonaccessible  hermetically  sealed compressors (motor and compressor are contained in a welded  steel  shell).  For  this  reason,  shipboard maintenance  of  the  motor-compressor  unit  is impractical.  The  thermal  expansion  valve  used  in  these units is preset and nonadjustable. However, a thermostat and fan speed control are normally provided for comfort adjustment. AIR  COMPRESSORS The air compressor is the heart of any compressed air  system.  It  takes  in  atmospheric  air,  compresses  it  to the desired pressure, and moves it into supply lines or into storage tanks for later use. Air compressors come in  different  designs  and  configurations  and  have different methods of compression. Some of the most common types used on gas turbine ships are discussed in this chapter. Before   describing   the   various   types   of   air compressors,  you  need  to  know  about  the  composition of air and some of the things air may contain. This discussion   should   help   you   understand   why   air compressors  have  special  features  that  prevent  water, dirt, and oil vapor from getting into compressed air piping  systems. Air is mostly composed of nitrogen and oxygen. At atmospheric pressure (within the range of temperatures for the earth’s atmosphere), air is in a gaseous form. The Figure  10-22.-Fan-coil  assembly. 10-24






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