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Air conditioning

Air conditioning

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Air conditioning

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  1. Air conditioning

  2. Air conditioning provides COMFORT condition by controlling : • Temperature of air (cooling or heating) • Humidity of air (dehumidifying or humidifying) • Movement of air • Noise level within the accommodation • Cleanliness of air To ensure proper working order of all electrical/electronic equipments and for the comfort of the crew

  3. Conditions affecting human comfort: • Temperature – cool surrounding allows the rate of heat transfer. • Humidity – rate of heat transfer (thru evaporation) depends on partial vapour pressure differential between the object & room temp. air at low humidity condition can absorb moisture very readily, resulting effective cooling. extreme low humidity dry air – causes (1) rapid of drying of skin - itchness (2) mucus membranes of the of the throat, nostril and lips to dry up - causing discomfort. Bleeding of the membranes in the nose. • Air movement – proper circulation and evenly distribution. - accommodation environment pressure should be higher than atmospheric pressure for tankers. • Noise level • Cleanliness of air – with suitable oxygen content

  4. Basic Terminology (of air) • Specific humidity (absolute) : ratio of mass of water vapour to the mass of dry air in a given volume of mixture. • Relative Humidity: mass of water vapour per m3 of air / mass of water vapour per m3 of saturated air AT THE SAME TEMPERATURE. • Dew point : temperature at which condensation starts when air is cooled at constant pressure. • Dry bulb temperature : Temperature of atmospheric air. • Wet bulb temperature : Temperature obtained with the thermometer bulb covered with cotton wick in water.

  5. Ideally for human body comfort : • Dry bulb temperature * 22 – 27 degree celsius • Relative humidity * 40 – 60 % • Air motion * 15 m/min • Noise level * 45 – 50 dbs • Cleanliness * no dust particles, fumes & foul odour. Pleasant sweet smell. oxygen content sufficient to sustain life. * : preferably

  6. Instrument • Hygrometer aka psychrometer • 2 thermometers used – dry bulb / wet bulb • Correct psychrometric chart ( different altitude and barometric pressure )

  7. See Page 33

  8. Dry Bulb : 27 deg C Wet bulb : 27 deg C Wet bulb : 14 deg C Wet bulb : 19 deg C IDEALLY , temperature : 22 – 27 Deg C ; Relative humidity : 40 – 60 %

  9. Fresh air intake ACCOMMODATION AIR CONDITIONING PLANT Recirculation air Condenser Expansion valve Filter element Cooling water in / out Evaporator Bulb Steam heating coils Steam supply Humidifier Refrigerant compressor Fan Port side Starboard side : Refrigerant flow

  10. sensor Fresh air intake Recirculation air ACCOMMODATION AIR CONDITIONING PLANT Thermostat Condenser / Receiver Solenoid stop valve Expansion valve Drier Filter element Cooling water in / out Sight glass Evaporator Bulb Oil separator Oil return to compressor sump Steam heating coils Steam supply HP pressure switch Oil pressure switch Humidifier Refrigerant compressor Fan LP pressure switch Port side Starboard side : Refrigerant flow See Notes, Page 32

  11. Air Conditioning Plant Recirculation from accommodation Dampers S Fresh air from outside M F C H Hu Fa Cabin Door M – Mixing of fresh air and return air Hu – Steam spray for humidification F – Filter element Fa – Circulation fan C – Cooling coil (evaporator coils after expansion valve) S – Sound trap / Silencer H – Steam heating coils (for winter application)

  12. Types of air filter : • Oiled meat type • Throw away type • Washable nylon or plastic type (commonly used nowadays) • Purpose : To ensure air cleanliness before reaching the AHU.

  13. Refrigeration system for cargo • Direct expansion grid system • Direct expansion battery cooling system • Brine grid cooling system • Brine battery cooling system

  14. Direct Expansion Grid System Cargo hold Grid compressor Condenser See Page 45

  15. Direct Expansion Battery Cooling Cargo hold evaporator compressor Condenser fan See Page 46

  16. Brine cooling system – use of a secondary refrigerants Advantages: • Reduces the use of expensive primary refrigerant • Reduces the use of more robust piping system for high pressure • Allows multilevel installations • Allows a wide range of temperature controls

  17. Brine – Mixture of calcium chloride and water Specific gravity 1.24 1.25 1.26 1.265 1.27 1.28 15 deg C Operating temperature -21 -23 -26 -29 -32 -34 Deg C Freezing temperature C -30 -32 -35 -37 -41 -43 Deg C Specific heat 0.685 0.678 0.671 0.667 0.661 0.658 Kcal / kg page 24 and page 49

  18. Brine Grid Cooling Brine Grid Cargo hold compressor Condenser Brine circulating pump expansion valve See Page 47

  19. Brine Battery Cooling brine evaporator cargo hold compressor Condenser brine circulating pump expansion valve See Page 48