Air handling unit power point presentation

Ahu ppt

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 comfortof 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. Dry bulb temperature
Dry bulb temperature line
Relative humidity line
Wet bulb temperature line
Wet bulb temperature
Psychrometric Chart
Relative humidity %
40%
60%
50%
Specific humidity
increasing 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. ACCOMMODATION AIR CONDITIONING PLANT
Condenser
Cooling water in / out
Expansion valve
Refrigerant
compressor
Evaporator
: Refrigerant flow
Bulb
Recirculation
air
Fresh air
intake
Port
side
Starboard
side
Fan
Steam supply
Humidifier
Steam heating
coils
Filter element

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

11. Air Conditioning Plant
Fresh air from outside
Cabin
Door
Recirculation from accommodation
M F C H Hu Fa
S
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)
Dampers

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
compressor
Condenser
Cargo hold
Grid
See Page 45

15. Direct Expansion Battery Cooling
compressor
Condenser
Cargo hold
evaporator
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 1.2651.27 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 heat0.6850.6780.6710.6670.6610.658
Kcal / kg
page 24
and
page 49

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

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