EKL404N Engineering Knowledge - HVAC.pdf

Engineering knowledge

1. AC, REFRIGERATION AND VENTILATION
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Refrigeration:
is a process in which the temperature of a space or its contents is reduced
to below that of surroundings.
The primary purpose of refrigeration is lowering the temperature of the
enclosed space or substance and then maintaining that lower temperature.
Air conditioning:
is the control of temperature and humidity in a space together with the
circulation, filtering and refreshing of the air.
Ventilation:
is the circulation and refreshing of the air in a space without necessarily a
change of temperature.

2. AC, REFRIGERATION AND VENTILATION
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HVAC–Heating, Ventilation and Air Conditioning.
Main Functions:
❖Temperature Control: Desirable value -24
0
~ 27
0
C
❖Humidity: Desirable value -40 ~ 60%
❖Air Quality
✓Filters
✓Ventilation
•Fresh Air
•Re-circulation

3. AC, REFRIGERATION AND VENTILATION
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4. AC, REFRIGERATION AND VENTILATION
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HVAC –Heating, Ventilation and Air Conditioning.
Temp Control 24 to 27 deg C Evaporator & Heater
Humidity 40% ~ 60% Evaporator & Humidifier
Air Quality
Filter
Ventilation
Fresh air
Recirculation

5. AC, REFRIGERATION AND VENTILATION
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HVAC

6. AC, REFRIGERATION AND VENTILATION
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7. AC, REFRIGERATION AND VENTILATION
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Principle of refrigeration:
A refrigerator is a device which works on the principle thatevaporation of a liquid gives
a cooling effect.
The absorption of the amount of heat necessary for the change of state from a liquid to
a vapor by evaporation, and the release of that amount of heat necessary for the change
of state from a vapor back to the liquid by condensation are the main principles of the
refrigeration process, or cycle.

8. AC, REFRIGERATION AND VENTILATION
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9. REFRIGERATION PLANT
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Low Pressure High Pressure
To other Evaporators

10. Components of Refrigeration plant:
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Compressor: Reciprocating single or two stagecompressor. It compresses the refrigerant to a high pressure and
sends it to the condenser.
Oil Separator: It prevents oil from the compressor from being carried over to the condenser.
Condenser: Shell & tube type condenser. It cools down the refrigerant, converting it from vapourback to liquid.
Receiver: The cooledrefrigerantin liquid form is stored in the receiver. Usually, the condenser itself acts as the
receiver.
Drier: It usually consists of silica gel to remove any moisture from the refrigerant.

11. Components of Refrigeration plant:
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Expansion valve: The Expansion valve regulates the flow of the refrigerant to the evaporator based on the
requirement. Here, the pressure of the refrigerant is dropped to the low-pressure value.
Evaporator: The evaporator unit act as aheat exchangerto cool down the space or media it is deigned for.
Here the refrigerant converts from liquid to vapourby taking heat from the space/media being cooled. Latent
heat is being used.
Refrigerant: The substance being circulated in the refrigeration plant for carrying out the heat transfer
process.

12. AC, REFRIGERATION AND VENTILATION
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13. AC, REFRIGERATION AND VENTILATION
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Types of Refrigerant:
Primary Refrigerant: The refrigerant flowing through the refrigeration plant.
Secondary Refrigerant: The media being cooled by the primary refrigerant which further
cools the space i.e., room, container etc.

14. AC, REFRIGERATION AND VENTILATION
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Alarms and Trips:
Ref room high temperature
Ref room door not closed
Ref compressor lube oil low pressure
Ref compressor high pressure
Ref leakage alarm
Gas alarm (fresh air intake)

15. VENTILATION SYSTEM
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Ventilation System may be :
✓Natural
✓Forced
✓Exhaust

16. AC, REFRIGERATION AND VENTILATION
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Marine Ventilation Systems
Marine ventilation systemsareof great importance.
The purpose of high-quality marine ventilationis two-fold:
-it contributes to maintenance of a vessel by reducing the growth of mold and removing
musty air and it benefits the comfort level onboard as well.
-Marine Ventilation is a necessity for the performance of Engines and other equipment.

17. AC, REFRIGERATION AND VENTILATION
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Engine Room ventilation: is basically done in a manner to maintain a Positive
pressure in the engine room:
•Important for turbocharged engines –Main Engine & Generator Engines
•Creates circulation which helps maintain a cooler temperature in the Engine room.
•Maintaining a fresh atmosphere for the Engine Staff.
Engine room ventilation systems consist of both
•Supply fans
•Exhaust fans
The capacity of the supply fans I greater that that of the exhaust fans.

18. AC, REFRIGERATION AND VENTILATION
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Galley
An efficient system of mechanical exhaust ventilation to draw off fumes from cooking
appliances must be provided in each galley, unless the natural ventilation provided is
adequate to ensure that the fumes escape only to the open air.
Hospital
The mechanical ventilation system must be such as to maintain 10 air changes per hour
under all conditions of weather and climate to which the ship is likely to be subjected
during the intended voyages.

19. AC, REFRIGERATION AND VENTILATION
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REASONS FOR CARGO HOLD VENTILATION
▪Removing toxic / hazardous gases and vapourswhich may be emitted by the cargo
▪Preventing excessive heating of the cargo, especially the self-heating type.
▪Maintaining oxygen level in the hold especially for the oxygen-depleting cargoes.
▪Minimizing the formation of sweat by dew point control
▪The occurrence of an explosive atmosphere in cargo holds shall be avoided.

20. AC, REFRIGERATION AND VENTILATION
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NATURAL VENTILATION SYSTEM
A natural ventilation system, as the name suggests, is based on nature’s law of air
circulation.
Air can enter and leave the hold through the vents located above the deck level.
This allows cool, heavier air from the outside atmosphere to replace the lighter, rising
warm air inside the cargo hold.
Some older designs of dry cargo ships were fitted with ventilator shafts leading to the
lower parts of the cargo hold. In these cases, air circulation in the cargo hold was
achieved by trimming the ventilators (cowl direction) with respect to the wind direction.

21. AC, REFRIGERATION AND VENTILATION
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NATURAL VENTILATION SYSTEM
On newer designs of dry cargo ships (particularly bulk carriers), the hinged-door type
ventilators are often fitted on the sides of the hatch cover.
These can then be opened depending on the relative wind direction to provide adequate
surface ventilation within the cargo hold.

22. AC, REFRIGERATION AND VENTILATION
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External view of hinged-door ventilator on cargo hold hatch cover side

23. AC, REFRIGERATION AND VENTILATION
23Internal view of hinged-door ventilator on cargo hold hatch cover side

24. NATURAL VENTILATION –CARGO HOLDS
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Gooseneck
ventilation pipe fitted
to hatch cover

25. FORCED VENTILATION
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Mechanical
mushroom-type
ventilator

26. FIRE DAMPERS
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Marine Fire dampersareused in air conditioning and ventilation ducts to cut-off oxygen to
a space having a fireand to prevent the spread of fire, smoke and gas.
In case of fire,
•The fire and gas dampers will
✓close automatically,
✓Need to be closed manually.
This will:
✓Prevent fresh air (oxygen) from entering the space having a fire.
✓Prevent the spread a fire, smoke and gas.