Refrigeration Air Cond Vent

D1MC Semester 2 / ECS / March 2007/LSC /10. Refrigeration, AC & ventilation 1

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Refrigeration, Air conditioning

& ventilation



Refrigeration System Cold Room

The refrigerant is drawn as vapour at low pressure from the evaporator into compressor.

The vapour is compressed in compressor to a high pressure and delivered into coils of condenser in the state of superheated vapour.

Vapour is cooled and condensed into liquid in the condenser at approximately sea water temp.

Liquid still at high pressure passes to thermal expansion valve. Some flashes off into vapour.

The liquid and vapour passes through evaporator where it receives heat to evaporate before being taken into compressor



Refrigeration System



Refrigeration, Air Conditioning & Ventilation

Desirable properties of a Refrigerant

Non-corrosive

High critical temperature

(temperature above which refrigerant gas cannot be condensed by pressure)

Non toxic

Non- flammable

Easy leak detection

High latent heat value

Low condensing pressure

( low pressure system to safeguard leakages)




Properties of refrigerants

Carbon Dioxide

Low specific volume, low critical temperature,

high condensing pressure, low latent heat, non-

toxic

Freon 12 (R12)

High critical temperature, low condensing

pressure,

high latent heat, low specific volume, non-toxic.

Ammonia

High specific volume, toxic, flammable




Properties of refrigerants

HFC 134a

zero Ozone Depletion Potential (ODP)

some Global Warming Potential (WMP)?

28 psi (2 bars) bp 32 deg F

160 psi (12 bars) bp 115 deg F.



Refrigeration for Container



Refrigeration for Cargo



Air Conditioning System

Provide a comfortable working environment.

Several central units are used to distribute conditioned

air to cabins/space via single duct.

In warm climate, a mixture of fresh and recirculated air

is cooled and dehumidified during its passage over the

refrigeration unit.

In cold climate air mixture is warmed and humidified

either by steam , hot water or electric heating elements.

Temperature and humidity of air is controlled

automatically at the central unit.



Air Conditioning System



Ventilation System for Cargo Holds

Ventilators are necessary to give adequate air circulation to under deck spaces and tanks.

The coaming of ventilators are to have a minimum height

above the weather deck of : position 1, exposed freeboard &

superstructure deck within forward 0.25L : 900 mm and

position 2, exposed superstructure deck abaft 0.25L: 760mm

Goose or swan neck type ventilators are mainly used for air

pipes to tanks. The height is not to be less than 760 mm on

freeboard deck and 450 mm on superstructure deck.

Air pipes are placed at opposite end to the filling pipe and

/or at the highest point of the tank.



Ventilation System for Cargo Holds



Ventilators

Concept: The coaming height is defined as the

vertical distance from the deck to the

lower edge of the access opening.

For gooseneck vents, the coaming height is measured to the underside of the gooseneck.

Wall vent fitted with an internal baffle, the coaming height is measured to the top of the baffle.

Requirements: In Position 1, minimum coaming height is to be 900mm.

In Position 2, minimum coaming height is 760mm.



Cargo Holds Ventilation System



Ventilators



Cargo Holds Ventilation System

Documents

Refrigeration Air Cond Vent