Air Conditioning System on board
Figure 1. Air Handling Unit
The figure above represents a typical AHU( Air Handling Unit).
It’s generally located at accommodation area,a bit away from the compressor unit.As shown in the figure it’s divided into a number of sections.
The air draft enters through mixing section & exists through distribution section.
At mixing section – mixing of the return air & the fresh air takes place. Flow of the return air & the fresh air is controlled by manually operated dampers.
A filter is fitted in the next section to remove dirt particles.
At the heating section -heating of air takes place(for operation in cold areas).Heating medium on board is generally steam.A steam trap is fitted at the steam outlet.
At cooling section – heat exchanger/evaporator is located. Heat exchange & cooling down of air draft takes place here.Refrigerant passes though the heat exchanger coils & air blown through externally.Refrigerant flow is regulated by the solenoid valve.A thermostat fitted at the fresh air inlet energizes /de-energizes the solenoid.Whenever set temp is reached thermostat shut off refrigerant supply by de-energizing the solenoid valve. Additionally,thermostatic expansion valve(EV) located right after the solenoid valve further fine tunes refrigerant flow to prevent carry over of the liquid refrigerant to the compressor.
Liquid refrigerant carry over to the compressor is extremely damaging.
At humidifying section- the humidity of air is brought up to the desired level in extremely dry atmospheric state.Here water is injected on air stream in the form fine mist through nozzles by mean of compressed air pressure.A humidistat(HU) located at the distribution section monitors humidity of air and regulates the solenoid valves fitted both in the water supply line and in the compressed air line.
At water eliminating section – precipitated condensate is removed and prevented from being carried over with the air stream. .
At fan section – a motor driven blower is located.The blower performs air circulation throughout the ducting system by drawing air draft from the up stream & forcing it downstream.
Finally from the distribution section air draft is delivered to the ducting.
the end.