Engineering - Royal Australian Navy

Naval Engineering Bulletin • June 2001
Compliance with Montreal
Protocols
There are typically between 150 and 300 kg of Cfc’s or
HCFC’s banked in a typical ship’s air conditioning and provision
plants.
It is estimated that 80% of the world’s shipping fleet uses
HCFC-based refrigerants, like R22, for primary air conditioning,
provisions, storage, and cargo cooling (food products
such as fish). It is anticipated that most existing ships
will continue to operate R22 systems. However ships owners
and operators will have to bear in mind that the reduction
in manufacture of HCFC’s by 35% is to have taken place
on a global scale by 2004.
The Montreal Protocol requires the complete phase out of
HCFC’s by 2030.
Thus replacements for R22 generally at the moment consist
of blends which constitute R134a, as one of the blends
however there is no clear preferred alternative at this point
in time.
Typical Compartments to be
Air Conditioned or Ventilated
Compartments generally air conditioned on a ship consist
of staterooms/cabins, lounges, recreation spaces, mess and
dining rooms, offices, vital electronic equipment compartments,
chart rooms, hospital or sick compartments, bridge
or wheelhouse.
Other compartments generally have ventilation requirements
depending on usage but are typically not air-conditioned.
Ventilation of the remaining compartments serves
two purposes as follows:
• Removal of heat.
• Removal of odours or dangerous gases.
Naturally as in air-conditioned compartments there have
to be limits on the air change rate per hour due to the small
compartment volumes.
Design Criteria
The design criteria for ships depend on the area of service
that is envisaged; in general they are as follows:
Cooling Cycle Outdoor Ambient
Temperatures
• North Atlantic; 350C Dry Bulb & 25.50C Wet Bulb.
• Semi-Tropical; 350C Dry Bulb & 26.50C Wet Bulb.
• Tropical; 350C Dry Bulb & 280C Wet Bulb.
Heating Cycle Outdoor Ambient
Temperatures
• -180C Dry Bulb unless vessel will always operate in
high temperature climates.
Seawater Temperature (as this is the
heat sink)
• 300C in Summer & -20C in Winter. Although
seawater temperatures can be hotter in various
equatorial parts of the world.
Compartment Temperatures
• Inside design temperatures range from 24.50C Dry
Bulb & 26.50C Wet Bulb with 50% relative humidity
in Summer and from 180C Dry Bulb to 240C Dry Bulb
in Winter.
Thermal Comfort
From a review undertaken by Lloyd’s Register it would appear
that typically air conditioning temperatures on board
ship are set lower than necessary due to high metabolic
“overheating” resulting from high occupancy rates.
Fresh Air Requirements
Fresh air ventilation could meet such standards as deemed
appropriate in the Flag State or alternatively a recognised
standard such as ASHRAE Standard 62 or other standards
such as ISO 7547 which relates specifically to ventilation
for passenger accommodation onboard ships.
Loyd’s Register have compiled guidelines that suggest the
following ranges:
• Dining rooms and bar areas 10 l/s to 15 l/s per person.
• Cabins 8 l/s per person.
• Smoking lounge 30 l/s per person.
Therefore varying outside air provisions are a possibility that
depends of course to some extent on the size and proposed
role of the ship and more particularly depending on the
compartment usage.
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