ships air conditioning

SHIPSSHIPS Air

Conditioning

SHIPSIntroduction

The importance of shipboard air conditioning depends on ship’s mission. Passenger vessels focus completely on passenger comfort, such as cruise ships and casino vessels, air conditioning is vital. Aboard commercial vessels (tankers, container ships, etc.), air conditioningprovides an environment in which personnel can live and work without heatstress. We are Going to talk about Merchant &Naval Ships’ Air Conditioning Systems.

Merchant Navy

Cooling Loads Heating Loads .

LOAD Calculations

Solar Radiation Heat transmission through hull, decks, and

bulk heads. Heat dissipation from occupants. Heat gain from lights. Heat gain from ventilation air. Heat gain from motors or other electrical

equipment. Heat gain from piping, machinery ,or other

equipment.

Heat Loss through hull, decks, and bulk heads. Heat loss from ventilation air. Infiltration

• Outside Temperature and Humidity:Based on temperature prevalent in ship’s area on operationFor Cooling Condition its 35◦c dB and 25 ◦c wb.For Heating Condition its -18 ◦c db.Seawater summer design temperature is 32 ◦c and -2 ◦c in winter

Design Criteria

• Solar GainFor compartments with only one outside boundary, Temperature difference across horizontal surfaces increases by 28 K and vertical surfaces by 17 K.And for those with more than outside boundary, the temperature difference increase across horizontal surfaces increases by 19 K and vertical surfaces by 11 K.

Comments on Load Calculations


Infiltration

• Transmission between spaces:For heating Loads it isn’t considered and for cooling loads the cooling effect of adjacent spaces isn’t considered unless temperatures are maintained with refrigeration or air-conditioning equipment .• People:Occupants are only Counted once in their most gathering location on shipboard.


• Ventilation:The people are counted once in the location where they create the greatest ventilation requirements. This concept can by applied by measuring the CO2 levels in a space and adjusting outside air accordingly.


Factors should be considered:1. Anti-Corrosive Construction Material2. Function properly under dynamic Roll and Pitch3. Designed for continuous uninterrupted operation

over all voyage period.4. No objectionable noise or vibration.5. Small size occupation.6. Climatic changes operation flexibility.

Equipment Design Consideration

• FansMust be selected for stable performance over full range of operation and have adequate isolation to prevent transmitting vibration to the deck. Because fan rooms are often adjacent to or near living quarters.

Equimpent Selection

• Cooling CoilIf more than 30% outside air is brought across a cooling coil, the use of copper tube, copper fin, epoxy-coated coils or other special treatment must be considered.• Electric Heaters:U.S. Coast Guard (USCG) approved sheathed element heaters are typically required

Equimpent Selection

• Air Diffusers:Care must be taken with the selection of air diffusers because of the low ceilings typical of shipboard applications.• Air-Conditioning Compressors:All types are used for marine applications . When high discharge temperatures are a concern, sea water cooled heads are not normally an option; other methods such as fan cooling or liquid injection must be considered for maintaining acceptable discharge temperatures.

Equimpent Selection

Direct refrigerant cooling systems:Often used for small zone applications. like control rooms and pilot houses lend themselves to a direct refrigerant system .Two pipe and Four pipe fan coil systems:Often used for large systems. The disadvantage is fan noise in the space being cooled .In addition, limited humidity control .

Typical Systems

C.V.S. V.S. V.A.S.constant-volume systems are most common .Their advantages include simplicity (for maintenance, operation , and repair) and low cost. However, for large passenger vessels, the energy efficiency and the tight control of zone temperature make variable-volume/temperature systems very attractive.

Typical Systems

Variable volume systemConstant volume system

The conditioning Load, even on a single voyage, varies over a wide range in a short period. Not only must the refrigeration plant meet these load variations, but the controls must readily adjust the system to sudden climatic changes. Accordingly, it’s general practice to equip the plant with automatic controls

Control

Naval Ships Air Conditioning

• Outside ambient temperature:Considering the large cooling plants required for internal heat loads generated by machinery, weapons, electronics, and personnel. Temperatures of 32◦c db and 27◦c wb are used for worldwide applications, with 29.5◦c seawater temperatures. Heating-Season temperatures are 12◦c for outside air and -2◦c for seawater. • Inside temperature:Naval ships are generally designed for space temperatures of 26.5◦c db with a maximum of 55%R.H. for most areas requiring air conditioning.

Comments on Load CalculationsDesign Criteria

• Air-conditioned Spaces:• Naval ships design requires that air conditioning systems serving living and

berthing areas on Surface ships replenish air in accordance with damage control classifications:

Class Z systems:2.4 L/s per personClass W systems for troop berthing areas:2.4 L/s per personAll other class W systems:4.7 L/s per peson

Comments on Load CalculationsDesign Criteria

Comments on Load CalculationsLOAD CALCUALTION

Equipment Selection• Fans:

A family of standard fans is used by the navy, including vane axial, tube axial, and centrifugal fans. No- belt driven fans are included.

Equipment Selection• Cooling coils:

The U.S. Navy uses eight standard sizes of direct expansion and chilled-Water cooling coilsChilled Water coils are most common and are selected based on 7.2◦c inlet water with 3.7K rise in water temperature through the coil.

Navy uses two standard types of heating coils:

Equipment Selection

Steam Duct Heaters Maximum face velocity is 9.1 m/s Preheater leaving air temperature is 5.5 to 10◦c Steam heaters are served from a 350 kpa(gauge) steam system

Electric Duct Heaters Maximum face velocity is 7.1 m/s Temperature rise through the heater is no case more than 27K

Equipment SelectionFilters:U.S. Navy uses seven standard filter sizes are as follows:1.Available in steel or aluminum2.Face velocity between 1.9 and 4.6 m/s

Air Diffusers:Uses types similar to that used in merchant ships

Equipment SelectionFilters:U.S. Navy uses seven standard filter sizes are as follows:1.Available in steel or aluminum2.Face velocity between 1.9 and 4.6 m/s

Air Diffusers:Uses types similar to that used in merchant ships

Air-Conditioning Compressors:Reciprocating compressors used to be used in the past .Now rotary types compressors is being used

Comments on Load CalculationsAir Distribution Methods

ControlTwo-position dual thermostat are main air conditioning control principle that controls a cooling coil and an electric or steam reheater .The thermostat can be set for summer operation .Resetting isn’t required in Winter

ships air conditioning

Engineering