REF & AC.ppt

SIMS/ GME / Ref & AC / Sem 1 / RVP 1
MARINE REFRIGERATION &
AIR CONDITIONING
SAMUNDRA INSTITUTE OF MARITIME STUDIES

MARINE REFRIGERATION & AIR CONDITIONING
TOPICS FOR STUDY
•Properties of Refrigerants
•Refrigeration Plant Equipments
•Plant Operation
•Comfort Conditions
•Special Features of Marine AC Plants
•Accommodation Ventilation
•Air Conditioning Systems
•Duct System
•Air Cleaning
•Sound Attenuation
•Testing & Balancing the System
•Operation & Maintenance

RECOMMENDED BOOKS
1. MEP Refrigerating Machinery & Air Conditioning Plant
2. Marine Air Conditioning by SD Srivastava
3. Reed’s General Engineering Knowledge
4. General Engineering Knowledge by HD McGeorge
5. Introduction to Marine Engineering by DA Taylor
AND
1. PAYATTENTION IN CLASS
2. CLASS NOTES
3. SELF STUDY

HISTORICAL PERSPECTIVE
STONE AGE Knew about ICE
CHINESE ICE improved taste of drinks; Cut Ice in winter & stored it under
straw & chaff for use in summer
EGYPTIANS Cooling of water by placing in a porous jar
17TH CENTURY Transportation of ICE by CLIPPER ships to principal cities of the world
1623 Francis Bacon – preservation of chicken by stuffed ice
1683 Anton van Leeuwnhoek (Dutchman) discovered microbes in clear water
Scientists: Microbes multiply in moist & warm conditions & spoil food
Fresh foods not spoiled at or below 50 oF
1834 Jacob Perkins (London) - First patent on mechanically driven
Refrigeration system using Ether
1857 James Harrison & DE Siebe - First commercially viable system using
Ethyl Ether

REFRIGERATION
Process of cooling or removing heat to lower the temperature of a space,
or items to be stored in the space, to a temperature below the temperature
of the surrounding area.

AIR CONDITIONING
Process of treating air, to simultaneously control its Temperature, Humidity,
Cleanliness, and Distribution, in order to meet the specific requirements of a given space
or group of spaces
CRYOGENICS
Use of refrigeration to produce very low temperatures <150 0C

• Refrigeration: The process of removing
heat.
• Air-conditioning: A form of air treatment
whereby temperature, humidity, ventilation,
and air cleanliness are all controlled within
limits determined by the requirements of the
air conditioned enclosure.
• BS 5643: 1984

NEED FOR REFRIGERATION & AIR CONDITIONING
REF SYSTEMS Preservation of food for passengers & crew
Carriage of liquefied gases and bulk chemicals
Cooling of bulk CO2 for fire fighting systems
Extending useful life of perishables, to enable their transportation to
distant markets in bulk
(Fruits, Vegetables, Flowers, Meats)
AIR CONDITIONING SYSTEMS
Provision of a controlled environment satisfactory for comfort and health
of passengers, crew & equipment

FOOD PRESERVATION
LIVE PRODUCTS DEAD PRODUCTS
(FRUITS, FLOWERS, VEGETABLES) (MEAT, FISH, POULTRY etc.)
Continue to generate & dissipate heat, absorb Do not generate & dissipate heat, or absorb
Oxygen and give out Carbon Dioxide or other gases, Oxygen.
even when separated from the plants, trees or soil
Carried in Unfrozen condition Carried in Frozen condition
Good air distribution required to prevent localized Good air circulation not so critical for Frozen
Spoilage products
High humidity (80 – 95 %) required for Fruits & Low humidity required
Vegetables to prevent wilting, shriveling & loss of
Flavor
CO2 & other gases produced need to be ventilated 10 % CO2 levels beneficial for chilled meat

FREEZING
1. Freezing DOES NOT destroy bacteria, molds or yeasts.
2. It RETARDS growth of bacteria, molds & yeasts
3. Meats may be safely frozen for 6 months or more
4. Dressed poultry, veal and lamb can be stored up to 11 months if frozen immediately
after killing.
Frozen products are known as ‘Dead’ Products

SPECIAL FEATURES OF MARINE REF & AC PLANTS
1. Less space
2. Ship is a mobile platform – Variation in solar loads on above waterline compartments
3. Extreme weather condition variations during a day
4. Must withstand Corrosive effects of sea water and salt laden air
5. Must operate under correctly under severe conditions of ship’s movements
6. Must produce minimum structure and air borne vibration and noise
7. Design must ensure fire safety and smoke control features.
FOR ACs:
8. Prevent intake of water into ship during severe weather conditions
9. Ventilation openings must ensure:
- adequate water protection
- no mixing of exhaust and supply intakes
- no blowing or drawing air across areas where crew or passengers are traversing

UNITS OF REF & AC
TR – Tons of Refrigeration
1 TR = Cooling effect of 1 ton of ice at 32 0F that melts in 24 hr
144 Btu energy required to melt a pound of ice at 32 0F in 24 hr
288000 Btu are required to melt a ton of ice at 32 0F in 24 hr
1 TR = transfer of 288000 Btu in 24 hr, in a cooling operation
= transfer of 12000 Btu in 1 hr
= 3.51 kW (3.412 Btu/ hr = 1 W)

PSYCHROMETRY
‘Science that deals with the air and water vapour mixtures’
PSYCHROMETRIC PROPERTIES:
1. Dry – bulb temperature: dbt: temperature recorded by a common thermometer
2. Wet – bulb temperature: wbt: temp.recorded by a common thermometer with
moistened wick around the bulb and a stream of air
passed over the wick
3. Dew Point temperature: dpt: temperature at which condensation of moisture
begins when the air is cooled
(At saturation, dbt = wbt = dpt)

4. Saturation Temperature: Temp at which a fluid boils or condenses. Varies with pressure
5. Relative Humidity: Ratio of actual water vapour pressure in the air to the saturated
water vapour pressure of the air at the same temperature.
(Expressed as a %)
6. Specific Humidity: Weight of water vapour in pounds of moisture per pound of dry
air
7. Enthalpy (Φ): a thermal property that indicates the quantity of heat in the air,
an arbitrary datum
(Expressed in Btu per pound of dry air)
8. Specific Volume: cu. Ft of air and moisture mixture per pound of dry air
9. Sensible Heat Factor: ratio of sensible heat to total heat

PSYCHROMETRIC CHART
Psychrometric data such as dry bulb temp., wet bulb temp., dew pt. temp., relative
humidity, specific humidity, enthalpy, specific volume, sensible heat factor, etc.,
presented on a chart for an air and water vapour mixture is referred as a Psychrometric
chart.
If any two properties are known, the remaining properties can be determined.

VAPOUR COMPRESSION CYCLE
COMPRESSOR
CONDENSOR
EVAPORATOR
EXPANSION
VLAVE
1
2
3
4

PHASES
1. COMPRESSION:
• Pressure of the Refrigerant vapour increases
• Saturation temperature increases above the temperature of the
cooling medium used in the condenser

PHASES
1. COMPRESSION:
2. CONDENSATION:
Refrigerant is liquified as it is cooled below its saturation
temperature.
Latent heat picked up in the evaporator is given out in the
condenser to the cooling medium

COMPRESSOR
CONDENSOR
EVAPORATOR
EXPANSION
VLAVE
1
2
3
4

PHASES
1. COMPRESSION:
2. CONDENSATION:
3. EXPANSION:
Pressure drop in the expansion valve causes saturation temp. to fall.
Refrigerant boils at the low temp. of the evaporator
As liquid passes through the expansion valve, the pr. drop makes its saturation temp
fall below its actual temp, causing some of the liquid to boil-off at the expansion
valve, taking latent heat from the remainder and causing its temp to drop.
Exp. v/v throttles the liquid ref. and maintains difference of pr in HP & LP side,
while supplying refrigerant to the evaporator at the correct rate

COMPRESSOR
CONDENSOR
EVAPORATOR
EXPANSION
VLAVE
1
2
3
4

PHASES
1. COMPRESSION:
2. CONDENSATION:
3. EXPANSION:
4. EVAPORATION:
Refrigerant enters at a temperature lower than that of the secondary coolant, receives
latent heat, and evaporates.

1
2
3
4
1-2 COMPRESSION
2-3 CONDENSATION
3-4 EXPANSION
4-1 EVAPORATION
ENTHALPY (h)
PRESSURE
(p)
COP =
REF. EFFECT
WORK DONE
COP =
H 1 – H 4
H 2 – H 1

REFRIGERANT
Substance used to cool other substances by
absorbing heat from them
Eg. Ice, dry ice (solidified CO2), NH3, brine,
Freon, etc.

DESIRABLE PROPERTIES OF REFRIGERANTS
1. Easily changed from liquid to vapour and back
2. Readily volatile (Low b.p.)
3. Freezing point lower than the intended operating point
4. High latent heat of vapourisation
5. Chemical stability
6. Non – toxic even at low concentrations
7. Non – flammable
8. Non –corrosive
9. Compatibility with lubricant and materials of construction
10. No adverse environmental effects (Low ODP)
11. Readily available
12. Reasonable cost

CHEMICAL PROPERTIES
1 Should be non-toxic, nonflammable and non – explosive
2. Should be chemically stable under conditions of use
3. Should be compatible with compressor lubricants and materials of
construction
of compressor and system components
4. Should not contaminate food stuff or other stored products in the event of
a leak
5. Should be environment friendly (Low ODP)

THERMODYNAMIC PROPERTIES
1. Should have high latent heat
2. Low sp. Volume of vapour
3. Low compression ratio
4. Low boiling point
5. Freezing point below lowest operating temperature
6. High critical point (as high as possible above the condensing
temperature)
7. High specific heat of liquid

PHYSICAL PROPERTIES
1. Low viscocity
2. Leak detection possibility
3. High thermal conductivity

OTHER CONSIDERATIONS
1. Should be readily available
2. Reasonable costt

PRIMARY AND SECONDARY REFRIGERANTS
PRIMARY – They transfer heat in the evaporator and condenser and undergo
cyclic phase changes during each cycle.
SECONDARY – Transfer heat from a remote place to the evaporator without
undergoing change of phase.

CLASSIFICATION OF REFRIGERANTS
CHEMICAL SAFETY
COMPOSITION CONSIDERATIONS
Halocarbons Flammability
Hydrocarbons Toxicity
Inorganics
Azeotropes

BASED ON CHEMICAL COMPOSITION
1. Halocarbons - Replacing one or more hydrogen atom from methane or ethane with
halogens (Cl, F, Br)
- Based on research by Charles Kettering & Thomas Migley Jr., 1928
- R 11, R 12, R 22 etc.
2. Hydrocarbons - methane, ethane, propane
- used in petrochemical industry
3. Inorganic compounds - Ammonia, Water, Sulphur Dioxide, air, etc.
4. Azeotropes - mixture of two substances in a fixed ratio
- mixture exhibits new set of properties
- evaporate and condense as a single substance
- eg. R 500 (mixture of R 12 & R 152a)

BASED ON SAFETY CONSIDERATIONS
INCREASING
FLAMMABILITY
Higher Flammability A 3 B 3
Lower Flammability A 2 B 2
No Flammability A 1 B 1
LOWER TOXICITY HIGHER TOXICITY
INCREASING TOXICITY
SAFETY GROUP

REFRIGERANTS IN USE
REF. No. CHEMICAL NAME CHEMICAL FORMULA
Group A1
R 11 Trichlorofluoro methane CCl3F
R 12 DichloroDifluoro methane CCl2F2
R 22 Chloro difluoro methane CHClF2
R 134a Tetra fluoro ethane CH2FCF3
R 744 Carbon Dioxide CO2
Group A2
R 142b 1Chloro Difluoro ethane CH3CClF2
R 152a 1,1- Difluoro ethane CH3CHF2
Group A3
R 170 Ethane C2H6
R 290 Propane C3H8

REFRIGERANTS IN USE
REF. No. CHEMICAL NAME CHEMICAL FORMULA
Group B1
R 123 DichloroTrifluoro ethane CHCCl2CF3
R 764 Sulphur Dioxide SO2
Group B2
R 40 Chloro methane (Methyl Chloride) CH3Cl
R 717 Ammonia NH3

COMPARISON OF REFRIGERANTS (per kW of Refrigeration, -15 0C evap & 30 0C condensor temp.)
REFRIGERANT
PROPERTIES
AMMONIA R 22 (CHClF2) R 134a (CH2FCF3)
EVAPORATOR PR. MPa 0.236 0.296 0.16
CONDENSOR PR. MPa 1.164 1.192 0.77
COMPRESSION RATIO 4.94 4.03 4.81
REFRIGERATING
EFFECT kJ / kg
1102.23 162.46 150.71
REFRIGERANT FLOW
RATE kg / s
0.00091 0.00616 0.00664
SP. VOL. OF SUCTION
GAS m3 / kg
0.5106 0.0774 0.1224
COMPRESSOR
DISLACEMENT l / s
0.463 0.476 0.812
COMP. POWER kW 0.207 0.210 0.226
COP 4.84 4.75 4.42
COMP. DISCH TEMP K 371 326 316

BRINES
Indirect refrigeration systems use Brines as secondary refrigerant
Water, brine, alcohol or some other refrigerant can be used
Coolants using a mixture of Calcium and Sodium Chloride are common ref. Brines
Glycols, Alcohols & some low temp. fluids also used.

PROPERTIES OF BRINES
SECONDARY
COOLANT
CONCENTRATION
by wt. %
FREEZING
PT. 0 C
FLOW RATE
L / s- kW
HT. TRANSFER
FACTOR
SP. HEAT AT 0 0 C
kCal / kg 0 C
SALTS
Calcium Chloride 22 - 22.1 0.0500 2.761 0.77
Sodium Chloride 23 -20.6 0.0459 2.722 0.79
GLYCOLS
Propylene Glycol 39 -20.6 0.0459 1.000
Ethylene Glycol 38 -21.6 0.0495 1.981

REFRIGERATION COMPRESSORS
TYPES OF COMPRESSORS
- BASED ON TYPE OF SEALING
- BASED ON TYPE OF MOTION IN COMPRESSOR

Definition Review
• Specific heat (Cp)
– Amount of heat required to raise the
temperature of 1 pound of substance 1F
(water is 1 Btu/lb F)
• Sensible heat - add energy and temp rises

SIMS/ GME / Ref & AC / Sem 1 / RVP
DEFINITIONS
 Latent Heat of Fusion
– The heat that must be removed from a
liquid to change it into a solid or added to
go from solid to liquid without any change
in temperature
 Latent Heat of Vaporization
– Amount of heat required to change the
state of a substance from liquid to a vapor
without a change in temperature

DEFINITIONS (cont.)
 BTU
– Standard unit of measurement for heat
• 1 Btu = 778.26 ft-lb
 Refrigeration Ton
– Unit of measurement for the amount of
heat removed
– Based on the cooling effect of 1 ton of ice
at 32F melting in 24 hours

Generic Cycle

Thermodynamic Cycle
Evaporator
Condenser
Compressor
TXV

Vapor-Compression Refrigeration Cycle
• Refrigerant
• Receiver
• Thermostatic expansion valve (TXV)
• Evaporator
• Compressor
• Condenser

Refrigeration
Cycle

Components
• Refrigerant
• Evaporator/Chiller
• Compressor
• Condenser
• Receiver
• Thermostatic
expansion valve
(TXV)

Refrigerant
• Must have the following properties
– High latent heat of vaporization - max cooling
– Non-toxicity - not a health hazard
– Desirable saturation temperature - for operating
pressures
– Stability - nonflammable/nonexplosive
– Ease of leak detection
– Low cost
– Readily available
• Commonly used FREON (R-22, R-134a, etc.)

Expansion
• Liquid Freon enters the expansion valve at
high pressure
• Refrigerant leaves TXV at a much lower
pressure
• As pressure drops, vapor formation begins
as Freon enters saturation region

Evaporation
• From TXV - Freon is a saturated mixture of
liquid and vapor
• Cooling coil acts as a heat exchanger
• Absorbs its latent heat of vaporization from
the surroundings
• Slightly superheated (10ºF) - ensures no
liquid goes to compressor

Compressor
• Superheated Vapor:
– Enters as low press, low temp vapor
– Exits as high press, high temp vapor
• Temp: creates differential (DT)
promotes heat transfer
• Press: Tsat allows for condensation at
warmer temps
• Increase in energy provides the driving force
to circulate refrigerant through the system

Condensation
• Refrigerant returned to starting point as a
high pressure/temperature subcooled liquid
• Latent heat of condensation (LHC)
• Sea water heat exchanger is used to absorb
the LHC and discharge it overboard

Receiver
• Temporary storage space and surge tank for
the sub-cooled refrigerant
• Serves as a vapor seal to prevent vapor from
entering the expansion valve

- BASED ON TYPE OF SEALING
- OPEN
- HERMETIC

- RECIPROCATING
- ROTARY

- RECIPROCATING
- SINGLE / TWO STAGE
- SINGLE ACTING / DOUBLE ACTING

- RECIPROCATING

- RECIPROCATING
- ROTARY
- CENTRIFUGAL
- SCREW
- SCROLL
- TROCHOIDAL
- ROLLING PISTON
- VANE
- FIXED / ROTATING

PARTS OF RECIPROCATING COMPRESSORS
1. Cylinder Block & Heads 11. Shaft Coupling/ Pulley
2. Cylinder Liners 12. Lubricating Oil Pump
3. Pistons 13. Capacity Control Device
4. Piston Pins 14. Suction & Discharge Shut off Valves
5. Piston Rings 15. Oil Filter
6. Connecting Rods 16. Oil Heater
7. Crankshaft 17. Oil Cooler
8. Main Bearings 18. Oil Separator
9. Valves (Suction & Discharge) 19. Filter Drier
10.Shaft Seal 20. Safety Cut outs (HP/ LP/ Diff Pr)

1. Cylinder Block & Heads
• Made in one piece with the crankcase and cast from
cast iron, or fabricated from pipe sections
• Suction inlet to the compressor through a suction
manifold with suction gas strainer to prevent ingress of
any foreign material into the compressor

1. Cylinder Block
2. Cylinder Liners
• Renewable cylinder liners are made from fine grain C.I.
and pressed into the cylinder jackets.
• Internal surface is made smooth by precision boring and
honing

1. Cylinder Block
2. Cylinder Liners
3. Pistons
• Made of Aluminium Alloy
• Oil rings provide gas sealing, oil control and heat
dissipation

1. Cylinder Block
2. Cylinder Liners
3. Pistons
4. Piston Pins
•Piston pins are hollow, made of S.S. and are case hardened
and machined to closest tolerances
•Fixed by internal circlips

PARTS OF RECIPROCATING
COMPRESSORS
1. Cylinder Block 2. Cylinder Liners 3. Pistons 4. Piston Pins
5. Connecting Rods:
I-section, die forged
Fine bored bronze bushes at small end bearing for piston pin,
White metal lined split shell bearings at big end for shaft bearing.

HP CUT OUT

FAULT FINDING
The steps are as follows:
1. Detection, i.e. detection of abnormal operation
2. Knowledge of the system to track down the cause
3. Observation of exact operating conditions
4. Identification of the fault
5. Decision: what to do? how? when? can it be left?
6. Action to rectify the fault
7. Test: is it now normal?
8. Record note in log, for future information

DUAL DUCT SYSTEM

THERMOSTATIC EXPANSION VALVE

THERMOSTATIC EXPANSION VALVE
WITH EXTERNAL EQUALIZATION

PLATE HEAT EXCHANGER

Boyle’s Law states that, for an ideal gas, the
product of pressure and volume at constant
temperature is a constant: pV = constant
Example A volume of an ideal gas in a cylinder and at atmospheric pressure is
compressed to half the volume at constant temperature. What is the new pressure?
p1V1= constant = p 2V2
so p2 = 2 p1
= 2 * 1.013 25 bar (101 325 Pa)
= 2.026 5 bar (abs.)
BOYLE’S LAW

Charles’Law states that, for an ideal gas, the volume at constant
pressure is proportional to the absolute temperature:
V/ T = constant
Example A mass of an ideal gas occupies 0.75 m3 at 20 0 C and is
heated at constant pressure to 90 C. What is the final volume?

SHUT OFF VALVE

Major Components of Vapour Compression System
Compressor
There are primarily four types of compressors used in the
air-conditioning industry:
Reciprocating,
Scroll,
Screw
Centrifugal.

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