Transcript Document
REFRIGERATION, COMPRESSED AIR SYSTEMS & EFFICIENT USE OF ENERGY
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Principles of Refrigeration
Refrigeration means to COOL AN OBJECT BELOW ITS SURROUNDING TEMPERATURE 2
Vapour Compression Cycle
Basic Components of the vapour compression refrigeration system
3 CONDENSER • Compressor • Condenser • Throttling Device • Evaporator EXPANSION VALVE 4 EVAPORATOR 2 COMPRESSOR 1 3
PRESSUR KN/m2 E
Vapour Compression Cycle
CONDENSER HEAT REJECTION Pd Pe 4 3 THROTTLING CONDENSATION EVAPORATION COMPRESSION 2 1 3 CONDENSER 2 EXPANSION VALVE 4 EVAPORATOR COMPRESSOR 1 ENTHALPY KJ/Kg REFRIGERATION EFFECT WORK DONE 4
VAPOUR COMPRESSION CYCLE COMPONENTS
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REFRIGERANTS
CHLOROFLUOROCARBONS (CFC)
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R-11
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R-12 HYDROCHLOROFLUOROCARBONS (HCFC) R- 22 R-123 HYDROFLUOROCARBONS (HFC) R-32 R-125 R-134a R-143a INORGANIC COMPOUNDS R- 717 R- 718 R- 729
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Unit of Refrigeration The unit of refrigeration is
TON OF REFRIGERATION ( TR )
1 TR = 12’000 Btu/hr
BRITISH UNITS
1 TR = 3.517 KW
SI UNITS 7
Refrigeration Cycle Efficiency
The refrigeration cycle efficiency is known as
COEFFICIENT OF PERFORMANCE (COP REF ) (COP REF )
= Refrigeration Effect Work Done KJ/Kg KJ/Kg
(COP HP )
= Condenser Heat Rejection KJ/Kg Work Done KJ/Kg 8
Refrigeration Equipment Efficiency
The equipment efficiency is given as EER or kW/TR
ENERGY EFFICIENCY RATIO (EER) Use for smaller capacity equipment such as Window type & Split type equipment (EER)
= Capacity Btu/hr Power Input Watts
kW/TR Use for large capacity equipment such as Chillers (kW/TR)
= Power Input Capacity TR kW 9
P-h DIAGRAM FOR REFRIGERANT 134a
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MONTRÉAL PROTOCOL OBLIGATIONS 1.
2.
3.
Face-out of CFC in year 2005 Introduction of Quota for HCFC in year 2015 Face-out of HCFC in year 2040
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ASHRAE Standard 34-1992 Refrigerant Safety Classifications
Higher Flammability Lower Flammability No Flame Propagation
Group A3 Group B3 Group A2 Group B2 Group A1 Group B1
Lower Toxicity
INCREASING TOXICITY
Higher Toxicity
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Refrigerant Data & Safety Classifications REFRIGERANT CHEMICAL FORMULA CHEMICAL NAME
R-11 R-12 R-22 R-134a R-717 CCl 3 CCl 2 F 2 CHClF 2 CH 2 FCF 3 NH 3 Trichlorofluoromethane Dichlorodifluoromethane Chlorodifluoromethane 1,1,1,2-tetrafluoroethane Ammonia
REFRIGERANT SAFETY CLASSIFICATION
A1 A1 A1 A1
AMOUNT OF REFRIGERANT PER OCCUPIED SPACE (ppm)
4’000 40’000 42’000 60’000
TLV-TWA (ppm)
C1’000 1’000 1’000 1’000 B2 500 25 13
AMMONIA (NH3) R-717
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In-expensive Refrigerant best suited for industrial use Higher refrigeration effect 474 Btu/lb, comparison; R-12 = 50 Btu/lb , R-22 = 70 Btu/lb, R-134a = 64 Btu/lb, R-404A = 48 Btu/lb
7- times higher refrigeration effect!!!
Specific volume of suction gas is high 8 ft 3 /lb compare to 1.2 ft 3 /lb of R-22, needs larger pipes, compressors Higher delivery temperatures 210 ºF, needs water cooled heads for compressor
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COOLING TOWER (CT)
INDUCED DRAUGHT
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COOLING TOWER (CT)
CROSS FLOW
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COOLING TOWER (CT)
FORCED DRAUGHT
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WATER PUMPS
VERTICAL IN-LINE
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FAILURES
DETECTION OF SIMPLE FAILURES
Refrigeration Plant should function properly, if the following checks are OK.
At a glance • Suction sweat • • • Warm liquid line & clear sight glass from bubbles Condenser outlet air warm Condenser water in & out has significant feel of temp deference Using measuring equipment • Manifold Gauge Set - measure the pressure of refrigerant • Clip-on Ammeter - measure the current flow and voltage • Sling Psychrometer - measure the dry bulb & wet bulb temp.
• Anemometer - measure the air flow 19
FAILURES
DETECTION OF SIMPLE FAILURES …cont.
Detection by observation - A/C unit malfunction if the following observations are found • Sweating down stream of the Filter/dryer – Filter Block • • Ice build up at compressor comp. valves – Over Charge, damaged Ice build up at evaporator – Under charge, gas leak, air filter clogged, cooling coil blocked, fan belts are loose • Bubbles in the sight glass filter/drier lack of refrigerant or blocked • Oil drops near refrigerant pipe fittings, components etc. – Refrigerant leaks in the system.
• Condenser shell cooler & evaporator shell warmer (Centrifugal Chiller) – at low condensing temperatures, refrigerant migrates to evaporator 20
COMPRESSED AIR SYSTEMS
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Compressed air system provides……..
Provides air under compression to pneumatic drives Use reciprocating or screw compressors with storage receiver Use pressure regulators at the air user point to reduce the air pressure Use water separators to prevent water vapour entering the air user equipment 22
ROTARY SCREW COMPRESSORS
Pulsation free air 100% continuous duty Quiet operation Energy efficient at full load Extended service intervals Reliable long life Improved air quality 23
TIPS FOR COMPRESSED AIR SYSTEMS
Locate the compressor closest to the largest air user to reduce pressure drop through the air line Ventilate the compressor well Keep 3 feet around the compressor unit Surrounding temperature should be below 115 ºF Avoid extreme humidity Keep air filters clean all the time Use refrigerated and desiccant dryers to reduce water vapour concentration 24
EFFICIENT USE OF ENERGY
Resources are limited and conserve energy Refrigeration Reduce heat transfer Select energy efficient equipments Compressed air systems Fix all leaks in the piping Regulate lowest pressure at air user Reduce blow-offs Shut-off air supply to off-line air users Consider multi staged compressors 25
THANK
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