07 refrigerants
Post on 21-Apr-2015
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Desirable Characteristics of Refrigerants
• Thermally stable• Safe (toxicity and flammability)• Low cost and widely available• Compatible with materials of construction• High performance
– High latent heat– Low compression superheat– Low throttling losses– High heat transfer properties
• Environmentally benign (ODP and GWP)
Refrigerant Classification
Refrigerants
MixturesPure
Zeotropes Azeotropes
R502
R507
R410A*
R404A*
R407C
Natural CFC HCFC HFC
Ammonia
Propane
R12
R114
R11
R22
R123
R134a
R32
R125
R143a
Iso-Butane
R290-R600a
*Near-Azeotropes
CO2
Used in or considered for Refrigeration
Propane/Iso-Butane
ASHRAE Refrigerant Safety Classification
B3R1140
A3R170, R290, R600a, R1150
High Flammability
B2NH3
A2R32, R142b, R143a, R152a
Low Flammability
B1R123, R764, R21
A1R11, R12, R22, R125, R134a, R407C,
R507, R404A, R410A, R744No Flammability
High ToxicityLow/No Toxicity
Refrigerants marked in Red are ozone depleting substances that are no longer used in new equipment.Refrigerants marked in Green are natural refrigerants that have low GWP,as well as no ODP.
Mixture Phase Diagrams
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Mole Fraction, x
Sat.
Tem
pera
ture
Tsat
Liquid Mole-Fraction Vapor Mole-Fraction
P1
P2
Mixture Phase Diagrams
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Mole Fraction, x
Sat.
Tem
pera
ture
Tsat
Liquid Mole-Fraction Vapor Mole-Fraction
P1
P2
Azeotrope
Oil-miscibility•Ability of the refrigerant and lubricating oil to disperse into each other.
•Dilution of oil in the compressor crankcasechange in viscosity… inadequate lubrication
•Fouling on heat transfer surfaceslow heat transfer coefficients … insufficient capacity
•Low oil level in the crankcaseinadequate lubrication
Solutions•Proper piping design and refrigerant velocity to ensure oil return.
•Oil separators for:•Low temperature applications•Nonmiscible refrigerants•Flooded liquid chillers•Systems with large capacity range•Systems with long suction or discharge risers
•Reactivity with Moisture
•Moisture in the refrigeration system: (a) in solution with the refrigerant(b) free water
•Moisture+refrigerant solution•Produce corrosive compounds
pitting and other damage on valves, seals, bearing journals, cylinder wals, etc•Deterioration of the lubricating oil•Formation of sludge
Gum up valves, clog oil passages, score bearing surfaces
•Free water•Freeze-ups may occur stopping the refrigerant flow
Solutions•Proper materials selection (refrigerant-construction material compatibility).
•Filter-driers (dessicants) and sight-glasses (hygroscopic materials).
Economic Considerations
•Refrigerant properties that improves the system performance
•Refrigerant properties which reduce
the size, weight and initial cost of the equipment
•Characteristics that minimize maintenance needs
•Cost and availability of the refrigerant
Refrigerant Pressure-Capacity Relationship
0.0
0.2
0.4
0.6
0.8
1.0
0 100 200 300 400 500Pressure Difference @ ARI [psi]
Volu
met
ric C
apac
ity @
AR
I [To
n/cf
m]
Best FitR123R11R245faR114R600aR12R134aR290R22R407CR717R507R410A
R22
NH3
R404A/R507Propane
R407C
R410A
R134a
R22 & its near neighbors
Comparison of Simple Cycle EER
R22 R134a R290 R407C R507 R410A0.80
0.85
0.90
0.95
1.00
1.05
1.10EER Relative to R22
ARICHEER
Relative ARI Capacity [Same Displacement]
0.0
0.5
1.0
1.5
2.0Capacity relative to R22
Relative Compressor Displacement [Same Capacity]
0.0
0.5
1.0
1.5
2.0
2.5
3.0Displacement relative to R22
Refrigerant Comparison
(1.0) means reference value
Refrigerant CO2 R12 R22 R134a R404A R410A C3H8 NH3
Natural? Yes No No No No No Yes Yes
Flammable? No No No No No No Yes Yes
Toxic? No No No No No No No Yes
Relative Cost 0.1 - (1.0) 4.0 5.0 5.0 0.3 0.2
Volum. Capacity 4.8 0.6 (1.0) 0.7 1.2 1.5 0.9 1.0
Critical Temp.(F) 88 234 205 214 163 158 206 270
P @ 70F (psia) 852 85 136 86 165 216 125 129
ODP 0 1.0 0.05 0 0 0 0 0
GWP (100yr) (1.0) 7100 1500 1300 3750 1730 3 0
Indirect Cooling Systems
(a) Indirect system (a) Indirect system with AHU
Secondary Refrigerants•Water
•BRINES: solution of salt in water•CaCl2 Teut = - 55 ºC weut = 30 %
Dehydrating and imparting a bitter taste
•NaCl (table salt) Teut = - 21 ºC weut = 23 %
Chilling and freezing of meat, fish, etc.
Caution! Corrosive and electrolytic
•ANTIFREEZE solutions•Ethylene glycol -32.5 ºC at 50 %
•Propylene glycol -57 ºC at 59 %
•Methanol(methyl alcohol) -40.5 ºC at 55 %
•Glycerine -38.0 ºC at 70 %
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