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 %