Refrigerants and their Application Presented by
Thomas E. Watson, P.E. Fellow ASHRAE McQuay International Staunton, Virginia USA 1
What is a Refrigerant? • In a refrigerating system, the medium of heat transfer which picks up heat by evaporating at a low temperature and pressure, and gives up heat on condensing at a higher temperature & pressure. • (Refrigerating fluid) fluid used for heat transfer in a refrigerating system which absorbs heat at a low temperature and low pressure of the fluid and transfers heat at a higher temperature and higher pressure of the fluid, usually involving changes of state of the fluid. Ref: ASHRAE Terminology of Heating, Ventilation, Air Conditioning, & Refrigeration
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Agenda / Topics • Introduction • History of Refrigerants • Basic Refrigerant Chemistry • Refrigerant Properties • Refrigerant Applications
• Refrigerants In The Future? • Alternative Refrigerants • Ozone Depletion & Montreal Protocol • Global Warming • Summary
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History of Refrigerants • • • • • • • • •
1830s - Jacob Perkins - Vapor Compression (ether) 1851 - John Gorrie - Patent for Air Cycle 1859 - R-717 / R-718 (Ammonia / Water) 1866 - CO2 - Marine Applications 1873 - R-717 (Ammonia) Commercial Refrigeration Carl Linde 1875 - R-764 (Sulfur dioxide) 1920s -R-600a (Isobutane) & R-290 (Propane) 1922 - Willis Carrier - R-1130 (Dielene) 1926 - R-30 (Methylene Chloride)
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Toxicity - Best Minds Tried to Solve Solving Problem of Toxicity was a Large Problem to Development of Refrigeration
1927 Leo Szilard & Albert Einstein Improved on von Platen / Munters Absorption Design Electromagnetic Pumping Patent
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Challenged to Find Refrigerant: • Non-flammable • Good Stability • Low Toxicity • Atmospheric Boiling Point between -40oC & 0oC
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Common Refrigerants in 1920s Ammonia (R-717)
NH3
Carbon Dioxide
CO2
Sulfur Dioxide
SO2
Hydrocarbons
CnHm
Methyl Choride
CH3Cl
Water
H2O
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History of Refrigerants
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History of Refrigerants Midgley Selections
C
N
O S
H F Cl Br
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Refrigerant Chemistry Hydrocarbon
Formula NBP
Methane
CH4
-260 F -162 ̊C
Ethane
C2H6
-127 F -88 ̊C
Propane
C3H8
-44 F
-42 C ̊
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Refrigerant Chemistry
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Refrigerant Chemistry
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Refrigerant Chemistry
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Refrigerant Chemistry
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Refrigerant Chemistry Fluorocarbons •
CFCs, HCFCs, HFCs & HFOs
•
Limited Combinations
HYDROGEN Flammable
– Adding Chlorine Or Bromine Increases ODP – Adding Fluorine Increases
Toxic
GWP – Adding Hydrogen Increases Flammability And Lowers Atmospheric Lifetime
CHLORINE
FLUORINE Long Atmospheric Lifetime (fully halogenated)
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Refrigerant Chemistry
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Refrigerant Chemistry
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Refrigerant Chemistry
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Refrigerant Chemistry • Refrigerant Blends – Two or More Refrigerants to Achieve Required Properties • • • •
Flammability Volumetric Capacity Limit Discharge Superheating for Lower Disch Temp etc
• Two Basic Types – Zeotropes – Azeotropes
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Refrigerant Chemistry Zeotropes ZEOTROPIC BEHAVIOR (32/134a) 55 T vap T liq
Temperature, °F
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P= 64 PSIA 25 15 5 -5 0
20
40
60
80
100
% R-32
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Refrigerant Chemistry Zeotropic Behavior • •
Fractionalization - Can be Separated by Distillation Service Procedures
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Refrigerant Chemistry Azeotropes AZEOTROPIC BEHAVIOR (R-125/R-143a) 39 T vap
Temperature, °F
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T liq
37 P=100 PSIA 36
35 R-507 = AZEOTROPIC MIXTURE R-125/R-143a (50/50) 34
33 0
10
20
30
40
50
60
70
80
90
100
% R-125
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ASHRAE Standard 34
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ASHRAE Standard 34
• Nomenclature • Toxicity Classification • Flammability Classification
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ASHRAE Standard 34 Nomenclature 000 Series 100 Series 200 Series 300 Series 400 Series 500 Series 600 Series 700 Series 1000 Series
Methane Based Ethane Based Propane Based Cyclic Organic Compounds Zeotropes Azeotropes Organic Compounds Inorganic Compounds Unsaturated Organic Compounds
Code Key Rule of 90 - Example R-12
R-
1
2
+
9
0
C
H
F
1
0
2
=
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ASHRAE Standard 34
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HFO--1234ye Stereoisomers HFO
Entgegen
Zusammen
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ASHRAE Standard 34 • Toxicity Classification based on Chronic (long term) Measure - Class A has PEL > 400 PPM - Class B has PEL < 400 PPM PEL = Permissible Exposure Limit
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ASHRAE Standard 34 • Flammability Classification based on:
ASTM E 681 with an Electrically Activated match
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ASHRAE Standard 34 Flammability Classification • Class 1 - No Flame Propagation • Class 2 - LFL > 0.10 kg/m^3 and hc < 19 MJ/kg • Class 2L – Cl 2 w/ flame speed < 10 cm / sec • Class 3 - LFL < 0.10 kg/m^3 or hc > 19 MJ/kg
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ASHRAE Standard 34
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A2L Refrigerants
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ASHRAE Standard 15
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ASHRAE Standard 15 What is ASHRAE 15?
• An industry standard that specifies safe design, construction, installation, and operation of refrigerating systems • Establishes safeguards for life, limb, health, and property, and prescribes safety standards
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ASHRAE Standard 15
Scope • Design, Construction, Installation, Operation & Inspection of Mechanical and Absorption Machines • Modifications if not Identical in Function and Capacity • Refrigerant Substitutions with Different Designation
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ASHRAE Standard 15 Requirements Based on 3 Classifications • Occupancy • Refrigerating System • Refrigerant
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ASHRAE Standard 15 Occupancy Classifications - Ability to Respond to Exposure •
Institutional - Assistance Required
•
Public Assembly - Large Numbers
•
Residential - Sleeping
•
Commercial - Business Transactions
•
Large Mercantile - 100 Persons or More
•
Industrial & Refrigerated Rooms - Access Controlled
•
Mixed - Two or More in Same Building
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ASHRAE Standard 15 Refrigerating System Classification
• High Probability - Leak Can Enter Occupied Space • Low Probability - Leak Cannot Enter Occupied Space
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ASHRAE Standard 15 Restrictions on Refrigerant Use - Section 7 •
Standard 15 Gives Rules based on Occupancy, System, & Refrigerant Classification
•
3 kg or Less of Flammable Refrigerants may be used in Listed Equipment
•
A2L Refrigerant Application Requirements NOT Included – Presently Under Consideration
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ASHRAE Standard 15 Refrigerant Qty/vol Limits - See Std 34 • Acute Exposure / Ability to Escape • Direct Systems • Volume - Space to which Refrigerant Disperses in Event of Leak
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ASHRAE 15 Users Manual
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Mechanical Room Safety Check Location of inlet vents in relation to exhaust outlets ?
Location of roof drains ?
Rupture disc outlet locations ?
Purge vents to outside ?
Is there a tight seal on doors ? Are safety rupture lines the right size ? Is access to mechanical room restricted ?
Are drain valves connected to evacuation devices ?
Are there any pit areas in the room ?
Where do the floor drains empty ?
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Mechanical Room Safety Check Relief discharge shall be located not less than 20 ft (6 m) from ventilation opening and not less than 15 ft (4.5 m) above ground level (9.7.8)
Purge systems and relief devices must be vented to outside (8.16)
All indoor machinery rooms must be vented to the outdoors utilizing mechanical ventilation 98.13.3 & 4 Access to mechanical room shall be restricted. Tight fitting doors opening outward (self closing if the open into the building) adequate in number to ensure freedom of escape. No other openings that would permit passage of escaping refrigerant (8.13)
Refrigerant sensors are located in areas where refrigerant vapor from a leak will be concentrated so as to provide warning at concentration not exceeding the refrigerant PEL
The total amount of refrigerant stored in a machinery room in all containers not provided with relief valves & piped in accordance with standard shall not exceed 330 lb (150 kg). (11.5)
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Sample Sensor Locations*
Entrance / Exits Refrigerant Storage Just Above floor Next to Chillers
Drains
Pits
*Examples not part of standard 45
Mechanical Room per ASHRAE 15 Periodic tests of detectors, alarms & ventilation must be performed in accordance with manufacturers recommendations and/or local jurisdiction. (11.7.3)
Mechanical room should be dimensioned for easy access to all parts and adequate space for service, maintenance, and operation. Clear head room of not less than 7.25 ft (2.2 m) below equipment situated over passageways. (8.12.1 &2,8.13.1)
No open flames that use combustion air from the machinery room (boilers) can be located within the mechanical as long as the combustion air is ducted from the outside to the boiler or shut down sensors are installed (8.13.6)
A change in the type of refrigerant in a system shall not be made without the notification of the authority having jurisdiction, the user and due observance of safety requirements. The refrigerant being considered shall be evaluated for suitability (5.3)
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IIAR 2
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Back to the Future
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Refrigerants in the Future? Low Direct Global Warming Potential • CO2 •
Ammonia
• Hydrocarbons • HFOs
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Natural Refrigerants •
Ammonia (NH3) R-717 – Efficient – B2L Classification – Industrial Applications
•
Water R-718 – Absorption Chillers – Centrifugal Compressors – Axial Flow Compressors
•
Carbon Dioxide (CO2) R-744 – Low Critical Point
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What about other stuff -HFOs?
Refrigerant Applications
•
pV = (m x Ru x T ) / MM
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Refrigerant Applications • What is Pressure? • Pressure = Average Impact of Molecules on a given area. • Pressure is dependent on the Kinetic Energy of the molecules.
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Volumetric Capacity 180.0 R-114 160.0 R-123 140.0
Molecular Mass
R-245fa R-12 R-1234ze
120.0 R-1234yf 100.0
R-134a
R-500 R-22
80.0
R-407C
R-410A 60.0 R-32 R-744
40.0 20.0
R-11
R-152a
R-40 R-290
R-718
R-717
0.0 0.1
1.0
10.0
100.0
1000.0
CFM/ton 54
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Compressor Types
Compressor Types
Positive Displacement
Reciprocating
Rotary
Singe Shaft
Twin Shaft
Orbiting
Three Shaft
Twin Screw
Single Screw
Dynamic
Centrifugal
Scroll
Tri-Screw
Axial
Trochoidal
Moving Vane
Fixed Vane (Rolling Piston)
Compressor Volumetric Capacities
Axial Centrifugal Screw Rotary Scroll Recip 0
1 NOTE: Log Scale
10
100
1,000
10,000
100,000
1,000,000
CFM
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Refrigerant Flow Requirements 1000 R-718
100
CFM/ton
R-123 R-11 R-245fa R-114
10
R-1234ze R-1234yf R-134a R-40 R-12 R-407C R-500R-22 R-290 R-717 R-410A R-32
1
R-744
0.1 0.1
1.0
10.0 Suction Pressure, PSIA
100.0
1000.0
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Basic Considerations •
•
Compressors –
Vapor Pressure
–
Temperature Lift
–
Tons
Evaporators –
•
Glide
Condensers –
Glide
–
Critical Temperature
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R-11 Alternatives Refrigerant
Molecular Mass
CFC-11
137.4
HCFC-123
153.0
HFC-245fa
134.0
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R-12 Alternatives Refrigerant
Molecular Mass
CFC-12
120.9
CFC-500
99.3
HFC-134a
102.0
HFO-1234yf
114.0
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R-22 Alternative Refrigerant
Molecular Mass
HCFC-22
86.5
HFC-407C
86.2
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Global Warming TEWI - Total Environmental Warming Impact Consists of •
Direct GWP, from refrigerant discharge +
•
Indirect, power plant CO2 discharge dominates - Over 95% for Well Maintained Equipment - CO2 from Power Generation depends on IPLV
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Global Warming
GWP Power Generation
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Summary - Refrigerant Choice Ozone saving Global warming issue - Total Environmental Warming Impact (TEWI) Safety Field availability Application Cost Compressor type
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Questions?
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Information Sources www.ahri.org www.ashrae.org www.epa.gov/docs/ozone/index.html ASHRAE Handbook – Fundamentals - Refrigerants ASHRAE Standards 15 & 34 IIR-2 Equipment, Design and Installation of Ammonia Mechanical Refrigerating Systems Fluorocarbon Refrigerants Handbook - Ralph C. Downing, Prentice-Hall Trade-Offs in Refrigerant Selections: Past, Present, and Future - James M. Calm and David A. Didion - Proceedings of ASHRAE/NIST Refrigerants Conference Oct 1997 HFOS – New Low Global Warming Potential Refrigerants – S. F. Brown, ASHRAE Journal August 2009
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