seminar 34 refrigerants today, tomorrow, and beyond
TRANSCRIPT
Seminar 34 – Refrigerants
Today, Tomorrow, and Beyond
Thermal Stability Studies to
Evaluate Low-GWP Refrigerants
m Bianca W. Hydutsky, Ph.D.
DuPont Chemicals & Fluoroproducts [email protected]
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Learning Objectives • Design refrigeration and air-conditioning systems with respect to the thermodynamic properties of
the new, low-GWP refrigerants, in comparison with the past and current refrigerants.
• Assess the overall economic aspects of the vapor-compression systems according to the performance of the refrigerant in vapor-compression cycles, accounting for the cycle efficiency, heat transfer, pressures, and material compatibility.
• Outline the design aspects of the refrigeration and AC systems with respect to the solubility of refrigerants and lubricants and their heat transfer characteristics.
• Explain how the molecular formula and structure of the refrigerants determine their thermodynamic properties, thermal stability, and their relationship with lubricants and construction materials.
• Describe the correlation between the chemical composition and molecular structure of the refrigerants and their environmental characteristics.
• Associate the composition of the refrigerant blends with their potential flammability, environmental impact, and performance in refrigerating and air-conditioning equipment.
ASHRAE is a Registered Provider with The American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to ASHRAE Records for AIA members. Certificates of Completion for non-AIA members are available on request.
This program is registered with the AIA/ASHRAE for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or
dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
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Acknowledgements
• Thomas Leck
• Barbara Minor
• Kostas Kontomaris
• Chuck Allgood
• DuPont Fluorochemicals Technical
Services Analytical Lab
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Outline
• Developing a new generation of refrigerants
• Current refrigerants & low GWP replacements
• Chemical Stability Evaluations
– Sealed glass tube testing
• AC&R fluid testing
• ORC and Heat Pump fluid testing
• Conclusions
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Developing a New Generation
of Refrigerants • Refrigerants continue to evolve, to exceed
regulatory requirements, environmental
challenges and consumer preferences, while
providing the best balance of properties for
each application
Comparable or better performance
Highly stable
No or low flammability
Low atmospheric lifetime
Zero ozone depletion
Favorable toxicity
Drop-in replacement
Safe
Sustainable
Many Promising Candidates
Optimal Balance of Properties
Leading Lower GWP Candidates – HFO Based
Nonflammable Mildly Flammable
Current GWP Name GWP Name GWP
HFC-134a 1430 XP10 630 1234yf 4
DR-14 389
HFC-404A 3902 DR-33 1397 DR-7 246
DR-34 2140
HFC-410A 2088 DR-5A 460
HCFC-22 1810 DR-91 988
HCFC-123 77 DR-2 9
Notes: GWP values AR4
“DR” designates under development
Current and Replacement
Refrigerants
Chemical Stability Testing of
Low GWP Refrigerants
• Stability evaluations by the ASHRAE
Standard 97 Sealed glass tube method
– Evaluate stability to compare current
refrigerants with new alternatives.
DR-7 (1234yf/HFC-32; 64/36)
DR-33 (1234yf/134a/125/32;
25.3/25.7/24.7/24.3)
R-134a
R-32
R-1234yf
R-1234ze
R-123
DR-2
R-404A
Sealed Tube Testing • Accelerated thermal aging studies simulate years of
exposure in HVAC&R equipment by testing fluids
and materials at very high temperatures for days or
weeks.
– Metal coupons (Aluminum, Copper, Steel)
– Optional addition of lubricant, air, water
– Compare effect on fluids and materials
• Testing to simulate AC&R system exposure
– 2 weeks at 175ºC
• Higher temperature applications; ORC, Heat pump
– 1 day, 7 days, 2 weeks at 250ºC
1234yf, 1234ze, 32, 134a with POE 175ºC for two weeks
20ppm water, 0.1% atmospheric air
DR-7 with POE 175ºC (347ºF) for two weeks, air and water
• DR-7 is thermally stable with POE
Refrigerant 32/1234yf 32/1234yf 32/1234yf 32/1234yf
Oil POE 32 POE 32 POE 32 POE 32
Water (ppm) None 500 None 500
Air (ppm) None None 2000 2000
Fluoride (ppm) 3.7 Non detect 5.2 Non detect
DR-33 with and without POE 175ºC (347ºF) for two weeks, air and water
• DR-33 is thermally stable with and without POE
Refrigerant 32/125/134a/yf 32/125/134a/yf 32/125/134a/yf 32/125/134a/yf
Oil POE 32 POE 32 No Oil No Oil
Water (ppm) None 500 None 500
Air (ppm) None 2000 None 2000
Fluoride (ppm) Non detect 7.8 Non detect Non detect
Stability Testing for Higher
Temperature Applications
• Modify criteria to simulate use in higher
temperature systems, such as ORC or High
Temperature Heat Pumps
– Increase from 175ºC to 250ºC
– Evaluate after 24 hr, 1 week, 2 week test periods
– Metal coupons (Aluminum, Copper, Steel)
– Optional additions: Air, Water, Experimental
POE Oil
DR-2 and R-123 Stability at
250ºC
0
1
2
3
4
5
6
7
8
9
0 7 14
pp
m
Days
Acidity as HCl equiv. (ppm)
DR-2 with airand moisture
DR-2
0
500
1000
1500
2000
2500
3000
3500
0 7 14
pp
m
Days
Acidity as HCl equiv. (ppm)
R-123
DR-2 with airand moisture
DR-2
• DR-2 (HFO-1336mzzZ) is
stable at 250ºC for 2 weeks,
even with 200ppm water
and 1% air additions
R-123, 7 days
Conclusions • The sealed glass tube method has been
used to compare several new and
incumbent fluids and blends.
• HFO-1234yf, DR-7 and DR-33 have
similar stability to current HFCs.
• DR-2 demonstrates higher stability than
HCFC-123 and is particularly well suited
for high temperature applications.
• These Low GWP fluids showed excellent
stability even with air and water added.
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