m Bianca W. Hydutsky, Ph.D. DuPont Chemicals & Fluoroproducts bianca.hydutsky@dupont.com Seminar 34 Refrigerants Today, Tomorrow, and Beyond Thermal Stability Studies to Evaluate Low-GWP Refrigerants 1
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. 2
Acknowledgements Thomas Leck Barbara Minor Kostas Kontomaris Chuck Allgood DuPont Fluorochemicals Technical Services Analytical Lab 3
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 4
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 Favorable toxicity Comparable or better performance Safe Low atmospheric lifetime Zero ozone depletion Highly stable Sustainable No or low flammability Drop-in replacement
Current and Replacement Refrigerants 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
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. R-134a R-32 R-1234yf R-1234ze R-404A DR-7 (1234yf/HFC-32; 64/36) DR-33 (1234yf/134a/125/32; 25.3/25.7/24.7/24.3) R-123 DR-2
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 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-7 is thermally stable with POE
DR-33 with and without POE 175ºC (347ºF) for two weeks, air and water 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 DR-33 is thermally stable with and without POE
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
ppm ppm DR-2 and R-123 Stability at 9 8 7 6 5 4 3 2 1 0 Acidity as HCl equiv. (ppm) 0 7 14 Days R-123, 7 days 250ºC DR-2 with air and moisture DR-2 3500 3000 2500 2000 1500 1000 500 0 DR-2 (HFO-1336mzzZ) is stable at 250ºC for 2 weeks, even with 200ppm water and 1% air additions Acidity as HCl equiv. (ppm) 0 7 14 Days R-123 DR-2 with air and moisture DR-2
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. 14
Questions? Dr. Bianca W. Hydutsky bianca.hydutsky@dupont.com 15