Introduction to Refrigerants

2. 6 Introduction to Refrigerants

3. Objectives • Recognize the effect of halogenated refrigerants on the ozone layer. • Summarize Environmental Protection Agency regulations governing refrigerants. • Differentiate between CFC, HCFC, HFC, and blended refrigerants. • Identify refrigerants according to their series number and cylinder color code.

4. Objectives • Interpret pressure-temperature curves, pressure-enthalpy tables, and pressure-enthalpy diagrams. • Summarize the properties and common applications of different refrigerants. • Identify which types of refrigerants are compatible with which lubricants.

5. Ozone Layer • Ozone filters ultraviolet radiation • Protects humans, plants, and animals • Maintains stable temperatures • Ozone depletion may have harmful effects • Increase in skin cancer and eye damage • Climate change

6. Refrigerants and the Ozone Layer • Montreal Protocol • Banned production of chlorofluorocarbons (CFCs) • Resulted in development of new refrigerants

7. Clean Air Act (CAA) • Federal law • Guidelines, restrictions, and penalties for releasing refrigerants into the atmosphere • Fines up to $37,500 per day for failure to comply • Results of Clean Air Act • Training and certification required to handle refrigerants • Prevention of significant purposeful releases of refrigerants into atmosphere • Exceptions allow HVACR technicians to do their job

8. Methods to Measure Impact • Ozone depletion potential (ODP) • Compares refrigerant to R-11 • Numeric value assigned to each refrigerant • Scale 0 to 1 • Value of R-11 = 1 • Global warming potential (GWP) • Ratio of substance’s warming effect to that of carbon dioxide • Higher GWP = higher risk of environmental damage

9. ODP and GDP of Refrigerants

10. CFC Refrigerants • First halogen-based refrigerants • Composed of chlorine, fluorine, and carbon • Chlorine atoms break apart ozone molecules • Major cause of ozone depletion • No longer manufactured • May still be found in equipment produced before 1995

11. HCFC Refrigerants • Composed of hydrogen, chlorine, fluorine, and carbon • Partially halogenated • Have less impact on ozone layer than fully halogenated CFCs • High GWP • EPA requires phase-out by 2030

12. HFC Refrigerants • Composed of hydrogen, fluorine, and carbon • Partially halogenated • No chlorine atoms • ODP = 0, but high GWP • Being replaced by lower GWP alternatives • Carbon dioxide • Hydrocarbons • Hydrofluoroolefins (HFOs)

13. Refrigerant Classifications

14. Refrigerant Blends • Mixture of two or more refrigerants • Classifications • Azeotropes • Zeotropes • Near-azeotropes • Never attempt to make a zeotropic or azeotropic blend

15. Azeotropic Refrigerant Blends • Respond to changes in pressure and temperature like a single refrigerant • Maintain consistent properties • Most contain a phased-out refrigerant • Often called “azeotropes”

16. Zeotropic Refrigerant Blends • Individual refrigerants in a blend respond differently to conditions • Operate under a range of boiling and condensing points • Separation (fractionation) of individual refrigerants • Individual temperature glides • Can change phase and temperature simultaneously • Near-azeotropic refrigerant blends • Similar to zeotropic blends • Narrower range of boiling and condensing points

17. Identifying Refrigerants • First digit indicates refrigerant series • Significance of remaining digits depends on refrigerant’s classification

18. Refrigerant Numbering System • 000, 100, 200, 300 series • 400, 500, 600, 1000 series • Third number from right indicates series • Next two numbers are assigned sequentially • 700 series • Third number from right indicates series • Next two numbers are molecular weight

19. Refrigerant Cylinder Color Code • Helps prevent accidental mixing • Not a requirement for all manufacturers • Always read label • Identify refrigerant by ASHRAE number

20. Refrigerant Toxicity and Flammability • Toxicity • Class A refrigerants not known to be toxic at or below 400 ppm • Class B refrigerants known to be toxic at or below 400 ppm • Flammability Ratings • 1: No flammability • 2: Low flammability • 2L: Low flammability and slow burn velocity • 3: High flammability

21. Toxicity and Flammability Ratings Adapted from ANSI/ASHRAE Standard 34–2010

22. Refrigerant Safety Classifications

23. Pressure-Temperature Curve • Shows relationship between refrigerant’s temperature and pressure • Used to determine if unit is operating at correct temperature or pressure • Other methods to determine temperature • Pressure-Temperature charts • Approximation using tubing (skin) temperature

24. Pressure-Temperature Curve

25. Pressure-Enthalpy Table • Lists actual operating temperatures and pressures • Shows volume of 1 lb vapor and density of liquid refrigerant at given temperature • Shows enthalpy (heat content) • Vapor heat content  liquid heat content = latent heat

26. Pressure-Enthalpy Table

27. Pressure-Enthalpy Diagram • Visual graph of thermodynamic properties • Same information contained in pressure-enthalpy table • Used to help understand how each component functions in refrigeration cycle • Shows temperature glide for zeotropic blends

28. Simplified Pressure-Enthalpy Diagram

29. Pressure-Enthalpy Diagram (R-134a)

30. Coefficient of Performance • Ratio of refrigeration effect to heat of compression • Higher coefficient means better efficiency • Used to determine which refrigerant will be most effective in specific system

31. Refrigerant Applications • Based on pressure, temperature, and heat properties of refrigerant • Items to be considered • Boiling point of refrigerant • Latent heat of refrigerant • Operating temperatures • Operating pressures • Equipment size

32. Phaseout of Refrigerants • CFCs • Phaseout completed in 1996 • May still be purchased from stockpile by EPA-certified technicians • HCFCs • Phaseout to be completed in 2020 in US • Illegal in new equipment since 2010 • Complete phaseout by 2030

33. Commonly Used New Refrigerants • R-134a • Automotive air conditioning • Transport refrigeration • R-404A • Medium- and low-temperature refrigeration • R-410A • Air conditioning

34. R-717 Ammonia • Chemical compound of nitrogen and hydrogen • Low boiling point • Temperatures below zero without pressures below atmospheric • Large refrigerating effect with smaller machinery • Hazards • Flammable at 150,000 to 270,000 ppm • Strong effect on respiratory system

35. Safety • When working with ammonia • Wear tight-fitting respirator • Stand to one side when operating ammonia valve • Use sulfur candle or spray vapor to detect leaks • Follow all training and safety protocols

36. Cryogenic Fluids • Often called freezants • Used in food processing plants to rapidly freeze food • Rapid freezing reduces ice crystals • Results in less damage to food during freezing • Must be kept in insulated-vacuum containers • Expendable

37. Safety • When handling cryogenic fluids • Never allow fluid to touch skin • Protect entire body with suitable clothing, helmets, and gloves

38. Expendable Refrigerants • Expendable refrigeration system • Releases refrigerant to atmosphere after one use • Uses expendable refrigerant • Refrigerant is not collected for reuse • Other names • Chemical refrigeration system • Open-cycle refrigeration system

39. Refrigeration Lubricants • Lubricant charged into refrigeration system with refrigerant • Lubricates contact between moving parts • Must be able to travel freely through all parts of the system • Characteristics of refrigeration lubricants • Low wax content • High thermal and chemical stability • Low pour point • Low viscosity

40. Wax Content • Wax separation • Precipitates out of lubricant at low temperatures • Can plug control orifices and clog system • Floc test • Determines how easily wax separates • Floc point: Highest temperature at which precipitate appears

41. Stability and Flash Point • Thermal stability • Ability to remain stable in high heat areas • Chemical stability • Ability to not react chemically with refrigerants or other substances • Flash point • Temperature at which vapors from lubricant surface ignite

42. Viscosity • Measure of liquid’s resistance to flow • Changes with temperature • Higher temperature reduces viscosity • Lower temperature increases viscosity • Pour point • Lowest temperature at which a lubricant will flow

43. Types of Refrigeration Lubricant • Categories • Mineral oils • Polyol ester • Alkylbenzene • Polyalkylene glycol • Type of lubricant should match type of refrigerant

44. Types of Refrigeration Lubricant

45. Handling Refrigeration Lubricants • Keep lubricants in sealed containers • Transfer lubricants in chemically cleaned containers and lines • Do not expose to air and moisture • Buy small sealed containers • Reseal container after withdrawing lubricant • Unused lubricant may pick up moisture or dirt

46. Adding Lubricant to a System • Ensure correct amount of lubricant • Too little shortens component life • Too much reduces refrigerant-pumping capacity • Follow manufacturer’s recommendations • Make sure lubricant is compatible with refrigerant • Add lubricant only if there are signs of leakage

47. Contaminated Lubricant • Lubricant should be translucent • Evidence of impurities • Discoloration • Odor • Metal shavings and chips • Replace contaminated lubricant • Replace driers and filters