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6 Introduction to Refrigerants. 6 Introduction to Refrigerants.

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Presentation on theme: "6 Introduction to Refrigerants. 6 Introduction to Refrigerants."— Presentation transcript:


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 Results of Clean Air Act
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 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
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
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 Floc test
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

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