6 Introduction to Refrigerants Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Objectives Recognize the effect

6Introduction to Refrigerants

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.

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.


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.


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


Refrigerants and the Ozone Layer• Montreal Protocol

– Banned production of chlorofluorocarbons (CFCs)– Resulted in development of new refrigerants


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


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


ODP and GDP of Refrigerants


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


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


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)


Refrigerant Classifications


Refrigerant Blends• Mixture of two or more refrigerants• Classifications

– Azeotropes– Zeotropes– Near-azeotropes

• Never attempt to make a zeotropic or azeotropic blend


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”


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


Identifying Refrigerants• First digit indicates refrigerant series• Significance of remaining digits depends on

refrigerant’s classification


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


Refrigerant Cylinder Color Code

• Helps prevent accidental mixing

• Not a requirement for all manufacturers

• Always read label• Identify refrigerant by

ASHRAE number


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


Toxicity and Flammability Ratings

Adapted from ANSI/ASHRAE Standard 34–2010


Refrigerant Safety Classifications


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


Pressure-Temperature Curve


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


Pressure-Enthalpy Table


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


Simplified Pressure-Enthalpy Diagram


Pressure-Enthalpy Diagram (R-134a)


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

• ncompressioofHeat

effectionRefrigeratCOP


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


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


Commonly Used New Refrigerants• R-134a

– Automotive air conditioning– Transport refrigeration

• R-404A– Medium- and low-temperature refrigeration

• R-410A– Air conditioning


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


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


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


Safety

• When handling cryogenic fluids– Never allow fluid to touch skin– Protect entire body with suitable clothing, helmets,

and gloves


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


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


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


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


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


Types of Refrigeration Lubricant• Categories

– Mineral oils– Polyol ester– Alkylbenzene– Polyalkylene glycol

• Type of lubricant should match type of refrigerant


Types of Refrigeration Lubricant


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


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


Contaminated Lubricant• Lubricant should be translucent• Evidence of impurities

– Discoloration– Odor– Metal shavings and chips

• Replace contaminated lubricant• Replace driers and filters

Documents

6 Introduction to Refrigerants Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Objectives Recognize the effect