Refrigeration System

Note: The source of the technical material in this volume is the ProfessionalEngineering Development Program (PEDP) of Engineering Services.

Warning: The material contained in this document was developed for SaudiAramco and is intended for the exclusive use of Saudi Aramco’semployees. Any material contained in this document which is notalready in the public domain may not be copied, reproduced, sold, given,or disclosed to third parties, or otherwise used in whole, or in part,without the written permission of the Vice President, EngineeringServices, Saudi Aramco.

Chapter : Process For additional information on this subject, contactFile Reference: CHE21001 R.A. Al-Husseini on 874-2792

Engineering EncyclopediaSaudi Aramco DeskTop Standards

Refrigeration Systems

Engineering Encyclopedia Process


Saudi Aramco DeskTop Standards

CONTENTS PAGES

TYPES OF REFRIGERATION SYSTEMS USED BY SAUDI ARAMCO .......................................1

SELECTING APPROPRIATE REFRIGERATION SYSTEMS .........................................................2

Vapor Compression-Expansion Refrigeration Systems .....................................................................2Operation .............................................................................................................................2Size and Achievable Temperatures ......................................................................................2Refrigerants..........................................................................................................................3

Absorption Refrigeration Systems.....................................................................................................4Operation .............................................................................................................................4Applications.........................................................................................................................6Advantages ..........................................................................................................................9

Steam Jet Refrigeration Systems .......................................................................................................9Operation .............................................................................................................................10Advantages ..........................................................................................................................10Disadvantages ......................................................................................................................10Applications.........................................................................................................................10

SELECTING THE MOST APPROPRIATE REFRIGERANTS .........................................................11

Commonly Used Refrigerants ...........................................................................................................11Physical Properties ............................................................................................................................15

Flammability........................................................................................................................16Compromises Between Conflicting Desirable Thermodynamic Properties .........................16Latent Heat...........................................................................................................................17Performance .........................................................................................................................19Effect on Construction Metals .............................................................................................22Ammonia (R-717)................................................................................................................23Ammonia Piping Requirements ...........................................................................................24

WORK AID 1: RESOURCES FOR SELECTING APPROPRIATEREFRIGERATION SYSTEMS..................................................................30

WORK AID 2 PROCEDURES AND RESOURCES FOR SELECTING THEMOST APPROPRIATE REFRIGERANTS ...............................................32

GLOSSARY .............................................................................................................................45

ADDENDUM ...........................................................................................................................46




LIST OF FIGURES

Figure 1. Saudi Aramco Refrigeration Units ..................................................................................................1

Figure 2. Vapor Compression-Expansion Refrigeration System.....................................................................3

Figure 3. Ammonia Absorption Refrigeration Systems .................................................................................4

Figure 4. Lithium Bromide-Water Single-Stage Absorption Systems............................................................5

Figure 5. Vertical Shell, Small Capacity, Lithium Bromide Cycle WaterChiller for Solar Cooling ............................................................................................................8

Figure 6. Steam Jet Refrigeration System ......................................................................................................9

Figure 7. (Page 1 of 3). ASHRAE Standard Designation of Refrigerants(ANSI/ASHRAE Standard 34-78) ..............................................................................................12



Figure 8. Frequently Used Refrigerants .........................................................................................................14

Figure 9. Latent Heat of Vaporization Versus Boiling Point..........................................................................18

Figure 10. Effects of Temperature on Capacity [Constant CompressorDisplacement = 2 L/s (4 cfm)] ....................................................................................................20

Figure 11. Effects of Temperature on Theoretical kW (HP) per kW (Ton)of Refrigeration...........................................................................................................................21

Figure 12. Purge Unit and Piping for Noncondensable Gas...........................................................................27

Figure 13. Summary of Refrigerant Applications ..........................................................................................29

Figure 14. Refrigeration Systems Schematic..................................................................................................30

Figure 15. Refrigeration System and Equipment Limits ................................................................................31

Figure 16. Temperature Limits for Refrigerants .............................................................................................32

Figure 17. Physical Properties of Refrigerants ...............................................................................................33

Figure 18. Specific Gravity of Aqueous Solutions of Lithium Bromide ........................................................34

Figure 19. Specific Heat of Aqueous Solutions of Lithium Bromide.............................................................35

Figure 20. Viscosities of Aqueous Solutions of Lithium Bromide.................................................................36

Figure 21. Velocity of Sound in Refrigerant Vapors, m/s (ft/s) .....................................................................37




Figure 22. Comparative Refrigerant Performance Per kW (Ton)[Based on 258°K Evaporation (5°F) and 303°K Condensation (86°F)]......................................38

Figure 23. (Page 1 of 4). Comparative Refrigerant Performance Per kW(Ton) at Various Evaporating and Condensing Temperatures ....................................................39




Figure 24. Relative Safety of Refrigerants .....................................................................................................43

Figure 25. Underwriters Laboratories Classification of Comparative Hazard toLife of Gases and Vapors............................................................................................................44

Figure 26. ASHRAE SI for HVAC and R Conversions .................................................................................47

Figure 27. Conversion Factors .......................................................................................................................48



Saudi Aramco DeskTop Standards 1

Types of Refrigeration Systems Used by Saudi ARAMCOFigure 1 lists some of the refrigeration systems currently used by Saudi Aramco. All of these systems use vaporcompression-expansion refrigeration systems. All of these systems, except one, use hydrocarbons (ethane,propane, butane, etc.) for their refrigerants. Most of the systems use only propane, but a few of them arecascade systems that use propane/ethane.

In addition to the refrigeration systems listed in Figure 1, Saudi Aramco uses many air-conditioning systems forbuildings. These air-conditioning systems may use absorption, steam jet, or vapor compression-expansion(with freon) refrigeration systems.

PLANT TYPE REFRIGERATION SYSTEM LOCATION

25 Deethanizer Overhead Condenser (PropaneRefrigeration System)

Ras Tanura

59 Propane/Butane Refrigeration Systems Ras Tanura Terminal

332 Propane Refrigeration System Abqaiq





470 Propane Refrigeration System Jubail

69 Ethane Storage Liquefaction Jubail

R-13 R-22 Refrigeration Zuluf

R-33 Feed Chill down and Ethane/Propane Refrigeration Uthmaniyah

R-42 Feed Chill down and Ethane/Propane Refrigeration Shedgum

R-84 Propane Refrigeration Ju'aymah

R-92 Propane/Butane Sub Cooling & Chilling Ju'aymah

R-93 Propane/Butane Refrigeration Ju'aymah Terminal

V-85 Ethane/Propane Refrigeration Yanbu

V-92 Propane/Butane Refrigeration Yanbu

Figure 1. Saudi Aramco Refrigeration Units




SelectING appropriate refrigeration SYSTEMSThis section introduces and briefly describes the following types of refrigeration systems that are covered inChE 210.

• Vapor compression-expansion• Absorption• Steam jet

The information contained in the following sections is used to narrow the choice of refrigeration systems. Thefinal selection of the most appropriate system will be made by comparing the capital and operating costs of thesystems and determining schedule availability.

Vapor Compression-Expansion Refrigeration Systems

OperationFigure 2 shows a simplified schematic of a vapor compression-expansion system. The compressor compressesthe vaporized refrigerant and then the condenser condenses the vapor to a liquid. The liquid from theaccumulator then expands across an expansion valve which causes it to flash and its temperature to dropsubstantially. The liquid portion of this flash is the refrigerant which then goes to a heat exchanger (the chiller).

In the chiller, the liquid refrigerant absorbs heat from the process stream, which lowers the process stream’stemperature. The heat vaporizes the liquid refrigerant. The system then returns this vapor and the vapor fromthe flash to the compressor to repeat the cycle.

Size and Achievable TemperaturesVapor compression-expansion systems can be built in very large sizes. These systems can also reach very lowtemperatures. A cascaded system consists of two or more vapor compression-expansion systems that areconnected in a series with each system having a different refrigerant. These systems can achieve temperatureslow enough to liquefy natural gas.




Figure 2. Vapor Compression-Expansion Refrigeration System

RefrigerantsVapor compression-expansion systems typically use hydrocarbons, freons, ammonia, and sulfur dioxide forrefrigerants.




Absorption Refrigeration SystemsAbsorption refrigeration systems are similar to vapor compression-expansion systems, except that they absorbthe refrigerant with a carrier liquid. Carrier liquids can use a pump instead of a compressor to increase thepressure of the system. This section covers ammonia-water and lithium bromide-water absorption systems.

OperationAmmonia Absorption Systems – Figure 3 shows a schematic of a simplified absorption refrigeration systemthat uses water to absorb the ammonia refrigerant.

Figure 3. Ammonia Absorption Refrigeration Systems

The system in Figure 3 uses ammonia for its refrigerant and water for its liquid carrier. In the absorber, water(the carrier liquid) absorbs ammonia vapor (the refrigerant). Next, the ammonia-water solution enters the pumpwhere the pressure of the solution is increased to a high level. After the solution leaves the pump, the generatorcolumn vaporizes the refrigerant (ammonia) from the water (the carrier liquid). The system returns the water tothe absorber and sends the ammonia vapor to the condenser.

At this point in the cycle, absorption systems are very similar to vapor compression-expansion systems. Theammonia vapor is condensed to form the liquid refrigerant stream, which is stored in the accumulator drum.The expansion valve flashes the liquid refrigerant, which reduces its temperature. In the chiller, the refrigerantabsorbs heat from the process stream and the absorbed heat boils the refrigerant. As in a vapor compression-expansion system, the boiled refrigerant and the flash vapor are sent to the absorber column to begin the cycleagain.




Lithium Bromide-Water Single-Stage Absorption Systems – Figure 4 shows a lithium bromide-waterabsorption system.

Source: 1989 Fundamentals

Figure 4. Lithium Bromide-Water Single-Stage AbsorptionSystems




The system shown in Figure 4 uses a lithium bromide-water solution as its absorbent (carrier liquid) and wateras its refrigerant. In this system, hot concentrated lithium bromide-water solution (in equilibrium at condenserpressure) leaves the generator and enters the heat exchanger. In the heat exchanger, the incoming solutioncools the concentrated lithium bromide-water solution. The cooled solution is then throttled through therestrictor to the absorber.

In the absorber, the cold concentrated lithium bromide-water solution absorbs low-pressure refrigerant (8 and 9)that is in equilibrium at evaporator pressure. This diluted solution is then pumped to the heat exchanger. In theexchanger, the diluted solution absorbs heat from the hot solution that leaves the generator. The heatedsolution then flows to the generator (5).

The generator then heats the hot, diluted solution and strips the refrigerant from the carrier liquid. The distilledrefrigerant (diluted solution) flows to the condenser (6) and the hot, concentrated solution flows to the heatexchanger (1).

The condenser condenses the hot, high-pressure refrigerant into hot, high-pressure liquid (7). The restrictorexpands the hot, high-pressure liquid to low-pressure, low-temperature liquid and vapor. In the evaporator, thelow- temperature, low-pressure refrigerant absorbs heat from the space being refrigerated. The low-pressurerefrigerant then flows to the absorber (3) where it is absorbed by the cold, concentrated lithium bromidesolution (the carrier liquid).

ApplicationsAbsorption refrigeration systems were once popular for a variety of cooling tasks in industry and for foodstorage. Recently, the absorption refrigeration cycle has found renewed use in medium- and large-size air-conditioning systems. Currently, these systems generally use lithium bromide for their absorbent and potablewater for their refrigerant.

Absorption refrigeration systems are popular where one or more of the following conditions exists:

• Electric rates are high.• Fuel costs are low.• Low-pressure heating boilers are not used during summers (the cooling season).• Steam or gas utility companies promote summer loads.• Waste steam is available.

Absorption refrigeration systems can be installed in almost any building with adequately strong and levelfloors. In absorption refrigeration systems, the absence of heavy moving parts minimizes noise levels andpractically eliminates vibration.




Small lithium bromide-water units of 10.5 kW to 105 kW (3 tons to 30 tons) capacity are designed forresidential or small commercial use. Indirect- and direct-fired liquid chiller, chiller-heater, and air-conditioningequipment (both single-stage and dual-effect configurations) have been produced. Currently, lithium bromide-refrigeration systems have one or more of the following unique features:

• Flat-plate solar collector heat sources with good efficiency, but with lower capacity, can be used tofire the refrigeration cycle.

• Heat can be derived from the cooling cycle by stopping the flow of the cooling water. In somedesigns, when the cooling water stops, a solution trap between the high and low sides opens andallows refrigerant vapor to flow to the evaporator coil. In the evaporator coil, the water that flowsinside the evaporator tubes is condensed and heated.

• Solution can be circulated either thermally by vapor-lift action in a pump tube, or by a mechanicalpump.

Lithium bromide absorption systems are available as package units. Figure 5 shows an example of a packagedlithium bromide-absorption system.




Source: 1988 Equipment

Figure 5. Vertical Shell, Small Capacity, Lithium Bromide Cycle Water Chiller for SolarCooling




AdvantagesAbsorption refrigeration systems have the following advantages:

• They do not require compressors.

• Uninsulated, small-diameter, low-pressure lines can circulate the liquid refrigerant and absorbent.

• Lithium bromide systems are not flammable.

• Low-level waste heat can frequently be used as the heat source for the generator.

• Many remotely-located refrigeration systems can be connected to one, central generator that islocated near a source of waste heat. Small diameter liquid refrigerant and adsorbent lines connectthe remotely-located refrigeration systems.

Steam Jet Refrigeration SystemsSteam jet refrigeration systems use a steam jet ejector to produce vacuum pressures. At these lower pressuresthe water flashes and its temperature is reduced. Steam jet refrigeration systems then use this chilled water fortheir refrigerant. Figure 6 shows a schematic of a simplified steam jet refrigeration system.

Figure 6. Steam Jet Refrigeration System




OperationIn Figure 6, chilled water is pumped from the evaporator to the chiller. In the chiller, the chilled water absorbsheat from the process stream that is being refrigerated and then flows to the evaporator. The evaporator flashesthe water and lowers its temperature. The flashed vapor leaves the evaporator through the steam jet ejector.Steam flowing through the steam jet ejector maintains the low-pressure (vacuum) in the evaporator.

The steam from the steam jet ejector and the flashed water from the evaporator flow to the condenser and arecondensed. The system diverts enough water to the evaporator to replace the flash vapor. The excess water canbe used for boiler feed water or other uses.

AdvantagesSteam jet refrigeration systems have the following advantages:

• The refrigerant (water) is not flammable.

• The refrigerant is not toxic.

• The refrigerant is a low-pressure liquid that can be transported in small lines.

• Waste steam can be used in the steam jet ejector.

DisadvantagesSteam jet refrigeration systems have the following disadvantages:

• The freezing point of water limits the temperatures these systems can achieve.

• The low operating pressures of the evaporator and the condenser require large equipment.

ApplicationsSteam jet refrigeration units are used for some cooling loads of 175 kW (50 tons) or more. These systems areused in many applications in which steam is available. Typical applications include comfort air conditioning,industrial process cooling, and other similar types of service. Recently, some large office buildings have steamjet refrigeration systems installed on the roof. These units provide the cooling needed for the buildings’ airconditioning systems.




SELECTING the most appropriate refrigerantsOnce a designer has selected a refrigeration system, he must choose a refrigerant. The following points must beconsidered when selecting the most appropriate refrigerants.

• The minimum temperature the refrigerant must achieve (refrigerant level).

• The suitability of the refrigerant.

• Environmental regulations and concerns.

The minimum temperature that the refrigerant must achieve (refrigerant level) narrows the list of possibleappropriate refrigerants and sets the system pressure. The suitability of the refrigerant derives from theavailability, cost, flammability, and toxicity of the refrigerant. Freon, for example, is becoming difficult toobtain because of environmental regulations and concerns which restrict its manufacture and use.

Hydrocarbons should be used in refinery applications because the material is readily available, can be ventedinto the refinery system during turnaround, and have a low cost. Flammability is not a large factor in thenormal refinery environment. Water is a good choice as long as freezing is not a constraint. Ammoniaabsorption could be considered if waste heat is available for solution regeneration.

Refrigerants often affect the materials they contact in refrigeration systems. Therefore, the consideration of arefrigerant’s thermal stability and its compatibility with other materials is important. Elastomers and theelectrical insulation of refrigeration systems must also be chosen carefully.

It is important to choose a refrigerant that will not operate under vacuum at the lowest pressure point in thesystem. Operation at sub-atmospheric conditions with a flammable refrigerant could cause an explosivemixture to form if there is any leakage. In the case of non-flammable material (freon), the in-leakage of air willcause problems when the refrigerant is condensed.

Commonly Used Refrigerants

Typically, a refrigerant is referred to by the refrigerant number ("R" Number) assigned to it by ASHRAE. Thetable in Figure 7 lists this refrigerant number, the chemical name, and the chemical formula of each refrigerant.




REFRIGERANTNUMBER CHEMICAL NAME CHEMICAL FORMULA

Halocarbon Compounds10 Carbontetrachloride CCl411 Trichlorofluoromethane CCl3F12 Dichlorodifluoromethane CCl2F213 Chlorotrifluoromethane CClF3

13B1 Bromotrifluoromethane CBrF314 Carbontetrafluoride CF420 Chloroform CHCl321 Dichlorofluoromethane CHCl2F22 Chlorodifluoromethane CHClF223 Trifluoromethane CHF330 Methylene Chloride CH2Cl231 Chlorofluoromethane CH2ClF32 Methylene Fluoride CH2F240 Methyl Chloride CH3Cl41 Methyl Fluoride CH3F50a Methane CH4110 Hexachloroethane CCl3CCl3111 Pentachlorofluorethane CCl3CCl2F112 Tetrachlorodifluoroethane CCl2FCCl2F112a Tetrachlorodifluoroethane CCl3CClF2113 Trichlorotrifluoroethane CCl2FCCIF2113a Terrachlorodifluoroethane CCl3CF3114 Dichlorotetrafluoroethane CClF2CClF2114a Dichlorotetrafluoroethane CCl2FCF3

114B2 Dibromotetrafluoroethane CBrF2CBrF2115 Chloropentafluoroethane CClF2CF3116 Hexafluoroethane CF3CF3120 Pentachloroethane CHCl2CCl3123 Dichlorotrifluoroethane CHCl2CF3124 Chlorotetrafluoroethane CHClFCF3124a Chlorotetrafluoroethane CHF2CClF2125 Pentafluoroethane CHF2CF3133a Chlorotrifluoroethane CH2ClCF3134a Tetrafluoroethane CF3CH2F140a Trichloroethane CH3CCl3142b Chlorodifluoroethane CH3CClF2143a Trifluoroethane CH3CF3150a Dichloroethane CH3CHCl2160 Ethyl Chloride CH3CH2Cl170a Ethane CH3CH3218 Octafluoropropane CF3CF2CF3290a Propane CH3CH2CH3

a Methane, ethane, and propane appear in the Halocarbon section in their proper numerical order, but these compounds are not halocarbons.b Ethylene and propylene appear in the Hydrocarbon section to indicate that these compounds are hydrocarbons, but they are properly

identified in the section Unsaturated Organic Compounds.Source:1989 Fundamentals

Figure 7 (Page 1 of 3). ASHRAE Standard Designation of Refrigerants(ANSI/ASHRAE Standard 34-78)





Cyclic Organic CompoundsC316 Dichlorohexafluorocyclobutane C4Cl2F6C317 Chloroheptafluorocyclobutane C4ClF7C318 Octafluorocyclobutane C4F8

Azeotropes

Refrigerants 12/152a (73.8/26.2) CCl2F3/CH3CHF2501 Refrigerants 22/12 (75/25) CHClF2/CCl2F2502 Refrigerants 22/115 (48.8/51.2) CHClF2/CClF2CF3503 Refrigerants 23/13 (40.1/59.9) CHF3/CClF3504 Refrigerants 32/115 (48.2/51.8) CH2F2/CClF2CF3505 Refrigerants 12/31 (78.0/22.0) CCl2F2/CH2ClF506 Refrigerants 31/114 (55.1/44.9) CH2ClF/CClF2CClF2

Miscellaneous Organic CompoundsHydrocarbons

50 Methane CH4170 Ethane CH3CH3290 Propane CH3CH2CH3600 Butane CH3CH2CH2CH3600a Isobutane (2 methyl propane) CH(CH3)3

1150b Ethylene CH2=CH21270b Propylene CH3CH=CH2

Oxygen Compounds610 Ethyl Ether C2H5OC2H5611 Methyl Formate HCOOCH3

Nitrogen Compounds630 Methyl Amine CH3NH2631 Ethyl Amine C2H5NH2

Inorganic Compounds702 Hydrogen (Normal and Para) H2704 Helium He717 Ammonia NH3718 Water H2O720 Neon Ne728 Nitrogen N2729 Air .21O2, .78N2, .01A732 Oxygen O2740 Argon A744 Carbon Dioxide CO2744a Nitrous Oxide N2O764 Sulfur Dioxide SO2

a Methane, ethane, and propane appear in the Halocarbon section in their proper numerical order, but these compounds are not halocarbons.b Ethylene and propylene appear in the Hydrocarbon section to indicate that these compounds are hydrocarbons, but they are properly identified in the section

Unsaturated Organic Compounds.Source: 1989 Fundamentals






Unsaturated Organic Compounds1112a Dichlorodifluoroethylene CCl2=CF21113 Chlorotrifluoroethylene CClF=CF21114 Tetrafluoroethylene CF2=CF21120 Trichloroethylene CHCl=CCl21130 Dichloroethylene CHCl=CHCl1132a Vinylidene Fluoride CH2=CF21140 Vinyl Chloride CH2=CHCl1141 Vinyl Fluoride CH2=CHF1150 Ethylene CH2=CH21270 Propylene CH3CH=CH252a Difluoroethane CH3CHF2

a Methane, ethane, and propane appear in the Halocarbon section in their proper numerical order, but these compounds are not halocarbons.b Ethylene and propylene appear in the Hydrocarbon section to indicate that these compounds are hydrocarbons, but they are properly identified in the section

Unsaturated Organic Compounds.Source: 1989 Fundamentals


When not presented in a table, the prefix "R" is normally used to indicate that the number is an ASHRAEnumber. The following are the refrigerants most frequently used:

Freons Hydrocarbons Other AbsorptionR-12 R-170 R-717 Li BrR-13 R-290 R-718 Ammonia (R-717)R-13 B1 R-1150 R-728R-22 R-1270 R-744R-502 R-764R-503

Figure 8. Frequently Used Refrigerants

Figure 16 in Work Aid 2 shows the approximate ranges of temperatures in which the more common refrigerantsare used. Industrial systems with temperatures down to about -50°C (-45°F) frequently use R-717 or R-22 insingle- or two-staged systems. Two-stage systems with temperatures in the -73°C to -101°C (-100°F to -150°F)range frequently use R-503 in the low range and R-22, R-12, or R-502 in the high range.




The ozone depletion potential of freons will probably cause their use to decline.

At any given temperature, R-503 has a higher suction pressure and density than R-13. Therefore, a givencompressor with a suction temperature of - 84°C(-120°F) and a condensing temperature of -29°C (-20°F) that uses R-503 instead of R-13 has 57% morecapacity. R-503 also maintains a positive suction pressure at temperatures lower than R-13. At about -87°C (-125°F), R-503 has a suction pressure of 0 kPa (gauge). In comparison, R-13 has a suction pressure of 0 kPa at -79°C (-110°F).

R-503, however, has a higher operating pressure at ambient temperature. At 16°C (60°F), R-503 has anoperating pressure of 3.9 MPa (560 psig) but R-13 has an operating pressure of only 2.77 MPa (402 psig). Theuse of R-503 or R-13 requires special designs and special handling. Systems that use these refrigerants requirean expansion tank to hold the refrigerant during periods of shutdown or power failure.

Physical PropertiesThe critical properties of a refrigerant represent the conditions under which the distinction between liquid andgas is lost. At temperatures above the critical point, a separate liquid phase is not possible. For refrigerationcycles that use condensation, a refrigerant must be chosen that will change between liquid and gas phases belowthe critical point of the refrigerant. Figure 17 in Work Aid 2 lists physical properties of refrigerants that areused in vapor compression systems.

Figure 17 lists the refrigerants in order of increasing boiling points. The boiling point of a refrigerant directlyindicates the temperature level at which a refrigerant can be used. The freezing point of a refrigerant must belower than any temperature in its intended application.

Figures 18, 19, and 20 show density, specific heat, and viscosity of lithium bromide solutions.




FlammabilityTo prevent the drawing of air into the refrigerant system, the use of extremely flammable refrigerants (propane,for example) should be limited to applications where pressures will remain above atmospheric pressure.

The Safety Code for Mechanical Refrigeration ANSI/ASHRAE 15-1598 and the IIAR Bulletin 109 MinimumSafety Criteria for a Safe Ammonia Refrigeration System (1988) should be referred to for safety and minimumdesign criteria of common refrigerants.

Compromises Between Conflicting Desirable Thermodynamic PropertiesOperating-Pressure – Desirable refrigeration systems have the highest evaporator pressures and the lowestcondenser pressures. Systems with high evaporator pressures have high vapor densities. Therefore, for a givencompressor, the higher the evaporator pressure, the higher the system capacity. However, increasing theevaporator pressure also decreases the efficiency of the system, especially as the condenser pressure approachesthe critical temperature.

Latent Heat of Vaporization – On a molar basis, fluids with similar boiling points have almost the same latentheat of vaporization. Since compressors operate on volumes of gas, refrigerants with similar boiling pointsproduce similar capacities in the same compressor. On a mass basis, the latent heat of fluids varies widely. In atheoretical vapor compression cycle, fluids with low vapor heat capacities produce the maximum efficiencies.Fluids with simple molecular structures and low molecular weights are associated with low vapor heatcapacities.

Transport Properties – The thermal conductivity and the viscosity of a refrigerant affect the performance ofheat exchangers and piping. Refrigerants with high thermal conductivity and low viscosity are desirable.




Velocity of Sound - Figure 21 in Work Aid 2 lists the velocities of sound in several refrigerants. The velocityof sound through a gas limits the practical velocity of a gas through piping and openings. The velocity ofsound increases as the temperature of the gas increases, and decreases as the pressure of the gas increases.

Equation A (shown below) can be used to calculate the velocity of sound in gases.

va = Gckdρdρ

T

For a perfect gas: va = GckRT/M (EQN

A)

where:

Va = Velocity of sound, m/s (ft/s)

Gc = Constant, 32.17 m/s2 (32.17 ft/s2)

k = cp/cv ratio of specific heats

R = Gas Constant, 8.314 gr-m/mole °K (1,546 lb-ft/mole °R)

T = Temperature, °K (°R)

M = Molecular Weight, gr/mole (lb/mole)dρdρ

T= Rate of change of pressured/rate of change of density, atconstant temperature

Latent HeatAccording to an empirical rule of chemistry (Trouton’s Rule), the latent heat of vaporization of a material at itsboiling point (on a molar basis) divided by the boiling temperature (in absolute units) is a constant for mostmaterials.

Figure 9 tabulates this constant for several refrigerants. Note that while this rule applies fairly well to theserefrigerants, the “constant” varies from 96.64 η/K to 73.36 η/K (23.086 η/°R to 17.52 η/°R). This rule canbe used to compare different refrigerants and to understand the operation of refrigeration systems.




NO.REFRIGERANT

NAME

NORMALBOILING

PT°C

LATENTHEAT ATBOILING

PT

λ kJ/kg•mol

TROUTONCONSTAN

T

λ /Kb

NORMALBOILING

PT°F

LATENTHEAT ATBOILING

PT

λ Btu/ibmol

TROUTONCONSTANT

λ /°RbRE

F

630 Methyl Aminea - 5.0 25 914 96.64 23.0 11141 23.086 4717 Ammonia -33.3 23 343 97.32 -28.0 10036 23.256 1764 Sulfur Dioxide -10.2 24 900 94.69 13.6 10705 22.626 2631 Ethyl Amine 20.0 27 086 92.40 68.0 11645 22.076 4611 Methyl Formatea 37.8 28 131 90.47 100.0 12094 21.616 4504 — - 57.2 19 264 89.21 -71.0 8282 21.316 123 Trifluoromethane - 82.1 17 039 89.19 -115.7 7325 21.29 121 Dichlorofluoromethane 8.8 24 556 87.09 47.8 10557 20.8 330 Methylene Chloridea 48.9 26 511 82.32 120.0 11398 19.66 4

C318 Octafluorocyclobutane - 5.8 23 298 87.14 21.5 10017 20.81 122 Chlorodifluoromethane - 40.8 20 207 86.97 -41.4 8687 20.76 140 Methyl Chloride - 23.8 21 644 86.80 -10.8 9305 20.73 3

506 — - 12.3 22 431 85.99 9.9 9644 21.44 3113 Trichlorotrifluoroethane 47.6 27 513 85.78 117.6 11828 20.49 1

152aDifluoroethane - 25.0 21 039 84.78 -13.0 9045 20.25 1

502 — - 45.5 19 258 84.59 -49.9 8280 20.21 3114 Dichlorotetrafluoroethane 3.8 23 273 84.03 38.8 10005 20.07 1216 Dichlorohexafluoropropane 35.7 25 943 84.00 96.2 11154 20.07 111 Trichlorofluoromethane 23.8 24 768 83.41 74.9 10648 19.92 1

505 — - 29.9 20 319 83.53 -21.8 8735 19.95 3500 — - 33.5 19 975 83.35 -28.3 8588 19.91 1290 Propane - 42.1 18 669 80.80 -43.7 8026 19.29 114 Tetrafluoromethane -127.9 11 969 82.40 -198.3 5146 19.69 1

600 Butane - 0.5 22 425 82.25 31.1 9641 19.64 113B1 Bromotrifluoromethane - 57.8 17 695 82.17 -72.0 7607 19.62 1

12 Dichlorodifluoromethane - 29.8 19 982 82.11 -21.6 8591 19.61 1142b

Chlorodifluoroethane - 9.8 21 624 82.11 14.4 9297 19.61 1115 Chloropentafluoroethane - 39.1 19 178 81.94 -38.4 8245 19.57 1503 — - 87.8 15 080 81.36 -126.1 6483 19.43 1

1270 Propylene - 47.7 18 448 81.83 -53.9 7931 19.55 1600a Isobutane - 11.7 21 174 80.99 10.9 9103 19.34 1

13 Chlorotrifluoromethane - 81.4 15 515 80.91 -114.6 6670 19.33 11150 Ethylene -103.7 13 475 79.52 -154.7 5793 19.00 1170 Ethane - 88.8 14 645 79.44 -127.9 6296 18.98 150 Methane -161.5 8 191 73.36 -258.7 3521 17.52 1

a Not at normal atmospheric pressure.b Normal boiling temperatures.1 Thermodynamic Properties of Refrigerants (Stewart et al. 1986)2 Handbook of Chemistry and Physics (CRC 1987)3 ASHRAE (1977)4 Chemical Engineer's Handbook (1973)

Source: 1989 Fundamentals (SI)

Figure 9. Latent Heat of Vaporization Versus Boiling Point




PerformanceFigure 22 in Work Aid 2 tabulates the theoretical calculated performance of several refrigerants. Thetheoretical performance of these refrigerants is based on a US standard cycle of 258 K (5°F) evaporation and303 K (86°F) condensation. Figure 23 in Work Aid 2 tabulates calculated data for other operating conditions.

Both Figure 22 and Figure 23 can be used to compare the properties of different refrigerants. Actual operatingconditions, however, usually differ from those that are tabulated. Most of the tabulated data was generated withthe assumption that the suction vapor is saturated and that the compression is adiabatic (constant entropy).

In Section F of Figure 22, the temperature of the suction gas is 291 K (65°F). A comparison of Section F withSection E illustrates the effect of suction gas superheating on the properties of refrigerants.

Figure 10 tabulates the effect of different evaporating and condensing temperatures on the theoretical capacityof refrigeration systems using R-12 and R-22. Figure 11 tabulates the effect of different evaporating andcondensing temperatures on the horsepower of compression of refrigeration systems when R-12 and R-22 isused. Figure 10 and Figure 11 below assume constant compressor displacement.




EVAP. TEMP. CONDENSING TEMPERATURE°C 15°C 25°C 35°C 45°C

R-12 CAPACITY, kW

-30 1.56 1.43 1.31 1.18

-20 2.36 2.18 2.00 1.81

-10 3.47 3.22 2.95 2.69

5 5.87 5.46 5.04 4.61

R-22 CAPACITY, kW

-30 2.58 2.40 2.21 2.02

-20 3.87 3.61 3.33 3.04

-10 5.62 5.24 4.85 4.44

5 9.37 8.76 8.13 7.47

EVAP. TEMP. CONDENSING TEMPERATURE°F 60°F 80°F 100°F 120°F

R-12 CAPACITY, Btu/h

-20 5241 4780 4307 3820

0 8280 7582 6864 6124

20 12585 11563 10513 9431

40 18511 17062 15571 14035

R-22 CAPACITY, Btu/h

-20 8694 8010 7297 6550

0 13539 12503 11422 10288

20 20320 18801 17218 15557

40 29563 27401 25148 22783


Figure 10. Effects of Temperature on Capacity [Constant CompressorDisplacement = 2 L/s (4 cfm)]




EVAP. TEMP. CONDENSING TEMPERATURE

°C 15°C 25°C 35°C 45°C

R-12 THEORETICAL kW/kW OF REFRIGERATION

-30 0.22 0.28 0.36 0.45

-20 0.15 0.21 0.27 0.34

-10 0.11 0.16 0.22 0.28

5 0.04 0.08 0.13 0.18

R-22 THEORETICAL kW/kW OF REFRIGERATION

-30 0.22 0.28 0.36 0.44

-20 0.16 0.22 0.28 0.36

-10 0.11 0.16 0.21 0.28

5 0.04 0.08 0.13 0.18

EVAP. TEMP. CONDENSING TEMPERATURE

°F 60°F 80°F 100°F 120°F

R-12 THEORETICAL hp/ton OF REFRIGERATION

-20 1.03 1.38 1.80 2.32

0 0.71 1.01 1.37 1.80

20 0.44 0.70 1.00 1.36

40 0.20 0.43 0.68 0.99

R-22 THEORETICAL hp/ton OF REFRIGERATION

-20 1.02 1.35 1.75 2.22

0 0.71 1.00 1.34 1.75

20 0.44 0.69 0.99 1.34

40 0.20 0.43 0.68 0.98


Figure 11. Effects of Temperature on Theoretical kW (HP) per kW (Ton)of Refrigeration




Figure 24 in Work Aid 2 summarizes the toxicity and flammability of many refrigerants. ANSI/ASHRAEStandard 15-78 classifies refrigerants according to the hazard involved in their use. Figure 24 tabulatesrefrigerants by their ANSI/ASHRAE Standard 15-78 safety code group and by their Underwriters’ Laboratories(UL) classification of comparative hazard to life. Group 1 refrigerants are the least hazardous and Group 3refrigerants are the most hazardous. Figure 25 in Work Aid 2 tabulates the UL group classifications.

Effect on Construction MetalsUnder normal conditions, halogenated refrigerants can be used with most metals such as steel, cast iron, brass,copper, tin, lead, and aluminum. Under more severe conditions, various metals affect the properties ofrefrigerants such as hydrolysis and thermal decomposition. Metals affect refrigerant properties in varyingdegrees. For instance, the metals listed below promote thermal decomposition of halogenated refrigerants. Themetals are listed in the approximate order of their promotion of thermal decomposition:

• Inconel (least decomposition)• 18-8 stainless steel• Nickel• Copper• 1340 steel• Aluminum• Bronze• Brass• Zinc• Silver (most decomposition)

These metals can have a similar effect on the hydrolysis of halogenated refrigerants. In systems when a trace ofwater may be present, magnesium, zinc, and aluminum alloys containing more than 2% magnesium are notrecommended for use with halogenated refrigerants. When water is present in sulfur dioxide systems, sulfurousacid is formed and attacks iron and steel rapidly and other metals more slowly.

Warning: Never use methyl chloride with aluminum in any form.This combination produces a highly flammable gas andis a great explosion hazard.




Ammonia (R-717)Ammonia is generally used in large, open-type compressors for industrial and commercial applications. Theusage of ammonia may increase, as it continues to become a substitute for freons. Ammonia has the followingadvantages as a refrigerant:

• High refrigerating capacity per unit of compressor displacement• Low-pressure losses in connecting piping• Low reactivity with refrigeration oils

In contrast with freon, ammonia is toxic and flammable. Ammonia is a strong irritant. Humans can detect it atconcentrations below 5 ppm. Within a narrow range of concentrations (16% to 25% by volume), ammonia airmixtures are flammable. These mixtures can explode if heated above 650°C (1200°F), but the maximumexplosive pressure is relatively low 350 kPa (50 psi). Therefore, ammonia is not considered a serious fire orexplosion hazard.

The thermal stability of ammonia often confuses people. At atmospheric pressure, at 300°C (570°F), and in thepresence of active catalysts such as nickel or iron, ammonia starts to dissociate into nitrogen and hydrogen.However, because such high temperatures are unlikely to occur in open type compressors, thermal stability isnot a problem in ammonia systems.

When moisture is present, ammonia attacks copper. Therefore, except for some specialty bronzes, copper-bearing metals must be excluded from ammonia systems.

Ammonia is a powerful solvent that strips any remaining dirt and scale from piping. To protect against thedebris that results from stripping. Most compressors are equipped with suction strainers, disposable strainerliners, or both.

Liquid ammonia that returns with the suction gas causes serious cylinder and ring wear. Ammonia slugs breakvalves or cause more serious damage. Low steady flow rates of ammonia liquid reduce cylinder lubrication.This loss of lubrication causes extremely rapid cylinder wall and ring abrasion.

A carefully and properly installed system, in which no foreign matter or liquid enters the compressor, willoperate for many years. When new piping is installed, it should be wire brushed and blown out withcompressed air.




Ammonia Piping RequirementsRecommended Material – Ammonia piping should conform to ANSI/ASME Code for Pressure Piping. Thiscodes specifies the following:

• Liquid lines 40 mm (1.5 in) and smaller shall not be less than schedule 80 carbon steel pipe.

• Liquid lines 50 mm (2 in) through 150 mm (6 in) shall not be less than schedule 40 carbon steelpipe.

• Vapor lines 150 mm (6 in.) and smaller shall not be less than schedule 40 carbon steel pipe.

Fittings – Coupling, elbows, and tees for threaded pipe should be built for a minimum design pressure of 14MPa (2000 psi) and constructed of forged steel.

Tongue and groove or ANSI flanges should be used in ammonia piping.

Pipe Joints – Joints installed between lengths of pipe or between pipe and fittings can be threaded if the size ofpipe is 32 mm (1.25 in) or smaller. Joints in piping that is sized 40 mm (1.5 in), or larger, should be welded.

To prevent contamination of the ammonia refrigeration system, excessive amounts of sealant should not beapplied to any joint, nor should any sealant be applied to female threads.

When flanges are used, 1.6 mm (0.063 in) fiber gasket should also be used. The pipe and bolt holes should beproperly aligned before tightening flange bolts to valves, controls, or flange unions. The use of flanges tostraighten pipe may put stress on adjacent valves, compressors, and controls. This stress can cause theoperating mechanism to break.

Steel (14 MPa = 2000 psi) ground joint unions should be used for gauge and pressure control lines withscrewed valves and for joints up to 20 mm (0.75 in).

Pipe Location – Where possible, piping for ammonia systems should be located at least 2.3 m (7.5 ft) abovethe floor. Piping for ammonia systems, especially if they are to be insulated, should be located carefully inrelation to other piping and structural members. Pipe hangers should be placed no more than 2.5 m to 3 m (8 ftto 10 ft) apart.




Oil in Ammonia Systems – Oil is miscible in liquid ammonia only in very small proportions. As temperaturesdecrease, oil separates from the liquid ammonia. The evaporation of ammonia increases the concentration of oiland causes the oil to form a separate layer below the ammonia liquid.

The periodic or continuous removal of oil prevents it from covering the evaporator’s heat transfer surface andreducing performance. Because the density of oil is greater than that of ammonia, oil will settle in low areas ofammonia systems. Unless temperatures are too low to allow the oil to flow, draining oil from these systems isnot difficult. In low-temperature situations, maintaining oil receivers at higher temperatures may be beneficial.

Oil Separators should be located in the discharge line of a compressor. A high-pressure float valve drains oilback into the compressor crankcase or oil receiver. To cool the discharge gas (ammonia vapor), oil separatorsshould be placed as far from the compressor as possible. The cooling of the ammonia vapor increases theeffectiveness of the separator.

Compressor Piping –The objective of suction mains is to return clean, dry gas to the compressor.

A good suction line system has a total friction drop 1 K (2°F) to 3 K (5°F) pressure drop equivalent. Practicalfriction losses should not exceed 0.01 K per meter equivalent length (0.5°F equivalent per 100 ft equivalentlength). The main suction line should slope toward a suction trap (1% vertical drop per horizontal lengthminimum).

A well designed discharge main has a total friction loss of 20 kPa to 35 kPa (3 psi to 5 psi). To hold downdischarge pressure and discharge temperature, a slightly oversized discharge line is generally used. To protectthe compressor, high- and low-pressure cutouts and gauges are installed on the compressor side of stop valves.

Discharge Check Valves located on the downstream side of each oil separator will prevent high-pressure gasfrom flowing into an inactive compressor and condensing. To prevent reverse rotation, screw compressors mustbe equipped with a check valve.

If the temperature of the engine room is below the condensing temperature of the refrigeration system, gas mayleak past the check valve and condense in the discharge line and oil separator. Liquid ammonia then drains intothe compressor from the float under the oil separator.




When the temperature of the engine room is below the condensing temperature of the refrigeration system,ASHRAE recommends the use of a positive method of equalizing the fluid level of the discharge and suctionlines. ASHRAE recommends that equalization always be used when compressors are located outside or inunheated spaces. Equalization can be done automatically or manually.

Accessories – Any ammonia vessel that can be valved off must have an automatic relief valve. The sizing ofthe valve should conform to Safety Code for Mechanical Refrigeration ANSI/ASHRAE 15-1989.

The use of dual relief valves allows the testing of each valve. The use of three-way stop valves allows one to beremoved for repair or testing.

A noncondensable gas separator (purge unit) is useful in most plants, especially when an ammonia system’ssuction pressure is equal to atmospheric pressure.




Source: 1990 Refrigeration

Figure 12. Purge Unit and Piping for Noncondensable Gas

In Figure 12, the high-pressure liquid expands through the coil in the purge unit. This expansion cools theliquid and the coil. The line from the coil then goes to a high-temperature suction main. Ammonia vapor andnoncondensable gas are drawn up into the purge drum. The ammonia then condenses on the cold surface of thecoil. The air and other noncondensable gases fill the purge drum. When the drum is full, a float valve opensand releases the noncondensable gases to the open water bottle.




The receiver should be equipped with an armored gauge glass to allow the measurement of the ammonia in thereceiver. The valves on each side of the gauge glass should be equipped with excess flow check valves toprevent the loss of refrigerant if the gauge glass breaks.

Enough liquid ammonia needs to be charged into the system to seal the outlet pipe of the receiver and toprevent hot gas from blowing from the high side to the low side. The lowest liquid level a receiver shouldoperate is the equivalent of two diameters of the outlet pipe for both the top and bottom outlet receivers.




REFRIG-ERANT

FLAM-MABLE TOXIC

USESLOW-

LEVELHEAT

MINIMUMACHIEVABLE

TEMPER-ATURE TYPICAL APPLICATIONS

R-717(ammonia)

Yes Yes No 241 K (-26°F) Used extensively in large, opencompressors for industrial andcommercial applications.

R-11

R-13B1

R-500

No Low No 297K +76°F216K -70°F241K -26°F

Used widely for specializedapplications.

R-12 No Low No 240 K (-20°F) Most widely used refrigerants.

R-22 No Low No 233 K (-40°F) Most widely used refrigerants.

Water(ammonia

absorption)

Yes Yes Yes 275 K (35°F) Used where absorption systemsare practical, except whereammonia’s flammability is notacceptable (occupied buildings,for example).

Water(Li Br

absorption)

No No Yes 275 K (35°F) Used where absorption systemsare practical. No toxicity orflammability limitations.

Water(steam jet)

No No Yes 275 K (35°F) Large number of applications inwhich steam is available.Applications include comfort airconditioning, industrial processcooling, and other similar typesof service.

Ethane Yes No 186 K (-126°F) Used for refinery operations.

Propane Yes No 232 K (-42°F) Used for refinery operations.

Butane Yes No 274 K (33°F) Used for refinery operations.

Ethylene Yes No 171 K (-153°F) Used for refinery operations.

Propylene Yes No 227 K (-51°F) Used for refinery operations.

Figure 13. Summary of Refrigerant Applications

Work Aid 2 describes the procedures and provides the resources required to select appropriate refrigerants.




Work Aid 1: Resources For Selecting appropriate refrigeration SYSTEMSDirections: Use Figure 14 and Figure 15 to help select an appropriate refrigeration system.

Figure 14. Refrigeration Systems Schematic




ABSORPTION

CONSIDERATIONVAPOR

COMPRESSION AmmoniaLithiumBromide STEAM JET

Minimum refrigeranttemperature

No limit 2°C (35°F) 2°C (35°F) 2°C(35°F)

Refrigerant toxic? Yes/No Yes No No

Flammable? Yes/No Yes No No

Reciprocating compressor Up to 1 400 kW (400tons*)

None None

Centrifugal compressor >1 400 kW(400 tons*)

None None

*tons of refrigeration

Figure 15. Refrigeration System and Equipment Limits




Work Aid 2: PROCEDURES AND RESOURCES FOR Selecting the mostappropriate refrigerants

To select the most appropriate refrigerant, analyze the refrigeration system (already selected) and the followingoperating considerations and refrigerant properties.

• Availability of low-level (waste) heat• Availability of steam• Availability (both generally and for the specific application)• Capital cost• Compatibility with system building materials• Environmental regulations (both existing and anticipated)• Flammability• Minimum achievable temperature• Operating cost• Thermal stability• Toxicity

Determine the relevance of each consideration and property for the application. For each relevant property,refer to the following appropriate Figures for more information. Based on the information in the relevantFigure and the information covered in the Information Sheet, select the most appropriate refrigerant.

Minimum Refrigerant Temperature°C °F

Ammonia Absorption/Water +2 +35Lithium Bromide/Water +2 +35Ammonia -32 -26Freon 12 -29 -20Freon 22 -40 -40Ethane -88 -126Propane -41 -42Butane 0 +33Ethylene -103 -153Propylene -46 -51

Figure 16. Temperature Limits for Refrigerants




REFRIGERANT CHEMI-CAL

MOLECULAR

BOIL -ING PT.

(NBP)AT

101.325

FREEZING

POINT

CRITICAL

TEMPERA

TURE,

CRITICAL

PRESSURE

CRITICAL

VOLUME,

SURFACETENSION,

REFRACTIVEINDEX OF

NO. NAME FORMULA MASS KPA,°C °C °C kPa L/kg mN/mb LIQUID b,c

704 Helium He 4.0026 - 268.9 None - 267.9 228.8 14.43 0.12 (- 269) 1.021 (NBP) 546.1 nm702n Hydrogen (normal) H2 2.0159 - 252.8 - 259.2 - 239.9 1315 33.21 2.31 (- 255) 1.097 (NBP) 579.1 nm702p Hydrogen (para) H2 2.0159 - 252.9 - 259.3 - 240.2 1292 31.82 2.172 1.09 (NBP)J720 Neon Ne 20.183 - 246.1 - 248.6 - 228.7 3397 2.070 5.50 (- 248) ...728 Nitrogen N2 28.013 - 198.8 - 210 - 146.9 3396 3.179 8.27 (- 193) 1.205 (83K) 589.3 nm729 Air ... 28.97 - 194.3 ... - 140.7 3772 3.048 Plait Point

- - 140.6 3764 3.126 Point of Contact740 Argon A 39.948 - 185.9 - 189.3 - 122.3 4895 1.867 13.2 (- 188) 1.233 (TP) 589.3 nm732 Oxygen O2 31.9988 - 182.9 - 218.8 - 118.4 5077 2.341 13.2 (- 183) 1.221 (92K) 589.3 nm50 Methane CH4 16.04 - 161.5 - 182.2 - 82.5 4638 6.18114 Tetrafluoromethane CF4 88.01 - 127.9 - 184.9 - 45.7 3741 1.5981150 Ethylene C2H4 28.05 - 103.7 - 169 9.3 5114 4.37 16.5 (- 104)1 1.363 (- 100)1503 f ... 87.5 - 88.7 ... 19.5 4182 2.035170 Ethane C2H6 30.07 - 88.8 - 183 32.2 4891 5.182744A2 Nitrous Oxide N2O 44.02 - 89.5 - 102 36.5 7221 2.216 1.75 (20)23 Trifluoromethane CHF3 70.02 - 82.1 - 155 25.6 4833 1.942 9.5 (- 40)313 Chlorotrifluoromethane CCIF3 104.47 - 81.4 - 181 28.8 3865 1.729 8.5 (- 40 )3 1.146 (25)4744 Carbon Dioxide CO2 44.01 - 78.4 - 56.6e 31.1 7372 2.135 1.16 (20) 1.195 (15)13B1 Bromotrifluoromethane CBrF3 148.93 - 57.75 - 168 67.0 3962 1.342 3.8 (26.7)3 1.239 (25)4504 g ... 79.2 - 57.2 ... 66.4 4758 2.0231270 Propylene C3H6 42.09 - 47.7 - 185 91.8 4618 4.495 16.7 (20)2 1.3640 (- 50)1

5025 h ... 111.64 - 45.4 ... 82.2 4075 1.785290 Propane C3H8 44.10 - 42.07 - 187.7 96.8 4254 4.545 1.3397 (- 42)22 Chlorodifluoromethane CHClF2 86.48 - 40.76 - 160 96.0 4974 1.904 8.0 (26.7)3 1.234 (25)4115 Chloropentafluoroethane CClF2CF3 154.48 - 39.1 - 106 79.9 3153 1.629 5.1 (26.7)3 1.221 (25)4717 Ammonia NH3 17.03 - 33.3 - 77.7 113.0 11417 4.245 23.4 (11.1) 1.325 (16.5)500 j ... 99.31 - 33.5 - 159 105.5 4423 2.01612 Diclorodifluoromethane CCl2F2 120.93 - 29.79 - 158 112.0 4113 1.792 8.9 (26.7)3 1.288 (25)4134a Tetrafluoroethane CF3CH2F 102.03 - 26.16 - 96.6 101.1 4067 1.81 ... ...152a Difluoroethane CH3CHF2 66.05 - 25.0 - 117 113.5 4492 2.741402 Methyl Chloride CH3Cl 50.49 - 12.4 - 97.8 143.1 6674 2.834 16.2 (20)600a Isobutane C4H10 58.13 - 11.73 - 160 135.0 3645 4.526 1.3514 (- 25)1

7646 Sulfur Dioxide SO2 64.07 - 10.0 - 75.5 157.5 7875 1.910142b Chlorodifluoroethane CH3ClF2 100.5 - 9.8 - 131 137.1 4120 2.2976306 Methyl Amine CH3NH2 31.06 - 6.7 - 92.5 156.9 7455 23 (- 20) 1.432 (17.5)C318 Octafluorocyclobutane C4F8 200.04 - 5.8 - 41.4 115.3 2781 1.611 7.3 (26.7)3600 Butane C4H10 58.13 - 0.5 - 138.5 152.0 3794 4.383 1.3562 (- 15)1114 Diclorotetraluoroethane CClF2CClF2 170.94 3.8 - 94 145.7 3259 1.717 12 (26.7)3 1.294 (25)9

217 Dichlorofluoromethane CHCl2F 102.93 8.9 - 135 178.5 5168 1.917 18 (26.7)3 1.332 (25)4

1602 Ethyl Chloride C2H5Cl 64.52 12.4 - 138.3 187.2 5267 3.028 21.2 (5)2

6316 Ethyl Amine C2H5NH2 45.08 16.6 - 80.6 183.0 5619 20.4 (9.6)11 Trichlorofluoromethane CCl3F 137.38 23.82 - 111 198.0 4406 1.804 18 (26.7)3 1.362 (25)4

6116 Methyl Formate C2H4O2 60.05 31.8 - 99 214.0 5994 2.866 25.08 (20)6106 Ethyl Ether C4H10O 74.12 34.6 - 116.3 194.0 3603 3.790 17.01 (20) 1.3526 (20)216 Dichlorohexafluoroprop

aneC3Cl2F6 220.93 35.69 - 125.4 180.0 2753 1.742

306 Methylene Chloride CH2Cl2 84.93 40.2 - 97 237.0 6077 26.5 (20) 1.4244 (20)J113 Trichlorotrifluoroethane CCl2FCClF2 187.39 47.57 - 35 214.1 3437 1.736 19 (26.7)3 1.357 (25)4

11308 Dichloroethylene CHCl=CHCl 96.95 47.8 - 50 243.3 547811206 Trichloroethylene CHCl=CCl2 131.39 87.2 - 73 271.1 5016 29 (30)i 1.4782 (20)J

7186 Water H2O 18.02 100 0 374.2 22103 3.128 71.97 (25)

Notes References aData are from Thermodynamic Properties of Refrigerants (Stewart et al. 1987) 1Kirk and Othmer (1956) bThe temperature of measurement (Celcius) is shown in parentheses. The 2Matheson Gas Data Book (1966) data are from Handbook of Chemistry and Physics (CRC 1987) unless 3Bulletin D-27 (duPont 1967) otherwise noted. cFor the sodium D line. 4Bulletin B-32A (duPont) dSublimes. 5Bulletin T-502 (duPont 1980) eAt 527 kPa. 6Handbook of Chemistry (1967) fRefrigerants 23 and 13 (40.1/59.9% by mass). 7Bulletin G-1 (duPont) gRefrigerants 32 and 115 (48.2/51.82% by mass). 8CRC Handbook of Chemistry and Physics (CRC 1987) hRefrigerants 22 and 115 (48.8/51.2% by mass). iData from Electrochemicals Department, E.I. duPont de Nemours & Co. jRefrigerants 12 and 152a (73.8/26.2% by weight). kDielectric constant data.


Figure 17. Physical Properties of Refrigerants




% LiBr By Mass


Figure 18. Specific Gravity of Aqueous Solutions of LithiumBromide





Figure 19. Specific Heat of Aqueous Solutions of LithiumBromide





Figure 20. Viscosities of Aqueous Solutions of LithiumBromide




TEMPERATURE, °CREFRIGERANT PRESSURE, kPa 10 50 100

11 100 a 145 156

12 100 144 155 167 22 100 176 188 201113 100 a 120 130114 100 118 127 137502 100 151 162 173 12 1000 a 138 156 22 1000 a 173 193502 1000 129 148 166 12 1500 a a 148 22 1500 a 164 187502 1500 a 138 159

TEMPERATURE, °FREFRIGERANT PRESSURE, psia 50 100 150

11 10 a 469 490 12 10 480 503 525 22 10 583 610 635113 10 a 390 409114 10 391 411 430502 10 501 525 547 12 100 a 457 490 22 100 a 574 607502 100 450 488 519 12 200 a a 442 22 200 a 523 572502 200 a 435 483

aBelow saturation temperature


Figure 21. Velocity of Sound in Refrigerant Vapors, m/s (ft/s)




REFRIGERANT

EVAPO-RATOR

PRESSURE,

CON-DENSING

PRESSURE,COM-

PRESSION,

NETREFRIG-ERATINGEFFECT,

REFRIG-ERANTCIRCU-LATED,

LIQUIDCIRCU-LATED,

SPECIFICVOLUME

OFSUCTION

GAS,

COM-PRESSORDISPLACE-

MENT, POWER,

COEFFI-CIENT

OFPER-

FORM-

COMP.DIS-

CHARGETEMP.

NO. NAME MPa Mpa RATIO kJ/kg kg/sec L/sec m3/kg L/sec kW ANCE K170 Ethane 1.623 4.637 2.86 162.44 0.00616 0.0232 0.0335 0.206 0.364 2.74 324744 Carbon Dioxide 2.291 7.208 3.15 134.24 0.00745 0.0123 0.0087 0.065 0.338 2.96 343

13B1 Bromotrifluoromethane 0.536 1.821 3.39 66.14 0.01512 0.0101 0.0237 0.358 0.274 3.65 313

1270 Propylene 0.362 1.304 3.60 286.48 0.00349 0.0070 0.1285 0.449 0.197 5.07 354290 Propane 0.291 1.077 3.71 279.88 0.00357 0.0074 0.1542 0.551 0.211 4.74 320502 22/115 Azeotrope 0.349 1.319 3.78 104.39 0.00958 0.0080 0.0500 0.479 0.226 4.43 310

22 Chlorodifluoromethane 0.296 1.192 4.03 162.46 0.00616 0.0053 0.0774 0.476 0.210 4.75 326

717 Ammonia 0.236 1.164 4.94 1102.23 0.00091 0.0015 0.5106 0.463 0.207 4.84 371500 12/152a Azetrope 0.214 0.879 4.11 140.95 0.00709 0.0062 0.0938 0.665 0.213 4.69 314

12 Dichlorodifluoromethane 0.183 0.745 4.07 116.58 0.00858 0.0066 0.0914 0.784 0.213 4.69 311600a Isobutane 0.089 0.407 4.60 262.84 0.00380 0.0070 0.4029 1.533 0.220 4.55 318

600 Butant 0.056 0.283 5.05 292.01 0.00342 0.0060 0.6641 2.274 0.214 4.68 318114 Dichlorotetrafluoroethanea 0.047 0.252 5.41 99.19 0.01008 0.0070 0.2700 2.722 0.225 4.44 303

11 Trichlorofluoromethane 0.020 0.126 6.24 156.22 0.00640 0.0044 0.7641 4.891 0.196 5.09 313113 Trichlorotrifluoroethanea 0.007 0.054 7.84 127.34 0.00785 0.0051 1.6793 13.187 0.173 5.77 303

a Saturated suction except R-113, 114. Enough superheat was added to give saturated discharge.

REFRIGERANT

EVAPO-RATOR

PRESSURE,

CON-DENSING

PRESSURE,COM-

PRESSION,

NETREFRIG-ERATINGEFFECT,

REFRIG-ERANTCIRCU-LATED,

LIQUIDCIRCU-LATED,

SPECIFICVOLUME

OFSUCTION

GAS,

COM-PRESSORDISPLACE-

MENT,HORSE-POWER,

COEFFI-CIENT

OFPER-

FORM-

COMP.DIS-

CHARGETEMP.

NO. NAME psia psia RATIO Btu/lb lb/min in3/min ft3/lb cfm hp ANCE °F170 Ethane 235.440 672.595 2.86 69.84 2.86382 299.1584 0.5366 1.537 1.719 2.74 124744 Carbon Dioxide 332.339 1045.360 3.15 57.71 3.46543 158.6275 0.1398 0.485 1.594 2.96 159

13B1 Bromotrifluoromethane 77.810 264.128 3.39 28.44 7.03356 129.8609 0.3797 2.671 1.291 3.65 103

1270 Propylene 52.547 189.086 3.60 123.17 1.62384 90.6458 2.0582 3.342 0.930 5.07 177290 Propane 42.142 156.249 3.71 120.33 1.66214 94.9694 2.4705 4.106 0.995 4.74 116502 22/115 Azeotrope 50.553 191.290 3.78 44.88 4.45636 103.4279 0.8013 3.571 1.064 4.43 98

22 Chlorodifluoromethane 42.956 172.899 4.03 69.85 2.86347 67.6965 1.2391 3.548 0.992 4.75 127

717 Ammonia 34.162 168.795 4.94 473.87 0.42205 19.6217 8.1790 3.452 0.975 4.84 207500 12/152a Azetrope 31.058 127.504 4.11 60.60 3.30046 80.2447 1.5018 4.957 1.005 4.69 105

12 Dichlorodifluoromethane 26.501 107.991 4.07 50.12 3.99039 85.4557 1.4645 5.844 1.005 4.69 100600a Isobutane 12.843 59.036 4.60 113.00 1.76990 89.9712 6.4537 11.422 1.037 4.55 113

600 Butant 8.116 41.007 5.05 125.54 1.59309 77.7557 10.6375 16.947 1.008 4.68 112114 Dichlorotetrafluoroethanea 6.745 36.493 5.41 42.64 4.68998 90.3560 4.3248 20.283 1.061 4.44 86

11 Trichlorofluoromethane 2.937 18.318 6.24 67.16 2.97785 56.2924 12.2400 36.449 0.926 5.09 104113 Trichlorotrifluoroethanea 1.006 7.884 7.84 54.75 3.65321 65.2540 26.8991 98.268 0.817 5.77 86

a Saturated suction except R-113, 114. Enough superheat was added to give saturated discharge. Sourc

e: 1989 Fundamentals (SI)

Figure 22. Comparative Refrigerant Performance Per kW (Ton) [Basedon 258°K Evaporation (5°F) and 303°K Condensation (86°F)]




No.

Refrigerant

Name

Suction Temp.

K

Evapo-rator

pressure MPa

Con-densingpressure

MPa

Com-pression

Ratio

Netrefrig-

eratingeffect,kJ/kg

Refrig-erantcircu-lated

kg/sec

Specificvolume

ofsuction

gas,m3 /kg

Com-pressor

displace-ment,L/sec

PowerkW

A. 183 K Evaporating, 233 K Condensing1150 Ethylene 183 0.211 1.446 6.84 330.40 0.00303 0.2422 0.733 0.373

170 Ethane 183 0.093 0.774 8.31 364.21 0.00275 0.5257 1.443 0.347

B. 200 K Evaporating, 238 K Condensing170 Ethane 200 0.212 0.909 4.29 503.14 0.00199 0.2396 0.476 0.168

22 Chlorodifluoromethane 200 0.017 0.132 7.87 211.70 0.00472 1.1347 5.360 0.221

C. 213 K Evaporating, 258 K Condensing1150 Ethylene 213 0.755 2.859 3.79 272.31 0.00367 0.0729 0.268 0.314

170 Ethane 213 0.377 1.623 4.31 322.65 0.00310 0.1430 0.443 0.279

290 Propane 213 0.042 0.291 6.91 342.79 0.00292 0.9343 2.726 0.25422 Chlorodifluoromethane 213 0.037 0.296 7.90 195.80 0.00511 0.5364 2.740 0.253

717 Ammonia 213 0.022 0.236 10.78 1511.93 0.00066 4.7169 3.120 0.21612 Dichlorodifluoromethane 213 0.023 0.183 8.09 138.57 0.00722 0.6396 4.615 0.248

D. 233 K Evaporating, 293 K Condensing744 Carbon Dioxide 233 1.005 5.726 5.70 179.50 0.00557 0.0383 0.213 0.469290 Propane 233 0.110 0.835 7.57 277.61 0.00360 0.3821 1.376 0.354

22 Chlorodifluoromethane 233 0.105 0.910 8.65 164.21 0.00609 0.2048 1.247 0.341717 Ammonia 233 0.072 0.855 11.95 1114.52 0.00090 1.5567 1.397 0.335500 12/152a Azeotrope 233 0.076 0.668 8.85 140.03 0.00714 0.2491 1.779 0.336

12 Dichlorodifluoromethane 233 0.064 0.567 8.84 114.91 0.00870 0.2426 2.112 0.339

E. 250 K Evaporating, 310 K Condensing12 Dichlorodifluoromethane 250 0.134 0.891 6.64 105.80 0.00945 0.1221 1.154 0.330

717 Ammonia 250 0.166 1.426 8.61 1057.36 0.00095 0.7097 0.671 0.31022 Chlorodifluoromethane 250 0.218 1.390 6.37 150.09 0.00666 0.1033 0.688 0.326

502 22/115 Azeotrope 250 0.260 1.563 6.01 91.91 0.01088 0.0662 0.720 0.391


Figure 23 (Page 1 of 4). Comparative Refrigerant Performance Per kW(Ton) at Various Evaporating and Condensing Temperatures




No.

Refrigerant

Name

Suction Temp.

K

Evapo-rator

pressure MPa

Con-densingpressure

MPa

Com-pression

Ratio

Netrefrig-eratingeffect,kJ/kg


kg/sec

Specificvolume

ofsuction

gas,m3/kg

Com-pressor

displace-ment,L/sec

PowerkW

F. 250 K Evaporating, 310 K Condensing (291 K Suction)12 Dichlorodifluoromethane 291 0.134 0.891 6.64 105.80 0.00945 0.1451 1.371 0.392


502 22/155 Azeotrope 291 0.260 1.563 6.01 91.91 0.01088 0.0796 0.866 0.471

G. 250 K Evaporating + Refrig. Effect to 291 K, 310 K Condensing12 Dichlorodifluoromethane 291 0.134 0.891 6.64 130.33 0.00767 0.1451 1.113 0.318


502 22/155 Azeotrope 291 0.260 1.563 6.01 119.81 0.00835 0.0796 0.665 0.361

H. 266 K Evaporating, 300 K Condensing290 Propane 266 0.380 1.000 2.63 297.39 0.00336 0.1196 0.402 0.157


12 Dichlorodifluoromethane 266 0.244 0.688 2.82 123.22 0.00812 0.0697 0.566 0.153600 Butane 266 0.075 0.258 3.44 310.75 0.00322 0.4701 1.513 0.148

I. 277 K Evaporating, 310 K Condensing290 Propane 277 0.534 1.275 2.39 281.59 0.00355 0.0461 0.164 0.080


12 Dichlorodifluoromethane 277 0.352 0.891 2.53 117.99 0.00848 0.0493 0.417 0.145600a Isobutane 277 0.181 0.493 2.73 270.81 0.00369 0.2072 0.765 0.145600 Butane 277 0.119 0.347 2.91 301.82 0.00331 0.3170 1.050 0.141






No.

Refrigerant

Name

Suction Temp.

°F

Evapo-rator

pressure psia

Con-densingpressure

psia

Com-pression

Ratio

Netrefrig-eratingeffect,Btu/lb


lb/min

Specificvolume

ofsuction

gas,ft3/lb

Com-pressor

displace-ment,cfm

Powerhp

A. -130°F Evaporating, -40°F Condensing1150 Ethylene -130 30.657 209.725 6.84 142.05 1.40799 3.8797 5.463 1.758

170 Ethane -130 13.509 112.236 8.31 156.58 1.27728 8.4214 444.126 1.635

B. -100°F Evaporating, -30°F Condensing170 Ethane -100 30.710 131.783 4.29 216.31 0.92459 3.8372 0.476 0.792

22 Chlorodifluoromethane -100 2.434 19.154 7.87 91.01 2.19745 18.1761 5.360 1.044

C. -76°F Evaporating, 5°F Condensing1150 Ethylene -76 109.504 414.648 3.79 117.07 1.70835 1.1678 0.268 1.480

170 Ethane -76 54.634 235.440 4.31 138.71 1.44181 2.2906 0.443 1.316

290 Propane -76 6.101 42.142 6.91 147.37 1.35710 14.9667 2.726 1.19822 Chlorodifluoromethane -76 5.438 42.956 7.90 84.18 2.37589 8.5925 2.740 1.195

717 Ammonia -76 3.169 34.162 10.78 650.01 0.30769 75.5575 3.120 1.01812 Dichlorodifluoromethane -76 3.277 26.501 8.09 59.57 3.35714 10.2448 4.615 1.172

D. -40°F Evaporating, 68°F Condensing744 Carbon Dioxide -40 145.763 830.530 5.70 77.17 2.59164 0.6128 0.213 2.210290 Propane -40 15.995 121.078 7.57 119.35 1.67573 6.1199 1.376 1.671

22 Chlorodifluoromethane -40 15.268 131.997 8.65 70.60 2.83296 3.2806 1.247 1.607717 Ammonia -40 10.376 124.009 11.95 479.16 0.41740 24.9359 1.397 1.578500 12/152a Azeotrope -40 10.959 96.949 8.85 60.20 3.32214 3.9894 1.779 1.584

12 Dichlorodiflouromethane -40 9.304 82.294 8.84 49.40 4.04838 3.8867 2.112 1.597

E. -10°F Evaporating, 100°F Condensing12 Dichlorodifluoromethane -10 19.455 129.192 6.64 45.49 4.39697 1.9557 1.154 1.556

717 Ammonia -10 24.027 206.809 8.61 454.58 0.43996 11.3681 0.671 1.46222 Chlorodifluoromethane -10 31.646 201.544 6.37 64.53 3.09947 1.6549 0.688 1.536

502 22/115 Azeotrope -10 37.730 226.694 6.01 39.51 5.06147 1.0599 0.720 1.846






No.

Refrigerant

Name

Suction Temp.

°F

Evapo-rator

pressure psia

Con-densingpressure

psia

Com-pression

Ratio

Netrefrig-eratingeffect,Btu/lb


lb/min

Specificvolume

ofsuction

gas,ft3/lb

Com-pressor

displace-ment,cfm

Powerhp

F. -10°F Evaporating, 100°F Condensing (65°F Suction)12 Dichlorodifluoromethane 65 19.455 129.192 6.64 45.49 4.39697 2.3243 1.371 1.849


502 22/155 Azeotrope 65 37.730 226.694 6.01 39.51 5.06147 1.2754 0.866 2.221

G. -10°F Evaporating + Refrig. Effect to 65°F, 100°F Condensing12 Dichlorodifluoromethane 65 19.455 129.192 6.64 56.03 3.56934 2.3243 1.113 1.501


502 22/155 Azeotrope 65 37.730 226.694 6.01 51.51 3.88281 1.2754 0.665 1.704

H. 20°F Evaporating, 80°F Condensing290 Propane 20 55.065 144.999 2.63 127.85 1.56427 1.9156 0.402 0.740



I. 40°F Evaporating, 100°F Condensing290 Propane 40 77.410 184.967 2.39 121.06 1.65205 0.7381 0.164 0.379








REFRIGERANT

ANSI/ASHRAE34-78

SAFETYUL

GROUP

NO. NAMECODE

GROUPCLASSIFI-CATION

EXPLOSIVE LIMITSIN AIR, % BY

VOLUME50 Methane 3 5b 4.9 to 15.014 Tetrafluoromethane 1 6a Nonflammable

1150 Ethylene 3a 5b 3.0 to 25.0744A Nitrous Oxide Nonflammable

13 Chlorotrifluoromethane 1 6 Nonflammable170 Ethane 3a 5ba 3.3 to 10.6744 Carbon Dioxide 1 5a Nonflammable

13B1 Bromotrifluoromethane 1a 6 Nonflammable290 Propane 3 5ba 2.3 to 7.3502 - - 1 5a Nonflammable22 Clorodifluoromethane 1 5ab Nonflammable717 Ammonia 2 2a 16.0 to 25.0500 - - 1 5a Nonflammable152a Difluoroethane - - - - 5.1 to 17.112 Dichlorodifluoromethane 1 6a Nonflammable505 - - - - 5c Nonflammable40 Methyl Chloride 2 4a 8.1 to 17.2506 - - - - 5c Nonflammable600a Isobutane 3a 5b 1.8 to 8.4764 Sulfur Dioxide 2 1a Nonflammable600 Butane 3a 5a 1.6 to 6.5114 Dichlorotetrafluoroethane 1 6a Nonflammable21 Dichlorofluoromethane 1 4-5c Nonflammable160 Ethyl Chloride 2 4aa 3.7 to 12.011 Trichlorofluoromethane 1 5a Nonflammable611 Methyl Formate 2 3a 4.5 to 20.030 Methylene Chloride 2 4aa Nonflammable113 Trichlorotrifluoroethane 1 4-5d Nonflammable

1130 Dichloroethylene 2 4a 5.6 to 11.4a Underwriters Laboratories Report MH-3134 c Underwriters Laboratories Report MH-3072b Underwriters Laboratories Report MH-2360 d Underwriters Laboratories Report MH-6138


Figure 24. Relative Safety of Refrigerants




GROUP DEFINITION EXAMPLES

1 Gases or vapors which in concentrations of about 1/2to 1 percent for durations of exposure of about 5minutes are lethal or produce serious injury.

Sulfur Dioxide

2 Gases or vapors which in concentrations of about 1/2to 1 percent for durations of exposure of about 1/2hour are lethal or produce serious injury.

Ammonia

Methyl Bromide

3 Gases or vapors which in concentrations of about 2 to2 1/2 percent for durations of exposure of about 1 hourare lethal or produce serious injury.

Carbon Tetrachloride

Chloroform

Methyl Formate

4 Gases or vapors which in concentrations of about 2 to2 1/2 percent for durations of exposure of about 2hours are lethal or produce serious injury.

Dichloroethylene

Methyl Chloride

Ethyl Bromide

Between

4 and 5

Appear to classify as somewhat less toxic than Group4.

Methylene Chloride

Ethyl Chloride

Much less toxic than Group 4 but somewhat moretoxic than Group 5.

Refrigerant 113

5a Gases or vapors much less toxic than Group 4 butmore toxic than Group 6.

Refrigerant 11

Refrigerant 22

Carbon Dioxide

5b Gases or vapors which available data indicate wouldclassify as either Group 5a or group 6.

Ethane

Propane

Butane

6 Gases or vapors which in concentrations up to at leastabout 20 percent by volume for durations of exposureof about 2 hours do not appear to produce injury.

Refrigerant 12

Refrigerant 114

Refrigerant 13B1


Figure 25. Underwriters Laboratories Classification of Comparative Hazard toLife of Gases and Vapors




GLOSSARY

ANSI American National Standards Institute

ASHRAE American Society of Heating, Refrigerating, and Air Conditions Engineers

ASME American Society of Mechanical Engineers

cascade Two refrigerating systems connected in series to produce a lower temperaturerefrigerant.

CFC A fully halogenated compound.

chiller Heat exchanger that provides the refrigeration to the process stream beingrefrigerated.

coefficient of performance(COP)

In a refrigeration cycle, the ratio of the heat energy extracted by the heat engineat the low temperature to the work supplied to operate the cycle.

critical temperature The temperature of the liquid-vapor critical point. The temperature abovewhich a substance has no liquid-vapor transition.

generator The stripper tower in an absorption refrigeration system. It separates therefrigerant from the carrier fluid.

halocarbon A compound of carbon and a halogen, sometimes with a hydrogen.

receiver Vessel, container, or tank, used to receive and collect liquid material from aprocess unit.

steam-jet ejector A fluid acceleration vacuum pump or compressor using the high velocity of asteam jet for entrainment.

suction line A pipe or tube feeding into the inlet side of a compressor.

ton of refrigeration 12 000 Btu/hr = 2.5 kW

UL Underwriters’ Laboratories




ADDENDUM

TABLE OF CONTENTS

Addendum A: ASHRAE SI for HVAC and R Conversions 47

Addendum B: Conversion Factors 48

Addendum C: Symbols Used in ChE 210.01 49

Addendum D: Equation Used in ChE 201.01 50




ADDENDUM A: ASHRAE SI FOR HVAC AND R CONVERSIONS

MULTIPLY BY TO OBTAIN

bar 100 kPa

Btu, IT 1.055 kJ

Btu/ft3 37.3 Kj/m3 = J/L

Btu • ft/hr • ft2 • °F 1.731 W/(m • K)

Btu • in/(hr • ft2 • °F)

(thermal conductivity, k)

0.144 W/(m • K)W/(m • °C)

Btu/hr 0.293 W

Btu/ft2 11.4 kJ/m2

Btu/(h • ft2) 3.15 W/m2

Btu/(hr • ft2 • °F)(overall heat transfer coefficient, U)

(thermal conductance, C)

5.68 W/(m2 • K)W/(m2 • °C)

Btu/lb 2.33 kJ/kg

Btu/(lb • °F)(specific heat, c)

4.19 kJ/(kg • K)kJ/(kg • °C)

centipoise, viscosity, m(absolute, dynamic)

1.00 mPa • s

centistokes, kinematic viscosity, u 1.00 mm2/s

dyne/cm2 0.100 Pa

in of mercury (60°F) 3.38 kPa

in of water (60°F) 249 Pa

kW • hr 3.60 MJ

mm of mercury (60°F) 0.133 kPa

mm of water 9.80 Pa

ppm (by mass) 1.00 mg/kg

ton of refrigeration (12,000 Btu/hr) 3.52 kWRounded to three or four significant figures.

Figure 26. ASHRAE SI for HVAC and R Conversions




ADDENDUM B: CONVERSION FACTORS

Pressurepsi In. Hg atm mm Hg bar kg/cm2 dyne/cm2 pascal1 2.0360 0.068046 51.715 0.068948 0.07030696 68,948 6894.8

Volume in3 ft3 gal litre metre3

1 5.787 x 10-4 4.329 x 10-3 0.0163871 1.63871 x 10-5

Energy Btu ft • lb calorie joule watt • sec1 777.65 251.9957 1054.35 1054.35

Density lb/ft3 lb/gal g/cm3 kg/m3(g/L)1 0.133680 0.016018 16.018463

Specific Heat Btu/lb • °F cal/(g • K) J/(g • K)1 1 4.184

Enthalpy Btu/lb cal/g J/g1 0.55556 2.3244

ThermalConductivity Btu/h • ft •

°F

cal/(s • cm • °C) J/(s • cm •

°C)W/(cm • °C) W/(m • K)

1 4.1338x10-3 0.17296 0.017296 1.7296

Viscositypoise

g/(cm•s) lbf • s/ft2 lbf • hr/ft2 kg/(m • s) N • s/m2 ibm/(ft • s)1 2.0885 x

10-35.8014 x 10-7 0.1 0.1 6.71955 x 10-2

Viscosity (1 poise = dyne•sec/cm 2 = 0.1 newton•sec/m2

Coefficient ofHeat

Transfer

Btu/h •ft2 • °F

cal/(s • cm2 • °C)

W/(cm2 • °C)

kcal/(h • m2 • °C) W/(m2 • K)

1 1.3562 • 10-4 5.6783 • 10-4 4.8823 5.6783Unit of

RefrigerationRefrigeration

Ton Btu/hr kJ/hr kW1 12,000 12,660 3.517

Figure 27. Conversion Factors




ADDENDUM C: SYMBOLS USED IN ChE 210.01

Va = Velocity of sound, m/s (ft/s)

k = The ratio of specific heats, cp/cv


Gc = Gravity constant, m/s2 (ft/s)

R = Gas constant, gr-m/mole °K (lb ft/mole °R)

M = Molecular weight, gr/mole (lb/mole)dpdρ

T

= Rate of change of pressured/rate of change of density, atconstant temperature




ADDENDUM D: EQUATION USED IN ChE 210.01

V = G kRT/M a c (EQN A)

where: Va = Velocity of sound, m/s (ft/s)

k = The ratio of specific heats, cp/cv


Gc = Gravity constant, m/s2 (ft/s)

R = Gas constant, gr-m/mole °K (lb ft/mole °R)

M = Molecular weight, gr/mole (lb/mole)dpdρ

T= Rate of change of pressured/rate of change of

density, at constant temperature

Documents

Refrigeration System