Thomas E. Watson, P.E. Fellow ASHRAE McQuay International Staunton, Virginia USA

Transcription

1 Refrigerants and their Application Presented by Thomas E. Watson, P.E. Fellow ASHRAE McQuay International Staunton, Virginia USA 1 What is a Refrigerant? In a refrigerating system, the medium of heat transfer which picks up heat by evaporating at a low temperature and pressure, and gives up heat on condensing at a higher temperature & pressure. (Refrigerating fluid) fluid used for heat transfer in a refrigerating system which absorbs heat at a low temperature and low pressure of the fluid and transfers heat at a higher temperature and higher pressure of the fluid, usually involving changes of state of the fluid. Ref: ASHRAE Terminology of Heating, Ventilation, Air Conditioning, & Refrigeration 2 1 1

2 Agenda / Topics Introduction History of Refrigerants Basic Refrigerant Chemistry Refrigerant Properties Refrigerant Applications Refrigerants In The Future? Alternative Refrigerants Ozone Depletion & Montreal Protocol Global Warming Summary 3 History of Refrigerants 1830s - Jacob Perkins - Vapor Compression (ether) John Gorrie - Patent for Air Cycle R-717 / R-718 (Ammonia / Water) CO 2 - Marine Applications R-717 (Ammonia) Commercial Refrigeration - Carl Linde R-764 (Sulfur dioxide) 1920s -R-600a (Isobutane) & R-290 (Propane) Willis Carrier - R-1130 (Dielene) R-30 (Methylene Chloride) 4 2 2

3 Toxicity - Best Minds Tried to Solve Solving Problem of Toxicity was a Large Problem to Development of Refrigeration 1927 Leo Szilard & Albert Einstein Improved on von Platen / Munters Absorption Design Electromagnetic Pumping Patent 5 Challenged to Find Refrigerant: Non-flammable Good Stability Low Toxicity Atmospheric Boiling Point between -40 o C & 0 o C 6 3 3

4 Common Refrigerants in 1920s Ammonia (R-717) NH 3 Carbon Dioxide CO 2 Sulfur Dioxide SO 2 Hydrocarbons Methyl Choride Water C n H m CH 3 Cl H 2 O 7 History of Refrigerants 8 4 4

5 History of Refrigerants Midgley Selections H C N O F S Cl Br 9 Refrigerant Chemistry Hydrocarbon Formula NBP Methane CH F -162 C Ethane C 2 H F -88 C Propane C 3 H 8-44 F -42 C

6 Refrigerant Chemistry 11 Refrigerant Chemistry

7 Refrigerant Chemistry 13 Refrigerant Chemistry

8 Refrigerant Chemistry Fluorocarbons CFCs, HCFCs, HFCs & HFOs Limited Combinations Adding Chlorine Or Bromine Increases ODP Adding Fluorine Increases GWP Adding Hydrogen Increases Flammability And Lowers Atmospheric Lifetime Toxic CHLORINE HYDROGEN Long Atmospheric Lifetime (fully halogenated) Flammable FLUORINE 15 Refrigerant Chemistry

9 Refrigerant Chemistry 17 Refrigerant Chemistry

10 Refrigerant Chemistry Refrigerant Blends Two or More Refrigerants to Achieve Required Properties Flammability Volumetric Capacity Limit Discharge Superheating for Lower Disch Temp etc Two Basic Types Zeotropes Azeotropes 19 Refrigerant Chemistry Zeotropes ZEOTROPIC BEHAVIOR (32/134a) T vap T liq Temperature, F P= 64 PSIA % R

11 Refrigerant Chemistry Zeotropic Behavior Fractionalization - Can be Separated by Distillation Service Procedures 21 Refrigerant Chemistry Azeotropes 39 AZEOTROPIC BEHAVIOR (R-125/R-143a) 38 T vap T liq Temperature, F R-507 = AZEOTROPIC MIXTURE R-125/R-143a (50/50) P=100 PSIA % R

12 ASHRAE Standard ASHRAE Standard 34 Nomenclature Toxicity Classification Flammability Classification

13 ASHRAE Standard 34 Nomenclature 000 Series Methane Based 100 Series Ethane Based 200 Series Propane Based 300 Series Cyclic Organic Compounds 400 Series Zeotropes 500 Series Azeotropes 600 Series Organic Compounds 700 Series Inorganic Compounds 1000 Series Unsaturated Organic Compounds Code Key Rule of 90 - Example R-12 R C H F =

14 ASHRAE Standard HFO-1234ye Stereoisomers Entgegen Zusammen

15 ASHRAE Standard 34 Toxicity Classification based on Chronic (long term) Measure - Class A has PEL > 400 PPM - Class B has PEL < 400 PPM PEL = Permissible Exposure Limit 29 ASHRAE Standard 34 Flammability Classification based on: ASTM E 681 with an Electrically Activated match

16 ASHRAE Standard 34 Flammability Classification Class 1 - No Flame Propagation Class 2 - LFL > 0.10 kg/m^3 and hc < 19 MJ/kg Class 2L Cl 2 w/ flame speed < 10 cm / sec Class 3 - LFL < 0.10 kg/m^3 or hc > 19 MJ/kg 31 ASHRAE Standard

17 A2L Refrigerants 33 ASHRAE Standard

18 ASHRAE Standard 15 What is ASHRAE 15? An industry standard that specifies safe design, construction, installation, and operation of refrigerating systems Establishes safeguards for life, limb, health, and property, and prescribes safety standards 35 ASHRAE Standard 15 Scope Design, Construction, Installation, Operation & Inspection of Mechanical and Absorption Machines Modifications if not Identical in Function and Capacity Refrigerant Substitutions with Different Designation

19 ASHRAE Standard 15 Requirements Based on 3 Classifications Occupancy Refrigerating System Refrigerant 37 ASHRAE Standard 15 Occupancy Classifications - Ability to Respond to Exposure Institutional - Assistance Required Public Assembly - Large Numbers Residential - Sleeping Commercial - Business Transactions Large Mercantile Persons or More Industrial & Refrigerated Rooms - Access Controlled Mixed - Two or More in Same Building

20 ASHRAE Standard 15 Refrigerating System Classification High Probability - Leak Can Enter Occupied Space Low Probability - Leak Cannot Enter Occupied Space 39 ASHRAE Standard 15 Restrictions on Refrigerant Use - Section 7 Standard 15 Gives Rules based on Occupancy, System, & Refrigerant Classification 3 kg or Less of Flammable Refrigerants may be used in Listed Equipment A2L Refrigerant Application Requirements NOT Included Presently Under Consideration

21 ASHRAE Standard 15 Refrigerant Qty/vol Limits - See Std 34 Acute Exposure / Ability to Escape Direct Systems Volume - Space to which Refrigerant Disperses in Event of Leak 41 ASHRAE 15 Users Manual

22 Mechanical Room Safety Check Location of inlet vents in relation to exhaust outlets? Location of roof drains? Purge vents to outside? Rupture disc outlet locations? Are safety rupture lines the right size? Is access to mechanical room restricted? Is there a tight seal on doors? Are drain valves connected to evacuation devices? Are there any pit areas in the room? Where do the floor drains empty? 43 Mechanical Room Safety Check Relief discharge shall be located not less than 20 ft (6 m) from ventilation opening and not less than 15 ft (4.5 m) above ground level (9.7.8) Purge systems and relief devices must be vented to outside (8.16) All indoor machinery rooms must be vented to the outdoors utilizing mechanical ventilation & 4 Access to mechanical room shall be restricted. Tight fitting doors opening outward (self closing if the open into the building) adequate in number to ensure freedom of escape. No other openings that would permit passage of escaping refrigerant (8.13) Refrigerant sensors are located in areas where refrigerant vapor from a leak will be concentrated so as to provide warning at concentration not exceeding the refrigerant PEL The total amount of refrigerant stored in a machinery room in all containers not provided with relief valves & piped in accordance with standard shall not exceed 330 lb (150 kg). (11.5)

23 Sample Sensor Locations* Entrance / Exits Just Above floor Next to Chillers Pits Refrigerant Storage Drains *Examples not part of standard 45 Mechanical Room per ASHRAE 15 Periodic tests of detectors, alarms & ventilation must be performed in accordance with manufacturers recommendations and/or local jurisdiction. (11.7.3) Mechanical room should be dimensioned for easy access to all parts and adequate space for service, maintenance, and operation. Clear head room of not less than 7.25 ft (2.2 m) below equipment situated over passageways. ( &2,8.13.1) No open flames that use combustion air from the machinery room (boilers) can be located within the mechanical as long as the combustion air is ducted from the outside to the boiler or shut down sensors are installed (8.13.6) A change in the type of refrigerant in a system shall not be made without the notification of the authority having jurisdiction, the user and due observance of safety requirements. The refrigerant being considered shall be evaluated for suitability (5.3)

24 IIAR 2 47 Back to the Future 24 24

25 Refrigerants in the Future? Low Direct Global Warming Potential CO2 Ammonia Hydrocarbons HFOs 49 Natural Refrigerants Ammonia (NH 3 ) R-717 Efficient B2L Classification Industrial Applications Water R-718 Absorption Chillers Centrifugal Compressors Axial Flow Compressors Carbon Dioxide (CO 2 ) R-744 Low Critical Point

26 What about other stuff -HFOs? Refrigerant Applications pv = (m x Ru x T ) / M M

27 Refrigerant Applications What is Pressure? Pressure = Average Impact of Molecules on a given area. Pressure is dependent on the Kinetic Energy of the molecules. 53 Volumetric Capacity Molecular Mass R-744 R-1234yf R-500 R-22 R-410A R-12 R-1234ze R-407C R-245fa R-134a R-152a R-32 R-40 R-290 R-114 R-123 R R-717 R CFM/ton

28 Compressor Types Compressor Types Positive Displacement Dynamic Reciprocating Rotary Orbiting Centrifugal Singe Shaft Twin Shaft Three Shaft Scroll Axial Single Screw Twin Screw Tri-Screw Trochoidal Moving Vane Fixed Vane (Rolling Piston) Compressor Volumetric Capacities Axial Centrifugal Screw Rotary Scroll Recip ,000 10, ,000 1,000,000 NOTE: Log Scale CFM 28 28

29 Refrigerant Flow Requirements 1000 R CFM/ton 10 1 R-123 R-11 R-245fa R-114 R-1234ze R-1234yf R-40 R-134a R-12 R-500R-22 R-407C R-290 R-717 R-32 R-410A R Suction Pressure, PSIA 57 Basic Considerations Compressors Vapor Pressure Temperature Lift Tons Evaporators Glide Condensers Glide Critical Temperature

30 R-11 Alternatives Refrigerant Molecular Mass CFC HCFC HFC-245fa R-12 Alternatives Refrigerant Molecular Mass CFC CFC HFC-134a HFO-1234yf

31 R-22 Alternative Refrigerant Molecular Mass HCFC HFC-407C Global Warming TEWI - Total Environmental Warming Impact Consists of Direct GWP, from refrigerant discharge + Indirect, power plant CO2 discharge dominates - Over 95% for Well Maintained Equipment - CO 2 from Power Generation depends on IPLV

32 Global Warming GWP Power Generation 63 Summary - Refrigerant Choice Ozone saving Global warming issue - Total Environmental Warming Impact (TEWI) Safety Field availability Application Cost Compressor type

33 Questions? 65 Information Sources ASHRAE Handbook Fundamentals - Refrigerants ASHRAE Standards 15 & 34 IIR-2 Equipment, Design and Installation of Ammonia Mechanical Refrigerating Systems Fluorocarbon Refrigerants Handbook - Ralph C. Downing, Prentice-Hall Trade-Offs in Refrigerant Selections: Past, Present, and Future - James M. Calm and David A. Didion - Proceedings of ASHRAE/NIST Refrigerants Conference - Oct 1997 HFOS New Low Global Warming Potential Refrigerants S. F. Brown, ASHRAE Journal August