CO 2 in Refrigeration: a Valuable Technology

Transcription

1 in Refrigeration: a Valuable Technology Daniel Giguère, CETC-Varennes, AQME Trois-Rivières, April 11, 2008 Presentation For several years, carbon dioxide ( ) has been making a comeback in the refrigeration industry. The goal of this presentation is to provide information on the current status of the technologies and applications that use as a refrigerant or coolant. The following points will be presented: a brief history of in refrigeration, its thermodynamic properties, safety measures, industrial, commercial and residential applications, and finally, some products available on the market. 2

2 History of transcritical cycle compressor Around 1900 Golden age of Initial concept of as a refrigerant (Alexander Twining, British patent) J&E Hall: first two-stage refrigeration system CFCs invented, 1928 Montreal protocol History of (G. Lorentzen) of Norway Jan. 1, First refrigeration system: Carle Linde Danfoss, Niels P Vestergaard Niels P Vestergaard Ver SI+US 3 The Thermodynamic Properties of

3 is now present in the atmosphere in a proportion approximately equal to % in volume or 375 ppmv (parts per million in volume). However, this concentration is increasing rapidly by about 2 ppmv/year as a result of human activities involving the consumption of fossil fuels: coal, oil, gas. used in refrigeration is a by-product of ammonia and hydrogen production processes (Wikipedia). 5 Properties Refrigerant R404A NH 3 Natural refrigerant NO YES YES Ozone Depletion Potential ODP Global Warming Potential GWP Critical condition [psi/ o F] 541/ / /88 Boiling point at 15 psig [ o F] Boiling point at 400 psig [ o F] BTU/cubic foot at -40 [ o F] Saturated ΔT / ΔP = 1 psi at -40 [ o F] Flammability NO (slight) NO Toxicity NO YES NO 6

4 87.8 o F Critical point: liquid density = gas density o F

5 Refrigeration cycles under critical conditions Cascade systems DX systems Secondary fluids Cascade System +86 o F R717/HFC404A -20 o C [-4 o F] -15 o C [+5 o F] R717 HX compressor Pressure R o C (12 bar) +86 o F (171 psi) -20 o C (1.9 bar) -4 o F(28 psi) -40 o C [-40 o F] - reservoir - evaporator -40 o F Pressure Enthalpy -15 o C (23 bar) +5 o F (333 psi) -40 o C (10 bar) -40 o F(135 psi) Danfoss,Niels P Vestergaard Niels P Vestergaard Ver SI+US 10 Enthalpy

6 DX 404A- Cascade System 11 12

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8 15 Cascade System with Two Temperature Levels (Used in Supermarkets) +30 o C [+86 o F] R717,R404, R134a, etc. -12 o C [+10 o F] -7 o C [+19 o F] -7 o C [+19 o F] as a secondary fluid DX system -20 o C [-4 o F] Danfoss,Niels P Vestergaard Niels P Vestergaard Ver SI+US 16

9 DX-404A secondary fluid- Cascade System 17 R717 or HFC- as a Secondary Fluid R717/HFC404A -45 o C [-49 o F] -40 o C [-40 o F] +30 o C [+86 o F] -R717 HX Pressure R o C (12 bar) +86 o F (171 psi) -45 o C (0.5 bar) -49 o F (7 psi) -40 o C [-40 o F] - reservoir - evaporator NO OIL -40 o C [-40 o F] Pressure Enthalpy -40 o C (10 bar) -40 o F (135 psi) Danfoss,Niels P Vestergaard Niels P Vestergaard Ver SI+US 18 Enthalpy

10 as a Secondary Fluid Only Scarborough Supermarket To Atmosphere HEAT RECOVERY LOOP LOW TEMP. REFRIGERATION SYSTEM Backpressure Regulator Pressure Relief Valves STANDBY PRESSURE SUPERVISION UNIT (OPTIONAL) CASCADE CONDENSER SEPARATOR/ RECEIVER Low Temperature Display Cases PUMP 19 Transcritical refrigeration cycles 20

11 0 x xx x Transcritical Cycle Pressure psi Ref. Gas 95 o F 203 o F -5.5 o C [22 o F] 10 o F o C [-40 o F] -40 o F 73 Enthalpy 21 Pressure Transcritical Cycle Influences Head Pressure psi 95 o F 1,450 psi 1,305 psi 1,160 psi COP COP = ,5 2 COP = ,5 145 COP = bar [1160] [1305] [1450] [psi] 110 Compressor outlet pressure [bar] 73 Max Enthalpy Δh evap Δh Comp-is COP = (Δh EVAP *m )/ (Δh Comp -is *m) 22

12 Transcritical Systems with Heat Recovery for Supermarkets RAC Cooling with Carbon Dioxide Conference 28 March 2007,A. Butler M.Inst.R, Space Engineering Services, Causeway Central, Pioneer Park, Bristol, BS4 3QB 23 24

13 Another Transcritical Cycle 25 Safety Measures

14 Classification of Refrigerant Source: CSA 27 Health/Toxicity Air contains between 0.03% (300 ppm) and 0.06% (600 ppm) carbon dioxide depending on location. Carbon dioxide concentration increases by 2 ppm per year because of human activities. A person exhales about 4.5% (45,000 ppm) of carbon dioxide (in volume). The CSA B52 refrigeration code determines the maximum refrigerant concentration in percentage by volume so that people can leave the premises without immediate danger to life and health (IDLH). For carbon dioxide, this value is 5%, or 50,000 ppm (5.7 lbs/1,000 cu. ft.) For example, a 50,000-square-foot supermarket that is 25 feet high can accept a quantity of 50,000*25*5.7/1,000 = pounds of carbon dioxide. For refrigeration engineers or people exposed to refrigerants for eight hours a day, the threshold limit value (TLV) they can withstand without adversely affecting their health is 0.5% or 5,000 ppm. Regarding air quality, 1,000 ppm causes discomfort in 20% of people. At 2,000 ppm, discomfort is generalized and may cause headaches or nausea. Given that carbon dioxide is odourless, a detector should be installed in a ventilated mechanical room. 28

15 Design Pressure Design pressure depends on: Operating pressure System shutdown pressure CSA Code B52 - Refrigeration CSA Code B51 - Pressure vessels and pressure piping 29 CSA Minimum Design Pressure Requirements 30

16 Maintaining Shutdown Pressure R717 Pressure regulation unit pressure regulator that flushes out to atmosphere Danfoss, Niels P Vestergaard Niels P Vestergaard Ver SI+US 31 Applications: Products Available on the Market

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18 Eco-Cute Water Heater Five million of these will be installed in Japan by

19 37 Nestlé In 2000, no commercial freezers with scraped-surface heat exchangers were available on the market. In 2001, Nestlé installed the largest -NH 3 cascade system ever built in the past 50 years at the Nescafé plant in Hayes, UK. Nestlé engineers and the R&D department, in collaboration with key suppliers such as Star Refrigeration ( took on the challenge of the in-house development of a first freezer to freeze coffee liqueur. 38

20 WATER HEATER DRYER 39 Horizontal Ground Loops A. PRESETSCHNIK(a), K. MITTERMAYR(b), C. KÖFINGER(a), I. MALENKOVIC(a) 7th IIR Gustav Lorentzen Conference on Natural Working Fluids, Trondheim, Norway, May 28-31,

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22 Commercial Refrigeration Equipment Transcritical Cascade Transcritical 43 Linde Kältetechnik GmbH & Co. KG as a Secondary Fluid Copper pipes pumps 44

23 Display Case Air Coil Copper pipes 45 Conclusions The development of products and applications that use has accelerated in the last 10 years. These applications cover all sectors. Low-temperature refrigeration and heat pumps are especially promising. Operating pressures can be high, but the equipment is more compact and often more efficient. is a natural refrigerant that is safe and inexpensive. 46

24 Conclusions It is a refrigerant that can be used as an efficient and safe secondary fluid for cold applications. Subcritical equipment is available on the market at competitive prices. Transcritical equipment is being developed. Every refrigeration equipment manufacturer around the world is interested in as a refrigerant. 47 Why? Strong arguments Environment Gradual elimination of substances that deplete the ozone layer, such as CFCs and HCFCs: (ODP (Ozone Depletion Potential), GWP (Global Warming Potential) ) Safety Toxicity and inflammability for systems using large ammonia loads Commercial/ Supermarkets Industrial refrigeration Costs Lower operating costs because of energy efficiency of compressors and improved heat transfer Lower refrigerant costs Lower component volume 48

25 is a HOT refrigerant. Thank you. Any questions? c-dig, the carbon dioxide interest group