Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Climate change, industry and society wikipedia , lookup
Mitigation of global warming in Australia wikipedia , lookup
Climate change feedback wikipedia , lookup
United Nations Climate Change conference wikipedia , lookup
Climate change in Canada wikipedia , lookup
Use of Hydrocarbons in Refrigeration and Air-Conditioning Systems Center for Environmental Energy Engineering (CEEE) University of Maryland Yunho Hwang 1 Outline Regulation Update: Especially EU’s response Properties of HCs Performance of HC Systems Design Guide of HC Systems Alternative Refrigerant Seminar: Hydrocarbons, 2003 2 Response to Climate Change The international community recognized the climate change as one of the greatest environmental and economic challenges facing humanity. The UN Framework Convention on Climate Change was adapted in 1992 to achieve stabilization of greenhouse gas (GHG) concentrations in the atmosphere at a level which prevents dangerous anthropogenic interference with the climate system. The Kyoto Protocol was adapted in 1997, which requires industrialized countries to reduce their collective emissions of greenhouse gases by 5.2% below their 1990 levels for the period 2008 to 2012. Alternative Refrigerant Seminar: Hydrocarbons, 2003 3 EU’s Response to Climate Change In 2001 the European Climate Change Program reported: Fluorinated gas emissions in 1995 were around 65 million tones of CO2 equivalent (2% of total GHG emissions in the EC). Emissions will increase to around 98 million tones of CO2 equivalent by 2010 (2-4% of total GHG emissions in the EC). The EC and the Member States have all ratified the Kyoto Protocol in 2002. Under the Kyoto Protocol the EC is committed to reduce its emissions by 8%, an overall reduction of 336 million tones of CO2 equivalent. Alternative Refrigerant Seminar: Hydrocarbons, 2003 4 EU’s Response to Climate Change In August 2003 Commission of the EC proposed “Regulation on certain fluorinated greenhouse gases.” The proposal is expected to reduce projected emissions of fluorinated gases by 23 million tones of CO2 equivalent by 2010. Highlights of the proposal are: Article 3: improve the containment of fluorinated gases. Duty to prevent and minimize leakage Mandatory inspections for leakage (3 kg or more: once/year, 30 kg or more: 4/year, 300 kg or more: monthly) Leakage detection systems: All owners of systems containing 300 kilograms or more of fluorinated gas are required to install leak detection systems. Maintenance of records Alternative Refrigerant Seminar: Hydrocarbons, 2003 5 EU’s Response to Climate Change Article 4: recovery Fluorinated gases must be recovered for recycling, reclamation or destruction from the cooling circuits of all refrigeration, airconditioning and heat pump equipment. Unused fluorinated gas contained in refillable containers must also be recovered. The recovery of fluorinated gases from all other products and equipment shall be done if it is technically feasible and costeffective to do so. Article 5: training and certification programs Member States will be required to establish programs to provide for the training and certification of personnel involved in making inspections for leakage, and for those involved in the recovery, recycling, reclamation and destruction of fluorinated gases. Alternative Refrigerant Seminar: Hydrocarbons, 2003 6 EU’s Response to Climate Change Article 6: reporting Data on the production, importation, export, recycling and destruction of fluorinated gases above one ton per year must be submitted to the Commission annually. Article 7: control of use The initial charging of the air-conditioning system of any passenger vehicle and light commercial vehicle placed on the market after 1 January 2009 should use a refrigerant with a GWP of 150 or less. This is to prevent such vehicles being placed on the market during the phase-out period with an empty air-conditioning system which could then be charged with R134a or any other fluorinated refrigerant gas with a GWP above 150. Alternative Refrigerant Seminar: Hydrocarbons, 2003 7 EU’s Response to Climate Change Articles 9 and 10: air-conditioning systems in new cars A/C systems containing fluorinated gases with a GWP higher than 150 (ex: R134a) for any new passenger cars and light commercial vehicles are subject to a maximum leakage rate. The leakage rate shall not exceed 40 g and 50g per year for single and dual evaporator systems, respectively. Phase out of A/C systems in new passenger cars and light commercial vehicles using R134a begins January 1, 2009 and ends December 31, 2013. In 2009 only 80% of a predetermined quota of passenger cars and light commercial vehicles can be placed on the market with A/C systems containing R134a. This level is reduced over the following years to 60%, 40%, 20% and 10% and in 2014 no A/C systems in new passenger cars and light commercial vehicles will contain R134a. Alternative Refrigerant Seminar: Hydrocarbons, 2003 8 Global Warming Consideration Regulations on High GWP Substances EU will impose more strict control Low GWP substances (GWP < 150) are wanted Two HFCs (R32 & R152a) are attractive. R32: 7% higher COP, 18% lower TEWI than R410A (Yajima, 2000) R152a: 2-17% higher COP than R134a (Andersen, 2002) Natural refrigerants have minimal GWP. HCs based refrigerators: EU (1992) & Japan (2002) HC heat pumps: Germany, Austria, Sweden, Netherlands (1997) CO2 water heaters: EU & Japan (2002) GWP (100 years; Calm, 1998) R404A R410A R134a R32 R152a R290 CO2 3,700 1,730 1,300 650 140 20 1 Alternative Refrigerant Seminar: Hydrocarbons, 2003 9 Leakage of R134a from Vehicle A/C R134a emissions Low High Assumptions Regular emissions occurring 0.96 during normal operation 0.96 53 g / year Irregular emissions resulting 0.29 from accidents, defects etc. 0.36 16/20 g / year in “low” and “high” cases Emissions during servicing 0.26 0.52 100/200 g / service in “low” and “high” cases Emissions at end of-life 0.14 0.35 20/50% of lost of the charge at the end of life in the “low” and “high” cases Total vehicle lifetime leakage 1.70 (ton of CO2 equiv.) 2.24 Vehicle life: 14 years Alternative Refrigerant Seminar: Hydrocarbons, 2003 10 Leakage from Vehicle A/C Case No. of Exposures to Vehicle Occupants in the U.S. Sudden medium leak ( > 5000 ppm) Sudden large leak 122 (4.5%) Sudden medium leak after recharge Leak caused by collision 673 (24.8%) 2 (0.1%) 1,913 (70.6%) No. of vehicles w A/C in the U.S. (automobiles & light truck): 150 million No. of exposure to Service Technicians are three orders of magnitude higher than the no. of exposure to vehicle occupants. Alternative Refrigerant Seminar: Hydrocarbons, 2003 11 Flammability Consideration HFC mixtures are current alternatives. R410A, R407C (R22 alt.) & R404A (R502 alt.): non-flammable R32, R143a & R152a: slightly flammable R143a R32 66% 60% R410A flammable flammable 25°C 100°C 58% 55% 51.5% R404A 33% R407C nonflammable 36% 60°C 33% 100°C nonflammable R125 R134a R125 Alternative Refrigerant Seminar: Hydrocarbons, 2003 R134a 12 Flammability Consideration ASHRAE Safety Classification no identified toxicity at concentrations <= 400 ppm Higher flammability A3 (R170,R290, R600,R600a) evidence of toxicity below 400 ppm B3 (R-1140) LFL <= 0.10 kg/m3 or DHcomb >= 19 MJ/kg LFL > 0.10 kg/m3 and DHcomb < 19 MJ/kg Lower flammability A2 (R32,R143a, R152a) B2 (NH3) No flame propagation A1 (R22, R125, R134a, R410A, R404A, CO2) B1 (R-123) Lower toxicity Higher toxicity [Reference] ASHRAE Standard 34-1992 Alternative Refrigerant Seminar: Hydrocarbons, 2003 13 Risk Analysis of HCs ‘Accepted’ in-use risk (UK) Ignition risk of R290: fire from gas cookers 8.7x10-4 fire from washing machine 1.6x10-4 fire from refrigerators 1.1x10-5 fire from gas central heating 4.0x10-5 fire from television 2.7x10-5 4.7x10-11 (normal use), 2.2x10-8 (service) Based on 1 kg R290 in 48m2 office operating 12 hrs/day All are higher than flammable refrigerant ignition risk Source: Calor gas, Purdue Conference, 2002 Alternative Refrigerant Seminar: Hydrocarbons, 2003 14 Regulations on HCs Region Automobile A/C Refrigeration & Air-conditioning USA SNAP (CAA Sec.612) HCs cannot be used. SAE (J 639) The refrigerant should be non-flammable. UL (250) HCs can be applied for small refrigerators up to 50 g. ASHRAE (Standard 15) The max. amount of refrigerant released into the occupied space is restricted (less than 1/5 of LFL) EU EN (378) HCs cannot be used in direct cooling and heating systems BS (4434) Highly flammable refrigerant can be used under the following conditions. Sealed system, Charge less than 1.5 kg The max. amount of refrigerant released into the space should be less than 1/5 of LFL. DIN (7003) & NPR (7600) Limited amounts of HC charge may be permitted within the living space Japan JIS (8620) The refrigerant should be non-flammable. None Alternative Refrigerant Seminar: Hydrocarbons, 2003 15 Characteristics of Hydrocarbons Environmentally benign (zero ODP, zero GWP) Possibly higher cycle efficiency Non toxic Miscible and compatible with mineral oil Lower discharge temperature Reduced refrigerant charge Flammable Need higher safety standards and designs (secondary loop, sealed electric parts) Lower volumetric capacity Need larger displacement compressors Alternative Refrigerant Seminar: Hydrocarbons, 2003 16 Properties: Vapor Pressure 10.00 A 410 Pressure [MPa] R- 2 R-2 07C R-4 90 R-2 1.00 34a R-1 0.10 0.01 -4.5 -4.0 -3.5 -3.0 -2.5 -1/T x 1000 [K] Alternative Refrigerant Seminar: Hydrocarbons, 2003 17 Properties: Density & Specific Heat Density Ratio & Specific Heat Ratio (R290/R22) 3.0 2.5 2.0 Liquid Vapor Liquid Vapor 1.5 Density Ratio Density Ratio Specific Heat Ratio Specific Heat Ratio 1.0 0.5 0.0 -40 -20 0 20 40 60 80 Temperature [°C] Alternative Refrigerant Seminar: Hydrocarbons, 2003 18 Thermal Conductivity Ratio & Viscosity Ratio (R290/R22) Properties: Thermal Conductivity & Viscosity 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 Liquid Thermal Conductivity Ratio Liquid Viscosity Ratio 0.2 Vapor Thermal Conductivity Ratio Vapor Viscosity Ratio 0.0 -40 -20 0 20 40 60 80 Temperature [°C] Alternative Refrigerant Seminar: Hydrocarbons, 2003 19 Properties: Single-phase HTC Heat Transfer Coefficient Ratio (R290/R22) 1.50 1.45 1.40 1.35 1.30 1.25 1.20 1.15 1.10 1.05 Liquid HTC Ratio Vapor HTC Ratio 1.00 -40 -20 0 20 40 60 80 Temperature [°C] for 1kW cooling capacity, 8.5mm id tube, mass flow rate of R290 is about 60% of R22 Alternative Refrigerant Seminar: Hydrocarbons, 2003 20 Properties: Single-phase Pressure Drop Pressure Drop Ratio (R290/R22) 0.80 0.75 0.70 0.65 0.60 0.55 Liquid Pressure Drop Ratio Vapor Pressure Drop Ratio 0.50 -40 -20 0 20 40 60 80 Temperature [°C] for 1kW cooling capacity, 8.5mm id tube, 1m length, mass flow rate of R290 is about 60% of R22 Alternative Refrigerant Seminar: Hydrocarbons, 2003 21 Properties: Pressure vs. Sat. Temperature Saturation Temperature [°C] 80 60 40 20 0 -20 R22 Saturation Temperature R290 Saturation Temperature -40 0 1000 2000 3000 4000 Pressure [kPa] Alternative Refrigerant Seminar: Hydrocarbons, 2003 22 Cycles in P-h Diagram 10.0 Pressure [MPa] R22 Cycle R290 Cycle 1.0 0.1 0 100 200 300 Enthalpy [kJ/kg] Alternative Refrigerant Seminar: Hydrocarbons, 2003 400 500 600 23 Cycles in T-s Diagram 120 R22 Cycle R290 Cycle 100 Temperature [°C] 80 60 40 20 0 -20 -40 0 0.5 1 Entropy [kJ/kgK] Alternative Refrigerant Seminar: Hydrocarbons, 2003 1.5 2 24 Performance of HCs: Refrigerator CEEE experimental results (1995) Test Unit: 566 liter, automatic defrost, top mount refrigerator/freezer Freezer/food compartments temps: -15.6/3.3 °C Energy consumption of R290/R600 is 7% less than that of R12 Parameter Energy consumption [kW/day] On-time ratio [%] Charge [g] R12 2.46 46 240 R290/R600 (70/30) 2.29 33 70 Ratio (compared to R12) 0.93 0.72 0.29 Americold (1994) Energy consumption of R600a is 2% less than that of R12 Alternative Refrigerant Seminar: Hydrocarbons, 2003 25 Performance of HCs: Unitary A/C CEEE experimental results (2002) Test Unit: 3 RT Unitary Heat Pump Charge: R22 4.0 kg, R290 1.9 kg Steady State Performance of R290 (ASHRAE A, B, 47S, 17L) 3 ~ 6% lower capacity; -3 ~ +2% variation in COP Cyclic Performance of R290 Unmatched superheat: 16% lower cyclic degradation Same superheat: 5% lower degradation Seasonal Energy Efficiency of R290 Unmatched superheat: 2% lower SEER Same superheat: 7% lower SEER Alternative Refrigerant Seminar: Hydrocarbons, 2003 26 Performance of HCs: Unitary A/C CEEE: 11% larger compressor displacement volume Test Conditions (baseline R22) Cooling A Cooling B Heating 47 Heating 17 Capacity Ratio 0.96 0.97 0.94 0.97 COP Ratio 0.97 0.98 0.99 1.02 Discharge Temp. Reduction [K] 15.1 13.0 11.7 18.2 AREP: 18% larger compressor displacement volume Test Conditions (baseline R-22) Cooling A Cooling B Heating 47 Heating 17 Capacity Ratio 1.09 1.08 1.04 1.09 COP Ratio 1.06 1.03 1.00 0.98 Alternative Refrigerant Seminar: Hydrocarbons, 2003 27 Performance of HCs: Commercial Refrigeration CEEE experimental results (2003) Test Unit: 5 HP unit cooler with condensing unit, 21% larger comp. displacement volume Charge: R404A 5.0 kg, R290 1.9 kg Full Load Performance of R290 (1.6/35 °C indoor/outdoor air temperatures) 1% higher COP for matched capacity Part Load Performance of R290 (1.6/18.5 °C indoor/outdoor air temperatures) 3% lower capacity, 1% higher COP Alternative Refrigerant Seminar: Hydrocarbons, 2003 28 R-290 Design Challenges Refrigerant: thermophysical properties & impurities Compressor: displacement volume selection TXV: degree of superheating Suction line pressure drop Cycle options: Suctionline heat exchanger (SLHX) Secondary loop (SL) Safety Alternative Refrigerant Seminar: Hydrocarbons, 2003 29 Temperature Profiles along the Cycle 80 ASHRAE B Conditions Temperature [°C] 70 1. 2. 3. 4. 5. 6. 60 50 R22 Compressor Discharge Condenser Inlet Condenser Outlet Evaporator Inlet Evaporator Outlet Compressor Suction R290 40 30 20 10 0 0 1 2 3 4 5 6 7 Position Alternative Refrigerant Seminar: Hydrocarbons, 2003 30 Compressor Temperatures in Cyclic Mode 70 ASHARE D Conditions 60 Temperature [°C] R22 discharge 50 R290 discharge 40 30 R22 suction 20 R290 suction 10 0 0 20 40 60 80 100 Time [min] Alternative Refrigerant Seminar: Hydrocarbons, 2003 31 Impurities of Propane Composition by Mass [%] Grade Propane C 3H 8 Isobutane C4H10 Butane C4H10 Ethane C 2H 6 Research (RG) 99.99 nil nil nil Instrument (IG) 99.53 0.40 0.07 0.01 Chemically Pure (CPG) 98.98 0.77 0.20 0.03 nil: less than 0.01% • • • • • Properties between 0.6 to 2 MPa Saturated liquid temperature: less than 0.2 K Saturated vapor temperature: 0.2 to 0.3 K higher (IG), 0.5 K higher (CPG) Saturation enthalpies & densities: within 0.1% variation Refrigerant-side capacity: within 0.5% variation Alternative Refrigerant Seminar: Hydrocarbons, 2003 32 Effects of Impurities on Saturation Temperature Saturated Liquid Temperature [°C] Pressure [MPa] Saturated Vapor Temperature [°C] Temperature Glide [K] Pure IG CPG Pure IG CPG IG CPG 0.6 7.9 7.9 8.0 7.9 8.2 8.4 0.2 0.5 0.8 18.3 18.4 18.4 18.3 18.6 18.8 0.2 0.4 1.0 26.9 27.0 27.0 26.9 27.2 27.5 0.2 0.4 1.2 34.4 34.4 34.5 34.4 34.6 34.9 0.2 0.4 1.4 41.0 41.0 41.1 41.0 41.2 41.5 0.2 0.4 1.6 46.9 47.0 47.0 46.9 47.1 47.4 0.2 0.3 1.8 52.3 52.4 52.5 52.3 52.5 52.8 0.1 0.3 2.0 57.3 57.4 57.4 57.3 57.5 57.8 0.1 0.3 Alternative Refrigerant Seminar: Hydrocarbons, 2003 33 Compressor Sizing: Volumetric Capacity Volumetric Capacity Ratio of R290/R22 1.00 0.98 0.96 0.94 0.92 0.90 0.88 0.86 0.84 0.82 0.80 -40 -20 0 20 40 60 80 Temperature [°C] Alternative Refrigerant Seminar: Hydrocarbons, 2003 34 Superheating Control by TXV Saturation Pressure 1000 R22 R22, 5K SH 900 R290 Pressure [kPa] R290, 5K SH 800 700 Fspring Fspring Sensor Pbulb 600 Psuction 5K External Equalizer Fspring 5K 500 Outlet 3K 400 270 275 280 285 290 295 300 Temperature [K] Inlet Force Balance: Pbulb x Adia = Psuction x Adia + Fspring Alternative Refrigerant Seminar: Hydrocarbons, 2003 35 Superheating Control by TXV Superheating matching - same hardware same temperature increase same amount of heat Mass flow rate of R290: 60% of R22 Specific heat of R290: 2.4 times of R22 R290 needs 43% more energy to make the same degree of superheating. R290 causes 70% of degree of superheating for the same amount of energy. Alternative Refrigerant Seminar: Hydrocarbons, 2003 36 Suction Line Pressure Drop R22-Comp. I (~1.1K) Suction Line Pressure Drop [kPa] 25 R290-Comp. I (~0.8K) R290-Comp. II (~1K) R290-same S/H (~1K) 20 15 10 5 0 ASHRAE A Alternative Refrigerant Seminar: Hydrocarbons, 2003 ASHRAE B ASHRAE C 37 Cycle Options Cycle was modeled for the following options: R22 & R290 Basic cycles R290 cycle with SLHX R290 cycle with secondary loop (SL) R290 cycle with SLHX + secondary loop Option R290, Base R290, SLHX R290, SL R290, SLHX+SL Capacity Ratio 0.99 1.07 0.82 0.91 COP Ratio 0.99 1.06 0.84 0.92 Same compressor efficiency, 11% lager R290 compressor, same indoor coil temp for SL Alternative Refrigerant Seminar: Hydrocarbons, 2003 38 Safety State-of-the-art technology Hermetic compressor operating in hermetically sealed systems Using brazed joints Brazed heat exchangers to minimize charge Avoid the use of suction accumulator Isolation of electrical components in air-tight Using sealed control devices and spark proof switches Leak detection system Alternative Refrigerant Seminar: Hydrocarbons, 2003 39 Conclusions New regulation in EU: Regulation of HFC-134a from 2009 Performance of HCs in single loop systems: Slightly better in low temperature applications Comparable in high temperature application within 6% variation Design challenges: Thermophysical properties of HCs: Good: high specific heat, low viscosity, high latent heat Poor: low volumetric capacity Impurities: The purity should be higher than 99%. Compressor selection: needs about 10-20 % larger displacement TXV: needs to set to lower degree of superheating Suction line pressure drop should be considered in tube sizing Cycle options: Suctionline heat exchanger (SLHX): improve 6-7% Secondary loop (SL): worsen 16-17% Alternative Refrigerant Seminar: Hydrocarbons, 2003 40 Conclusions-Continued Additional safety measures are required. HCs are immediate options for applications with small charge less than 50g. HCs garners more attention due to climate changes. Increase of natural refrigerants use is expected in EU > Japan > USA Alternative Refrigerant Seminar: Hydrocarbons, 2003 41 Gas Price Grade Butane Iso-Butane Propane Ethane R22 R407C 1.43 9.78 Research (99.9%) n/a n/a 25.84 80.67 Instrument (99.5%) 10.12 6.13 9.38 11.98 C.P. (99.0%) 8.50 8.75 7.88 15.21 Natural (96.0%) - - 3.92 - Price checked January 2003 HCs: from Air Products, Cylinder rental free for 30 days, $0.2/day R22, R407C: from DuPont local dealer, include cylinder price Alternative Refrigerant Seminar: Hydrocarbons, 2003 Unit: $/lb 42