Refrigeration systems & heat pumps with co2

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Refrigeration systems & heat pumps with co2

  1. 1. REFRIGERATION AND HEAT PUMP SYSTEMS WITH CO2 AS A REFRIGERANT S. Girotto Enex S.r.l., Italy sergio.girotto@enex-ref.com
  2. 2. INDEXWHY NATURAL REFRIGERANT CO2ENVIRONMENTAL IMPACT OF CO2 / R404AEXAMPLE – TYPICAL “COLD CLIMATE”INVESTMENT & OPERATING COSTEFFICIENCYFLASH VAPOR RECOMPRESSIONCOMMERCIALLY AVAILABLE REFRIGERATION SYSTEMSHEAT PUMPS FOR HOT WATER
  3. 3. WHY NATURAL REFRIGERANT CO2Zero ODP / Zero GWPNon toxic / Non flammableNo further changes of refrigerant in future (with synthetic refrigerants: R12, R502, R22 -> R404A/R507, R134a + tens of blends ->HF1234yf -> ?? what comes after?)CO2 is largely available all over the world as a by-product, low costNo subject to legislation constraints (F-Gas Directive in EC)
  4. 4. ENVIRONMENTAL IMPACT OF CO2 / R404A EXAMPLE – TYPICAL “COLD CLIMATE”
  5. 5. INVESTMENT & OPERATING COST (1)For a refrigeration system of one supermarket energy cost during lifetime is85% of the total running costDue to above investment running cost must be considered togetherComparison between a DX-CO2 and a conventional HFC system cost splittingfor a reference system 100 kW MT / 30kW LT 80000 70000 60000 refrigerant 50000 pipi ng/ins. € 40000 condenser 30000 elec.panel 20000 compr.unit 10000 0 CO2 HFC R404A
  6. 6. INVESTMENT & OPERATING COST (2)In a proper economical analysis other factors must be considered:a) cost for refilling of refrigerant during the lifetime of the systemb) cost for inspections due to leak emission control (F-GAS Directive)c) unforeaseeable cost increase and unavailable of synthetic refrigerantd) disposal cost
  7. 7. EFFICIENCY (1)CO2 itself is not “more efficient” or “less efficient” than other fluids.Efficiency theoretically does not depend on the fluid used (Carnot’s law) butfrom the combination of plant design and refrigerant.Guideline should be: for a given refrigerant (operating fluid) to improve asmuch as possible the design of the system so as to obtain maximumperformance.Compared with other refrigerants CO2 has a lower critical temperature, whichmight require a modified cycle for some applications.
  8. 8. EFFICIENCY (2)A simple comparison with HFC solution cannot enhance differences due to betterheat transfer characteristics or lower influence of pressure drop on efficiencyEfficient CO2 – only systems use one or more of the following:1) maximum heat recovery2) extremely low condensing pressure in winter time when no Heat Recovery isrequired3) LPR design – standard solution for some heat pumps and single compressor units4) recompression of flash vapor in warm ambient conditions(air cooled systems)Not – in – kind solutions (like expander, ejector) do exist, but they are still underevaluation and/or laboratory test
  9. 9. FLASH VAPOR RECOMPRESSION (1)
  10. 10. FLASH VAPOR RECOMPRESSION (2) SIMULATION FOR BARCELLONA CLIMATE Temperature profile July Temperature profile September 40 40Te m pe rature [°C] Tem perature [°C] 30 30 average 20 20 max_daily average 10 10 0 0 0 5 10 15 20 0 5 10 15 20 hour hour
  11. 11. FLASH VAPOR RECOMPRESSION (3) Temperature profile July average
  12. 12. FLASH VAPOR RECOMPRESSION (4) Temperature profile July max_daily
  13. 13. FLASH VAPOR RECOMPRESSION (5) Temperature profile September average
  14. 14. COMMERCIALLY AVAILABLE REFRIGERATION SYSTEMS - 1 “New” CO2 systems are on the market since 2006, after a long development started in late ‘90s (first CO2 only installation : 1999 – Italy /first CO2–only multi-compressor rack : 2001 - Italy) Now there are standardized and proven design concepts Example : booster system for supermarkets CO2 as a refrigerant was used in early 20th century (until ’50s) but the application was completely different, so a complete re-invention of technology was necessary.
  15. 15. COMMERCIALLY AVAILABLE REFRIGERATION SYSTEMS - 2 Other concepts using only CO2 as a refrigerant are well proven and available on the market: -Single stage, with a capacity up to 300 kW at -10° eva poration for large C cold rooms, hypermarkets, water and brine chilling -2-stage internal compound up to 100 kW at -35°C evaporation for deep freezing (cold rooms, hypermarkets) - Cascade for LT (supermarkets, freezing tunnels,…)
  16. 16. COMMERCIALLY AVAILABLE REFRIGERATION SYSTEMS - 3
  17. 17. COMMERCIALLY AVAILABLE REFRIGERATION SYSTEMS - 4
  18. 18. COMMERCIALLY AVAILABLE REFRIGERATION SYSTEMS - 5
  19. 19. HEAT PUMPS FOR HOT WATERFor one specific applications CO2 transcritical concept has no rivals : sanitarywater heat pumps.The gliding temperature for an isobaric/non-isothermal heat rejection reducesthermodynamic losses bringing performances at a level that cannot be reachedwith any other existing commercial solution :- Water heating in one pass from 10° up to 90° C C-COP higher than 4,0 for air-source heat pump with air 7° C-50% R.H. and waterin-out 10-65°C
  20. 20. HEAT PUMPS – FOR HOT WATER AIR HEAT 25Best applications:- Hotels- Hospitals- Laundries – Elderly people houses- Wheneven hot water is needed in large amounts
  21. 21. Many thanks for your attention

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