Samer Sawalha Department of Energy Technology Kungliga Tekniska Högskola Stockholm-Sweden

1. Evaluation of refrigeration and heating systems in supermarkets -Field measurements and modeling- Samer Sawalha Department of Energy Technology Kungliga Tekniska Högskola Stockholm-Sweden

2. Project background-Projects • CO2 in supermarket refrigeration • 2002-2008: Modeling and experimental • 2008-2011: Fieldmeasurementsproject • 2008-2011: Heat recoveryproject • 2011-2014: • A comprehensive evaluation of refrigeration and heating systems in supermarkets based on field measurements and modeling

3. Project background-Subjects • Mainly CO2 systems, compared to conventional • Coolingevaluation • Computer Modelling • Experimental • Fieldmeasurements • Heat recovery • Computer Modelling • Experimental • Fieldmeasurements • Currentproject: • Cooling and heating, modelling, experimental and fieldmeasurments. • Build and test a ”state of the art system”

4. CO2 in supermarket refrigeration Indirect-forfreezing Cascade system Trans-critical

5. High stage-Propane, ammonia or R404A • Brine at medium temperature, possibility for CO2 • Reasonable pressure on the CO2 side • Several lay-outs of the cascade system CO2 cascade system Brine or CO2 CO2

6. CO2 in supermarket refrigeration Indirect-forfreezing Cascade system Trans-critical

7. CO2 trans-critical variations

8. Cascade-Transcritical-R404A Modeling Work

9. Systems’ total COP Cascade R404A DX R404A Indirect at Medium

10. Annual energy consumption

11. Conclusions of modelling work • CO2 trans-critical system solutions have high COP at low ambient temperatures. Lower annual energy consumption than conventional. • NH3/CO2 Cascade system has highest COP at high heat rejection temperatures (good for hot and cold climates)

12. Projects are in cooperation between IUC Sveriges Energi- & Kylcentrum and KTH and sponsored by the Swedish Energy Agency and several companies. Systems tested: Cascade-Transcritical-R404A Experimental Work

13. The R404A system experimental rig

14. Comparisons: Cascade, Trans-critical and R404A 50-60%

15. Main experimental evaluation conclusions • Trans-critical CO2 system hadcomparable COP to R404A • NH3/CO2 Cascade system has the highestCOP

16. Projects conducted by IUC Sveriges Energi- & Kylcentrumin cooperation with KTH. Sponsored by the Swedish Energy Agency and several companies. Systems tested: Cascade-Transcritical-R404A Field measurements Work

17. Cascade systems with CO2 NH3/CO2 cascade R404A/CO2 Cascade

18. Systems included in fieldmeasurementanalysis 1 pump circulation 2 cascade systems 5 trans-critical CO2 3 convintional systems: R404A+Brine

19. Total COP comparison

20. Main field measurements findings • Coolingefficiencies of ”new” CO2 systems are comparable to advancedconventional systems • Largedifferencesbetween CO2 systems-due to design butmostlycontrol

21. Heat recovery analysis • CO2 seems to be good solution in cold climates, how about heat recovery? • Which is the best HR solution to be used in CO2 systems? • How should it be controlled?

22. Different HR solutions

23. System performance in HR mode • Increase in discharge pressure to recover heat

24. Heating COP of the booster system • 8% lowerenergyconsumptionthan a conventional R404A system with a separate heat pump

25. Conclusions on heat recovery • CO2 trans-critical systems for supermarkets refrigeration are efficient solutions in cold climates. Lowest energy consumption • Experimental and field measurements are needed to investigate potential problems in • Controlling the gas cooler in cold ambient • The minimum condensingtemperature • The pinchpoint in the de-superheater

26. The currentproject, 2011-2014 Cooling and heating: modelling, experimental and field measurements. Focus on CO2, will investigate potential alternatives Use the available data bank to study system control and detailed components analysis Use the methods developed for new systems analysis-Guidelines Build and test a ”state of the art” system

27. Thank you