XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoD...
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XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoE...
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XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoC...
XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoC...
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Alberto Cavallini - Università di Padova - APPLICAZIONI A MINICANALI PER SISTEMI DI REFRIGERAZIONE A CARICA RIDOTTA

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Alberto Cavallini - Università di Padova - APPLICAZIONI A MINICANALI PER SISTEMI DI REFRIGERAZIONE A CARICA RIDOTTA

  1. 1. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoDavide Del Col, Marco Azzolin, Stefano Bortolin, Alberto CavalliniUniversity of PadovaDepartment of Industrial EngineeringMINICHANNEL DEVICES FORLOW CHARGEREFRIGERATING SYSTEMSXV EUROPEAN CONFERENCE
  2. 2. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoOutlineEnvironmental impact and introduction tominichannel technologyHeat transfer in minichannelsEffect of channel shapeRefrigerant properties and specific chargeHeat exchangers with minimum refrigerant chargeConclusions
  3. 3. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoEnvironmental impactThe worldwide alert about global warming has led to anincreasing interest in new HVAC (heating, ventilation andair conditioning) technologies with low environmentalimpactEffects to be considered:Indirect EffectEnergy consumptionDirect EffectLeakage of refrigerant
  4. 4. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoWhy minichannel technology ?- The refrigerant charge minimization can be consideredone of the most important targets for HVAC&R applicationsto cope with the new environmental challenges.- Minichannel technology appears to be a very goodopportunity to minimize the charge without energyperformance loss.- Instead, minichannel technology can help reducinggreenhouse gas emissions by improving component andsystem energy efficiencies.
  5. 5. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoSQUARECIRCULARResarch on minichannels
  6. 6. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoEnlarged picture taken with amicro-endoscopeSquare cross section minichannel(1.18 mm side length)
  7. 7. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoCondensation HTC: square vs. circularG = 200 kg/(m2s)HEAT TRANSFER COEFFICIENT [W/(m2K)]010002000300040005000600070000.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0VAPOUR QUALITY [/]HTC[Wm-2K-1]05101520253035404550Tsat-Twall[K]G200G200G200 tG200 tT SAT - T WALL [K]
  8. 8. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoCondensation HTC: square vs. circular02000400060008000100001200014000160000.0 0.2 0.4 0.6 0.8 1.0VAPOUR QUALITY[/]G790 SQUAREG800 CIRCULAR02000400060008000100000.0 0.2 0.4 0.6 0.8 1.0VAPOUR QUALITY[/]HTC[Wm-2K-1]G400 SQUARE xin=0.92G400 SQUARE xin=0.68G400 CIRCULARG = 800 kg/(m2s)G = 400 kg/(m2s)
  9. 9. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoCondensation: effect of channel shapeG=400 kg m-2 s-1Modelled liquid-vapour interface in circular and square minichannel with R134a
  10. 10. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoG100 zero-gravity x=0.8G100 normal gravity x=0.8G100 zero-gravity x=0.6G100 normal gravity x=0.6Liquid-vapour interface during condensationx = 0.6G = 100 kg m-2s-1x = 0.8G = 100 kg m-2s-1
  11. 11. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoUniversity of PadovaTube sheet of minichannel HX
  12. 12. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoCondenser internal volumeBPHE80 plates8.4 LMINICHANNEL S&T2 mm i.d. tubes2.9 LVolume reduction = -65%Charge reduction = -0.8 kg
  13. 13. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoPropane chargeEvaporator PHE PHE PHE PHECondenser PHE MC PHE MCIHX no no yes yesMeasured charge ~3.9 kg ~ 3.1 kg ~ 5.1kg ~ 4.3 kgTarget charge ~ 3.1 kg ~ 2.3 kg ~ 3.5kg ~ 2.7 kgPiping length not minimized (around 1 kg of R290)~0.5 kg of R290 in the liquid receiver~0.4 kg of R290 in the dehydrating filterTARGET CHARGE: 0.5m liquid line, no receiver, with filter
  14. 14. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoHeat exchanger data0.00.20.40.60.81.01.21.4ROUHANI NIÑO CISE ZIVI BAROCZY HOMOGEN. EXPERIMENTALR290ChargeReduction[kg]R 290LOCKHARTMARTINELLICONDENSER CHARGE REDUCTIONMINICHANNEL vs PHEComparison between experimental and calculated charge reduction for minichannelcondenser vs. PHEEXP
  15. 15. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoRefrigerants propertiesFluid psat [bar] pRED [ - ] ρl [kg m-3] ρv [kg m-3] µl [µPa s] µv [µPa s] λl [W m-1K-1] GWPR32 24.783 0.429 893.0 73.3 94.99 13.83 0.115 550R134a 10.166 0.250 1146.7 50.1 161.45 12.37 0.075 1430R410A 24.256 0.495 975.33 101.71 95.861 14.882 0.081 2100R22 15.336 0.307 1128.5 66.193 138.67 13.359 0.077 1810R1234ze 7.666 0.211 1111.3 40.7 167.00 12.93 0.069 6R290 13.694 0.322 467.46 30.165 82.844 8.8918 0.087 3R717 15.554 0.137 579.44 12.034 114.04 10.325 0.443 <1Properties at TSAT = 40°C
  16. 16. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di Milano00,20,40,60,8Charge[kg]CiseZiviBaroczy00,20,40,60,811,2Charge[kg]CiseZiviBaroczyCalculated refrigerantcharge in minichannelsHEXs for differentrefrigerants (80 kW heatflux at theevaporator, 100 kW atthe condenser, 5Ksubcooling and 5Ksuperheating)CONDENSERComparisonof refrigerantchargeEVAPORATOR
  17. 17. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoSpecific charge for systems usingHCs and ammoniaCapacity [kW] Refrigerant Specific charge [g/kW]Cavallini et al. (2010) 100 Propane 25-30Fernando et al. (2004) 5 Propane 37Hrnjak and Litch (2008) 13 Ammonia 20Corberan (2008) 14 Propane 30-40Park and Jung (2009)3.8 (H)3.5 (C)R170/R290157 (H)142 (C)(H): Heating(C): Cooling
  18. 18. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoConclusions- The refrigerant charge reduction in refrigerating systems is a goalto reduce the refrigerants contribution to the greenhouse effectand to reduce atmospheric emissions.- Minichannels are used to reduce the refrigerant charge in the HEswithout decreasing performance.- The understanding of dominant mechanisms during boiling andcondensation in minichannels is the fundamental basis for thedevelopment of accurate design methods.- To evaluate the refrigerant charge in the heat exchangers voidfraction correlations must be used.- Systems using minichannels heat exchangers that could work witha specific charge of 30 g/kW with propane have already beendeveloped.
  19. 19. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoThank youfor your attention !davide.delcol@unipd.itUniversità degli Studi di PadovaDipartimento di Ingegneria Industriale
  20. 20. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoSpecific charge: potential charge reductionSpecific charge in thecondenser [g/kW]Specific charge in theevaporator [g/kW]Ammonia (R717) 13.4 5.38Propane (R290) 34.4 4.24Carbon dioxide (R744) 29.8 2.49R32 44.9 5.34R134a 124.2 23.16R410A 65.6 6.51(Padilla Fuentes Y., Hrnjak P., 2012, Charge reduction potentials of several refrigerants …, Int. Refr. Conf. at Purdue, July 16-19;Padilla Fuentes Y., Hrnjak P., 2012, Experimentally validated microchannel heat exchanger performance …, 10th IIR G-L Conf. onNatural Refrigerants, Delft.)
  21. 21. XV EUROPEAN CONFERENCE – ITALYTHE LATEST TECHNOLOGY IN AIR CONDITIONING ANDREFRIGERATION INDUSTRY - Politecnico di MilanoHeat exchangers data (KTH)Propane heat pump developed at KTH of StockholmReferences: Fernando et al. (2004)Heating capacity 4-7.23 kWHydraulic diameter 1.42 mmNumber of channels 6Tube length 651 mmBaffle plates 31Refrigerant R290Evaporator CondenserNumber of tube 30 36Outer area 0.822 m2 0.985 m237 g/kWof R290Fernando P., Palm B., Lundqvist P., Granryd E., 2004, Propane heat pump with low refrigerant charge: design and laboratory tests, Int. J.of Refrig., 27, 761-773

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