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Experimental Performance of a Semi-Hermetic Reciprocating Compres

Aug 04, 2015



Purdue UniversityPurdue e-PubsInternational Compressor Engineering Conference School of Mechanical Engineering2010Experimental Performance of a Semi-HermeticReciprocating Compressor working with PropaneEnrico Dai RivaUniversity of PadovaDavide Del ColUniversity of PadovaAlberto CavalliniUniversity of PadovaFollow this and additional works at: htp:// document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] foradditional information.Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at htps://, Enrico Dai; Col, Davide Del; and Cavallini, Alberto, "Experimental Performance of a Semi-Hermetic Reciprocating Compressorworking with Propane" (2010). International Compressor Engineering Conference. Paper 2029.htp:// 1448, Page 1 International Compressor Engineering ConIerence at Purdue, July 12-15, 2010

Experimental Performance of a Semi-Hermetic Reciprocating Compressor working with Propane Enrico DA RIVA*, Davide DEL COL, Alberto CAVALLINI University oI Padova, Dip. di Fisica Tecnica, Via Venezia 1, 35131 Padova, Italy (Tel.: 390498276885, Iax: 390498276896, * Corresponding Author ABSTRACT The experimental perIormance oI a semihermetic reciprocating compressor working with propane as the reIrigerant isreported.TestshavebeenperIormedbothwithandwithoutaninternalheatexchangerbetweensuctionvapour andliquidline.ThesuctionvapoursuperheatingisshowntoimprovevolumetriceIIiciencyand,thereIore,global compression eIIiciency.TwodiIIerenthypotheseshavebeendiscussedinordertoexplainexperimentalresults:thehighsolubilityoI propane on the lubricating mineral oil and the possibility oI condensation on a cold spot inside the cylinder. 1. INTRODUCTION Environmental issues about the use oI hydroIluorocarbons (HFCs) have arisen, since mostly used HFCs are strong greenhouse gases. According to the IPCC (2007), in terms oI CO2 equivalent, the share oI the Iluorinated gases in the emissions oI anthropogenic greenhouse gases was estimated to be 1.1 in 2004. A great stimulus to the search Ior substitutes Ior HFCs has been given within the EU by the Directive 2006/40/EC which regulates the phase out oI Iluids with GWP~150 in mobile air-conditioning systems. Chemical manuIacturers have redirected their Iocus to Iluoro-oleIins (R-1234yI in particular), in order to Iind a substitute Ior R134a (Minor and Spatz, 2008). Fluoro-oleIins generally are more reactive than compounds with only single carbon-carbon bonds, thisgreatlyreducingODPandGWP.However,thehigherreactivitygenerallyleadstohighertoxicityandlower stability; Iurthermore, these Iluids tend to decompose in proximity to the location oI release, giving birth to products which could be smog progenitors or contribute to the Iormation oI other chemicals with higher GWP (Calm, 2008). The adoption oI substances naturally occurring in the environment, and displaying null ODP and negligible GWP, hasbeensuggested.Amongthe'naturalIluids,hydrocarbons(HCs)arethemostchemicallyrelatedwiththe halogenatedreIrigerants.ThemainproblemistheirIlammabilitywhichhaspreventedtheiruseinlargescale:Ior this reason, additional saIety restrictions and reIrigerant charge minimization are required. Isobutane(R600a)nowadaysdominatestheEuropeanmarketoIdomesticreIrigeratorsanditsuseisincreasingin countries like Japan and Korea, since the required charge is very low, thereIore no saIety concerns are present. It is interestingtonoticehow,mainlybecauseoItortlawswhichleadmanuIacturerstoIearhavingtodeIendagainst assertions oI contribution to domestic fres, HCs are not used in reIrigerators in the USA (Calm, 2008). Regardingapplicationslikeheatpumps,air-conditionersandcommercialreIrigerationsystems,propane(R290) displays very interesting properties and, Irom a technical point oI view, could be easily adopted as drop-in Ior R22 intraditionallydesignedequipment.However,medium-capacityhermeticcompressorsdesignedtooperatewith R290 lack due to the small market and to the additional certiIications and approvals required. SomemanuIacturershaveexperiencedintolerablyhighIailureratesoIcompressorswhenusingHCs,andthishas beenexplainedbythehighsolubilityoIR290intheoil,whichcanleadtoasubstantialdecreaseoIthelubricant viscosity.OthermanuIacturers,instead,withtheuseoIhigherviscosityoil,crankcaseheatersand/orinternalheat exchanger, have reported Iewer Iailures with HCs than with HFCs or HCFCs (Palm, 2008). TheperIorcompressobetween 4 without anA 2 kW cothis unit a hFive hermePOEoilassigniIicant In the presas the lubrminichannreIrigerant working co 2 A semi-herthecomprdesign andthem to setThe experiwith and wIor the hotTemperatumeasured bR290 displa substanticompressodecreasesbmanuIactustandstillcinstalled inThepresenTecnica de InternrmanceoIaRor used was desand 5 K. A Ieny problem (Palooling capacityhermetic recipetic reciprocatslubricantby diIIerence betsent paper, the ricant is reporteelshell-and-tuchargeandionIigurations (2. COMPRErmetic reciprocressorsIorhald protection devt the capacity timental Iacilitywithout IHX cat water line anure and pressurby an electricalays a very higial decrease oIoris chargedwbyincreasing reroIthecomcondition,a14n temperate surntexperimentaepartment buildFig. national ComprR290heatpumsigned to operaew scroll complm, 2008). y reIrigeration srocating comping compressoNavarroetaltween the oil bexperimental ped. The comprubecondenser installedtogethDel Col et al., ESSOR DEcating compreslogenatedreIrivices. The comto 66. SpeciIiy used in this wan be tested at td the propane re are measuredl power analyzgh solubility wI the viscosity, witha higher bthetemperaturmpressor.Ino40kWcrankcarroundings andalIacility,howding, in order t1: Experimentressor Engineermphasbeenmate with R407Cpressors have bsystem using pressor was useors designed tol.(2005).Testehaviour with perIormance oressor has beenandaninternaherwithcomm2010, CavallinESCRIPTIOssor by Bitzer digerants,thisdmpressor has 6 Iications oI the work is depictethe same operaline, while an d at the points zer. The instrumith conventionespecially at lasic viscosity re,atleast20 ordertoreducaseheaterisind insulted iI necwever,hasbeeo provide somal Iacility. ring ConIerenceasuredbyFeC, ester oil wasbeen operated ipropane has beeed with mineralo operate with shavebeenpR290 and R40I a semi-hermen installed in a alheatexchanmercialplate ni et al., 2010)ON AND OPdesigned to opdevicedisplaycylinders withcompressor aned in Fig. 1. Byating conditionelectromagnetdepicted in Figmentation meanal lubricants alow oil tempermineraloil.FuKsuperheatinehighIoaminnstalledinthe cessary (Bitzerensituatedoue level oI intrince at Purdue, Juernandoetal. s used as the luin total 8-1000en studied alsol oil as lubricanR407C havebperIormedwith07C. etic reciprocati100 kW heatinger(IHX)havheatexchange.PERATIONperate with R29ysadjustmentsh the possibilitynd the lubricany switching thens. Two Coriolitic Ilow meter g.1 and the posurement unceand ester oils. Srature and highurthermore,sinngatsuctionang,especially compressor.Br, 1997).utsideintheonsic saIety. Table 1: C NumbercylinderBore Stroke VolumetIlow rateCapacityCrankcaOil typeOil viscoOil charuly 12-15, 201(2004,2007). ubricant and the00 h during thiso by (Hrnjak annt. been characterih11.1Ksupering compressoing capacity prvebeendesignersinordertoN WITH PRO90 has been tessconcerningoy to shut-oII tht are reported ie on/oII valves,is eIIect mass Iis installed inower supplied ertainty is reporSince this charah suction pressnceat Iixed pranddischargeaiIstaringthe Besides,thecoopenaironthCompressor andr oI rs tric e(y control ase heater Mosity rge 1448, Pa0 Thehermetic e superheat was experimentalnd Hoehne, 200ized using R29rheatingshowior using a mineropane heat punedtominimiocomparediIOPANE sted. As compaoilcharge,elee suction oI a pin Table1. , both conIigurIlow meters arn the cold wateto the comprerted in Table 2acteristic can lsure (see Fig. 8ressure thesoluaresuggestedbcompressorIompressorshouerooIoIthe d oil speciIicat6 75 mm 55 mm 126.8 m3/h(1450rpm,50100 - 66140 W Mineral oil 'ShClavus Oil 6868 cSt at 404.75 dm3 age 2 scroll as kept l study 04). In 90 and ingno eral oil mp. A izethe IIerent ared to ectrical pair oI rations e used er line. ssor is .lead to 8), the ubility bythe Iroma uldbe Fisica tions. h 0Hz) hell 8 C 1448, Page 3 International Compressor Engineering ConIerence at Purdue, July 12-15, 2010 Table 2: Instrumentation 'type B measurement uncertainty (68 conIidence level). InstrumentUncertainty Compressor suction pressure transducerr 0.035 bar Compressor discharge pressure transducerr 0.17 bar Condenser diIIerential pressure transducerr 0.00043 bar Evaporator diIIerential pressure transducerr 0.0035 bar Condenser and expansion valve pressure transducerr 0.03 bar Evaporator outlet pressure transducerr 0.01 bar Propane mass Ilow meterr 0.0018 kg/s Hot water volumetric Ilow meterr 0.017 L/s Cold water mass Ilow meterr 0.005 kg/s Electric power analyzerr 0.35 oI reading T-type thermocouples ice pointr 0.05 K 3. OPERATING CONDITIONS AND TEST PROCEDURE Experimental tests have been carried out at both Iull and 66 compressor capacity, at suction pressure varying Irom 4.4 bar up to 5.2 bar, corresponding to around 0C saturation temperature, and discharge pressure varying Irom 13.8 upto19.6bar,correspondingtosaturationtemperatureIrom40Cupto55C.Thecorrespondingwater temperatures ranges Irom 12-7C/30-35C to 10-5C/ 45-50C. In the test runs without the IHX, the superheat at the compressor suction was varied Irom SH14K up to SH114K bychangingthesettingoIthethermostaticexpansionvalve;thecorrespondingsuperheatatthecompressor dischargevariedIromSH320KuptoSH330K.WhenusingtheIHX,theachievedsuperheatdependsonthe temperaturediIIerencebetweenthesubcooledliquidandth