Saving Energy on WA Dairy Farms 1

Milk Cooling Systems• Switchtotimeofusemeteringwheremorningmilkingactivitiesarecompletedby8am.

• Useaplatecoolerwithasinglepassofcoolwaterthatisnotrecirculatedunlessitisre-coolediewithcoolingtower.

• Ensureplatecooleristhecorrectsizeforthevolume,pressureandmilkflowrate.Thiswillensureeffectivecoolingofmilksovatcompressorsarenotrunningforextendedlengthsoftime.

• Considerdoublebankplatecoolerswherethecoldestsourceofwaterflowsthroughthefirstplatecooler.Thesecondplatecoolercanuseglycolorchilledwatertocoolthemilkevenfurther.Itisbeneficialifthechillercanberunduringoffpeakpower.

• Haveyourplatecoolerregularlyservicedbyatechnician.

Coolingmilkfrom35°Cto4°Caccountsforthebiggestproportionoftotaldairyenergycosts(43percentinWAaudits).Designingandoperatinganefficientmilkcoolingsystemcanreduceenergydemandandoperatingcosts.Inmanycasesthetechnology,suchasplatecoolers,isnotnewbutneedstobeevaluatedtoensureitisworkingefficientlyandnotcostingyoumoney.

PlateCoolersPlatecoolersareanextremelycosteffectivewaytocoolmilk,butinmanycasesarepoorlyutilised.Thereareseveralfactorsthatimpactontheeffectivenessofplatecoolers.

Flow RatesThe system needs to be designed according to the peak flow rate of milkexpectedfromthemilkpump.Providinganevenflowofmilkfromthemilkpumpbyinstallingavariablespeeddrivewillhelpmaketheplatecoolersystemeasier tosizeandmakeefficientuseof thecoolingwater.Usinga transfer(ratherthanpressure)pumpisapreferablewaytosupplythecoolingfluid.

Surface AreaThelatestplatecoolersaredesignedtohavemoresurfaceareagivingthemgreater heat exchange capacity which improves their cooling efficiency.Differenttypesofplatecoolersrequiredifferentflowratesforthecoolingmedium.Thestandard‘M’and‘P’seriesplatecoolersoperateonaratioof2.5-3Lofwaterto1Lofmilkpassingthroughthecooler.Newerindustrialmodelsworkon1.5–2Lwaterto1Lofmilk.

Plate CompressionPlatesthataretootightrestrictflowsoaimfor3mmforeachplateandgasket.

Plate CleanlinessContaminantsofeitherthewaterormilkthatadheretotheplateswillaffecttheheatexchangecapacity,flowrateandefficiencyoftheplatecooler.

Source WaterThe temperature of the source water is the greatest limitation to platecoolers. Inwinterwhenwater temperaturesare lowplatecoolersoperatevery efficiently. In summer, when water temperatures increase, there canbeverylittlemarginbetweenthewatertemperatureandmilktemperature.Thismeans thevatwilldo themajorityof thechillingwhichusesa lotofelectricity,usuallyatpeaktariffrates.

PlumbingTomaximiseheattransferthewatershouldflowthroughtheplatecoolerintheoppositedirectiontothemilk.

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Saving Energy on WA Dairy Farms 2

Isyourplatecoolerdoingthejob?Thebestwaytocheckifyourplatecoolerisuptothetaskistocomparethetemperatureofthemilkleavingtheplatecoolerwiththeincomingtemperatureofthecoolingwater.Aplatecoolerworkingproperlyshouldcoolmilktowithin2°Coftheincomingcoolingfluidieifwatercomingintotheplatecooleris18°Cthenthetemperatureofthemilkshouldbeabout20°C.

Step 1 Identifywaterinletandmilkoutletpipes.

Step 2 Applystripthermometerstowaterinletandmilkoutletpipesandmeasurethetemperatureofthewaterandmilkduringpeakmilkflowasitexitstheplatecooler.

Step 3 Ifyougetmorethan3°Cdifferencethereisroomtoimprovetheperformanceofyourplatecooler.

Step 4 Measuretheflowrateofwaterleavingtheplatecooler.Thisisdonebytiminghowlongittakestofilla20Lbucketwhenthepumpisoperatingatnormalspeedandflowrate.Ifthewaterisbeingrecycledorrecirculatedintoatankputthebucketunderthedischargepipe.Forexampleifittakes13secondstofilla20Lbuckettheflowrateis20÷13=1.5L/sec).

Step 5 Measurethetimetakentofillthebucketwithmilkatthevatentrypointwhilethemilkpumpisworkingatcapacity(ieallcupson).Ifittakes40secondstofilla20Lbuckettheflowrateis20÷40=0.5L/sec.Ifitisnotpossibletomeasureduringmilk,simulateusingwateratalaterpoint.

Step 6 Dividethecoolingfluidflowratebythemilkflowratetodeterminetheratio.Usingthenumbersmentionedinsteps4and5theflowratewouldbe1.5÷0.5=3.Thewaterflowrateis3timesthemilkflowrateor3:1.

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How hot is it?Therearetwoquickandeasywaystotestthetemperatureofeithermilkorwaterrunninginandoutoftheplatecooler.ThermometerTestStrips-temperaturedifferenceiseasytomeasurebyapplyingstripthermometerstothewaterinletpipeandtothemilkoutletpipe.Cost$4.DigitalNon-ContactInfraredThermometerGun–canmeasuresurfacetemperatureofhot,hazardousorhardtoreachobjects. Simply point the red light at the pipe/object to be measured and pull the trigger to get a quick temperaturereading.Theyareagreattoolforaroundthefarm.Coststartat$30.

Saving Energy on WA Dairy Farms 3

BringintheExpertTesting the efficiency of your plate cooler is an important first step that you can do yourself. If you have ascertained that there is a problem it may be a good idea to call on the services of a skilled technician. They will be able to clean the plates (a harder job than it looks) and ensure the plate cooler is reassembled properly. They will also be able to advise on resizing, extra pumping capacity, additional cooled water storage or a complete dismantle and service. The additional capital and cost of the servicing should be compared to the cost of an inefficient plate cooler. The cost of an inefficient plate cooler can run into the thousands of dollars a year depending on milk production and the difference in temperature of the water and milk entering and exiting the plate cooler.

Cutting Costs at Scott RiverRossWoodhousemilks1100cowsina60standrotaryonhisScottRiverproperty.Theeverincreasingcostofelectricity,andadesiretoimproveefficiency,promptedRosstomakeseveralkeychangestohisdairy.

After a particularly hot summer Ross realised that the vat was struggling to reduce the temperatureof themilk, consistentlyproducing theerrormessage ‘tooslow tocool’.AfterconsultingKimNorwellfromDeLaval,itwasdecidedthattheplatecoolerneededanoverhaul.Itwascleanedandservicedandtenmoreplateswereaddedtoimproveitscoolingefficiency.Inaddition,afilterwasputontothewatersupplyingtheplatecoolertoensureanycontaminationfromleavesandsludgecouldnotinhibittheflowthroughtheplatecooler.Withtheplatecoolernowtakingmoreheatoutofthemilk,thevathaslessworktodoreducingelectricitycosts.

RosshasalsolookedtomakefurthersavingsbyinstallingaVSDonhisvacuumpumpandnegotiatingabetterdealonhiselectricitysupply.HehasbeenabletonegotiateanewtwoyearcontractwithPerthEnergytosupplyhiselectricityrequirementsatacompetitiverate,withpeakelectricitybeingreducedby5c/kW.HeisalsopartoftheEnerNOCSdemandresponseprogram.

Saving Energy on WA Dairy Farms 4

CoolingTowersIfyoudiscoverthatthewaterenteringyourplatecooleristoowarm,acoolingtowercouldbeaconsideration.Theyalsoallowforwaterfromtheplatecoolertobecooledsoitcanberecirculatewithoutjeopardisingmilkcooling.Coolingtowerscanbeveryeffectiveatcoolingwaterinareasoflowhumidity.

Acoolingtowerisaheatrejectiondevice.Acoolingtowerreliesonevaporationtoremoveheatfromthewater.Thetowerallowsasmallportionofthewaterbeingcooledtoevaporateintoamovingairstreamtoprovidesignificantcoolingtotherestofthatwaterstream.Theheatfromthewaterstreamtransferredtotheairstreamraisestheair’stemperatureanditsrelativehumidity,andthisairisdischargedtotheatmosphere.Watercanbecooledtowithin5°Cofthewetbulbtemperature*inatowerthatisproperlydesigned.

• Coolingtowersarearelativelycheaptechnology.

• Theydonotworkwellondaysofhighrelativehumidityandhighwetbulbtemperatures.

• Theycanreducethetemperatureofthewaterenteringtheplatecoolerimprovingitsefficiencyandreducingthecostofmilkcooling.Checkthetemperatureofthewaterenteringtheplatecoolertoseeifacoolingtowercouldbeanoption.

• Boreandwellwaterwillhavearelativelystabletemperatureallyearroundbutthetemperaturemayriseconsiderablyinhotweatherdependingonhowthiswaterisstored.

• Positioning,burying,screeningorplantingshadearoundtanksareoptionstohelpinsulate.

• Mechanical-draftcoolingtowersrelyonpower-drivenfanstodraworforcetheairthroughthetowerandaremoreeffectivethannaturaldraftcoolingtowers.

*Wetbulbtemperatureismeasuredusingastandardmercury-in-glassthermometer,withthethermometerbulbwrappedinmuslin,whichiskeptwet.Theevaporationofwaterfromthethermometerhasacoolingeffect, so the temperature indicated by the wet bulb thermometer islessthanthetemperatureindicatedbyadry-bulb(normal,unmodified)thermometeragainstthewarmingeffectsdirectsunlight.

ImprovedRefrigerationA new product, the Mysticool Max, is an add-oncomponent that can help to improve the performanceofmilk vat refrigeration. It isa valve thatchanges theliquid dynamics of the refrigerant gas allowing moreof it to come intocontactwith thecopperandcoolingplates. This reduces the temperature faster and moreefficiently.Italsoenablestemperaturestobeheldmoreconsistently. It canbe installedwithoutalteringanyoftheothersystemcomponents.Thestartingcostis$2400+GSTwithreturnoninvestmentbetween9-36months.

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