Freshairinlet
Freshairinletlocation
(1)Itshouldbelocatedinacleanoutdoorplace,andthecontentofharmfulsubstancesinoutdoorairattheairinletshouldnotbegreaterthanindoors30%ofthemaximumallowableconcentrationattheworksite.
(2)Whenarranging,keeptheexhaustventandtheairintakeasfarawayaspossible.Theairinletshouldbeplacedontheupwindsideoftheexhaustoutletasfaraspossible(referstotheupwindsideofthemainwinddirectionoftheseasonwhentheinletandexhaustareusedatthesametime),andtheairinletshouldbelowerthantheexhaustoutletfordischargingharmfulsubstances.
(3)Inordertoavoidinhalingoutdoorgrounddust,thebottomoftheairinletshouldnotbelessthan2mawayfromtheoutdoorfloor;whenitisarrangedinagreenbelt,itshouldnotbelessthan1m.
(4)Inordertolowertheoutdoorairtemperatureinsummer,theairinletshouldbesetintheshadeofthebuilding,onthenorthwall,andavoidontheroofandwestwall.
Otherrequirementsfornewairoutlets
(1)Theairinletshouldbeequippedwithshutterstopreventrainwaterfromentering,andtheshuttersshouldbefixedshutters.Inrainyareas,waterproofshuttersshouldbeused.
(2)Inordertopreventbirdsfromentering,metalnetsshouldbeinstalledintheblinds.
(3)Forcentralizedsystemsthatusealargeamountoffreshairduringthetransitionseason,itisadvisabletosetuptwofreshairoutlets,oneofwhichisthesmallestfreshairoutlet,anditsareaiscalculatedaccordingtotheminimumfreshairvolume;theotherisanewairvolumewithvariableairvolume.Theareaofthetuyereiscalculatedbysubtractingtheminimumfreshairvolumefromthemaximumfreshairvolumeofthesystem(thewindspeedcanbelarger).
Freshairunit
Mainfunction
Themainfunctionofthefreshairunitistoprovideconstanttemperatureandhumidityairorfreshairfortheair-conditionedarea.Thecontrolofthefreshairunitincludessupplyairtemperaturecontrol,supplyairrelativehumiditycontrol,antifreezecontrol,carbondioxideconcentrationcontrol,andvariousinterlockingcontrols.
Structure
Thefreshairunitiscomposedofafreshairoutlet,asupplyairoutlet,afreshairvalve,afilter,asurfacecooler,ahumidifier,andablower.Thesensorsusedmainlyincludetemperatureandhumiditysensors,differentialpressureswitches,andantifreezeswitches:actuatorsincludefreshairvalvedrivers,electrictwo-wayvalvesthatcontroltheflowofchilledwater,andblowers.
Workingprinciple
Outdoorfreshairentersthefreshairunitthroughthefreshairoutlet,andthefreshairunitwillfiltertheincomingoutdoorairtofilterouttheparticulatedustintheair,andthencooltheair.Afterdehumidificationorhumidificationtreatment,thetreatedcoldairwithsuitabletemperatureandhumidityissenttotheair-conditionedareathroughtheblower.
Thefreshairunitisahorizontalstructurewithahighheatexchangeperformancecold(heat)exchanger(surfacecooler)andalow-noisefan.Thehorizontalfreshairairconditioningunitdoesnothaveitsowncoldandheatsource.Wheninuse,theairpassesthroughthefilter,andtheniscooledorheatedbythecold(heat)exchanger(surfacecooler),andthensenttoeachroombytheairduct.
Afterthefreshairunitintroducestheoutdoorfreshairandperformscoolingandhumidificationordehumidificationtreatment,thecoldairwithsuitabletemperatureandhumidityistransportedtodifferentroomsandareasofthebuildingthroughtheairsupplyduct,andsentoutfromtheairsupplyoutlet.asshowninpicture2.
Thesupplyairtemperaturecontrolandindoortemperaturecontrolofthefreshairunit
I, thesupplyairtemperaturecontrol
Ifthefreshairunitismainlytomeetthecleanandhygienicairintheair-conditionedareaTherequirementisnottocarrythecoolingloadorheatloadoftheair-conditioningarea,anditisnecessarytocontrolthesupplyairtemperature.Inthesupplyairtemperaturecontrolmode,thesupplyairtemperatureisalwaysmaintainedtomaintainaconstantvalue.Ofcourse,thesupplyairtemperaturehasasummertemperaturecontrolvalueinsummerandawintersupplyairtemperaturecontrolvalueinwinter.
Therefore,itisnecessarytoensurethenormalconversionofthecontrollerinsummerandwinteroperatingconditions.Thecontrolmethodoftheairsupplytemperatureofthefreshairunitinsummerismainlytoimplementcontrolbyadjustingtheflowofchilledwaterinthecoil;inwinter,thecontrolisimplementedbyadjustingtheflowofhotwaterinthecoil.
2.Indoortemperaturecontrol
Manyairconditioningareasrequirefreshairunitstobeabletocarryindoorcoolingorheatingloads,whichisreflectedintheneedtocontrolindoortemperature.Sincetheindoorcoolingloadorheatingloadisalwayschangingdynamically,onlytheconstanttemperaturecontrolofthesupplyairtemperaturecannotmeettherequirementsoftheindoordynamicloadchange.Itisnecessarytocontroltheindoortemperature.Thespecificcontrolmethodistodetecttheindoortemperaturethroughthesensor.Andinputthetemperaturesignaltothecontroller.Ifthetemperatureishigherthanthesettemperature,thecontrollerwillgothroughthefollowingprocessing:usethedifferencebetweenthedetectedtemperatureandthesettemperatureascontrolofthechilledwaterflowingthroughthecoilorThebasiccontrolparametersofhotwaterflow.Whenthedifferenceislarge,theopeningoftheelectricvalvethatcontrolstheflowincreases,andviceversa,theopeningdecreases,increasingtheflowofchilledwaterorhotwater,thatis,increasingthecoldorheatThesupply,andthenrealizethereal-timecontrolofthetemperatureoftheair-conditionedarea.
Fromtheperspectiveoftheannualoperationcontrolofthefreshairunitandconsideringtheoperationofthetransitionseason,thecombinedcontrolmethodofthesupplyairtemperatureandtheindoortemperatureshouldbeadopted.