ASHRAE.HandBook_14-2008 MEDIUM- AND HIGH-TEMPERATURE WATER HEATING SYSTEMS

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1、RelatedCommercialResourcesCHAPTER14MEDIUM-ANDHIGH-TEMPERATUREWATERHEATINGSYSTEMSSystemCharacteristics............................................................14.1AirHeatingCoils....................................................................14.8BasicSystem.........................

2、..................................................14.2SpaceHeatingEquipment........................................................14.8DesignConsiderations............................................................14.2InstrumentationandControls...........................................

3、......14.8DistributionPipingWaterTreatment......................................................................14.9Design.................................................................................14.7HeatStorage......................................................................

4、......14.9HeatExchangers.....................................................................14.8SafetyConsiderations..............................................................14.9MEDIUM-TEMPERATUREwatersystemshaveoperatingThischapterpresentsthegeneralprinciplesandpracticesthattempera

5、turesbelow175°CandpermitdesigntoapressureapplytoHTWanddistinguishesthemfromlow-temperaturewaterratingof860to1030kPa(gage).High-temperaturewatersystemssystemsoperatingbelow120°C.SeeChapter12forbasicdesignareclassifiedasthoseoperatingwithsupplywatertemperaturesconsiderationsapplicabletoall

6、hot-watersystems.above175°Canddesignedtoapressureratingof2000kPa(gage).Theusualpracticaltemperaturelimitisabout230°CbecauseofSYSTEMCHARACTERISTICSpressurelimitationsonpipefittings,equipment,andaccessories.TherapidpressurerisethatoccursasthetemperaturerisesaboveThefollowingcharacteristics

7、distinguishHTWsystemsfrom230°Cincreasescostbecausecomponentsratedforhigherpressuressteamdistributionorlow-temperaturewatersystems:arerequired(seeFigure1).Thedesignprinciplesforbothmedium-andhigh-temperaturesystemsarebasicallythesame.Inthischap-•Thesystemisacompletelyclose