Refrigeration, air-conditioning and cooling technology - 2007.pdf

PLH_KKK_32_85.QXP 25.05.2007 10:11 Uhr Seite 59EXAMPLES FOR THE PUMP SELECTION IN THE CONDENSER CIRCUITOpen cooling tower systemThe condenser circuit is cooled via an opencooling tower. At the same capacity of 200 kWand a temperature difference of 5 K, the followingvolume flow results:Formula for the pressure / the delivery head HH Ges = H geo + H AH A = H VL + H VAFormula for volume flow V PUQ· NV·PU =m 3 /h1.16 · ∆ϑCalculationH Ges = H geo + H VL + H VAV·PU =2001.16 · 5V·PU = 34.48 m 3 /hm 3 /hH VL = R · IH VL = 400 · 88H VL = 35 200 PaH VA= ZZ = Σζρ · w 22PaFor the pressure loss calculation, a pipe length of88 m is given with 14 bends, 4 stop valves and analtitude difference of 2.2 m between the minimumwater level and nozzle fitting. PVC pipework isselected with a nominal diameter of 80. This resultsin a resistance coefficient of ζ = 59.7.The result is:Result999.6 · 1.9 2Z = 59.7 ·2Z = 107 230 PaPaH Ges = H geo + H VL + H VAH Ges = 22 000 Pa + 35 200 Pa + 107 230 PaH Ges = 164 430 PaA monobloc pump with a flow rate of Q = 34.48m 3 /h and H = 16.5 m is to be selected.AbbreviationDescription1.16 Spec. heat capacity [Wh/kgK]∆Dimensioned temperature difference[K]10-20 K for standard systemsQ NH AH geoH GesH VLH VARHeat demand [kW]Pressure loss of the system in PaGeodetic pressure head difference in Pa (1 m WS ˜ 10 000 Pa)Total pressure loss in PaPipeline pressure loss in PaFitting pressure loss in PaPipe friction resistance in Pa/mLPipe lengthζResistance values in Paρ Density of fluid in kg/m 3w 2 Flow rate in m/s 2ZΣPressure loss in fittings in PaTotal lossesWilo Planning Guide - Refrigeration, air-conditioning and cooling technology 02/2007 59