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

PLH_KKK_32_85.QXP 25.05.2007 10:11 Uhr Seite 65EXAMPLES FOR THE PUMP SELECTION IN THE CONDENSER CIRCUITGround collector systemTo protect against freezing, the system is filledwith a glycol mixture (40% Antifrogen N + 60%water). The circulated volume is determined asfollows:Formula for the pressure / the delivery head HH Ges = (H geo + H A ) · f pH A = H VL + H VAFormula for volume flow V PUQ· NV·PU =m 3 /h0.97 · ∆ϑCalculationH Ges = (H geo + H VL + H VA ) · f pCalculationH VL= R · IH VA= Z + collector resistanceV·PU =2000.97 · 6m 3 /hH VL = 50 · 75H VL= 3 750 PaZ = Σζ ·ρ · w 22PaV·PU = 34.29 m 3 /hZ = 109.63 ·1 070 · 0.8 22PaThe desired pump head results from the pipelinerequirements. PVC pipeline material is selectedwith a nominal diameter of 125. The R value is50 Pa/m at a flow rate of about 0.8 m/s. Basedon the installed fittings, bends and the condenserresistance, the addition of 8 bends and2 shut-off valves results in a value of 109.63.Another 20 kPa are to be included in the calculationfor the collector and the pipe length to beconsidered is 75 m.Z = 37 537 PaResultH Ges = (H geo + H VL + H VA ) · f pH Ges = (0 + 3 750 Pa + 57 537 Pa) · 1.47H Ges = 90 092 PaA pump with a flow rate of Q = 34.29 m 3 /h andH = 9.0 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 65