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

PLH_KKK_32_85.QXP 25.05.2007 10:11 Uhr Seite 63EXAMPLES FOR THE PUMP SELECTION IN THE CONDENSER CIRCUITHeat recovery via building heating and hot water productionIn the case of heat recovery, the flow rate can bedetermined with a larger temperature difference.A difference of 20 K is reasonable. At the samecapacity of 200 kW and a temperature differenceof 20 K, the following volume flow results:Formula for volume flow V PUFormula for the pressure / the delivery head HH Ges = H geo + H AH A = H VL + H VACalculationV·PU =Q· N1.16 · ∆ϑm 3 /hH Ges = H geo + H VL + H VACalculationV·PU =2001.16 · 20V·PU = 8.62 m 3 /hm 3 /hH VL = R · IH VL = 160 · 36H VL = 5 760 PaH VA= Zρ · w 2Z = Σζ · Pa2977.7 · 0.98 2Z = 74.9 ·2PaSteel pipework is selected with a pipe length of36 m with a nominal diameter of 50, with 8 bendsand 4 flat slide valves. This results in a resistancecoefficient of = 74.9. The result is:ResultH Ges = H geo + H VL + H VAZ = 35 165 PaH Ges = 0 + 5 760 Pa + 35 165 PaH Ges = 40 925 PaTo minimise maintenance costs, a glandlesspump with a flow rate of Q = 8.62 m 3 /h andH = 4.09 m is 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 63