Book - School of Science and Technology

Water systems ± applications 243that, whereas unit pressure loss in a 32 mm pipe is 140 Pa/m, it is five times greater in a25 mm pipe.. Having established the total pressure loss of the system based upon a number of initialassumptions, it is necessary to consider whether the result achieved has invalidated anyof these to the extent where it might be necessary to repeat the calculation routine usingcorrected figures. Furthermore, the question arises as to whether, by selecting adifferent temperature drop or by varying the pump pressure, a more economicalsolution might have been produced.Sectionof pipe(1)Loadcarried(kW/K)(2)Total length,(L ‡ EL)(m)(3)Pipe size(mm)(4)Unitpressureloss (Pa/m)(5)Sectionpressureloss (3) (5)(6)AB 23.85 41.1 80 140 5760BC 16.70 23.6 80 70 1652CD 9.37 21.3 65 58 1235DF 7.52 11.1 50 120 1332FG 5.72 11.2 50 70 784GH 3.88 11.1 40 120 1332HJ 1.98 14.0 32 60 840Emitter 1.98 ± ± Catalogue 5000Total for circuit ˆ 17935 PaSay, 18 kPaHydraulic gradientsAlthough, as noted above, it is rarely possible to select pipe sizes for intermediate circuitssuch that the pressure loss there is in exact balance with that of the index circuit, it1 2 3 4 5 6 7Pressure LossBACFigure 9.7 Hydraulic gradientslength