Book - School of Science and Technology

Water systems ± characteristics 147–4100Per-cent energy requirement (alternate operation)90 80 63 33 6 1 0100External ambient temperature ºC–2024681012141618Per-cent of heating demand90807060504030201099.999.298948674584020Per-cent energy requirement (parallel operation)200100 90 80 70 60 50 40 30 20 10 0Per-cent of heating season0Figure 6.1 Analysis chart for application to bivalent energy systemsTable 6.4 Water content of steel (BS 1387: medium) and copper (BS 2871: Table X) pipesNominalpipe size(mm)Water content (litre/m)NominalWater content (litre/m)pipe size(mm)Steel Copper Steel Copper15 0.205 0.145 40 1.376 1.23420 0.367 0.321 50 2.205 2.09525 0.586 0.540 65 3.700 3.24532 1.016 0.837 80 5.115 4.210system maintenance are usually minimal, a safety margin of the order available is still tobe preferred.The difference of temperature, boiler outlet to boiler inlet, or flow to return in morecommon parlance, is a matter for the designer to determine. The differentials recommendedare included in Table 6.2. There is some evidence that wider differentials are used