3.5 kW 4 kW I 4.5 kW 3kW 103 Sm 15m es; radiator 1.50, valve3.00, 0.4, branching-2.0, pump3.5 WE 11 2m 7 The supply water temperature of a heating system is 70C and the return 55C. Calculate the pressure requirement and flow rate of the pump to feed (Ap this hydraulic system (Ap between points A and B). The diameter of the main pipes is 30 mm and the branch pipes 20 mm, where the friction resistance is 10 Pa/m for the main) and 15 Pa/m for the branch pipes. E-Z values are given in the table. Z 8.7 8 17.5 9 26.5 10 35 11 44 12 50 13 62 14 70 15 79 87 96 16 17 18 105 19 116 21 128 22 140 23 155 24 16