Building Services Engineering 5th Edition Handbook

100 Heating
Table 4.3 Flow of water in copper pipes of various diameters.
Δp/EL (N /m 3 ) Water flow rate q (kg/s) for diameters of
6mm 15mm 22mm 28mm 35mm 42mm
200 0.013 0.065 0.174 0.381 0.656 1.060 v = 1.0
260 0.015 0.075 0.202 0.441 0.760 1.230
300 0.016 0.081 0.219 0.478 0.823 1.330
360 0.018 0.090 0.242 0.529 0.910 1.470
400 0.019 0.096 0.257 0.561 0.965 1.560
460 0.020 0.104 0.278 0.607 1.040 1.680 v = 1.50
500 v = 0.50 0.021 0.109 0.291 0.635 1.090 1.760
560 0.023 0.116 0.310 0.677 1.160 1.880
600 0.024 0.120 0.323 0.703 1.210 1.950
660 0.025 0.127 0.340 0.741 1.270 2.050
700 0.026 0.131 0.352 0.766 1.320 2.120
760 0.027 0.138 0.368 0.802 1.380 2.220
800 0.028 0.142 0.379 0.825 1.420 2.280
Note: v, water velocity (m/s); p/EL, rate of pressure loss due to friction.
Source: Reproduced from CIBSE Guide by permission of the Chartered Institution of
Building Services Engineers.
EXAMPLE 4.2
Figure 4.20 shows the arrangement of a two-pipe low-temperature hot-water heating
system serving three radiators. The pipe dimensions indicated apply to both flow and
Vent
Cold feed
Boiler
10 m
3m
q x
q 1
q 2
X
Radiator 1
d x
q Y
10 m d Y
Each radiator has 3.0 kW emission
t f =85°C
t f =72°C
Radiator 3
3m
q 3
d Z
5m
5m
Radiator 2
10 m
4.20 Low-temperature hot-water heating system.