Steel pipes and tubes - pressure loss diagram hot water heating
systems
The diagram below can be used to estimate pressure loss in hot
water piping heating systems.

The heat flow is based on temperature difference 20oC.
- 1 Pa = 10-6 N/mm2 = 10-5 bar =
0.1020 kp/m2 = 1.02x10-4 m H2O =
9.869x10-6 atm = 1.45x10-4 psi (lbf/in2)
- 1 kW = 1,000 Watts = 3,412 Btu/h = 737.6/550 British hp = 1.341
British hp = 103/9.80665 kgf m/s = 737.6 ft
- 1 liter/s = 10-3 m3/s = 3.6 m3/h
= 0.03532 ft3/s = 2.1189 ft3/min (cfm) =
13.200 Imp.gal (UK)/min = 15.852 gal (US)/min = 792 Imp. gal (UK)/h
- 1 m/s = 3.6 km/h = 196.85 ft/min = 2.237 mph
- m (meter) = 3.2808 ft = 39.37 in = 1.0936 yd = 6.214x10-4
mile
Example - Pressure Loss in Hot Water Heating Pipe
The pressure loss in a 2" BS 1387 hot water heating pipe with
heat flow 100 kW can be estimated as indicated below

-
With a temperature difference of 20oC the flow
is 1.2 liter/s
-
The flow velocity is 0.54 m/s
-
The pressure loss is 60 Pa/m
© The Engineering ToolBox 2005
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