Pressure loss diagram hot water heating systems - steel pipes and
tubes
The diagram below can be used to estimate the 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 viewed 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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