Hot Water Boiler - Circulation Rates

The relation between

• boiler capacity (or power)
• temperature drop of the water flow in a system serviced by boiler
• circulated water flow

are indicated in the diagrams below:

Water Circulation - Boiler Capacity in BHP - Temperature drop in degrees Fahrenheit

• 1 gal (US)/min = 6.30888×10^-5 m³/s = 0.0227 m³/h = 0.06309 dm³(liter)/s = 2.228×10^-3 ft³/s = 0.1337 ft³/min = 0.8327 Imperial gal (UK)/min
• 1 hp (English horse power) = 745.7 W = 0.746 kW = 550 ft lb/s = 2,545 Btu/h

Water Circulation - Boiler Capacity in MBtu/h - Temperature drop in degrees Fahrenheit

• 1 Btu/h = 0.293 W

Water Circulation - Boiler Capacity in kW - Temperature drop in degrees Celsius

• 1 kW = 3,412 Btu/h = 1.341 British hp

Example - Water flow through Boiler

A boiler with capacity 50 kW increases the temperature of the circulated water with 20 ^oC - the water flow through the boiler according the diagram above is 

0.6 kg/s