Chilled Water Pipe Sizing & Pump Head Lab
Turn the cooling load into a chilled water flow, size the riser floor by floor and the branches to the far AHU, then add the coil, control valve, chiller or ETS and strainer to get the pump head. Size the pump motor and the expansion vessel, and see the pressure profile around the index circuit.
How to use: enter the load and the building, and the riser sizes itself. Use the pipe sizer below for any single flow. Tap i for plain explanations.
1. Load and building
Direct return riser feeding one AHU or FCU group per floor.
2. Riser and index circuit
Pipe sizes floor by floor, colour shows velocity. 4D shows the pressure profile around the index circuit.
3. Checks
4. Pipe sizer for any flow
5. Index circuit
6. How it works
Flow from load
Flow = load / (ρ × cp × ΔT). For water, 1 L/s carries about 4.19 kW per kelvin. A wider ΔT, as district cooling providers ask for, cuts the flow, the pipe sizes and the pump energy.
Sizing
Each pipe gets the smallest nominal size whose friction is at or below the limit and whose velocity is within the band for its size: about 1.2 m/s up to DN50 and up to 3 m/s for large mains. Friction is Darcy-Weisbach with the Colebrook friction factor at the water temperature.
Pump head
The index circuit is the path to the top floor in a direct return riser. Pump head adds supply and return pipe friction with a fittings allowance, the coil, the control valve, the chiller or ETS heat exchanger and the strainer. A valve authority of 0.5 means the valve drop equals the rest of its branch.
Expansion
Chilled water expands when the plant is off and warms to room temperature. The vessel is sized from the system volume, the expansion from 4 °C to the maximum ambient, and the fill and maximum pressures.
Learning and checking tool. Final pipe sizing and pump selection need the equipment data, the district cooling provider's rules where relevant, and the design software results.