From cooling duty to water flow
Use this chilled water pipe sizing calculator to translate a cooling duty into an estimated water flow and circular internal diameter. It supports an initial sizing discussion for a branch, coil connection or other water-side segment. Calculate without an account and keep the result alongside the assumed duty and temperature difference. The output is an internal hydraulic diameter estimate, not an automatic nominal pipe or pump selection.
Formula and input units
Enter cooling load, water temperature difference and target velocity with their displayed units. The existing calculator uses flow in L/s = cooling load in kW / (4.187 × ΔT in °C), treating the fluid as water. It converts flow to m³/s and calculates diameter from D = √(4Q / πv). Supported inputs include kW or BTU/hr, temperature differences in °C or °F, and velocity in m/s or ft/s.
Worked example: assumed 100 kW branch
Assume cooling duty 100 kW, supply-to-return temperature difference 5°C, and target water velocity 1.5 m/s. Enter these three values in their SI units. The calculated flow is 100 / (4.187 × 5) = 4.77669 L/s. This is 0.00477669 m³/s. Applying the circular-area equation gives an internal diameter of 0.063676 m, or approximately 63.68 mm, at the assumed velocity.
Selecting a practical pipe
The 63.68 mm answer does not mean a pipe labelled DN65 necessarily provides exactly that internal bore. Actual internal diameter depends on material, wall thickness, pipe schedule and manufacturer dimensions. Select a candidate size from the project pipe standard, then check its real bore and recalculate the operating velocity. Consider connection sizes, available space, insulation and supports, together with access for valves and maintenance on the installed route.
Hydraulic and fluid limitations
This calculator does not evaluate Darcy friction, fittings, strainers, control valves, balancing valves, coil pressure losses or the complete index circuit. It cannot establish pump head or confirm system balancing. Its water heat-capacity assumption is unsuitable for an unreviewed glycol mixture or unusual fluid conditions. The engine warns when target velocity falls outside its illustrative 1–3 m/s range; that warning is not a universal approval criterion for every project.
Singapore project review
Treat this output as a draft for review, not a stamped design or an approval. For a Singapore submission, check the applicable SS553 requirements and the project specification with the responsible designer. Verify the input schedule, record the assumptions, and reconcile the calculation with drawings and manufacturer data. This tool does not identify every applicable requirement, certify compliance, or replace professional judgement about installation, operation, safety, and maintenance. Retain the calculation date and revision so later changes can be traced to their original assumptions.