Inputs
Example Data Table
| Case | Heat (kW) | ΔT (°C) | Cp (kJ/kg·°C) | Safety (%) | Mass Flow (kg/s) | Flow (m³/h) | Pipe ID (mm) | Head Loss (m) |
|---|---|---|---|---|---|---|---|---|
| A | 350 | 6 | 4.186 | 10 | 15.34 | 55.30 | 100 | ≈ 13.2 |
| B | 120 | 5 | 4.186 | 5 | 6.02 | 21.71 | 80 | ≈ 11.0 |
| C | 900 | 8 | 4.186 | 15 | 30.82 | 111.11 | 150 | ≈ 6.0 |
Formula Used
How to Use This Calculator
- Enter the heat load using the best available duty value.
- Select how you will define temperature rise: temperatures or ΔT.
- Confirm Cp, density, and viscosity for your fluid conditions.
- Add a safety factor if load growth or fouling is expected.
- If checking hydraulics, enter pipe diameter, length, roughness, and K.
- Press Calculate to view results above the form.
- Use the download buttons to export results for documentation.
Article
Heat Rejection and Flow Sizing
Cooling water flow is sized from the required heat rejection and the allowable temperature rise across the load. A higher rise reduces flow and piping cost, but may increase approach temperatures and limit equipment performance. For preliminary sizing, use the duty from equipment datasheets or process calculations, then select a realistic rise, often 4–10 °C for circulating loops.
Understanding Fluid Properties
Specific heat, density, and viscosity shift with temperature and additives such as glycol or corrosion inhibitors. Specific heat directly affects required mass flow, while density converts mass flow to volumetric flow for pump and pipe selection. Viscosity influences Reynolds number and friction, which can materially change head loss in long runs, small diameters, or colder fluids.
Interpreting Velocity, Losses, and Head
After flow is known, pipe velocity provides a quick check for erosion, noise, and air entrainment risk. Head loss combines major friction losses and minor losses from fittings and valves. The calculator estimates friction using a standard correlation and then reports total head and pressure drop. Use these values to compare alternatives such as larger diameter, shorter routing, or fewer fittings.
Applying Safety Factors in Practice
A safety factor can cover future heat-load growth, exchanger fouling, instrument uncertainty, or seasonal changes. Apply safety thoughtfully: oversizing increases pumping energy, while undersizing risks temperature excursions. Many projects begin with 5–15% and refine during commissioning using measured temperatures and verified duty, adjusting balancing valves and setpoints accordingly.
Example Data and Field Review
Example: a 350 kW load with a 6 °C rise and 10% safety gives about 15.34 kg/s and 55.30 m³/h. With a 100 mm inner diameter, velocity is roughly 1.95 m/s, supporting stable transport and reasonable losses. Use the exported CSV/PDF to record assumptions, then confirm with site measurements and pump curves. Document pump curve margin and verify control valve authority onsite.
FAQs
1) What temperature rise should I use for cooling water?
Start with 4–10 °C for recirculating loops. Lower rise increases flow and may reduce equipment temperatures. Higher rise reduces flow but can limit approach temperature and capacity.
2) How does glycol affect the required flow?
Glycol typically lowers specific heat and increases viscosity. Lower specific heat increases required mass flow for the same duty, and higher viscosity increases friction losses and pump power.
3) Why does the calculator ask for pipe roughness?
Roughness changes friction factor in turbulent flow. Older or scaled pipes can behave rougher, increasing head loss. Use a conservative value when pipe condition is uncertain.
4) What do minor losses (K) represent?
K is the combined loss coefficient for fittings, valves, strainers, and entrances. Add typical K values for each item to estimate additional head loss beyond straight-pipe friction.
5) Is the pump power result a final selection value?
No. It is an estimate based on flow, head loss, and efficiency. Final pump selection should use the full system curve, static head, control strategy, and vendor performance curves.
6) What velocity range is typically acceptable?
Many projects target roughly 1–3 m/s in closed-loop water lines, depending on materials and noise limits. Check project specifications and erosion/corrosion guidance for your service.
7) Can I use this for open cooling towers?
Yes for duty-based flow sizing, but verify allowable rise, approach limits, and tower performance. For open systems, also consider fouling, filtration, drift losses, and seasonal wet-bulb conditions.