Calculator Inputs
Example Data Table
| Case | Flow (m³/h) | Hot / Cold / WB (°C) | Heat Rejected (kW) | Effectiveness (%) | Makeup Water (m³/h) |
|---|---|---|---|---|---|
| Process Loop A | 300 | 35 / 28 / 25 | 2,558.80 | 70.00 | 4.807 |
| Central Utility B | 450 | 37 / 29 / 24 | 4,173.44 | 61.54 | 8.372 |
| High Duty Plant C | 600 | 40 / 31 / 26 | 6,120.02 | 64.29 | 11.060 |
Formula Used
1) Heat rejected: Q = ṁ × Cp × (Th − Tc) × CF
2) Mass flow: ṁ = (ρ × V̇) / 3600
3) Range: Range = Th − Tc
4) Approach: Approach = Tc − Twb
5) Effectiveness: Effectiveness = Range ÷ (Th − Twb) × 100
6) Evaporation loss: E = (Q × 3600 ÷ hfg) ÷ ρ
7) Blowdown: B = max((E ÷ (COC − 1)) − Drift, 0)
8) Makeup water: M = E + Drift + B
For quick imperial checks, many engineers also use: Heat load (BTU/h) ≈ gpm × 500 × Range (°F) × correction factor.
How to Use This Calculator
- Enter the circulating water flow and pick the correct flow unit.
- Select the temperature unit, then enter hot water, cold water, and ambient wet bulb temperatures.
- Review or adjust specific heat, density, latent heat, cycles of concentration, drift, fan power, and correction factor.
- Press the calculate button to display the results above the form.
- Read the range, approach, effectiveness, heat load, and water balance outputs.
- Use the CSV or PDF buttons to export the result summary for design reviews, maintenance records, or client documentation.
FAQs
1) What does cooling tower load mean?
Cooling tower load is the total heat the tower must reject from circulating water. It depends mainly on water flow, temperature drop, and operating corrections.
2) What is the difference between range and approach?
Range is the hot-water to cold-water temperature difference. Approach is the cold-water temperature above ambient wet bulb. Lower approach usually means stronger tower performance.
3) Why is wet bulb temperature important?
Wet bulb temperature reflects the air’s cooling potential. A tower cannot cool water below the entering air wet bulb under normal evaporative operation.
4) Why include fan power in total tower load?
Fan motors add heat to the overall system and affect operating cost. Including fan power gives a broader picture of the total rejection duty handled by the tower system.
5) What does cycles of concentration affect?
Cycles of concentration influence blowdown and makeup water. Higher cycles reduce blowdown but may increase scaling risk if water treatment and chemistry are not controlled.
6) Can I use this for process cooling and HVAC loops?
Yes. The same thermal principles apply to condenser water, industrial process loops, and other recirculating systems, provided the input data represents actual operating conditions.
7) Why does the calculator estimate evaporation loss?
Evaporation is the main heat-rejection mechanism in a cooling tower. Estimating it helps size makeup water demand and evaluate operating water consumption.
8) When should I change the correction factor?
Use the correction factor when design standards, fouling margins, off-design conditions, or manufacturer guidance require a practical adjustment to the basic heat-load calculation.