Cooling tower performance test

Tower capability from three readings off the maker's curves — the performance-curve method with fan-power correction.

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How this calculator works

This is the performance-curve method in its simplest form. From the maker's curves, read the cold water at the test wet-bulb and range for 90, 100 and 110 % of design flow. The flow at which the curves give the measured cold water is the predicted flow. The test flow is corrected for fan power (air flow ∝ fan power^1/3). Capability = adjusted flow ÷ predicted flow.

The example follows a published CTI-style test form: 9,730 m³/h measured, 150/142 kW fans → adjusted 9,909 m³/h, predicted 9,800 m³/h, capability about 101 %.

The five steps of the performance-curve method for tower capability.

Effectiveness is not capability. A tower can show 60 % effectiveness and still meet its guarantee. Only a comparison with the maker's curves at the same conditions — or a formal test — tells you whether it performs as designed.

Limits: linear interpolation, fan-power correction for small differences only (about ±10 %), no air-density correction. Use the fan shaft power on both sides and do not apply the correction twice. For official acceptance tests, use the procedure and edition named in your contract (CTI ATC-105) and a qualified test agency.

Learn the method step by step in Cooling Towers Made Simple, Chapters 6 and 7. The first three chapters are free.