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Plant Engineering Calculator

Cooling Tower Wet-Bulb Margin Calculator — Approach, Design Margin & Effectiveness

Compare measured cooling-tower leaving-water temperature with current and design wet-bulb conditions to expose approach, weather margin and thermal effectiveness.

Inputs

Results

Range 6.00 °C
Current approach 3.00 °C
Effectiveness 66.7 %
Design-WB approach at same cold water 1.00 °C
Wet-bulb margin 2.00 °C

Formula

approach=Tcold−Twb; effectiveness=(Thot−Tcold)/(Thot−Twb).

Worked example

At 35°C hot, 29°C cold and 26°C wet bulb, range is 6°C, approach 3°C and effectiveness about 66.7%.

Assumptions & limits

  • Use representative entering-air wet-bulb measurements.
  • Performance guarantees require applicable CTI/OEM test procedures, not this screening calculation.

FAQs

What does this Cooling Tower Wet-Bulb Margin Calculator calculate?

Compare measured cooling-tower leaving-water temperature with current and design wet-bulb conditions to expose approach, weather margin and thermal effectiveness.

Is this suitable for final design?

Use it for transparent engineering screening and diagnostics. Verify final design or operating changes against measured site data, OEM curves and applicable standards.

Why are assumptions shown?

Plant calculations depend on operating boundaries. Explicit assumptions make scenarios auditable and prevent false precision.

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Last updated: 17 September 2026