Estimate cooling-tower evaporation, blowdown, drift and makeup water from circulating flow, cooling range and concentration assumptions.

Hot-water minus cold-water temperature. 10 ยฐF is a typical design range; enter yours if known.

Optional settings
Blank uses 4. Must exceed 1; actual chemistry limits the target.

Blank uses 0.02%. Use the towerโ€™s specified drift rate.

Blank uses 24 hours. Total assumes a constant rate throughout this time.

Related Calculators

Cooling Water Consumption Formula

The calculator estimates evaporation E = 0.00085 ร— circulation ร— cooling range in ยฐF, with consistent flow units. In balance mode, drift D = circulation ร— drift%/100; blowdown B = max(0, E/(cycles โˆ’ 1) โˆ’ D); makeup = E + D + B. If the unclamped B is negative, the requested cycles cannot be achieved and the calculator reports that limitation. The following separate heat-balance formula describes circulating flow, not makeup consumption:

dotV = (H) / (ฯ c ฮ” T)

Variables:

  • Vฬ‡ is the cooling-water volumetric flow rate (mยณ/s)
  • H is the heat load (kW)
  • ฯ is the fluid density (kg/mยณ)
  • c is the specific heat capacity of the fluid (kJ/kgยทยฐC)
  • ฮ”T is the temperature difference between outlet and inlet water (ยฐC)

The background heat balance gives circulation needed to carry a heat load; it is not an input mode above. Recirculated volume is not the same as volume consumed. Multiply makeup rate by operating time to estimate replacement volume. The calculatorโ€™s default time is 24 hours and its evaporation factor is an empirical approximation.

What is Cooling Water Consumption?

Cooling towers recirculate water and consume replacement water through evaporation and liquid losses. Makeup covers evaporation, drift and blowdown; leaks or other losses must be added separately. This differs from a once-through systemโ€™s required circulation rate. A rate becomes a volume only after specifying operating time.

How to Calculate Cooling Water Consumption?

The following steps outline how to calculate the Cooling Water Consumption.

  1. First, enter the circulating water flow and its unit.
  2. Next, enter the hot-to-cold cooling range as a temperature difference in ยฐF or ยฐC.
  3. For makeup balance, review the target cycles of concentration and specified drift percentage in Optional settings.
  4. Select Evaporation only when you do not need drift, blowdown or total makeup.
  5. Select Calculate to estimate the selected water-loss rate. The model uses the disclosed 0.00085 factor, not a detailed weather-dependent heat and mass transfer analysis.
  6. Review operating time for a total volume; the default assumes 24 hours of constant operation.
  7. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Circulating flow = 1,000 US gpm; cooling range = 10ยฐF

Target cycles = 4; drift = 0.02% of circulation

Evaporation = 8.5 US gpm; drift = 0.2 US gpm; blowdown โ‰ˆ 2.6333 US gpm. Makeup โ‰ˆ 11.3333 US gpm. Over 24 hours this is 16,320 US gallons, approximately 61.78 mยณ.