Cooling Tower Evaporation Loss, Cycles of Concentration (CoC) & Blowdown Calculator

Compute cooling tower evaporation, blowdown, and total make-up water (GPM) from ΔT and CoC.

Total Cooling Tower Make-Up Water
12.34 GPM
Evaporation Loss Rate 9.6 GPM
Bleed / Blowdown Rate 2.74 GPM
24-Hour Make-Up Water Volume 17,773.71 gal/day
Inputs
⚡ Scenarios:
GPM
Circulating condenser water flow rate in GPM.
°F
Hot-to-cold water temperature drop ΔT in °F (10 °F = 1 ton per 3 GPM).
CoC
Target Cycles of Concentration (CoC = Blowdown Conductivity ÷ MakeUp Conductivity).
Results & Graph
Total Cooling Tower Make-Up Water
12.34 GPM
Evaporation Loss Rate
9.6 GPM
Bleed / Blowdown Rate
2.74 GPM
24-Hour Make-Up Water Volume
17,773.71 gal/day

Total Cooling Tower Make-Up Water

Graph 1 • Cooling Tower Water Balance • Domain Architecture & Live Telemetry Maps Condenser Water Flow Gpm, Cooling Range Delta T F, Cycles Of Concentration Coc through Cooling Tower Water Balance Formula.
INPUT PARAMETERS • Condenser Water Fl: 1200 GPM • Cooling Range Delt: 10 °F • Cycles Of Concentr: 4.5 CoC ∑ F(x) Cooling Tower Water Balanc DESIGN OUTPUT 12.34 GPM Evaporation Loss Rate: 9.6 GPM Bleed / Blowdown Rate: 2.74 GPM
Graph 2 • Total Cooling Tower Make-Up Water Across Condenser Water Flow Gpm Sweep (40% → 160%) Evaluates Evap_GPM = 0.0008 × Flow_GPM × Range_ΔT_F; Blowdown_GPM = Evap_GPM / ( across 7 operating points (current input highlighted).
0 GPM 10.86 GPM 21.73 GPM 4.94 480GPM 7.41 720GPM 9.87 960GPM 12.34 1.2kGPM 14.81 1.4kGPM 17.28 1.7kGPM 19.75 1.9kGPM
Graph 3 • Joint Sensitivity: Condenser Water Flow Gpm × Cooling Range Delta T F Compares Total Cooling Tower Make-Up Water when Cooling Range Delta T F is shifted +25% (solid) vs. −25% (dashed).
0 GPM 11.03 GPM 22.07 GPM --- Cooling Range Delta T F @ 75% 10.80 -30% 13.11 -15% 15.43 +0% 17.74 +15% 20.06 +30%
Summary: At 1200 GPM and 10°F range (400 tons), evaporation is 9.6 GPM and blowdown at 4.5 CoC is 2.74 GPM, requiring 12.34 GPM total make-up water.
Summary: At 1200 GPM and 10°F range (400 tons), evaporation is 9.6 GPM and blowdown at 4.5 CoC is 2.74 GPM, requiring 12.34 GPM total make-up water.
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Formula & Mathematical Methodology: Cooling Tower Water Balance Formula

EvapGPM = 0.0008 × FlowGPM × Range_ΔTF
BlowdownGPM = EvapGPM / (CoC − 1)
MakeUp = Evap + Blowdown
Evap_GPM = 0.0008 × Flow_GPM × Range_ΔT_F; Blowdown_GPM = Evap_GPM / (CoC − 1); MakeUp = Evap + Blowdown
  • condenserWaterFlowGpm: Condenser Water Flow Gpm (GPM)
  • coolingRangeDeltaTF: Cooling Range Delta T F (°F)
  • cyclesOfConcentrationCoc: Cycles Of Concentration Coc (CoC)

Rounding: Engineering outputs round to 2–3 decimal places; discrete material bag/unit counts round up via ceiling.

Worked Example: Engineering Scenario: Cooling Tower Water Balance

Compute cooling tower evaporation, blowdown, and total make-up water (GPM) from ΔT and CoC.

  1. Enter your system dimensions, electrical/RF ratings, or environmental conditions.
  2. Evaluate the governing equation: Evap_GPM = 0.0008 × Flow_GPM × Range_ΔT_F; Blowdown_GPM = Evap_GPM / (CoC − 1); MakeUp = Evap + Blowdown.
  3. Inspect the primary design output, supporting allowances, and 3 SVG schematics.
Result: Computes Cooling Tower Water Balance via Evap_GPM = 0.0008 × Flow_GPM × Range_ΔT_F; Blowdown_GPM = Evap_GPM / (CoC − 1); MakeUp = Evap + Blowdown.

Frequently Asked Questions

How does the Cooling Tower Evaporation Loss, Cycles of Concentration (CoC) & Blowdown Calculator calculate results?

It evaluates Evap_GPM = 0.0008 × Flow_GPM × Range_ΔT_F; Blowdown_GPM = Evap_GPM / (CoC − 1); MakeUp = Evap + Blowdown directly in your browser and updates three custom SVG visualizations in real time.

Can I use Goal Seek to solve backwards for a required dimension or rating?

Yes. Click "🎯 Goal Seek" in the results toolbar to solve backwards for any numeric input parameter.

Does this engineering calculator work offline?

Yes. All calculations run 100% locally in your browser and work offline via the CalculatorGraph PWA.

Science & Engineering · Thermodynamics & HVAC Systems

Cooling Tower Evaporation Loss, Cycles of Concentration (CoC) & Blowdown Calculator: inputs, method, and how to read the result

Compute cooling tower evaporation, blowdown, and total make-up water (GPM) from ΔT and CoC.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Condenser Water Flow Gpm: Circulating condenser water flow rate in GPM.
  • Cooling Range Delta T F: Hot-to-cold water temperature drop ΔT in °F (10 °F = 1 ton per 3 GPM).
  • Cycles Of Concentration Coc: Target Cycles of Concentration (CoC = Blowdown Conductivity ÷ MakeUp Conductivity).

What the calculation includes

With the default values shown, Total Cooling Tower Make-Up Water is 12.34 GPM. The calculation follows Cooling Tower Water Balance Formula; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Condenser Water Flow Gpm from 1,200 GPM to 1,320 GPM changes Total Cooling Tower Make-Up Water from 12.34 GPM to 13.58 GPM. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses standard NREL, IEEE, ASHRAE, and IRC design equations.
  • Verify final structural, electrical, and mechanical specifications against local building codes.

Scope: Global Engineering & Building Code Standard Check the assumptions and limitations against your situation before relying on the estimate.

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