Calculator Form
Example Data Table
| Case | Flow m³/h | Range °C | Cycles | Target ppm | Active % | Estimated Product L/day |
|---|---|---|---|---|---|---|
| Small tower | 250 | 5 | 3.5 | 20 | 35 | 3.30 |
| Medium tower | 500 | 6 | 4 | 25 | 40 | 8.44 |
| High load tower | 900 | 8 | 5 | 30 | 45 | 22.81 |
Example values are for demonstration only. Site testing should confirm final settings.
Formula Used
Evaporation: E = 0.0018 × circulating flow × temperature range.
Drift: D = circulating flow × drift percent ÷ 100.
Blowdown: B = E ÷ (cycles − 1) − D.
Makeup: M = E + B + D.
Active kg/day: target ppm × daily makeup liters ÷ 1,000,000.
Product L/day: active kg/day ÷ (density × active fraction) × safety factor.
Pump setting: product L/day × 1000 ÷ operating minutes.
Slug dose: target ppm × system liters ÷ 1,000,000 ÷ (density × active fraction) × safety factor.
How to Use This Calculator
Enter tower circulation flow and temperature range. Add known evaporation if you already measured it.
Enter cycles of concentration and drift percentage. These values estimate blowdown and makeup demand.
Enter system volume for slug dosing. Add the target residual in ppm.
Enter product active strength and density from the product sheet.
Add a safety factor when field conditions vary. Use 1.00 when no extra allowance is needed.
Press Calculate. The result appears above the form and below the header.
Use CSV for spreadsheet logs. Use PDF for simple maintenance reports.
Cooling Tower Dosing Guide
Cooling tower chemical control protects heat transfer surfaces. It also limits scale, corrosion, and biological growth. A dosing plan connects water losses with the target chemical residual. This calculator estimates evaporation, drift, blowdown, makeup, feed rate, slug dose, inventory life, and daily cost.
Why Dosing Changes
Tower demand changes when load, ambient temperature, or cycles change. More heat rejection increases evaporation. Higher evaporation concentrates dissolved minerals. Blowdown removes concentrated water, but it also removes treatment chemical. Drift carries small droplets from the tower. Each loss affects the chemical feed requirement.
Interpreting the Result
The result shows the product volume needed per day. It also converts that number into milliliters per minute. That value helps set a metering pump. The slug dose shows the product needed to raise the full system volume to the selected residual. Operators often use this number after cleaning, draining, or a major refill.
Good Input Practice
Use measured makeup flow when possible. If it is not available, use the calculated makeup from evaporation, blowdown, and drift. Enter product strength as active percent. Enter density from the product sheet. A safety factor can cover losses, pump calibration error, and field variation. Keep the factor reasonable. Excess chemical can waste money and create discharge issues.
Physics Behind the Tool
The evaporation estimate uses circulation rate and temperature range. A warmer range means more heat leaves through water vapor. Cycles of concentration set the bleed requirement. Product dose is based on mass balance. The required active mass equals target ppm multiplied by treated water volume. Product volume then depends on density and active strength.
Using the Calculator in Practice
Start with normal operating data. Review the calculated blowdown and makeup. Compare them with plant readings. Large differences may show meter errors, leaks, or wrong cycles. Export the report for records. Use the PDF for maintenance notes and the CSV for logs. Always confirm final chemical settings with water tests and site limits.
For best control, compare calculated feed with residual tests. Adjust slowly and document every change. Inspect injection points, strainers, and pump tubing. Small maintenance faults can cause large dosing errors, even when the calculation is correct. Retest water after any major load changes.
FAQs
1. What does this calculator estimate?
It estimates evaporation, drift, blowdown, makeup water, active chemical demand, product feed rate, slug dose, cost, and tank life.
2. What is target ppm?
Target ppm is the desired active chemical residual in the tower water or makeup treatment stream. Use your water treatment plan for this value.
3. Why is product strength needed?
Product strength converts active chemical mass into actual product volume. A weaker product needs more liters to deliver the same active dose.
4. What does the safety factor do?
It increases calculated product feed to cover site variation, pump errors, and normal losses. Use it carefully to avoid overdosing.
5. Can I enter measured evaporation?
Yes. Enter a known evaporation value if available. The calculator will use it instead of the estimated evaporation formula.
6. What is slug dose?
Slug dose is the product volume needed to raise the whole system volume to the selected target ppm at one time.
7. Is blowdown always positive?
No. Very high drift or low evaporation may produce a negative value. The calculator limits blowdown to zero for practical reporting.
8. Should field testing confirm this result?
Yes. Use this calculator for planning. Confirm final pump settings with residual tests, conductivity readings, and site discharge limits.