Advanced Calculator
Example Data Table
| Flow Rate | Hot Temp | Cold Temp | Range | Cycles | Evaporation | Makeup Water |
|---|---|---|---|---|---|---|
| 1000 gpm | 95°F | 85°F | 10°F | 4 | 10.00 gpm | 13.35 gpm approx. |
| 750 gpm | 92°F | 82°F | 10°F | 5 | 7.50 gpm | 9.39 gpm approx. |
| 1500 gpm | 100°F | 85°F | 15°F | 4 | 22.50 gpm | 30.04 gpm approx. |
Formula Used
Evaporation Rate:
Evaporation gpm = Circulating Flow gpm × Cooling Range °F ÷ 1000
Blowdown Rate:
Blowdown gpm = Evaporation gpm ÷ (Cycles of Concentration − 1)
Drift Loss:
Drift gpm = Circulating Flow gpm × Drift Percentage ÷ 100
Windage Loss:
Windage gpm = Circulating Flow gpm × Windage Percentage ÷ 100
Makeup Water:
Makeup gpm = Evaporation + Blowdown + Drift + Windage
Heat Load:
Heat Load BTU/hr = Flow gpm × 500 × Cooling Range °F
How to Use This Calculator
Enter the circulating water flow first. Choose the correct unit. Add the hot water temperature and cold water temperature. The difference becomes the cooling range.
Next, enter cycles of concentration. This value controls blowdown. Higher cycles usually reduce blowdown, but they may increase scaling risk.
Add drift and windage percentages if known. Use small default values when exact plant data is unavailable.
Enter operating hours, days, and water cost. Press calculate. The result appears above the form and below the page header.
Cooling Tower Evaporation Rate Guide
Why Evaporation Matters
A cooling tower removes heat by evaporating a small part of the circulating water. This process is simple, but the water loss can be large. The evaporation rate helps engineers estimate makeup water demand. It also supports chemical dosing and operating cost planning.
Understanding Cooling Range
Cooling range is the difference between hot return water and cold supply water. A larger range means more heat is removed. More removed heat also means more evaporation. This is why temperature input is very important. A wrong temperature reading can change the final water balance.
Cycles of Concentration
Cycles of concentration describe how much dissolved solids build up in the tower water. As water evaporates, minerals remain behind. Blowdown removes part of this concentrated water. Higher cycles reduce blowdown volume. However, very high cycles may increase scaling, corrosion, and fouling problems.
Makeup Water Demand
Makeup water replaces all tower losses. These losses include evaporation, blowdown, drift, and windage. Evaporation is often the largest part. Blowdown may also be significant in hard water areas. Drift and windage are usually smaller, but they should not be ignored.
Practical Plant Use
This calculator is useful for plant operators, facility engineers, and energy managers. It can compare different operating conditions. It can also estimate monthly water use. The cost field converts makeup volume into a budget figure. Use measured site data whenever possible. Check tower performance during seasonal changes. Warmer weather often raises cooling load and water demand.
Engineering Notes
The evaporation formula used here is a common field estimate. It works well for quick planning. It does not replace a full psychrometric tower analysis. For detailed design, include wet bulb temperature, approach, air flow, fill type, and tower efficiency. Still, this tool gives a clear first estimate for daily reports and water planning.
FAQs
1. What is cooling tower evaporation rate?
It is the amount of water lost as vapor while the tower removes heat from circulating water. It is usually reported in gallons per minute.
2. Why does higher cooling range increase evaporation?
A higher cooling range means more heat is removed from water. More heat rejection requires more water evaporation inside the tower.
3. What are cycles of concentration?
Cycles show how concentrated dissolved solids become compared with makeup water. Higher cycles reduce blowdown but may increase scaling risk.
4. What is blowdown in a cooling tower?
Blowdown is water intentionally discharged to control dissolved solids. It helps limit scale, corrosion, and fouling inside tower systems.
5. Does drift affect water loss?
Yes. Drift is small water droplets carried out with air. Modern drift eliminators reduce this loss, but it still matters in reports.
6. Is this calculator suitable for design work?
It is best for estimates, planning, and operating checks. Detailed design should also consider wet bulb temperature and tower manufacturer data.
7. What unit should I use for flow rate?
You can use gpm, cubic meters per hour, or liters per minute. The calculator converts values internally for the main formula.
8. How can I reduce makeup water?
Improve cycles safely, reduce drift, repair leaks, optimize treatment, and monitor blowdown control. Always protect equipment from scaling and corrosion.