Cooling tower sizing depends on getting several interrelated numbers right at once: range and approach temperature define the thermal duty, the L/G ratio and tower characteristic define how much fill and airflow are needed, and the water balance determines makeup water demand. The Cooling Tower Design Excel Sheet from GrowMechanical calculates all of these together in one workbook, replacing scattered psychrometric charts and water-balance spreadsheets with a single auditable calculation.
It is built for mechanical, process, and HVAC engineers sizing new cooling towers, evaluating existing tower performance, or estimating water consumption for a cooling water system.
What This Cooling Tower Sheet Calculates
- Range (hot water temperature minus cold water temperature)
- Approach temperature (cold water temperature minus design wet-bulb temperature)
- Design wet-bulb temperature input and psychrometric reference
- L/G ratio (liquid-to-gas mass flow ratio)
- Tower characteristic (KaV/L) for fill sizing reference
- Evaporation loss, drift loss, and blowdown
- Total makeup water demand and cycles of concentration
Why These Calculations Matter Together
Range and Approach Define Tower Duty
Range is fixed by your process heat load and water flow rate, while approach temperature (the gap between cold water and ambient wet-bulb) is a key driver of tower size — a tighter approach requires a larger, more expensive tower for the same heat rejection duty.
L/G Ratio and Tower Characteristic Size the Fill
The L/G ratio and tower characteristic (KaV/L) together determine how much fill media and airflow are required to achieve your target range and approach, which is the core sizing relationship for mechanical-draft cooling towers.
Water Balance Drives Operating Cost
Evaporation loss is set by the heat rejected, but drift loss, blowdown, and cycles of concentration determine total makeup water demand — a significant operating cost and a common design check requested by water-stressed facilities.
Key Features
- Fully editable Excel workbook with visible, auditable formulas
- Range, approach, and L/G ratio calculation from your process data
- Tower characteristic (KaV/L) estimate for fill sizing reference
- Complete water balance: evaporation, drift, blowdown, and makeup
- Cycles of concentration calculation for water treatment planning
- Works offline in Microsoft Excel — no macros or subscriptions required
Technical Specifications & Calculation Basis
| Parameter |
Calculation Basis |
| Range |
Hot water temperature minus cold water temperature |
| Approach |
Cold water temperature minus design wet-bulb temperature |
| Evaporation loss |
Heat rejected divided by latent heat of vaporization, per standard cooling tower practice |
| Drift loss |
Percentage of circulating water flow, per typical mechanical-draft tower allowance |
| Cycles of concentration |
Ratio of dissolved solids in blowdown versus makeup water |
| File format |
Microsoft Excel (.xlsx), fully editable formulas |
Typical Applications
- Process cooling water system design
- HVAC chiller condenser water cooling towers
- Power plant circulating water cooling towers
- Cooling tower performance verification and troubleshooting
- Water balance and makeup water demand estimation for water-stressed sites
Who Should Use This Calculator
Mechanical, process, and HVAC engineers sizing new cooling towers, evaluating existing tower performance against design conditions, or estimating water consumption and treatment requirements for a cooling water system.
What You’ll Receive
- One fully editable Excel workbook covering thermal duty and water balance
- Instant digital download after purchase
- Lifetime access to your downloaded file
- Free updates if the calculation sheet is revised
Compatibility
Compatible with Microsoft Excel 2010 and later, and Excel for Microsoft 365, on Windows and Mac.
How to Use This Cooling Tower Design Sheet
- Enter your process heat load and circulating water flow rate
- Input the design wet-bulb temperature for your site location
- Review the calculated range, approach, and L/G ratio
- Check evaporation, drift, and blowdown results in the water balance section
- Export the summary sheet for your design documentation or water treatment planning
For the pump circulating water to and from the tower, see our centrifugal pump design and selection tool. If the tower serves a shell-and-tube or plate condenser, see our shell and tube heat exchanger Excel sheet or plate heat exchanger design Excel sheet. For makeup water filtration, our filter sizing calculation spreadsheets are directly relevant. For a full utility system package, see the Engineering Design & Calculation Master Excel Bundle, or browse our full library of process engineering Excel calculators.
Frequently Asked Questions
What is the difference between range and approach?
Range is the temperature drop across the tower (hot water in minus cold water out), fixed by your heat load and flow rate. Approach is the gap between the cold water temperature and the ambient wet-bulb temperature, and is the main driver of tower size and cost.
Why does design wet-bulb temperature matter so much?
Cooling towers reject heat through evaporative cooling, so the achievable cold water temperature is limited by ambient wet-bulb temperature, not dry-bulb temperature. Using the correct site design wet-bulb value is essential for accurate sizing.
Does this spreadsheet calculate makeup water demand?
Yes. It calculates evaporation loss, drift loss, and blowdown, then sums them into total makeup water demand, along with cycles of concentration for water treatment planning.
Can I use this to check an existing cooling tower’s performance?
Yes. Enter your tower’s actual operating data and compare the calculated range, approach, and L/G ratio against the original design values to identify performance degradation.
How is the file delivered?
As an instant digital download immediately after purchase, so you can begin your cooling tower design or evaluation the same day.
Get Your Cooling Tower Design Sheet Today
Stop piecing together psychrometric charts and water-balance spreadsheets separately. Download the Cooling Tower Design Excel Sheet and get thermal duty and water balance results in one auditable workbook.
