Efficiency of Induced Draft Cooling Tower

The efficiency of an induced draft cooling tower measures how effectively the tower cools hot water by evaporative heat transfer. It is typically expressed as a percentage based on how close the cooled water temperature gets to the wet-bulb temperature (WBT) of the ambient air.

Efficiency of Induced Draft Cooling Tower Formula for Efficiency

Efficiency% = （T_hot - T_cold）/（T_hot - T_wb） _* 100

Where:

T_hot = Hot water inlet temperature (°C or °F)

T_cold = Cold water outlet temperature (°C or °F)

T_wb = Ambient wet-bulb temperature (°C or °F)

Efficiency of Induced Draft Cooling Tower Example Calculation

If:

Hot water inlet = 40°C

Cold water outlet = 30°C

Wet-bulb temperature = 27°C

Then:

Efficiency = （40-30）/（40 - 27）* 100 ≈76.9%

Cooling tower efficiency = ~77%

Typical Efficiency of Induced Draft Cooling TowerRange

Induced draft towers:70–80% (sometimes up to 85% with optimal conditions)

Forced draft towers: slightly lower (~65–75%) due to less uniform air flow.

Factors Affecting Efficiency of Induced Draft Cooling Tower

1. Ambient Wet-Bulb Temperature: Lower WBT improves cooling potential.

2. Water Flow Rate: Proper flow ensures good contact with air.

3. Air Flow Rate (Fan Performance): Induced draft fans pull uniform air through the fill, improving heat transfer.

4. Fill Media Design: High-efficiency film fill increases surface contact.

5. Drift and Distribution: Even water distribution avoids dry spots.

6. Maintenance: Clean fill, nozzles, and fan blades maintain design efficiency.

7. Approach Temperature = T_cold- T_wb → smaller approach = higher efficiency.

Key Performance Terms

Range: T_hot - T_cold → larger range = more heat removed

Approach:T_cold - T_wb → smaller approach = better efficiency

Here is a diagram showing the temperature relationships and efficiency formula visually for an induced draft cooling tower