How To Calculate Cooling Tower Efficiency

 Introduction

In industrial cooling, HVAC systems, and manufacturing processes, cooling towers play a vital role in removing heat from circulating water. Their performance directly influences energy efficiency, operational cost, and equipment life. To ensure that a cooling tower—especially one from **Mach Cooling (https://www.machcooling.com/)**—operates reliably, understanding how to calculate cooling tower efficiency is essential.

This article explains the principles, formulas, examples, diagrams, and real-world evaluation methods for calculating cooling tower efficiency, and provides practical suggestions for improvement.

 Principles and Key Concepts of Cooling Tower Efficiency

 1. Key Parameters in Cooling Tower Performance

Before calculating efficiency, two main parameters must be understood:

(1) Range

Range represents the actual temperature drop achieved by the cooling tower:

Range = Hot Water Inlet Temperature – Cold Water Outlet Temperature

Example: from 45°C (inlet) to 30°C (outlet), Range = 15°C.

(2) Approach

Approach represents how close the cooling tower’s cold-water temperature is to the wet-bulb temperature of the incoming air:

Approach = Cold Water Temperature – Wet Bulb Temperature (WBT)

A lower wet-bulb temperature means the cooling tower can potentially cool water more effectively.

 2. Definition of Cooling Tower Efficiency (Effectiveness)

Cooling Tower Efficiency (or “effectiveness”) reflects the ratio of actual cooling to the maximum theoretical cooling possible.

Standard formula:

Efficiency (%) = Range / (Range + Approach) × 100%

Equivalent formula:

Efficiency (%) = (t_i – t_o) / (t_i – t_wb) × 100%

Where:

• t_i = Hot water inlet temperature

• t_o = Cold water outlet temperature

• t_wb = Air wet-bulb temperature

Under normal operating conditions, industrial cooling towers typically achieve 70%–75% efficiency, with high-performance designs capable of even better results.

 How to Measure and Calculate Efficiency (Practical Procedure)

 1. Required On-Site Measurements

 Only three temperatures are needed:

2. Example Calculation

Assume the following measurements:

• t_i = 45°C

• t_o = 30°C

• t_wb = 25°C

Then:

• Range = 45 – 30 = 15°C

• Approach = 30 – 25 = 5°C

• Efficiency = 15 ÷ (15 + 5) × 100% = 75%

This indicates excellent cooling performance close to design specifications.

 Factors Affecting Cooling Tower Efficiency

1. Weather Conditions (Wet-Bulb Temperature)

• Low wet-bulb temperature → better cooling

• High humidity → larger Approach → lower efficiency

• Efficiency typically decreases during hot and humid seasons

2. Tower Design and Structure (Advantages of Mach Cooling)

Cooling towers from Mach Cooling generally enhance efficiency through:

(1) Optimized Airflow Design

Strong and stable fan airflow improves evaporative cooling.

 (2) Advanced Fill (Packing) Structure

Increases contact area between air and water, boosting heat transfer.

(3) Uniform Water Distribution

Prevents short-circuiting and uneven flow, maintaining high effectiveness.

 3. Water Quality & Maintenance

• Scale, algae, or debris will clog fills and reduce heat transfer

• Poor circulating water quality causes uneven water distribution

• Regular cleaning and chemical treatment maintain peak performance

4. Heat Load and Circulation Flow Rate

• Excessive load or insufficient flow causes outlet temperature to rise

• Low water flow reduces contact time → lower efficiency

Cooling Tower Efficiency Monitoring Table

It is recommended to record operation data weekly or monthly to determine maintenance needs.

Practical Tips to Improve Cooling Tower Efficiency

The following measures apply to Mach Cooling towers and all other brands:

 1. Improve Airflow

• Inspect fans periodically

• Remove obstructions around louvers and air intakes

• Ensure proper clearance around the cooling tower

2. Enhance Water Distribution

• Check for clogged spray nozzles

• Ensure uniform distribution across the fill

• Replace aged or damaged fill material

3. Manage Water Quality

• Use chemical dosing for scale & algae control

• Prevent sediment accumulation

• Perform regular blowdown to control TDS

 4. Seasonal Operating Strategies

• Increase airflow and water supply during peak summer loads

• Reduce fan speed during light loads to save energy

• Utilize low wet-bulb temperatures to reduce operational cost

 Conclusion

Calculating cooling tower efficiency is the most direct method to evaluate equipment performance. Understanding Range, Approach, and Efficiency allows operators to accurately assess the operating condition of a cooling tower—especially one from Mach Cooling (https://www.machcooling.com/).

By regularly measuring, recording, and analyzing efficiency data, operators can:

• Detect performance problems early

• Improve operating efficiency

• Reduce maintenance costs

• Extend equipment life