If you are evaluating an industrial evaporative cooler, you will eventually encounter the term wet-bulb temperature.

It is one of the most useful concepts for understanding what evaporative cooling can realistically achieve.

Dry-Bulb vs. Wet-Bulb Temperature

The temperature shown by an ordinary thermometer is generally called the dry-bulb temperature. Wet-bulb temperature reflects the cooling effect associated with water evaporation.

When water evaporates, it absorbs heat.

The more easily water can evaporate into the surrounding air, the greater the potential evaporative cooling effect.

Why Humidity Matters

Imagine two factories with the same outdoor temperature.

Factory A is in relatively dry weather.

Factory B is in very humid weather.

Even though the dry-bulb temperatures are the same, evaporative cooling may perform differently because the air in Factory B is already carrying more moisture.

There is less remaining capacity for additional evaporation.

This is why evaporative cooling generally has greater potential in hot, dry conditions.

The Wet-Bulb Depression

The difference between dry-bulb and wet-bulb temperature is often referred to as the wet-bulb depression.

A larger difference generally indicates greater potential for evaporative cooling.

A smaller difference indicates that the air is already relatively humid and the achievable cooling effect is more limited.

Why This Matters for Industrial Cooler Selection

This is one reason why a cooler should not be selected based only on the outdoor temperature.

A proper assessment should consider:

• temperature

• relative humidity

• airflow

• building volume

• heat sources

• required air distribution

•ventilation strategy

Wet-Bulb Temperature Does Not Tell the Whole Story

Even if outdoor conditions are favorable, the actual result depends on the equipment and installation.

Cooling-pad performance, airflow through the pad, water distribution and air leakage all influence realworld performance.

A theoretical wet-bulb temperature is therefore not the same thing as the actual supply-air temperature a particular cooler will deliver.

Final Takeaway

Wet-bulb temperature helps answer an important question:

How much evaporative cooling potential exists in the surrounding air?Understanding it helps engineers and buyers set realistic expectations and choose cooling equipment based on actual environmental conditions rather than simply choosing the largest available unit.