Cooling Water Tower Approach Temperature

In cooling towers, approach temperature is a key performance indicator.

Cooling Water Tower Approach Temperature Definition

Approach Temperature = Cooling Tower Cold Water Temperature – Ambient Wet Bulb Temperature

It represents how close the cooling tower can cool the water to the ambient wet bulb temperature (the theoretical lowest temperature achievable by evaporative cooling).

Cooling Water Tower Approach Temperature Typical Values

Standard cooling towers: 2.8 °C – 5.5 °C (5 °F – 10 °F)

High-performance towers: as low as 1.7 °C – 2.2 °C (3 °F – 4 °F)

A smaller approach means better cooling tower efficiency, but it requires **larger size, higher fan power, and more water consumption**.

Cooling Water Tower Approach Temperature Example

Wet bulb temperature = 25 °C

Cooling tower cold water temperature = 30 °C

Approach = 30 – 25 = 5 °C**

Cooling Water Tower Approach Temperature Importance

Lower approach = higher efficiency but more costly design.

Higher approach = lower cost but less cooling capacity.

Often specified during design stage to balance cost and performance.

Here’s the diagram  — it shows how wet bulb, cold water, and hot water temperatures relate, with the approach (cold water vs wet bulb) and range (hot water vs cold water) clearly marked.

Mach cooling tower have 16 years experience of design cooling towers, our towers can well meet the requirement about the approach tempareture.