Closed Loop Cooling Tower System

A closed loop cooling tower system (also called a closed circuit cooling tower) is a heat rejection system where the process fluid (such as water, glycol, or oil) circulates in a sealed loop and is cooled indirectly through a heat exchanger built into the tower. Unlike open towers, the process fluid does not come into direct contact with ambient air.

Closed Loop Cooling Tower System Working Principle

1. Closed Loop Cooling Tower System Primary loop (process fluid):

The process fluid (e.g., chilled water or glycol solution) flows through coils (usually copper or steel) inside the cooling tower.

Since the loop is closed, the fluid stays clean and uncontaminated.

2. Closed Loop Cooling Tower System Secondary loop (spray water + air):

Ambient air is drawn or forced over the coil.

At the same time, water is sprayed over the coil, which evaporates partially, removing heat from the process fluid inside the coil.

The heated spray water then collects in a basin and is recirculated (with some water loss replaced by make-up water).

3. Closed Loop Cooling Tower System Heat rejection:

Heat transfers from the process fluid → coil wall → spray water + air → atmosphere.

Closed Loop Cooling Tower System Advantages

Clean Process Fluid – No exposure to airborne dirt, scale, or biological contaminants.

Reduced Water Treatment – Only the spray water loop requires treatment, not the main process fluid.

Year-Round Operation – Can operate in both hot and cold climates with proper design.

Lower Maintenance – Process equipment (chillers, heat exchangers) protected from fouling.

Closed Loop Cooling Tower System Typical Applications

HVAC chilled water loops

Data centers & server cooling

Industrial process cooling (plastics, chemical, food, pharma)

Closed circuit refrigeration systems (glycol/brine cooling)

Closed Loop Cooling Tower System Key Components

Coil/Heat Exchanger (steel, copper, or stainless steel)

Spray pump & spray nozzles

Fan system (induced draft or forced draft)

Basin for spray water

Make-up water system & bleed-off

Water treatment system (for the spray loop)

Here is a diagram of a closed loop cooling tower system with labeled parts