www. refrigerationandaircon. co. za RACA Journal I June 2025 11
Associations
THE EFFICIENCY AND EVOLUTION OF COOLING TOWERS
By Eamonn Ryan, technical data from IWC area agent John Burgess
At a technical talk hosted by SAIRAC Cape Town Centre on 11 March, John Burgess, area agent of IWC presented‘ The Magic of Evaporative Cooling’ exploring the principles and applications of cooling towers.
He emphasised their cost-effectiveness, simplicity and efficiency in heat transfer through evaporation. The discussion opened with Burgess’ enthusiastic endorsement of cooling towers as one of the most efficient methods for dissipating heat. He illustrated the principle of evaporative cooling with a relatable analogy— the cooling sensation experienced when stepping out of a warm shower. Just as water evaporates from the skin, removing heat, cooling towers utilise this effect to regulate temperatures in industrial settings.
He traced the evolution of evaporative cooling, comparing early logistics vehicles with modern air-conditioned transport trucks. Historically, truck drivers used rudimentary methods like canvas water bags hanging in front of radiators to cool drinking water. This principle, which dates back to ancient Greek and Roman terracotta storage vessels, remains foundational in cooling technology today.
“ Cooling towers are used in most industries – they dissipate heat from a heat producing process into the atmosphere. Small package cooling towers are used in HVAC, refrigeration, small food and beverage, as well as light manufacturing applications. Larger field-erected cooling towers are used in steel mills, refineries, power industries and mining. It is currently estimated that more than 400 000 package cooling towers are today installed in South Africa,” said Burgess.
A key portion of the presentation covered the differences between open and closed-circuit cooling towers. Open circuit towers, while more affordable and efficient, require frequent water treatment to prevent contamination and bacterial growth, including Legionella. Burgess highlighted water treatment practices and suggested probiotics as a potential solution for maintaining water quality.
HOW COOLING TOWERS WORK Evaporative cooling towers are devices which make use of a natural principle which is as simple as it is effective.“ The forced evaporation of a minimum quantity of water, compared to the main mass, takes place by the dissipation of heat from the mass itself. The mass therefore cools down through the latent heat of evaporation. A well-designed evaporative tower will provide the water with as much air contact as possible in order to optimise the latent heat exchange,” he explained.
The presentation categorised cooling towers into three main types: natural draft, induced draft and forced draft:
• Natural draft towers, commonly seen in power plants, are now less prevalent except in high-energy-demand facilities
• Induced draft towers use a fan at the top
• Forced draft towers push air from the bottom, are more widely utilised across industries such as steel production, petroleum refining and manufacturing
Burgess further examined cooling towers in terms of their versatility, with smaller packaged units ideal for HVAC and refrigeration applications, while larger field-erected towers support heavy industry.“ As technology advances, professionals are encouraged to explore innovative water treatment methods and efficiency improvements for enhanced performance and sustainability,” he noted.
A detailed discussion on cooling tower sumps clarified that they are not designed for storage but function as collectors, facilitating water movement through the system. Their shallow design allows pumps to efficiently redistribute water. In applications requiring greater water capacity, a separate tank may be necessary.
“ The role of evaporative cooling relies on latent heat of evaporation. The effectiveness of this process depends on maximising air-to-water contact, achieved through the fill pack, a critical component that increases surface area exposure and enhances the cooling effect. The fill enhances the surface area of the water, thereby increasing the air-water contact ratio and boosting the cooling effect. Common fill materials include high-efficiency PVC, heat-resistant polypropylene, and durable ABS. While highefficiency fills deliver superior performance, they are more prone to fouling, which makes lower-efficiency splash fills a better choice in contamination-prone environments.”
Burgess discussed the effect of fill packs. Film pack has the best thermal performance per volume of all types of packing, but its use is limited to applications with clean air and water and where maintenance can readily be performed on the cooling tower. Trickle pack and splash tubes offer reduced cooling efficiency. However, these types of fill are an option for moderately dirty water and dusty environmental conditions.
“ Drift eliminators, another essential component, help prevent excessive water loss. Installed at the top of the cooling tower, these honeycomb panel-type devices capture airborne water droplets, significantly reducing drift loss. Proper installation is crucial, as any gaps can compromise efficiency, which is typically 0.02 % of water recirculating flow rate.” Burgess then detailed the intricate crosssection design of drift eliminators, which enhances their ability to minimise water carryover.
The discussion also covered inlet
www. refrigerationandaircon. co. za RACA Journal I June 2025 11