In the long term, why are closed-circuit cooling towers more economical than open-circuit cooling towers?

Both closed-circuit and open-circuit cooling towers serve as industrial heat dissipation equipment. However, due to differences in materials and manufacturing processes, the initial procurement cost of closed-circuit cooling towers is higher than that of open-circuit counterparts.

But why is it claimed that, over the long haul, enterprises find closed-circuit cooling towers more economical than open-circuit ones?

 

1. Water-saving advantages

Circulating water within closed-circuit cooling towers is completely isolated from the atmosphere, eliminating evaporation and consumption. These systems automatically switch operating modes according to operational conditions. During autumn and winter, simply activating the air-cooling mode ensures effective cooling while conserving water resources.

Water loss in closed-circuit cooling towers is 0.01%, whereas open-circuit towers experience 2% loss. Taking a 100-tonne cooling tower as an example, an open-circuit tower wastes 1.9 tonnes more water per hour than a closed-circuit counterpart. This not only squanders water resources but also increases operational expenditure. If the machinery operates for 10 hours daily, consuming an additional 1.9 tonnes per hour equates to 19 tonnes over 10 hours. With industrial water currently costing approximately £4 per tonne, this equates to an extra £76 daily in water charges. This calculation is based on a 100-tonne tower; for 500-tonne or 800-tonne units, the daily additional cost rises to around £300. Monthly, this amounts to roughly £10,000, translating to an extra £120,000 annually.

Consequently, employing closed-loop cooling towers yields annual water cost savings of approximately £120,000.

 

2. Energy Efficiency

Open cooling towers feature only air cooling systems and fan systems, whereas closed cooling towers incorporate not only air cooling and fan systems but also spray systems. At first glance, open cooling towers appear more energy-efficient than closed ones.
However, closed-loop cooling towers prioritise system-level energy efficiency. What does this entail? Statistics indicate that for every 1mm increase in equipment scale, system energy consumption rises by 30%. Within closed-loop systems, circulating water remains entirely isolated from air, preventing scaling and blockages while ensuring stable performance. Conversely, open-loop systems expose circulating water directly to air, making scaling and blockages commonplace.
Consequently, closed-loop cooling towers generally achieve superior energy efficiency compared to open-loop counterparts.

 

3. Land Conservation

Open cooling towers require excavated water basins for operation, whereas closed systems eliminate this need and occupy minimal footprint, making them ideal for enterprises with stringent workshop layout requirements.

 

4. Post-Installation Maintenance Costs

As the internal circulation within closed cooling towers remains isolated from atmospheric contact, the entire system is less prone to scaling and blockages, resulting in lower failure rates and reduced need for frequent shutdowns for maintenance.

Conversely, the circulating water in open cooling towers directly contacts the atmosphere, making them prone to scaling and blockages with a higher failure rate. Frequent shutdowns for maintenance are required, increasing both maintenance costs and production losses due to downtime.

 

5. Winter Operating Conditions

Closed cooling towers can operate normally in winter after replacing the antifreeze solution, without disrupting production schedules. Open cooling towers, however, require temporary shutdowns to prevent freezing.