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20 September 2019

Is your cooling tower working correctly?

Gary Dicker, technical director at DHD Cooling, explains the importance of thermal performance testing on evaporative cooling towers.

Gary Dicker, technical director at DHD Cooling.

A number of DHD Cooling's UK customers have operated cooling systems on their site for many years and have seen changes in their process equipment.

These changes will vary the demand placed on the cooling systems. In some cases, cooling systems are able to cope with the increased or reduced demand of the new cooling duties, but in others water temperatures can reach critical levels in the hot months and freeze systems in the cold months. This can lead to higher overall power consumption, despite reduced thermal loads.

With cooling systems, the balance of flows across multiple units can have an effect on overall performance. The addition of access platforms, changes in the internal or external components, additional plants being placed local to the existing systems and so on, can all lead to performance degradation of cooling systems.

Common misconceptions

It is a common misconception that running reduced loads over cooling towers 'should make it easier to achieve colder water temperatures' because the installed capacity is greater than the new cooling load requirements. Unfortunately, this often is not the case.

If a reduction in load results in lower water flow then problems with cooling towers can quickly occur; low water flow over cooling towers will encourage the airflow to channel through dry areas in the towers, reducing the effectiveness of the air leading to high motor powers and lower performance.

It’s not just recent changes in systems that can lead to poor performance, some older plants have always run like that.

How to overcome problems

Thermal testing can be done cost effectively and quickly by providing information on flows and temperatures that can give valuable information on the systems operating parameters.

Combine this information with the physical condition of the equipment and surrounding systems and DHD Cooling can start to identify whether there are changes that can be made to improve thermal performance, adjust operating philosophies, reduce power consumption or improve cold water temperatures.

In some cases the solution only requires altering the way the cooling towers are operated, which can cost absolutely nothing but save in operating costs.

The testing process

To undertake the test DHD Cooling does three things:

  1. Access the cooling towers to identify the condition of all the critical systems and build up a picture of the complete cooling system.
  2. Install measurement devices to log data for as long as necessary to find out the heat load profile and flow rates over the system.
  3. Talk to the operators to find out whether they experience any operational problems and what those problems may be.

After gathering this data, it prepares a detailed report which includes the test data and findings as a basis of further discussion, then the next steps are then determined.

Audit to improve performance and reduce costs

In the pursuit of these tests DHD Cooling has found many problems including incorrect operating philosophies, pipework sizing, low flow issues, broken equipment, old systems interfering with performance, to name but a few. All have led to recommendations that have helped to improve overall performance and or reduce operating costs.

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