A number of our UK customers who have operated cooling systems on their site for many years have seen changes in their process equipment. These changes will vary the demand placed on the cooling systems, and in some cases cooling systems are able to cope with the increased or reduced demand of the new cooling duties, but in other cases water temperatures can reach critical levels in the hot months, can freeze systems in the cold months and can also 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 plant being placed local to the existing systems and so on, can all lead to performance degradation of cooling systems.

Some evaporative cooling towers display obvious signs that they will clearly be under performing.
Some evaporative cooling towers display obvious signs that they will clearly be under performing – DHD Cooling

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 can often not be 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 just always run like that. In some cases the people that were involved in operating and designing the plant are no longer available, there is limited documentation available on the systems, and with the many other important tasks that people are required to do, getting to grips with the cooling systems from anything other than a regulatory and reliability perspective is not a priority.

A typical larger evaporative cooling tower which will benefit from thermal testing to ensure optimum performance.
A typical larger evaporative cooling tower which will benefit from thermal testing to ensure optimum performance – DHD Cooling

How to overcome problems

Thermal testing can be done cost effectively and quickly, providing information on flows and temperatures that can give valuable information on the systems operating parameters, and can easily be done over an extended length of time, if heat loads vary with process demand.

Couple this information with the physical condition of the equipment and surrounding systems and we can very quickly 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 £1,000s in operating costs.

The testing process

To undertake the test we do three things. We access the cooling towers, to identify the condition of all the critical systems, and build up a picture of the complete cooling system. We install measurement devices to log data for as long as necessary to find out the heat load profile and flow rates over the system. And we talk to the operators to find out whether they experience any operational problems and what those problems may be.

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

Audit to improve performance & reduce costs

A fully priced and justified list of potential changes that can be made to a given system to improve thermal performance, lower operating cost, or both.

In the pursuit of these tests we have 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.