EVAPORATIVE COOLING HAS CLEANED UP ITS ACT, BUT IS IT UNDER-PERFORMING?

Mark DONOGHUE, DIRECTOR AT DHD COOLING, EXPLAINS WHY CHECKING MECHANICAL SYSTEMS IS JUST AS IMPORTANT AS COMPLYING WITH WATER SAFETY IN COOLING TOWERS

As cases of Legionnaires’ disease continue to be reported throughout the world we must acknowledge the due diligence that UK owners, operators, water treatment companies and the HSE have applied in ensuring that evaporative cooling systems meet some of the most stringent industry standards in order to avoid these outbreaks. This is a single minded and worthwhile pursuit, but key industry figures are questioning if this is what’s best for overall plant performance and the environment.

Achieving regulatory compliance of operating cooling towers means that organisations have appointed the right people to correctly treat their systems to prevent the build-up of harmful bacteria. By utilising the skills of a water treatment company, your business is fulfilling its responsibilities to implement processes in order to prevent putting employees or the public at risk.

However, cooling towers have a primary function which also depends on the mechanical condition of the equipment, and the many nuances of the individual components selected to produce the cold water that your processes demand to make them work. One fan is not necessarily the same as another, one type of heat

exchange media is not the same as another, and one distribution system is not the same as another. The bottom line is: one model does not fit all.

Cooling towers are not too complicated; they promote the efficient transfer of heat mostly through evaporation into a stream of air in order to remove that heat from a process to keep it operating within

acceptable temperature limits. While these temperature limits vary from one process to another, a lot of processes can benefit from being cooler, which can lead to increased output and increased profit.

Whilst it is essential that the internal components are the right ones for your cooling systems, industry experts are urging plant owners to consider options that can increase airflow, improve water distribution, increase safety and contribute to increased heat transfer performance.

Plant Owners are reporting that they are benefiting from improved efficiency and performance by applying different operating philosophies and exploring alternative methods of control in addition to looking at performance enhancements through equipment upgrades.

Maximising performance is all about getting the most out of each and every component in a system. Cooling systems play a pivotal role in overall system performance, so simply valeting a system on an ad hoc basis isn’t sufficient to improve or even maintain its performance. Just like a car, the bonnet needs to be opened to see what’s going on inside, and to consider each and every part as critical in achieving the best overall results.

In addition to improved performance, businesses may be surprised to see how much revenue can be saved with a small investment in their cooling towers. Their cooling towers could be preventing them from realising the full potential of their plant.

NEW BROCHURE ON COOLING TOWER MAINTENANCE AND PERFORMANCE ENHANCEMENT

DHD Cooling, one of the leaders in cooling towers solutions, has just published a new brochure covering its range of services.

The new 12-page full colour brochure carries individual sections on preventative and on-going maintenance, cooling solutions, performance enhancement, and a range of complementary systems that can be supplied for cooling towers.

DHD Cooling firmly believes that a cooling system shouldn’t just be a piece of forgotten plant but that it should perform correctly to provide valuable cooling for the processes that are used to keep operations running at optimal performance.

The section in the brochure covering preventative and on-going maintenance illustrates how DHD Cooling has worked successfully with many major multi-national clients to benchmark their cooling plant and provide them with a targeted maintenance plan across all of their sites so as to maximise efficiency and reliability. This gives companies the opportunity to plan their maintenance spend and focus on the systems that can offer the greatest return or need the most essential works.

Where new cooling solutions are required, the brochure explains how DHD works directly with an organisation to provide cooling solutions to suit any plant or requirement. Evaporative, hybrid, dry and adiabatic cooling systems and equipment can be supplied and designed to assist and enhance cooling. Here a full service can be supplied from planning, specification and design to installation, commissioning and handover of new cooling system projects.

An increasingly popular area for plant operators is where DHD Cooling provides performance enhancement. This process involves comparison of current operating performance against calculated potential performance by carrying out detailed condition and thermal assessments of the cooling equipment. This assessment enables easy ROI calculations on any improvement works recommended, and this will consider items such as the fill pack, smart controllers, distribution systems, fan machinery and fan casings.

The final section of the brochure covers additional and complementary systems which can be installed for maximum efficiency from the plant throughout the seasons. The range of purpose designed solutions includes Plume Abatement control systems, airborne particulate filters, wind reduction screens, winter protection screens and bird protection screens. These highly cost-effective rolling or fixed shielding options can help reduce the cost of cleaning and maintenance.

At DHD Cooling, the company bases everything on an analytical approach to problem solving, providing information in a clear concise way so that customers can make decisions that provide them with the greatest benefits to their plant or processes, and most importantly keep their systems operating at peak efficiency for as long as possible. DHD provides products and services that not only prolong the life of cooling equipment but improve efficiency and performance too.

For a copy of the new DHD Cooling brochure call 01905 317370, email info@dhdcooling.co.uk or visit the company’s website at www.dhdcooling.co.uk where the brochure can be downloaded.

IS YOUR EVAPORATIVE COOLING TOWER PERFORMING CORRECTLY?

Gary Dicker, Technical Director at DHD Cooling explains the importance of thermal performance testing of evaporative cooling towers.

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.

Common misconceptions

It is a common misconception that running reduced loads over cooling towers, quote ‘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.

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 £1000s in operating costs.

The testing process

To undertake the test we do 3 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.

For a brochure or more information on evaporative cooling towers call 01905 317370, email info@dhdcooling.co.uk or visit the company’s website at www.dhdcooling.co.uk

BOOST COOLING TOWER PERFORMANCE AND SAVE COSTS

Mark Donoghue, Director at DHD Cooling illustrates how cooling towers can be fine-tuned for improved performance and cost savings

Cooling tower OEMs often assemble their systems from a collection of components manufactured by multiple suppliers selected to meet both technical and commercial challenges to create a bespoke range of cooling towers.

There are a number of key components that are essential for effective heat exchange to occur, and it’s often the case that changes and improvements can be made to optimise your cooling tower performance.

As with most systems it is usually possible to take the Cosworth, Cooper or AMG approach and fine-tune your system to achieve better results.

Tuning basically means creating the best possible conditions from the right pieces of equipment to achieve the greatest performance, and in cooling towers it is no different.

This is not just to say that each individual component of your cooling plant can be tweaked to achieve better results, it also considers how these individual components work as a collection of systems.

In a car the important parts of your engine performance rely on getting the fuel to the right places at the right time, sufficiently aerating that fuel and effectively handling the exit gases from the engine.

This is no different in a cooling tower, where the water entering the system needs to be evenly distributed across an effective heat exchange surface, which needs to come into contact with a sufficient volume of air that is also evenly distributed, for optimal heat exchange to occur.

In our travels around the UK looking at cooling systems some of the easiest successes when tuning a cooling system come from getting the water balanced across multiple units as well as evenly distributed throughout the equipment. Maldistribution of water flow will generally spread the system load unevenly across the available cooling surface. This will mean that the units with the highest water flow will need to reject the largest heat load, which will drive cold water temperatures higher which can be detrimental to your process; the units with the lower water loading may be able to deliver water at a lower temperature, but may also suffer from maldistribution leading to areas of low or no water flow.

Where cooling towers suffer from low or no flow throughout the cooling surface, air flow will be concentrated as these areas offer the lowest resistance to airflow, this results in the wetted areas of the towers being starved of air and thermal performance rapidly decreasing. This also leads to higher potential drift rates as the higher air velocity through the partially wetted channels can drag water out of the tower.

While some towers can handle larger variations in flow, many do not. Your system in many cases will review the outlet temperature and drive the airflow to achieve set point, and if the airflow is not effective, then your fans will run faster (if using VFDs) absorbing more power to try and achieve the cold water set point, with much of this energy wasted due to air/water bypass.

Couple this with a changing demand on your system, where maybe your cooling requirement has reduced, then you have an oversized unit running flat out to try and reject the heat with only a portion of the airflow being effective.

While the interaction of air and water flow is the key to evaporative heat exchange, having the right distribution system, the correct heat exchange media, and all the other systems operating effectively have an effect on cooling tower performance.

This scenario coupled with changing demand and condition, means the right equipment then may not be the right equipment now.

Taking this approach to each and every key component of your cooling tower can yield some great benefits.

Modifying fill choices, optimising fans, improving distribution, preventing air bypass, and improving air flow in general can get your cooling towers singing the right tune, and cost you less to run whilst delivering colder water to your process.

Here at DHD Cooling we offer an initial review on your system to see if there are things that can be done to improve performance and reduce operating cost. For more information call 01905 317370, email info@dhdcooling.co.uk or visit the company’s website at www.dhdcooling.co.uk

 

NEW PARTNERSHIP PROVIDES COMPLETE FILTERING SOLUTION TO HVAC USERS

Four UK companies have recently teamed up to provide a complete filtering solution to HVAC users. RABScreen, Galebreaker, DHD Cooling, and GVS Filter Technology, all specialists in their fields, have come together to offer comprehensive filtering and filter screen systems for HVAC equipment.

RABScreen external filter screens have become a proven method of protecting all air movement equipment saving energy, time and money through their external fitment.

Working with Galebreaker means that HVAC users can now have either fixed or rolling systems, both of which protect equipment from windy conditions.  With experience in the HVAC and cooling tower market, DHD Cooling is also concerned with filtering to remove airborne debris but provides a comprehensive service including looking at thermal performance of cooling systems too.  GVS Filter Technology, as one of the leading manufacturers of filters and components, provides energy efficient filters which work perfectly with RABScreen external filters.

Reducing the amount of airborne debris entering a cooling system can drastically reduce the effects of fouling on performance and help reduce the chemical demands of open evaporative systems by reducing the amount of nutrients in the water. Filtration prevents large quantities of airborne contaminants from blocking coils, and collecting in cooling fills which can quickly build up. Catching this debris in an easy to access external location and simple regular cleaning can keep equipment clean and running more efficiently for longer periods, improving performance and reducing maintenance time. The benefits are enormous as a 1mm layer of dirt insulating coil fins can reduce efficiency by 21% and increase energy use by as much as 30%.

Wind reduction screens have proved to be a great success in the large air cooled condenser and air cooler markets globally using Galebreaker systems.  These help reduce the effects of wind sheer during periods of high winds, improving year round thermal performance and reducing the effects of varying wind loads on mechanical components.

Winter protection screens can also help improve thermal efficiency by reducing the glycol content of closed circuit cooling systems, which can increase thermal capacity or simply by protecting units from the effects of freezing winds.

Further information is available from RABScreen on 01635 248633 by emailing info@rabscreen.com or by visiting the company’s website at www.rabscreen.com