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.

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

 

HEWITECH UK EXPANDS INTO PLASTIC MEDIA FOR COOLING TOWERS

Continuing its expansion Hewitech UK has appointed Neil Watson as Projects Manager for its cooling tower business where the company offers a range of specialist plastic media.

Neil Watson brings with him a wealth of experience in the industry, some 24 years in total, most recently with PSSP and GEA.  Neil is NEBOSH qualified for health and safety in the industry and is qualified in Legionnaires awareness.  His expertise is not confined to advice on the best products to use in a cooling tower application but also extends to first hand experience of project installation.

Hewitech has a wide range of products for the cooling tower market including fill packs, drift and mist eliminators which prevent water droplets escaping to stop Legionnaires.  The company is an established supplier in the use of these products in the German market where they have been proven for some fifteen years with organisations such as EDF.

Hewitech UK Managing Director Dave Fozzard commented, “Neil Watson is an expert in his field and we are delighted he has joined us.  At the same time we are introducing local manufacture of the cellular fills at our Cheltenham base so as to offer the UK market very competitively priced products.”

A good proportion of the industry includes cooling towers which are not compliant with the recently updated Code of Practice ACOP L8, having wooden slats and louvres which harbour bacteria so increasing the risk of Legionnaires.   Commenting on this, Hewitech’s Neil Watson said, “Our products allow companies to become compliant to the national legislation and so offer peace of mind to their own workforce and others that they are protected from the risks associated.   We also have software to allow clients to choose the correct fill pack and drift eliminators matching to fan size and airflow”.  Neil continued, “A large part of the cooling tower market is already using plastic media but many of these are old installations coming up for replacement as the PVC material becomes brittle over time.”  Here, Hewitech offers an inspection and maintenance service to advise on the best solution.

With cooling towers evident across many industries from water and energy to the chemical and building industries, Hewitech UK is able to offer high quality advice and products for any of these applications and also recommendations for installation.

Further information on plastic media for cooling towers is available from Hewitech UK on 01242 821678, emailing sales@hewitech.co.uk or by visiting the company’s website at www.hewitech.co.uk

HEWITECH SETS UP UK MANUFACTURING OF PLASTIC MEDIA

stLess than twelve months after setting up the Hewitech UK subsidiary in Cheltenham, the plastic media company has moved to much bigger premises to set up UK manufacturing and cater for its growing business.

The company’s new premises located at Andoversford comprise factory, offices and storage facilities of over 11,000sq.ft. It’s a significant move for Hewitech UK and Director Dave Fozzard is excited about the future prospects, “We have won some excellent contracts this year with some leading names, both for our waste water treatment media and stormwater management media. These new premises are very much part of our expansion plan and we are already gearing up for business under AMP6 from the utilities market”. He continued, “ We have taken on new factory operatives and an operations manager, as well as project specialists for different parts of the country, including someone for the expanding cooling tower business where Hewitech is able to offer specialist plastic media”.

Successful on-target first year sales has seen some big name customers coming to Hewitech UK including Morrisons Utility Services, Barhale and Attack Solutions for its waste water treatment products and the likes of GB Building Solutions, Keir, Carillion, Rydon, and Brookfield Multiplex working with the company on stormwater management products.

The move by Hewitech UK to set up manufacturing makes it the fifth country in the world to manufacture Hewitech products, the other manufacturing centres being in Russia, Poland, Romania, and its central headquarters manufacturing operation in Germany. Based in Ochtrup, Germany, Hewitech is an innovator of recycled polypropylene and PVC media for a variety of applications from cooling towers and cool pads for air treatment to stormwater management and wastewater treatment. It’s an extremely versatile company that makes its own tooling, has 3D design, manufactures the product and completes the cycle with installation on site.

The company’s Variobox product is Hewitech’s volume product for stormwater management and has been very successful due to it being the strongest product in the market. Much experience in this field of modular drainage cells for attenuation has resulted in Dave Fozzard joining the steering committee for this product group on CIRIA (the Construction Industry Research & Information Association).

Dave Fozzard is very confident about the future commenting, “The introduction of local UK manufacturing makes us even more competitive in the UK market and we are looking to capitalise on this through recruitment of further sales people in the next twelve months. We will also be continuing to expand manufacturing and production and the company is currently developing two new products which will be launched early next year”.

Such is the versatility of Hewitech UK that where a project is big enough, say over 5,000m³, the company is able to employ one of its specialist machines on site for welding polypropylene filter media modules, this being highly sophisticated and controlled via GPS.

Hewitech UK’s key markets are the municipal and industrial waste water, schools, construction, retail, offices, defence, housing and also commercial and industrial for cooling towers.

Further information on stormwater, wastewater, and cooling tower plastic media is available from Hewitech UK on 01242 821678, email sales@hewitech.co.uk or by visiting the company website http://www.hewitech.co.uk

HEWITECH INTRODUCES COOLING TOWER PLASTIC MEDIA

Hewitech is offering one of the most comprehensive ranges available of plastic media for use in cooling towers.

The company offers a variety of fill and drift eliminators suitable for all types of natural draught and induced draught cooling towers as used in the energy and water industry, as well as for industrial and HVAC purposes.

For fill packs, the company offers the Hewitech CF19 and the Hewitech NB25 products. The CF19 comprises a module of 2400 x 310mm with a height of either 600mm or 300mm. Made from PP and PVC, the module is cross-flow welded with an opening of 2 x 19mm.   The NB25 is a vertical fill product with standard dimensions of 480 x 500mm and a height of 445mm but modules can be made up to 3600mm long. The vertical channels of this PP and PE material are 50mm.

Both fill products are designed for fast and safe installation due to their high module strength, have a high surface area for maximum cooling performance, and have excellent temperature performance up to 80°C. Where required, the fill can be supplied in loose formed sheets for reduced shipment costs and then assembled on site with welding machines.   These products are ideal for use in new cooling tower installations, and also by maintenance service providers for the cooling tower industry.

Drift eliminators are the last line of defence in any evaporative system and are vitally important in reducing the risk from Legionella. For this application Hewitech offers both blade eliminators and cellular eliminators to satisfy the requirements of most applications.   Made from PP and PVC, Hewitech’s DEP156, 177 and 187 provide opening spaces of 33, 38, and 44mm respectively, with respective blade heights of 156, 177 and 187mm. Hewitech’s cellular eliminator DE125 is Eurovent, Paris certified, and is a module measuring 2400 x 600 x 125mm with an opening of 34mm.   Both blade and cellular eliminators are made to operate at temperatures of up to 80°C.

With a 20-year pedigree, Hewitech works with experienced specialists who have fundamentally developed cooling tower installations in recent years.   Hewitech’s products provide greatly increased water treatment, a significantly longer service life of installations, and high thermal efficiency. The company also offers full technical support to ensure best practice use of its products in cooling tower applications.

Further information on cooling tower products is available from Hewitech UK on 01242 821678 or by emailing sales@hewitech.co.uk or by visiting the company’s website at www.hewitech.co.uk