Coolers and their problems; capacity, noise, energy consumption, plot space, pollution and cross-winds
In air-cooled coolers, the ambient air is used to cool (part of a) process. That is why coolers are always positioned outside. However, this also makes them more sensitive to factors that affect their capacity, such as cross-winds, pollution by dust and pollen, and air pollution (see photograph no.1). Furthermore, because they are situated outside, the noise of the fans result in coolers often being one of the greatest causes of noise in a process. Besides that, they take up a lot of space and consume a lot of energy. This article proposes a number of solutions for these three problems and even for all three problems at the same time.
CAPACITY PROBLEMS DUE TO POLLUTION
Pollution of the bundles is a well known problem that occurs everywhere where bundles are located close to trees, roads, agricultural land and cities - in other words, practically everywhere on land. And what if your bundle looks like the one in photograph no.1?! You've probably long-since resigned yourself to the fact that your cooling capacity is limited or that it has become a bottleneck in your process, yet you need to find a solution fast because you have very little cooling capacity left! There are solutions, but they're often temporary or they only clean the bundles on the outside (because deep cleaning is difficult), which means that your cooling capacity will still not be optimal and is likely to deteriorate again in the course of time anyway. But suppose there were some as yet unknown solutions that might yield unprecedented benefits?! And suppose you could take them just that little bit further?!
SITUATION
In Gunzenhausen, Germany, there is a rendering factory that is situated in a beautiful location between woods, farms and a B-road intersection - the perfect recipe for polluted bundles, as shown in photograph no.1. This bundle obviously needs cleaning, and the most obvious way to do that would be to use water. However, if you don't choose the right method (high-pressure water or foam on the inside of the machine), there is a good chance that you'll only manage to clean the first row and not the rows behind. Added to that, the fins often get sprayed flat, and this actually reduces heat transfer. Other solutions are also possible, but many of them require the equipment to be switched off as it cannot be cleaned while the fans are still running. This could cost you a lot.
ALTERNATIVE SOLUTION
The alternative is dry cleaning, which is ideal for induced and forced draft cooling bundles. A special (non-toxic, biologically degradable) powder is sprayed on the bundles using low air pressure (5-6 bar), and in effect this blows the dirt off the fins. With this method, you no longer need to walk over the bundles, the fins remain undamaged, all the rows of fins are actually cleaned, and, if you use induced draft, you don’t even have to switch off the fans. In the rendering factory in Gunzenhausen, the bundles were cleaned using this method in
March 2015. The process was managed and supervised by Bronswerk. The result was a very satisfied and enthusiastic customer thanks to the efficient maintenance solution and ultimate result, as shown in photograph no.2. The lower costs and increased effectiveness of the process added up to efficiency in terms of minimal downtime, greater reliability and availability and maximum output of the asset.
ONE STEP FURTHER
After dry cleaning, the cooling capacity returns to the desired level – that is, if you don't take into account cross-winds or wind in general. The maximum wind speed at which an A-frame cooler is tested and which it must withstand in order to officially achieve the required capacity is 3m/s, which is almost no wind at all. Wind plays a major role in an A-frame as the pressure drop over the bundle – and therefore the air speeds – are relatively low. The rendering industry often uses flat condensers in which the speeds are higher and the wind indeed has less effect. But of course there is always some kind of effect. Moreover, many coolers (whether A-frames or not) are situated in areas where, during the summer months, capacity problems are caused by the high temperatures of the ambient air. Or they must comply with the stricter European regulations for noise and energy consumption that will come into effect in Germany, for example, in 2017. A number of our customers are encountering these problems or combinations of these problems. For example, a Waste to Energy in Germany had to reduce its production to 60% because of noise violations. And a refinery in Germany even had to close its plant because it was unable to comply with the permitted noise levels with the equipment it was using at that time! These new regulations affected our customer in Gunzenhausen too, but in terms of energy consumption.
RETROFIT
In all of these cases, the situation involves an existing plant, with existing coolers and usually limited plot space and sometimes also limited capacity and cable diameters, all of which need to be taken into account to implement the desired or required improvements. Despite the considerable challenges, solutions do exist for these situations of this kind. Using high efficiency cooling with the Whizz-Wheel® fan, the existing plant can be retrofitted. The existing fan and part of the housing are replaced by these very efficient Whizz-Wheel® fans and specially designed inlet and control systems. With a retrofit, we leave the existing plant as it is, but the adjustment still brings about the desired or required changes. In the examples given above, the retrofit had the following results. At the Waste to Energy plant, production had been cut to 60% due to noise violations that restricted the system's cooling capacity. After the retrofit, production returned to 100% – and to top that, the company realised energy savings of 56%! At the before mentioned refinery, where the plant had to close temporarily due to noise restrictions, the company not only returned production to 100% but also realised unprecedented energy savings of 53%. Our customer in Gunzenhausen realised energy savings of 50% thanks to the retrofit with a maximum noise pressure of 72 dB(A). Moreover, our experience thus far has been that bundles under which a Whizz-Wheel® is suspended are less sensitive to pollution and also cost less to maintain.
CONCLUSION
If you have capacity problems with your cooling equipment, the logical first step is to check the condition of the bundles. If there is dirt on the bundles (and this is often the cause, even if the dirt is not visible on the outside of the bundle), you can now safely and efficiently clean the bundles using our dry cleaning method. This will be a vast improvement in itself, but if you aim to keep increasing the cooling capacity and want even less dirt in the future, we would be more than happy to pay you a visit to inform you about the retrofit options we can offer you. Even more importantly, given the forthcoming regulations: if you are facing possible noise constraints and restrictions in your energy consumption, we recommend that you check your cooling equipment and contact us.
Contact details:
For more information send an email to femke@bronswerk.com