The requirements for operating evaporative cooling systems are becoming increasingly strict. The requirements of VDI Guideline 2047-2 “Hygienically sound operation of evaporative cooling systems”, in particular, not only impose obligations on the operators of evaporative cooling systems in Germany, rather also assert specific requirements with respect to the design and equipping of the units used. All open and closed cooling towers are affected by the requirements of the guideline.
The Güntner Group ensures that all design measures are taken that can contribute to hygienic operation of evaporative coolers. Therefore, both the JAEGGI HTK Hybrid Dry Cooler (capacity range: 100 – 4.000 kW) and the JAEGGI ADC Adiabatic Dry Cooler (capacity range: 50 – 2,000 kW) have thus now also been certified specially in line with the requirements of VDI 2047, Sheet 2, by the Institute for Air Hygiene (ILH). The design of the units also considers national regulations, however, such as the Approved Code of Practice (ACoP) L8 guidelines applicable in Great Britain and Ireland. These were supplemented by the publication of HSG274 Part 1, which places stricter demands on the risk assessment of these units.
The design measures employed with the JAEGGI HTK Hybrid Dry Coolers are based on the different phases of the event chain for legionella proliferation: entry of legionella, uncontrolled proliferation, spread of infection caused by aerosol contamination.
Requirements include minimising the entry of biological material and germ-promoting substances in general and especially through make-up water, without exceeding the legal limits of the biocide dosage. In order to achieve these aims, the JAEGGI HTK Hybrid Dry Cooler also incorporates precise regulation in addition to constructive measures such as tray covers. The proliferation of legionella bacteria is countered using a variety of measures, from selection of the design material through to ease of maintenance and servicing.
In terms of the central issue of spreading of contaminated aerosols, the Hybrid Dry Cooler offers especially reliable protection, which again was specially certified. Year-round vapour-free operation was verified by an aerosol measurement performed by the DMT in Essen with a so-called blotting paper test.
The JAEGGI ADC Adiabatic Dry Cooler is an advanced dry cooler variant. The simplicity of its dry cooler is particularly convincing. When the outdoor temperature is high, the ambient air can also be pre-cooled to ensure low coolant outlet temperatures.
Adiabatic pre-cooling is achieved via humidification pads in an angular arrangement in front of the dry cooler. Both modes can provide excellent dry cooler performance with a small footprint and low operating costs. The cooling limit, i.e. the theoretically best possible return temperature for the ADC Adiabatic Dry Cooler is tied to the wet bulb temperature of the ambient air at the dry cooler.
The angle arrangement of the HydroPad humidification pads offers several benefits. On one hand, this solution provides an ideal mix of good air supply and distribution; and on the other hand, it ensures hygienic operation as the formation of aerosols is prevented and the wetting water is not recirculated. The units can, of course, also be operated in dry mode; without wetting, the energy is dissipated to the ambient air via convection just as with conventional finned dry coolers. In periods of prolonged dry operation, the lower pad sections can be suspended in front of the upper sections. This reduces the pressure drop for the air supply, thereby reducing the energy consumption of the fans.