Corrosion resistent plastic fans integrated in Air Handling Units


COLASIT has built a corrosion-resistant roof top ventilation unit with plastic fans for sterilisation exhaust air in UKD plant for ENGIE in Dresden.

End of 2022, Colasit is allowed to build an exhaust air unit in plastic with corrosion-resistant plastic fans for ENGIE Deutschland GmbH in Dresden installed on the roof of the renovated building 58 of the University Hospital Dresden (UKD).

The University Hospital Carl Gustav Carus Dresden combines 26 clinics and polyclinics, 6 institutes and 17 interdisciplinary centres. As early as 1748, the Collegium medico chirurgicum was founded to teach basic medical skills to military surgeons and wound doctors. Today it is a public institution of the Free State of Saxony and one of the largest hospitals and, according to Focus 2023, the best hospital in Saxony. As part of the renovation of the first construction section of building 58, the planning office Waidhas GmbH from Chemnitz and the plant constructor ENGIE were commissioned via a public procurement procedure.

The fans were pre-selected in size 315 for the intended volume flows with our fan selection programme ColaVent to match the existing operating condition of the system characteristic curve. Neither too large (increased space requirements and costs as well as vibrations due to pumps) nor too small (increased resistances and noise due to excessive flow velocities) fans have to be selected. At the same time, a good overall efficiency is necessary for upstream components defined appropriately for the design point. I.e. the heat exchanger should work in its best range if possible and should not be unnecessarily oversized, but also not too tightly sized. To minimise losses, Filters, silencers and dampers were also designed under these important aspects in order.

Exhaust air systems in hospitals, especially in operating theatres and sterilisation areas, are exposed to heavy loads due to the use of cleaning agents and disinfectants and the associated high humidity. For blank metallic surfaces, these chemicals are corrosive and harmful in highly concentrations. For this reason, all components that come into contact with the exhaust air flow, are made of thermoplastic or at least protected with plastic surfaces . The condensate drains are located at the lowest points of the plastic casing. Inspection openings in the housing and filter monitoring enable the operator to detect contamination in good time and to start maintenance work on schedule.

For safety reasons, a completely separate KVS system is used for contaminated exhaust air to transfer the heat to the supply air. For volume flows starting at approx. 3,000 m³/h, a short payback time results for these additional investment costs at the current energy costs. The small Air Handling Unit (AHU) installed for corrosive exhaust air of 5,970 m3/h results in a transferred power of 40 kW at an exhaust air temperature of 22°C (outside air -14°C in the "deepest" winter) and still of 24 kW in the transition period (outside air +5°C).

The fans can be used flexibly in terms of speed and adapted to system requirements, due to the frequency converter's variable control. Energy can therefore also be saved during operation. The fans are in accordance with the EU Ecodesign Directive 2009/125/EC, which was adopted by EU Regulation 327/2011. The energy requirement is so low that they can be subsidised as high-efficiency fans including frequency converter and heat exchanger via BAFA. The Federal Promotion of Efficient Buildings (BEG) accepts the thermal work recovered in heat recovery systems as regenerative energy in verification procedures.

Projektbild UKD 2022 ©

Air handling unit with plastic fans