Counterflow heat exchanger with „adiabatic“ evaporative cooling

Further development of Adconair heat recovery

Menerga GmbH now also offers a version of the Adconair central air conditioning units complete with indirect "adiabatic" evaporative cooling. The ventilation and air conditioning equipment manufacturer announced this on the occasion of the ISH 2013. Here, the natural cooling technique of evaporative cooling is integrated directly into the counterflow plate heat exchanger of the unit series and the entire process is executed with maximum efficiency thanks to the extremely large evaporation surface in the recuperator. In connection with the high heat recovery rate of the recuperator of over 90 %, it is possible to reduce the temperature of the outside air by more than 14 K. At air flow volumes of up to 30,000 m³/h, the systems reach an "adiabatic" cooling capacity of up to 100 kW, therefore significantly reducing the load peaks in the event of cooling demand for the air conditioning of the building. According to the manufacturer's information, it is possible to reduce the mechanical cooling capacity through evaporative cooling by approximately a third, whereby the investment costs and the required electrical connection capacity also drop accordingly. In order to cover the remaining cooling demand, the central air conditioning units can be equipped with an additional compressor refrigeration system.

"During the introduction of the Adconair systems, we initially concentrated entirely upon the outstanding innovation of the ultra-efficient counterflow plate heat exchanger for large air flow rates in compact units. In view of the extremely positive responses and the great demand, we are now taking the logical next step and are also equipping our unique heat recovery system with the "adiabatic" evaporative cooling," explains Executive Director, Dr. Christian Hennerkes. "Ultimately, we performed pioneering work in this sector over 20 years ago and, with our Adsolair unit series, we continue to be a performance leader in the field of "adiabatic" cooling systems today. We now present a new unit generation, the development of which involves 20 years of experience in the field of "adiabatic" evaporative cooling systems and which, in view of the diverse advantages, will replace our tried-and-trusted Adsolair system in the medium term."

In order to achieve an overall high efficiency of the process, the return air is humidified directly in the plate heat exchanger during the indirect "adiabatic" evaporative cooling from the Mülheim manufacturer. During this process, water is sprayed into the system to such an extent that the humidification is still performed within the heat recovery system and the warm outside air is immediately cooled in a sensitive manner. In doing so, the necessary electrical power consumption is limited to the circulation pump of the "adiabatic" cooling system; it was reduced even further in the new central air conditioning units. The heat exchanger itself is manufactured from plastic; the maximum service life of the heat recovery system is ensured thanks to the use of a corrosion-free material. A hygienically safe air supply can be guaranteed due to the absolute airtight separation of both air flows.

A significant advantage of the direct integration of the "adiabatic" cooling system into the counterflow plate heat exchanger is the fact that no additional pressure losses occur in winter and transitional periods as a result of the humidification system – for example, through the honeycomb-type humidifier or droplet eliminator. With conventional solutions, the air flow is continually restricted by the upstream humidifier, thus increasing the electrical power consumption of the return air fan throughout the year – even though it only serves to provide cooling during a few months in areas such as Central Europe. As a result, the central air conditioning units by the Mülheim-based company achieve an energy efficiency level of above 75 % according to EN 13053 throughout the year at extremely low pressure losses of only 150 Pa. Here, the extremely strict requirements placed upon heat recovery class H1 are greatly exceeded across the entire working range.

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