Experimental analysis of novel wetting structures for evaporative cooling.

Small central ventilation units for apartments and single family houses have in most cases the disadvantage of not being equipped with a cooling function. For summer operation at high ambient temperatures a bypass is generally used or the devices are switched off. In winter operation state-of-theart ventilation units work with high efficient heat recovery. To enable summer operation of these ventilation units an extension of functionality by implementing indirect evaporative cooling is under development. Although indirect evaporative cooling is a well-known physical concept, the challenges for its implementation in common heat recovery ventilation units are many-sided, especially when aiming at small size ventilation units. The main focus of the development is to make use of the energy-efficient evaporative cooling effect and provide additional comfort to users of heat recovery ventilation units.
Work on novel compact and easy-to-clean wetting structures is presented. This includes the presentation of newly designed evaporation structures, their surface characteristics and their wetting and water holding capacity. Working with low pressure nozzles is aimed at in order to reduce the energy consumption of the water spray system. In the presentation an overview is given on the approach and on first experimental results with special focus on the parameters influencing the energy efficiency of the ventilation device. In this context, pressure drop and the cooling capacity of the analyzed structures as well as the different wetting modes are presented.