Introduction of a simple diagram-based method for analyzing evaporative cooling

Direct evaporative cooling can be profitable in hot arid climates, whereas favourable situations are not frequent in temperate zones. First the climate limits to direct operation are set on the psychrometric diagram. Then an alternative process is considered that can provide free cooling via evaporation for a lot of climatic conditions not particularly dry and very common in temperate climate: indirect evaporative cooling. Air is cooled in an adiabatic humidification process, and then in turn the same air is used to reduce – via a heat exchanger – the temperature of a second stream of air, whose moisture content consequently remains unchanged. The cooling effect is particularly strong when the air to be humidified is the ambient air being discharged. The potential of indirect evaporative cooling in analysed in every climatic condition, dividing the Mollier psychrometric diagram in different zones where the use of this free cooling techniques is advisable or not.