DETERMINATION OF AEROSOL DELIQUESCENCE AND CRYSTALLIZATION RELATIVE HUMIDITY FOR ENERGY SAVING IN FREE-COOLED DATA CENTERS

This study examines an innovative application of the aerosoldeliquescence and crystallization determination, for corrosion prevention and energy-saving strategies in free-cooled data centers. Aerosoldeliquescence and crystallization were investigated by combining standardized aerosolsampling techniques (i.e. EN-14907) with the assessment of the electrical effects of aerosol, while varying relative humidity within a specially designed aerosolexposure chamber. Aerosolsamples collected in the Po Valley (Northern Italy) were analysed; a clearly defined hysteresis cycle (deliquescence and crystallization at 60.5 ± 0.8 and 47.9 ± 0.7 % of RH, respectively) was found. Results were applied to a data centerdesigned for the Italian National Oil and Gas Company, making it possible to identify a critical areafor direct free coolingat this data center. As a result, aerosolhydration was avoided (thus preventing aerosolfrom damaging electrical components) and a large amount of energy saved (using free coolinginstead of air-conditioning); the potential energy saving achieved in this way was 79 % (compared to the energy consumption of a traditional air-conditioning system): 215 GWh of energy was saved, and 78 fewer kt of equivalent CO2 was emitted per year. Moreover, in order to evaluate whether a real-time estimation of the aerosolhydration state within a data centercould be performed, measured deliquescence and crystallization were compared through simulations performed using three different models: two thermodynamic models for deliquescence and a parametric model for crystallization. The results obtained tend to converge in terms of deliquescence, whereas in the case of crystallization, they failed to effectively simulate experimental aerosolbehaviour.