Determination of aerosol deliquescence and crystallization relative humidity for energy saving in free-cooled data centers

Abstract

This study examines an innovative application of the aerosol deliquescence and crystallization determination, for corrosion prevention and energy-saving strategies in free-cooled data centers. Aerosol deliquescence and crystallization were investigated by combining standardized aerosol sampling techniques (i.e. EN-14907) with the assessment of the electrical effects of aerosol, while varying relative humidity within a specially designed aerosol exposure chamber. Aerosol samples 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 center designed for the Italian National Oil and Gas Company, making it possible to identify a critical area for direct free cooling at this data center. As a result, aerosol hydration was avoided (thus preventing aerosol from damaging electrical components) and a large amount of energy saved (using free cooling instead 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 CO 2 was emitted per year. Moreover, in order to evaluate whether a real-time estimation of the aerosol hydration state within a data center could 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 aerosol behaviour.

Experimental Measurements of Particulate Matter Deliquescence and Crystallization Relative Humidity: Application in Heritage Climatology

“…On the other hand, during the phase transitions the two curves differ significantly, thus revealing the hysteresis loop. According to Ferrero et al (2014), observing the conductivity curves registered during the humidification and dehumidification steps, it is possible to identify both a DRH and a CRH region. The DRH region occurs when a strong increase of conductivity led to the wet condition.…”

“…The proposed method is in agreement with Schindelholz et al (2014), who performed similar measures on pure salt samples. A detailed comparison between experimental data obtained with the presented procedure and DRH and CRH values predicted by theoretical models has been reported in Ferrero et al (2014).…”

“…These are the relative humidity (RH) thresholds at which a phase change of the PM water-soluble fraction occurs: from solid to a saturated solution at DRH, and vice versa at CRH (Potukuchi and Wexler, 1995a, b;Martin, 2000;Speer et al, 2003;Seinfeld and Pandis, 2006). In the case of atmospheric particles, or other similar complex systems, CRH is generally lower than DRH, thus generating a hysteresis loop in the hydration levels (Seinfeld and Pandis, 1998 and references therein; Martin, 2000;Martin et al, 2003;Randriamiarisoa et al, 2006;Ferrero et al, 2013aFerrero et al, , 2014.…”

“…However, these studies mainly focused on the problem of salts contaminants derived from capillary rising damp, while in the case of PM, and its possible effects on stone surfaces, the whole hysteresis loop has to be considered (Ferrero et al, 2014).…”

“…DRH and CRH of PM samples collected within this area were experimentally measured in an Aerosol Exposure Chamber (Ferrero et al, , 2014. The experimental DRH and CRH values were used to accurately calculate both TOW and Ncy in Milan during the last decade (2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013).…”