Multidisciplinary Research Journal

Unexpected Thermal Properties of Water Diffusion in Very Porous Materials

Signanini P1, De Santis A1,2,*, Di Fazio M3, Greco P1, Merla A1,4, Monosi S5, Piazza F6, Rainone ML1, Fenzi F7, Torrese P8

1Centro di Ricerche e Studi per le Geotecnologie, Università “G. d’Annunzio” di Chieti-Pescara, Campus Universitario, Chieti, Italy
2Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma 2, Roma, Italy
3Dipartimento di Ingegneria e Geologia, Università “G. d’Annunzio” di Chieti-Pescara, Campus Universitario, Chieti, Italy
4Dipartimento di Neuroscienze e Imaging, Università “G. d’Annunzio” di Chieti-Pescara, Campus Universitario, Chieti, Italy
5Dipartimento di Scienze e Ingegneria della Materia, dell’Ambiente ed Urbanistica, Università Politecnica delle Marche, Ancona, Italy
6Dipartimento di Ingegneria dell’Informazione, Università Politecnica delle Marche, Ancona, Italy
7Istituto di Chimica Inorganica e delle Superfici, Consiglio Nazionale delle Ricerche, Padova, Italy
8Dipartimento di Scienze della Terra e dell’Ambiente, Università di Pavia, Pavia, Italy

*Correspondence E-mail: angelo.desantis@ingv.it

Key Words: Water diffusion; Temperature; Capillarity; Porous material; Phase transition

Received March 22nd, 2014; Revised Oct 13th, 2014; Accepted Dec 1st, 2014; Published Dec 11th, 2014; Available online Oct 20th, 2015

doi: 10.14294/WATER.2014.6

Abstract

Significant and persistent decreases in temperature have been observed in very porous materials when they are partially immersed in water at room temperature. As the sample sizes were much smaller than the maximum height of the typical capillary rise, this represents a far-from-equilibrium system. We attribute this thermal decrease to two concurrent actions: (i) the highly porous property of the material used; and (ii) a transition-phase-like process of the water. Thus, the water not only cools down the material surface through evaporation at the sample–air interface, but it also expands within the material, causing a further internal decrease in temperature that cannot be explained solely through evaporation. This latter process is persistent enough to maintain the decrease in temperature over time. This unexpected characteristic of water and its persistence when diffusing inside an extremely porous medium are the most original results of this study. Our results seem in agreement with the recent model on the fourth phase of water by Pollack.


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