Modelling and Experimental Characterization of Unsaturated Flow in Absorbent and Swelling Porous Media: Material Charact
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Modelling and Experimental Characterization of Unsaturated Flow in Absorbent and Swelling Porous Media: Material Characterization Tommaso Santagata1 · Roberto Solimene2 · Gilberto Aprea3 · Piero Salatino1 Received: 27 February 2020 / Accepted: 12 August 2020 © Springer Nature B.V. 2020
Abstract A comprehensive experimental protocol is presented for the characterization of physicochemical and morphological properties of absorbent hygiene products (AHPs), composite materials, mainly made of super absorbent polymer (SAP) granules blended with cellulose fibres (fluff). The protocol is based on a combination of experimental methods for the characterization of the material properties varying SAP/fluff ratio (SFR): absorption rate, porosity, hydraulic conductivity, retention model and swelling. Major findings were that: (1) liquid absorption rate by the SAP particles was nonlinear; (2) the hydraulic conductivity could be expressed as a function of the porosity of the composite medium for any sample and liquid uptake; and (3) the retention model showed moderate variability with SFR, in the range investigated. Experimental results have been used to determine the constitutive equations for the multiphase flow model developed in the literature (Diersch et al. in Theory Transp Porous Media 83:437–464, 2010. https://doi.org/10.1007/s11242-009-9454-6) for the prediction of the performance of AHPs during cycles of imbibition and drainage (Chem Eng Sci 224:115765, 2020. https://doi.org/10.1016/j.ces.2020.115765). Keywords Swelling media porosity · Hydraulic conductivity · Retention model · Super absorbent polymer · Diaper core flow modelling List of Symbols Roman Letters asl Saturation-dependent fraction of the solid–liquid interface area, 1 C̄ Bulk concentration, M L−3 c Lucas–Washburn parameter, L T−0.5
* Roberto Solimene [email protected] 1
Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università degli Studi di Napoli Federico II, P.le Tecchio, Naples, Italy
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Istituto di Ricerche sulla Combustione, Consiglio Nazionale delle Ricerche, P.le Tecchio, Naples, Italy
3
Fater S.p.A., Via Alessandro Volta, 10, Pescara, Italy
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d Diameter of the sample, L dp Diameter of the SAP particles, L ds Volumetric solid strain, 1 e Gravitational unit vector, L g Acceleration due to gravity, L T−2 h Thickness of the sample, L J s Volume dilatation function, 1 L Wicking length, L k Coefficient of power-law absorption rate, 1 K Hydraulic conductivity, L T−1 m Mass, M ms2 SAP liquid uptake, 1 n Van Genuchten curve fitting parameter, 1 p Pressure, M L−1 T−2 q Specific flux s Saturation, 1 t Time, T W Weight of the sample, M Z Cartesian coordinate, L Greek Letters 𝛼 van Genuchten curve fitting parameter, L−1 𝛽 Kozeny–Carman equation shape parameter, 1 𝛤 Reference boundary, L Δt Time interval, T 𝛿 Exponential fitting parameter, 1 ΔW Weight loss, M Δ𝜓 l Pressure head loss, L 𝜀 Porosity, 1 𝜌 Density, M L−3 𝜋 ≈ 3.14 Ma
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