CHEMICAL ENGINEERING TRANSACTIONS VOL. 39, 2014 A publication of The Italian Association of Chemical Engineering www.aidic.it/cet Guest Editors: Petar Sabev Varbanov, Jiří Jaromír Klemeš, Peng Yen Liew, Jun Yow Yong Copyright © 2014, AIDIC Servizi S.r.l., ISBN 978-88-95608-30-3; ISSN 2283-9216 DOI: 10.3303/CET1439027 Please cite this article as: Gross U., Iljins U., Skujans J., Gajevskis A., 2014, Modeling of multi - layer foam gypsum drying process, Chemical Engineering Transactions, 39, 157-162 DOI:10.3303/CET1439027 157 Modeling of Multi - Layer Foam Gypsum Drying Process Uldis Gross a* , Uldis Iljins a , Juris Skujans b , Antons Gajevskis a a Latvia University of Agriculture, Dep. of Information Technologies 2 Liela Street, Jelgava, LV-3001, Latvia b LatviaUniversity of Agriculture, Dep. of Rural Engineering, 19 Akademijas Street, Jelgava, LV-3001, Latvia uldis.gross@llu.lv Foam gypsum is a perspective material in construction. According to the requirements for the manufacturing process of foam gypsum, the initial moisture content should be very high. Drying of these products is obligatory requirement to obtain material with sufficient properties. It is possible to change the density of foam gypsum with hemp fibrous reinforcement technologically varying mechanical strength, thermal conductivity and sound absorption coefficients. In the constructions of buildings foam gypsum can be used as filler bounded by gypsum paperboard. In this work we aim to study the moisture transfer in multi-layered wall as usual in construction design. It is important to clarify the structural drying time and the factors that allow it to shorten. For this sample arrangement it is not possible to correct analytical description of drying process. A numerical method is used for calculation of moisture content. Drying process of foam gypsum coated with gypsum paperboard was researched with gravimetric and electrical methods. The validity of the numerical model was verified by comparison with experimental results. 1. Introduction Nowadays multilayer walls, consisting of a framework, which on both sides is attached to the gypsum board, the mid- filled with a light, porous or fibrous material, became popular in the field of building construction. These walls, consisting of several layers are significantly better than the same material single layer, since they have many environmental benefits like low thermal conductivity, good sound absorption qualities and humidity buffering capacity. Light party wall structure may be formed by gypsum plates between which is placed absorbent material such as mineral wool, or by filling the void with solid lightweight filler as foam gypsum or hemp concrete. In this case some compaction of the material over a period of time or any problems arising during material drying must be taken in account. For different constructive systems the authors developed a new foam gypsum with hemp fibrous reinforcement composite, characterized by good heat (Skujans et al., 2007) and sound insulating properties (Brencis et al., 2011). Material with density 250 to 300 kg/m 3 is characterized by 0.07 to 0.08 W/(m K) thermal conductivity coefficient (Skujans et al., 2007) and the design, consisting of plasterboard with 10 cm foam gypsum hemp fibers composite filling, show sound insulation index R values greater than 45 dB (Brencis et al., 2012). According to the requirements for the manufacturing process of foam gypsum, the initial moisture content should be very high. Therefore it is important to clarify the structural drying time and the factors that allow it to shorten. Covering porous media with plasters significantly changes the hydrothermal properties of walls. When plasters are applied on hemp concrete, heat transfers are almost not modified, but moisture transfers are noticeably dampened (Colinart et al., 2013). The same results are obtained for gypsum walls coated with paint layer (Goosens, 2003). Therefore indoor humidity variations are more dampened compared with the external environment. Drying process in foam gypsum is described by means of two mathematically connected models (Iljins et al., 2009). Theoretical model makes it possible to calculate local humidity conditions in different layers of sample during drying time. It is particularly important in the case of foam gypsum with hemp fibrous reinforcement to detect the moment, when moisture content during drying is about 10 kg/m 3 , because under these conditions the material changes its physical - mechanical characteristics very quickly (reach