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A theoretical, experimental and numerical investigation of combined heat and mass transfer in unsaturated sand is described. The theoretical formulation adopted is that of Philip & de Vries but slightly different forms of the vapour transfer dif-fusivities are developed. Experimental work is reported on the determination, for a medium sand, of the full set of material parameters incorporated in the formulation, using both methods developed by the Authors and standard techniques. Explicit equations are given for the capillary potential, unsaturated hydraulic conductivity and thermal conductivity as functions of moisture content and temperature. Laboratory experimental results are presented for the steady temperature distribution within an unsaturated sample of the sand in which a rod is buried and heated. The pattern of moisture content values achieved reveals a two region response, a dry zone surrounding the rod and wet sand elsewhere. The development of a numerical simulation of the heating experiment using a finite difference solution algorithm is described. A self implicit scheme, driven to steady state through a false transient, was employed. Good agreement was found between temperatures in the simulation and the experiment. The work described is unusual in that equal emphasis has been placed on experimentation, especially the determination of the soil's physical properties, and numerical modelling and the two-dimensional coupled partial differential equations describing combined heat and mass transfer have been solved without simplification. L'article présente une étude théorique, expérimen-tale et numérique du transfert combiné de chaleur et de masse dans du sable non-saturé. La formulation th&cuate;orique adoptée est celle de Philip et de Vries, mais on développe des formes légérement différentes des diffusivités du transfert des vapeurs. Des expériences sont décrites concernant la détermination pour un sable moyen d'un jeu complet des paramétres du matériau incorporés dans la formulation a l'aide des méthodes développées par les auteurs et des techniques usuelles. Des équations explicites sont données pour le potentiel capillaire, la conductivité hydraulique non-saturée et la conductivité thermale en fonction de la teneur en eau et la température. Des résultats des expériences effectuées dans le laboratoire sont présentes pour la distribution stationnaire de température au sein d'un échantillon non-saturé de sable dans lequel une tige est enfouie et chauffée. La distribution des valeurs de teneur en eau révéle une réponse à deux zones, c'est-à-dire une zone séche entourant la tige et du sable humide ailleurs. L'article décrit le dé-veloppement d'une simulation numérique de l'expérience de chauffage à l'aide d'un algorithme de solution a différences finies. On a employé une méthode implicite en soi et poussée à l'état stationnaire en passant par une fausse transition. On a trouvé que les températures de la simulation et de l'expérience s'accordaient bien 1'une avec l'autre. Le travail decrit a été orienté également sur l'expérimentation, surtout la détermination des propriétés physiques du sol, et sur la simulation numérique. Les équations différentielles partielles bidimensionnelles associées décrivant le transfert combiné de chaleur et de masse ont été résolues sans aucune simplification.

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SUMMARYThe finite element method is used to analyse heat and mass transfer problems in porous media, in which the thermophysical properties are allowed to vary as functions of temperature and moisture. An example is given of the application of the method to the problem of timber drying.

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This article examines the CO 2 adsorption−desorption kinetics of bituminous coal under low pressure injection (0.5 MPa) in the context of CO 2 sequestration in shallow level coal seams. This study used two different sizes of intact core samples of bituminous samples from seam no. 30 at the Experimental Mine Barbara (EMB) in Katowice, Poland. Manometric adsorption kinetics experiments were conducted on 50 mm dia. 60 mm long coal core samples (referred to as EMB1) and 50 mm dia. 30 mm long coal core samples (referred to as EMB2). The kinetics of adsorption at injection pressures ranging from 0.1 to 0.5 MPa were compared to those at elevated pressures ranging from 0.5 to 4.5 MPa. For the first time, intact sample adsorption−desorption data were fitted in pseudo first order (PFO), pseudo second order (PSO), and Bangham pore diffusion models. The PSO model fits the data better than the PFO model, indicating that bulk pore diffusion, surface interaction, and multilayer adsorption are the ratedetermining steps. Comparing the equilibrium amount of adsorbed (q e ) obtained for the powdered samples (9.06 g of CO 2 /kg of coal at 0.52 MPa) with intact samples (11.68 g/kg at 0.53 MPa and 7.58 g/kg at 0.52 MPa for the intact EMB1 and EMB2 samples) showed the importance of conducting experiments with intact samples. The better fit obtained with the Bangham model for lower pressure equilibrium pressures (up to 0.5 MPa) compared to higher pressure equilibrium pressures (4.5 MPa) indicates that bulk pore diffusion is the rate-determining step at lower pressures and surface interaction takes over at higher pressures. The amount of CO 2 trapped within the coal structure following the desorption experiments strengthens the case for intact bituminous coal samples' pore trapping capabilities.

SUMMARYAn analysis of coupled heat and moisture movement in unsaturated soil in terms of the fundamental potentials for flow is examined. The approach adopted is based on the assumption that the total potential for liquid flow consists of two components, the elevation and the capillary potential. The fundamental potentials employed in the work are, therefore, temperature and capillary potential.The full theoretical formulation of the problem is presented, together with full details of the solution algorithm employed. Spatial discretization is achieved via the use of the finite element method, with the time-varying behaviour described by a finite difference technique. Soil parameter variations as functions of both temperature and moisture content are included in a one-dimensional approach.The work is applied to a practical engineering problem, namely heat and mass transfer in the upper layers of a soil stratum. This problem is of importance to the utilities, since many services are buried in this zone.Material parameters obtained from an associated programme of experimental work are employed. Moisture content and temperature profiles indicating the extent and rate of penetration of drying and heating fronts are produced.