Modelling of transport processes in porous media for energy applications
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Journal Title
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Helsinki University of Technology |
Doctoral thesis (article-based)
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Author
Date
1996
Department
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Mcode
Degree programme
Language
en
Pages
87
Series
Abstract
Flows in porous media are encountered in many branches of technology. In these phenomena, a fluid of some sort is flowing through porous matrix of a solid medium. Examples of the fluid are water, air, gas and oil. The solid matrix can be soil, fissured rock, ceramics, filter paper, etc. The flow is in many cases accompanied by transfer of heat or solute within the fluid or between the fluid and the surrounding solid matrix. Chemical reactions or microbiological processes may also be taking place in the system. In this thesis, a 3-dimensional computer simulation model THETA for the coupled transport of fluid, heat, and solute in porous media has been developed and applied to various problems in the field of energy research. Although also applicable to porous medium applications in general, the version of the model described and used in this work is intended for studying the transport processes in aquifers, which are geological formations containing groundwater. The model highlights include versatile input and output routines, as well as modularity which, for example, enables an easy adaptation of the model for use as a subroutine in large energy system simulations. Special attention in the model development has been attached to high flow conditions, which may be present in Nordic esker aquifers located close to the ground surface. The simulation model has been written with FORTRAN 77 programming language, enabling a seamless operation both in PC and main frame environments. For PC simulation, a special graphic user interface has been developed. The model has been used with success in a wide variety of applications, ranging from basic thermal analyses to thermal energy storage system evaluations and nuclear waste disposal simulations. The studies have shown that thermal energy storage is feasible also in Nordic high flow aquifers, although at the cost of lower recovery temperature level, usually necessitating the use of heat pumps. In the nuclear waste studies, it was found that the heat generation of the spent fuel has a marked effect on the groundwater flow near the repository for thousands of years, increasing the flow rate at most to five-fold compared to the natural situation. In the applications, the model has proven to be a versatile tool and easily applicable in various situations. As a future development, the inclusion of unsaturated zone simulation as well as improvements in solute transport routines are being considered.Description
Keywords
virtaus, hydrologia, simulointi, energiatalous, lämpö, vätskors fysik, värmeöverföring, simulering
Other note
Parts
- M.T. Kangas and P.D. Lund, THETA - An advanced simulation program for 3D fluid, heat and solute transfer in porous media. Helsinki University of Technology, Department of Technical Physics, Report TKK-F-A732, 55+125 p.
- M.T. Kangas and P.D. Lund, MicroTheta - a PC-based tool for aquifer thermal energy storage systems including environmental impact analysis. Proc. of CALORSTOCK ‘94, 6th International Conference on Thermal Energy Storage, August 22-25,1994, Espoo, Finland, 10р.
- M.T. Kangas and P.D. Lund, Validation of simulation model THETA for thermohydraulic and environmental analysis of aquifers using the Rajamäki long-term experiments. Proc. of CALORSTOCK ‘94, 6th International Conference on Thermal Energy Storage, August 22-25, 1994, Espoo, Finland, 10р.
- M.T. Kangas and P.D. Lund, Modelling and Simulation of Aquifer Storage Energy Systems. Solar Energy, Vol.53, No.3,1994, pp. 237-247.
- M.T.Kangas, Thermohydraulic analysis of ground as a heat source for heat pumps using vertical pipes. Accepted for publication in Journal of Energy Resources Technology, 1997.
- M.T. Kangas, The effect of temperature gradients in the ground on groundwater flow patterns. Helsinki University of Technology, Department of Technical Physics, Report TKK-F-A750, 28 p.
- M.T. Kangas and P.D. Lund, Thermohydraulic Analysis of a Potential Nuclear Waste Repository Site in Bedrock. Waste Management, Vol.10, pp.3-10, 1990.
- M.T. Kangas and P.D. Lund, Microcomputer Design Tool for Aquifer Thermal Energy Storage with Extension to Environmental Analysis. Proceedings of THERMASTOCK '91, the 5th International Conference on Thermal Energy Storage, Scheveningen, the Netherlands, May 13-16. 6p.
