Heat and Mass Transport

LIAG investigates the upper areas of the earth crust, which are anthropogen  influenceable and important for an economic use and for the services of general interest. Depending on the elective spatial and temporal scale, these areas are described statically by geo-structure models or dynamically by geo-process models. The latter are determined in the essentials by the coupled transport of energy (thermally and mechanically) and mass (in the essential fluids) and their changes.

These processes can be subdivided in thermal (T), hydraulical (H), mechanical (M) and chemical (C) processes. Summarized, they will be called coupled THMC processes.

Examples of the THMC related problems researched by Section 4 are:

• In the production of geothermal energy by using open circulation systems (e.g. Hot Dry Rock), the need for THMC consideration becomes especially clear as a forecasting action. By the hydraulics in the drillings, the rock will be fractured, and hydraulic connections between two neighbored occur. Then fluid circulation produces temperature changes in the rock leading to changes of the mechanical rock tension. Moreover, the chemical attack of the circulating fluid on the rock is of particular importance, because after some time the mineral cargo of the fluid may increase considerably.
• In the coal mining, if the coal starts to burn by supply of oxygen (see Coal Fire Project), especially strong couplings between hydraulical, chemical, transport-mechanical and rock-mechanical processes occur. The burnt coal creates cavities which lead to mechanical stress and to rock fracturing. These fractures create new oxygen paths feeding the coal fire.
• A particular challenge is the quantitative description of the flow and transport processes in the unsaturated ground zone. Here the gas flow and the water flow are coupled in the pore space.