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Heat from the depths
Increasing the potential of geothermal energy from abandoned mines with CFD simulation

CFD Simulation of energy transfer between mine water and heat tube

Branch : Machinery and plant engineeringSpecialist field: Fluid mechanics

Underground mine water is a geothermal resource that may be used as an alternative form of energy in the future. CFD simulations were carried out to prepare an energy plan. The analysis of the flow and temperature field enables the determination of the thermal extraction rates.

Summary

M.Sc. Michel Gross
Ruhr-Universität Bochum

With the help of the CADFEM simulation services we were able to answer the complex dynamic task very efficiently

Task

Within the framework of a research project, the flow and energy transport in the shafts used to circulate the water in former mines is to be determined. The findings should enable exact energy planning.

Solution

The varying buoyancy of the water in the mine shaft, caused by thermal differences, is disturbed by cross flows. The flow simulation with Ansys CFD allows an exact insight into the complex flow conditions within the mine shaft.

Customer benefits

With the simulations carried out by CADFEM, the flow and temperature fields were analysed and visualised. Thus, the extraction performance of the heat probe could be determined exactly. A target-oriented conception of the energy generation is guaranteed.

Project Details

Task

The change to green energy is one of the most relevant tasks of our time. To achieve this, the energy supply must increasingly be converted to renewable energies. In this context, the site owner and planner of a new inner-city district in Essen has the unique opportunity to use geothermal energy from the water in the abandoned mines. With the ESSEN51 project, a new city district is being created near Essen's city centre, with the former colliery sites of Schacht Amalie and Marie in the middle. The project will provide a continuous flow of water from the mine with a constant temperature of around 25 C all year round from two of the former shafts. The energy stored in the water from the mine will be transported to the surface by a heat tube.


Customer Benefit

With the simulation, it was possible to show the flow condition that developed both in the shaft and in the gallery. The temperature distribution in the mine water and in the heat tube as well as the extracted energy were also analyzed.

  • Based on the results obtained, validated statements can be made about the extraction performance. These are then incorporated into the preparation of the energy concept.
  • In this research project for Grubenwasser-Ruhr, the results can also be mapped to other shafts, resulting in an efficient solution for many mines.

 


Solution

The mine water is heated by the surrounding rock, which reaches temperatures of up to 40 C at this depth. At the same time, the heat tube extracts energy from the mine water. The warmer, lighter water rises and the cooled, heavier water sinks again. This creates a complex, uplift dominated flow state in the shaft, which is influenced with the crossflow of the connected ninth gallery. With Ansys CFD, both the temperature distribution and the flow have been calculated and visualized. The particular challenges were, firstly, the different time scales that had to be used on the transport processes in the different areas of the computing domain. Secondly, there were high demands on the fineness of the mesh in order to resolve the heat transfer with sufficient accuracy, coupled with the large extent of the model.


CAE Engineer

Products applied in the project