Seyed Ali Ghoreishi-Madiseh

A transient natural convection heat transfer model for geothermal borehole heat exchangers

The effect of buoyancy-driven natural convection on the performance of ground-coupled heat exchangers of closed loop geothermal systems is investigated. The governing equations of continuity, momentum, and energy balance are derived, taking into account a porous ground medium fully saturated with liquid water. Boussinesq approximation is used to model the effect of buoyancy forces in water. A three-dimensional finite-volume discretization method over a structured mesh is used to solve the governing equations numerically. The performance of the ground-coupled heat exchanger system is assessed based on the rate of energy extraction and the outlet fluid temperature. The effects of hydraulic conductivity of the heat exchange medium and seasonal variations of heat load on the heat transfer phenomenon are studied. The results are evaluated by comparing them against the results of existing conduction-based heat transfer models. The influence of natural convection on the sustainable rate of heat extraction from a geothermal resource is underlined and interpreted.

A study into extraction of geothermal energy from tailings ponds

Assessing the performance of ground-coupled heat exchangers (GCHE) of closed-loop geothermal systems installed in tailings ponds is studied. A heat transfer model is constructed, taking into account heat conduction as well as groundwater advection. A three-dimensional finite volume discretisation method over a structured mesh with variable grid size is used to solve the governing equations. The performance of a GCHE system installed in tailings ponds is assessed based on the rate of energy extraction and the outlet fluid temperature. The geothermal capacity of mine tailings ponds and its sustainable rate of heat extraction are estimated. Effects of tube network configuration and horizontal and vertical underground advection on the performance of the system are investigated. It is found that two-dimensional heat transfer models may lead to over-designed systems and the effect of advection cannot be neglected in highly pervious tailings.

Evaluation of the Hydraulic Recovery Potential in a Lake-Sourced Underground Mine Refrigeration System

The foray of underground mines to ever deeper deposits has elevated mine refrigeration into an integral part of the operations. The air temperature limit, established through legislation, aims to ensure that workers in the mine are not exposed to temperatures extreme enough to cause heat stress. Because of the scale of refrigeration demanded by an underground mine, electricity/operating costs will constitute a significant portion of the budget. Using a lake for a cold-water source is a novel alternative to conventional refrigeration plants for subsurface cooling. The kinetic energy from the cold lake water flowing down the mineshaft can be harnessed with turbines, to reduce water pressure and produce usable energy. The scenarios examined includes ignoring the use of a turbine, using a turbine-generator combination, and using a turbine-pump combination. Considering the energy required to pump the return water from the bottom of the mine to the surface, the turbine-pump scenario is most economical. The scenario considering no turbine demonstrated the highest energy costs, while the turbine-generator combination was slightly less economical than the turbine-pump scenario.