A combined moving boundary and discretized approach for dynamic modeling and simulation of geothermal heat pump systems

The major goal of this study is to demonstrate the feasibility of the dynamic modeling and simulation of both conventional and direct exchange geothermal heat pump applications particularly with regard to performance evaluations. A direct exchange geothermal heat pump system is a geothermal heat pump system in which the refrigerant circulates through tubing placed in the ground. In this research, dynamic models for the simulation of geothermal heat pump systems with the working fluid propane for the application in building-scale energy systems have been developed based on the Moving Boundary approach and the challenges of dynamically evaluating these kind of energy systems have been hereby met. Additionally, the performance of both horizontal (slinky-coil) and vertical (borehole) geothermal heat exchangers, which have been modeled based on the Conventional Discretized approach, for such systems has been evaluated. Since these two modeling approaches are not compatible with one another, the coupling of the moving boundary model with the discretized model is therefore another challenge and of great importance. On the basis of a case study, the complete conventional and direct exchange geothermal heat pump systems with vertical and horizontal heat exchangers have been simulated and energetically and exergetically analyzed.