CFD simulations of horizontal ground heat exchangers: A comparison among different configurations

Abstract This work deals with the efficiency and the energy behavior of Ground Source Heat Pumps (GSHPs) used for heating and cooling of buildings. In particular horizontal type heat exchangers have been investigated for different configurations, in order to evaluate the characteristics of these systems in the most common layouts and in different working conditions. The main results pointed out the heat fluxes transferred to and from the ground and the efficiency of the system. The calculations were made with the CFD code Fluent and the simulations covered one year of system operation, both in summer and winter for typical climate conditions of the South of Italy. The most important parameter for the heat transfer performance of the system resulted the thermal conductivity of the ground around the heat exchanger and the optimal ground type was that with the highest thermal conductivity (3 W/m K in the cases analyzed in this work). The choice of the velocity of the heat transfer fluid inside the tubes was another key factor. The depth of installation of the horizontal ground heat exchangers did not play an important role on the system performance. The helical heat exchanger arrangement resulted as the best performing one.