Date of Award
Master of Science (MS)
The heat transfer of ground heat exchangers used in geothermal heating and cooling of buildings partially depends on the velocity, or more specifically the Reynolds number (Re), of the fluid circulating inside the geothermal pipe. Higher Re induces higher heat exchange, which can be achieved with higher fluid velocity. However, the pumping energy necessary to achieve the high fluid velocity is significant. Alternatively, turbulence generators (turbulators) in the form of helical wings inserted inside the pipe can generate and maintain a turbulent flow even at small fluid velocities, thereby inducing higher heat transfer. However, the inclusion of helical turbulators creates obstruction in the flow, which gives rise to a pressure drop across the turbulators that also increases the pumping energy. This thesis describes a parametric study comparing different helical turbulators in terms of size and shape, and investigates their impact on the heat exchange and the pumping energy. The comparison is made using multi-physics numerical models. The models represent the actual heat transfer from the fluid to the pipe and to the surrounding ground. Trade-off analysis is performed for each model where both heat transfer and pump consumption are considered, and net savings for each case are determined. The results of the simulations are presented and discussed in terms of improvements compared to traditional geothermal pipes without turbulators. The overarching goal of this research is to optimize the design and the number of turbulence generators in geothermal pipes to maximize heat transfer while minimizing pumping energy.
Rao, Rohit Ashok, "A Computational Evaluation of Turbulence Generators in Co-Axial Ground Heat Exchangers" (2021). All Theses. 3646.