Study of the effect of medium flow parameters on heat transfer in the laboratory coaxial model of a borehole heat exchanger.
Tomasz Śliwa, Łukasz Gałuszka
Vol. 30, no. 4 (2013), s. 421-430, 
Reynolds number defines the fluid flow character. Three types of flow are distinguished: laminar, transitional and turbulent flows. By changing the flow conditions in the coaxial vertical borehole heat exchanger, a research was carried on energy (heat) exchange. The authors analyzed the flow of fluids through a model of concentric vertical heat exchanger in the Laboratory of Geoenergetics in AGH University of Science and Technology, Faculty of Drilling, Oil and Gas. Measurements for different materials and dimensions of internal column were performed.