TY - JOUR TI - The heat transfer enhancement of concurrent flow and counter current flow concentric tube heat exchangers by using hexagonal boron nitride/water nanofluid AU - Sözen Adnan AU - Güçlüer Sinan AU - Kilinç Cuma JN - Thermal Science PY - 2019 VL - 23 IS - 6 SP - 3917 EP - 3928 PT - Article AB - Heat exchangers are used in many applications including chemical, oil and gas power generation, refrigeration, pharmaceuticals and food processing. Because of their widespread usage, they have various types to serve at different working conditions. Increasing the performance of heat exchangers has become a very interesting field of study since the efficiency of various industrial and domestic systems depend on them. In this study, a coaxial double tube experimental setup was prepared, and the effect of using nano hexagonal boron nitride nanofluid as hot working fluid on the heat transfer performance increase was investigated. The experiments were carried out in concurrent flow and counter flow conditions for various hot fluid flow rates to obtain the heat transfer coefficients. Nano hexagonal boron nitride obtained in powder form was used to prepare the nanofluid by a two-step method. 4kg nanofluid containing 2% nano hexagonal boron nitride with 0.5% Triton X-100 as a surfactant in terms of mass ratio was prepared for the experiments. Heat transfer experiments were carried out three times by using the prepared nano hexagonal boron nitride/water nanofluid and pure water as hot fluid to reach more precise results. In the result of this study, the total heat transfer coefficient showed an average improvement of 48.78% for the concurrent flow heat exchanger, while an average improvement of 0.36% was observed in the counter flow conditions compared to the base fluid. This study shows the potential of application of nano hexagonal boron nitride/water nanofluid in heat management applications.