Heat TransferEnhancement in Tube in Tube Heat Exchanger with Helical Wire Coil Inserts and CuO Nanofluid

ABSTRACT In the present work, heat transfer enhancement in tube in tube counter flow heat exchanger with helical wire coil inserts and CuO nanofluid for turbulent flow has been investigated. Different parameters affecting the heat transfer characteristics were investigated so that the influence of each parameter can be determined. The Copper Oxide nanoparticles of 40nm size with volumetric fractions of 0.25% are used to prepare the nanofluid for the experiment. The helical wire coil inserts of three different pitch lengths of 14.2, 16.124 and 20.36 mm which correspond to pitch ratios of P/D = 1.29, 1.47 and 1.85 respectively are used to strengthen the heat transfer efficiency for heat exchangers. The Reynolds number varied from 10000 to 35000, the convective heat transfer coefficients were determined. The results gained in the study showed that dispersion of CuO nanoparticles in water significantly increased the overall heat transfer coefficient and convective heat transfer coefficient. The results also revealed that heat transfer improvement could be achieved by the coil having lower pitch ratio i.e. 1.29 as compared with that of coils with P/D=1.47 and 1.85. The overall heat transfer coefficient, Nusselt number, convective heat transfer coefficients for different configurations with and without inserting helical wire coil and nanofluid are compared.