Özet:

This study numerically investigates the heat transfer and hydraulic performance of Al2O3-water nanofluids flowing through a horizontal smooth pipe exposed to a constant heat flux. The nanofluids were regarded as four different varying concentrations in the range from 0.01 to 0.04 by a 0.01 increment (by volume) of the nano-particle, Al2O3. Numerical analyses were performed using the finite volume method to solve governing equations in the created three-dimensional domain. The heat transfer and hydraulic characteristics of the nanofluids were separately investigated as a function of both Re number and flow velocity corresponding to the turbulent flow regime. The results show that the convective heat transfer coefficients increase remarkably with the increase of Al2O3 fraction, and the maximum overall enhancement ratio was found by 1.30, in the case of the same Reynolds number. In contrast, in the case of the same flow velocities to the base fluid, the convective heat transfer coefficients of the nanofluids worsened with relative to the base fluid due to higher viscosity values of the nanofluids which cause a decrease in Reynolds numbers. Moreover, friction factors with nanofluids increased, which gave rise to the overall enhancement ratios to be at lower than 1.0.

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