An Experimental Study of Different Criteria for Laminar Thermal Judgment of Nanofluids in a Finned Heat Exchanger

This work is devoted to find an appropriate criterion for thermal judging of nanofluids. The importance of this issue arises from the possible misleading which asserts an existence of extra heat transfer for nanofluid compared to the base fluid, neglecting the hydraulic effects such as increasing the pressure drop. To clarify the issue, an experimental apparatus with ability of making fixed Reynolds number and constant pumping power was constructed and thermal behavior of silicon oxide/ water nanofluid and distilled water are investigated in the laminar and developing regions. In this regard, heat transfer coefficient inside the finned air cooled heat exchanger is evaluated. Results are provided for different inlet temperatures and different nanofluid concentrations for two criteria of fixed Reynolds number and constant pumping .According to the results, the concentration of the nanoparticles in the base fluid will have a huge impact on the amount of deflection of these two measures, so that by increasing the concentration of nanofluids, the difference between these two measures becomes greater, hence in this work due to the low concentration of nanofluids, the use of any of the criteria did not make a significant difference in the results.