Heat Transfer in Laminar Graetz and Taylor Flows Incorporating Nanoparticles

This study investigates the thermal and hydrodynamic effects of incorporating nanomaterials to the continuous and gas-liquid Taylor flows in mini scale tubes. Aluminum Oxide nano-powder was dispersed in distilled water to produce three nanofluid concentrations: 1, 2 and 4 wt% using a two-step method. Heat transfer enhancement in miniscale tubes (similar to 1.5 mm) was assessed using Nusselt number and dimensionless mean wall heat flux. The experiments were conducted under laminar developing flow with isothermal boundary condition. In addition, nanofluid experiments covered: thermal conductivity measurements, scanning electronic microscopy, and performance efficiency analysis. The thermal and hydrodynamic effects of incorporating nanoparticles to the base fluid were evaluated using performance efficiency analysis which considers friction factor and Nusselt number. The results demonstrated that heat transfer enhancement is associated with the nanoparticles concentration when compared with Graetz theory. Total enhancement in segmented nanofluid flows was observed to be a combination of the individual contributions of internal circulations within the liquid slugs and the interaction between the nanoparticles. Overall, the present study highlights the potential of heat transfer enhancement within mini/micro tubes using segmented nanofluid flows.