Using CFD To Assess The Impact of Helical Baffle On The First- Law And Second-Law Performance of Water-CuO Nanofluid Inside A Hairpin Heat Exchanger

This study is devoted to the numerical assessment of the influence of helical baffle on the hydrothermal aspects and irreversibility behavior of the turbulent forced convection flow of water-CuO nanofluid (NF) inside a hairpin heat exchanger. The variations of the first-law and second-law performance metrics are investigated in terms of Reynolds number (Re), volume concentration of NF (φ) and baffle pitch (B). The results showed that the NF Nusselt number grows the rise of both the Re and φ whereas it declines by boosting with the rise of baffle pitch. In addition, the outcomes depicted that the rise of both the T and φ results in the rise of pressure drop, while it declines with the increase of baffle pitch. Moreover, it was found that the best first-law performance of the NF belongs to the case B=33.3 mm, φ=2% and Renf=10000. Furthermore, it was shown that irreversibilities due to fluid friction and heat transfer augment with the rise of Re while the rise of baffle pitch results in the decrease of frictional irreversibilities. Finally, the outcomes revealed that with the rise of baffle pitch, the heat transfer irreversibilities first intensifies and then diminishes.

Analytical solutions for unsteady forced convection pulsating flow in a microchannel in the presence of EDL effects

A forced convection flow driven in a microchannel by an applied pressure gradient that fluctuates with small amplitude harmonically in time in the presence of electrical double layer effects is investigated. An analytical expression for the electrostatic potential is obtained via Poisson’s equation. Based on this solution, we further obtain analytical solutions for velocity and temperature for both the cases Pr ≠ 1 and Pr = 1. Results show that they match each other as Pr → 1− and Pr → 1+. The explicit expression of the transient Nusselt number is derived. We notice that the Debye–Hückel parameter γ and the angular velocity Ω are key factors for flow behaviours. Our proposed study adds some new insights by including the time-dependent pressure term that is usually overlooked in previous works. It is expected that this work could help to understand the transportal mechanisms of forced convection flow in microfluidic equipment and instruments.