Numerical Study on the Fluid Flow and Heat Transfer Characteristic in Channel Using Small Turburators and Nano-fluid

Abstract

In the current study, the heat transfer and fluid flow of nanofluid in channel with different baffles shapes have been investigated numerically via developed CFD code based on FORTRAN 90 which is able to simulate the laminar flow regime. The governing continuity, momentum and energy equations in body-fitted coordinates are iteratively solved using finite volume method and SIMPLE technique. One baffle mounted on the top wall of channel with a distance of 10 from the inlet of channel and another one mounted on the bottom wall of channel with different distances of 5, 10, 15 and 20 from the inlet of channel. Three different shapes of baffles oval, triangular and trapezoidal with dimensionless baffle height of 0.1, 0.2 and 0.3 have been considered. SiO2-water nanofluid with nanoparticles volume fraction range of 0-0.04 and nanoparticles size diameter of dp=30 nm has been considered for Reynolds number ranging from 100 to 1000. The effect of nanoparticles volume fraction, baffles height, baffles location and baffles shapes on the average Nusselt number, pressure drop, entropy generation and thermal-hydraulic performance have been presented and discussed. Results show that average Nusselt number, pressure drop, entropy generation as well as the thermal-hydraulic performance increase with increasing the nanoparticles volume fraction. Furthermore, the average Nusselt number, pressure drop and entropy generation increase with increasing baffle height and Reynolds number. Moreover, using triangular baffles in a channel provides the highest thermal-hydraulic performance followed by trapezoidal and oval baffles when the volume fraction concentration 4%, baffle height 0.3 and the upper and lower baffles are located at distances of 10 and 15, respectively from the inlet of channel. The maximum value of thermal-hydraulic performance factor can be observed for triangular, trapezoidal and oval baffles were 1.398, 1.377 and 1.264 at Reynolds numbers of 1000, 1000 and 600 respectively. Therefore, using nanofluid instead of traditional heat transfer fluids as well as using small baffles inside channels can potentially achieve considerable improvement in the heat transfer performance, which can lead to design more compact heat exchangers.