Laminar nanofluid flow over periodic two dimensional rectangular baffled channels

Abstract

A numerical study is performed to consider the effects of different geometrical and positional parameters of baffles and nanofluids on the thermal and flow fields in a rectangular channel the Reynolds number was in the range of 100 to 1200 and the upper and lower walls of the channel were kept at the constant temperature of 330 K. The problem is solved in two dimensional forms of continuity, Navier-Stokes and energy equations using FVM (Finite Volume Method). The optimization through periodic baffled channel with two staggered baffles, one at the top wall and another at the bottom wall, having a height of 20mm and length of 40mm, was studied by changing the geometrical parameters of the channel such as shape of the baffles (diamond and vertical flat plate) with different block ratios (BRs; 0.1H, 0.3H and 0.5H) and different angles of the baffles (?; 5°, 10° and 15°). The goal of the study is to improve the heat transfer rate through baffled channels by using conventional fluid and nanofluids. Different nanoparticles such as Al2O3, CuO, SiO2, and ZnO with different concentrations ranging from 1% to 4% and assorted diameters from 30mm to 80mm are used in water as base fluid to see their effects on the rate of the heat transfer enhancement. The influence of Reynolds variation from 100 to 1200 is also analyzed. The results showed an improvement in both Nusselt number and friction coefficient but the Thermal Enhancement Factor (TEF), was greater than unity for Re>700. Using nanofluids rather than water helped the Nusselt number to increase but with being perceived an additional increase in friction factor. It is found that a raise in volume fraction and a decrement of the diameter of the particles led to an increase in Nusselt number