Effect of an inward-facing baffle on the laminar forced convection heating along a cylindrical horizontal pipe for different nanofluids

Abstract

Improving heat exchange intensity is a major goal in the heat exchanger industry. The use of baffles is one of the techniques employed to achieve this goal. In this numerical work, the effect of an inward-facing baffle placed on the wall of a cylindrical horizontal pipe is treated for the case of nanofluid. A sequential analysis is offered to better understand the different effects and their consequences, particularly on the average exchange rate, in addition to somewhat filling the gap identified in the literature for the case of nanofluid with various shapes of the baffle. The study, divided into three parts, begins for 10Re250 with the case of pipe without baffle, where the water-based nanofluid effect is treated. Three types of nanoparticles (Cu, Al2O3 and TiO3) at volume concentration 0ϕ10% are considered. An insulated primary pipe is placed to ensure dynamic establishment at the entrance to the heating pipe assumed to be under imposed temperature. The results showed the clear effects of modifying the kinematic viscosity and thermal diffusivity on the dynamic and thermal lengths respectively with the addition of nanoparticles compared to the base fluid. Correlations are proposed for their determination. A heat exchange rate that improves as the volume concentration increases is recorded, particularly for nanoparticles with high thermal conductivity. In the second part, a rectangular baffle is assumed in the heated pipe, where the effects of its position, length and width are analyzed respectively. The results showed a greater interest in placing the baffle close to the entrance, especially if it is longer. In the last part of the work, three other shapes of the baffle are proposed (Trapezoidal, Triangular and Elliptical). The results confirm that the non-smooth shape of the baffle creates more disturbances in the dynamic and thermal fields, and therefore a greater improvement in the heat exchange rate. For the last two parts, the nanofluid effect remains similar to that recorded for pipe without baffle.