The convective heat transfer of Al2O3-water nanofluids through a circular tube with a constant heat flux boundary condition is studied numerically. Turbulent flow conditions are considered with a Reynolds number ranging from 3500 to 20000. The numerical method used is based on the single-phase model. Four volume concentrations of Al2O3-water nanoparticles (0.1, 0.5, 1, and 2%) are used with a diameter of nanoparticle of 40 nm. A considerable increase in Nusselt number, axial velocity, and turbulent kinetic energy was found with increasing Reynolds number and volume fractions. However, the pressure losses were also increased with the raise of Re and nanoparticles concentration.

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Details on the hydrothermal characteristics of turbulent flows in a solar channel heat exchanger (CHE) are highlighted. The device has transverse T-shaped vortex generators (VGs). Two staggered VGs (baffles) are inserted on the lower and upper walls of the CHE. The working fluid is Newtonian and incompressible, with constant physical properties. The ANSYS Fluent 17.0 is utilized in this survey. The second-order upwind and QUICK schemes were utilized to perform the discretization of pressure and convective terms, respectively. The SIMPLE algorithm was employed to achieve the speed-pressure coupling. The residual target 10−9 was selected as a convergence criterion. The effects of the T-VGs’ geometrical shape and Reynolds numbers were inspected. At the baffle level, the wall effect was augmented due to the reduction of the passage area of flows, which is estimated here to be 55%, resulting thus in a considerable resistance to the movement of fluid particles. The thermal distribution is highly dependent on the flow structures within the CHE. Since the fluid agitation yields an enhanced mixing, it allows thus an excellent heat transfer. The most considerable rates of thermal transfer were obtained with high Re, which resulted from the intensified mixing of fluid particles through the formation of recirculation cells and the interaction with the walls of the T-VGs and the CHE. The T-baffles with intense flow rates yielded negative turbulent speeds and intensify the fluid agitation, which improves the thermal exchange rates.

This research is based on an experimental investigation of four different types of heatsinks, which was backed up by a simulation analysis. The goal of this study is to determine the relevance of various heatsink forms and sizes, as well as to enhance the best situation. The cooling strength of these heatsinks was next investigated experimentally and then numerically, while adjusting in the same initial conditions, finding in principle that the experimental and numerical results agree, with a contrast ratio of less than 10.24%. As a consequence, we concluded that the coolant D3, which is circular and has a heat resistance of 0.582 K. W-1, is stronger than the D2 compact circular cooler, which has a resistance of 0.590 K. W-1. These two varieties were far superior to the regular D1 heatsink, which first debuted in the early days of computers and had a resistance of 0.595 K. W-1, but the best was the mixed engineering D4 heatsink, which had a heat resistance of 0.50 K. W-1. Changes were also made to the geometry of the best heatsink D4, by varying its heights (28, 23, 19, and 15 mm). The heat resistors were arranged in sequence (0.50, 0.560, 0.568, 0.586 kg/s), and the weights were arranger in order (3.12N, 2.56N, 2.11N and 1.67N).