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The heat transfer phenomena inside a horizontal channel with an open trapezoidal enclosure subjected to a heat source of different lengths was investigated numerically in the present work. The heat source is considered as a local heating element of varying length, which is embedded at the bottom wall of the enclosure and maintained at a constant temperature.The air flow enters the channel horizontally at a constant cold temperature and a fixed velocity. The other walls of the enclosure and the channel are kept thermally insulated. The flow is assumed laminar, incompressible, and two-dimensional, whereas the fluid is considered Newtonian. The results are presented in the form of the contours of velocity, isotherms, and Nusselt numbers profiles for various values of the dimensionless heat source lengths (0.16 ≤ ε ≤ 1). while, both Prandtl and Reynolds numbers are kept constant at (Pr = 0.71) and (Re = 100), respectively. The results indicated that the distribution of the isotherms depends significantly on the length of the heat source. Also, it was noted that both the local and the average Nusselt numbers increase as the local heat source length increases. Moreover, the maximum temperature is located near the heat source location.

For an efficient energy harvesting by the PV/thermoelectric system, the maximum power point tracking (MPPT) principle is targeted, aiming to operate the system close to peak power point. Under a uniform distribution of the solar irradiance, there is only one maximum power point (MPP), which easily can be efficiently determined by any traditional MPPT method, such as the incremental conductance (INC). A different situation will occur for the non-uniform distribution of solar irradiance, where more than one MPP will exist on the power versus voltage plot of the PV/thermoelectric system. The determination of the global MPP cannot be achieved by conventional methods. To deal with this issue the application of soft computing techniques based on optimization algorithms is used. However, MPPT based on optimization algorithms is very tedious and time consuming, especially under normal conditions. To solve this dilemma, this research examines a hybrid MPPT method, consisting of an incremental conductance (INC) approach and a moth-flame optimizer (MFO), referred to as (INC-MFO) procedure, to reach high adaptability at different environmental conditions. In this way, the combination of the two different algorithms facilitates the utilization of the advantages of the two methods, thereby resulting in a faster speed tracking with uniform radiation distribution and a high accuracy in the case of a non-uniform distribution. It is very important to mention that the INC method is used to track the maximum power point under normal conditions, whereas the MFO optimizer is most relevant for the global search under partial shading. The obtained results revealed that the proposed strategy performed best in both of the dynamic and the steady-state conditions at uniform and non-uniform radiation.

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The present study addresses theoretically and computationally the performance of electrically conducting water-Fe3O4/CNT hybrid nanofluid in three-dimensional natural convective heat transfer and entropy generation within a wavy-walled trapezoidal enclosure. The enclosure has two layers -a hybrid nanofluid layer and a porous medium layer. A transverse magnetic field is applied in the upward direction. Newtonian flow is considered and the modified Navier-Stokes equations are employed with Lorentz hydromagnetic body force, Darcian and Forchheimer drag force terms. The wavy side planes are heated down while the top and vertical planes are thermally insulated. A rectangular heated fin is placed in the lower plane and several different locations of the fin are considered. The transformed, non-dimensional system of coupled non-linear partial differential equations with associated boundary conditions is solved numerically with the Galerkin finite element method (FEM) in the COMSOL Multiphysics software platform. The effects of Darcy number, Hartmann number, volume fraction, undulation number of the wavy wall and Rayleigh number (thermal buoyancy parameter) on the streamlines, isotherms and Bejan number contours are studied. Extensive visualization of the thermal flow characteristics is included. With increasing Hartmann number and Rayleigh number, the average Bejan number is reduced strongly whereas average Nusselt number is only depleted significantly at very high Rayleigh number and high Hartmann number. With increasing undulation number, there is a slight elevation in average Bejan number at intermediate Rayleigh numbers, whereas the average Nusselt number is substantially boosted, and the effect is maximized at very high Rayleigh number. Increment in Darcy number (i. e. reduction in permeability of the porous medium layer) is observed to considerably elevate average Nusselt number at high values of Rayleigh number, whereas the contrary response is computed in average Bejan number. The simulations are relevant to hybrid magnetic nanofluid fuel cells and electromagnetic nano-materials processing in cavities.

The purpose of this work was to conduct a numerical examination of mixed convective heat transfer in a three-dimensional triangular enclosure with a revolving circular cylinder in the cavity’s center. Numerical simulations of the hybrid Fe3O4/MWCNT-water nanofluid are performed using the finite element approach (FEM). The simulation is carried out for a range of parameter values, including the Darcy number (between 10−5 and 10−2), the Hartmann number (between 0 and 100), the angular speed of the rotation (between −500 and 1000), and the number of zigzags. The stream function, isotherms, and isentropic contours illustrate the impact of many parameters on motion, heat transfer, and entropy formation. The findings indicate that for enhancing the heat transfer rates of hybrid nanofluid in a three-dimensional triangular porous cavity fitted with a rotating cylinder and subjected to a magnetic field, Darcy number > 10−3, Hartmann number < 0, one zigzag on the hot surface, and rotation speed > 500 in flow direction are recommended.

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