Entropy generation of MHD flow of sodium alginate (C6H9NAO7) fluid in thermal engineering

In this paper, impacts of magnetic field and porosity on the entropy generation of sodium-alginate (C6H9NaO7) fluid are studied. C6H9NaO7 is taken over a moving and heated vertical wall. Heat transfer is due to free convection. Initially, the problem is formulated in the form of PDEs along with physical conditions and then written in non-dimensional form. Problem is solved via Laplace transform and expression in analytical form is established for temperature and velocity field. The related relations for entropy generation and Bejan number and entropy generation are also examined. Nusselt number and Skin-friction are calculated and plotted in graphs. For numerical computations, a finite difference scheme is used using MATLAB software. The results in tables and graphs are discussed for embedded parameters. It is found that the magnetic field and porosity have strong influence on velocity, entropy generation and Bejan number. For greater Hartman number, entropy generation magnitude is greater compared to the Bejan number, conversely, this variation in Bejan number is more efficient. The porosity effect showed that if the medium is more porous, the entropy generation can decreases 50% when porosity increase from Ka = 1 to Ka = 2, however the Bejan number increases.

Coupling of BGK lattice Boltzmann method and experimental rheological/thermal behavior of Al2O3–oil nanolubricant for modeling of a finned thermal storage

Purpose The purpose of the present work is to investigate the hydrodynamic and thermal performance of a thermal storage based on the numerical and experimental approaches using the lattice Boltzmann method and the experimental observation on the thermo-physical properties of the operating fluid. Design/methodology/approach For this purpose, the Al2O3 nanoparticle is added to the lubricant with four nanoparticle concentrations, including 0.1, 0.2, 0.4 and 0.6Vol.%. After preparing the nanolubricant samples, the thermal conductivity and dynamic viscosity of nanolubricant are measured using thermal analyzer and viscometer, respectively. Finally, the extracted data are used in the numerical simulation using provided correlations. In the numerical process, the lattice Boltzmann equations based on Bhatnagar–Gross Krook model are used. Also, some modifications are applied to treat with the complex boundary conditions. In addition, the second law analysis is used based on the local and total views. Findings Different types of results are reported, including the flow structure, temperature distribution, contours of local entropy generation, value of average Nusselt number, value of entropy generation and value of Bejan number. Originality/value The originality of this work is combining a modern numerical methodology with experimental data to simulate the convective flow for an industrial application.

Conjugate Free Convection Heat Transfer and Thermodynamic Analysis of Infrared Suppression Device with Cylindrical Funnels

A convection system can be designed as an energy-efficient one by making a considerable reduction in exergy losses. In this context, entropy generation analysis is performed on the infrared suppression system numerically. In addition, results due to heat transfer are also shown. The numerical solution of the Navier-stokes equation, energy equation, and turbulence equation is executed using ANSYS Fluent 15.0. To perform the numerical analysis, different parameters such as the number of funnels, Rayleigh number (Ra), inner surface temperature, and geometric ratio are varied in the practical range. Results are shown in terms of heat transfer, entropy generation, irreversibility (due to heat transfer and fluid friction), and Bejan number with some relevant parameters. Streamlines and temperature contours are also provided for better visualization of temperature and flow field around the device. Results show that heat transfer and mass flow rate increase with the increase in Ra. Entropy generation and the irreversibility rise with an increase in the number of funnels and geometric ratio. Also, the Bejan number decreases with an increase in Ra and the number of funnels. A cooling time is also obtained using the lumped capacitance method.

Natural convection and thermal radiation analysis inside the square cavity filled with non-Newtonian fluid via heatlines and entropy generation

In the present analysis, natural convection heat transfer coupled with thermal radiation of bi-viscosity fluid contained inside the cavity has been studied through heatlines and entropy generation. Heat is provided to the cavity through heated source with length L/2, which is placed at the middle of bottom wall. Side walls of the enclosure at low temperature i.e. T_c ad rest of the walls are kept an adiabatic. The idea of Bejan heatlines and average Bejan number have been used to visualized the convective heat folw and dominant irreversibility due to fluid flow or heat transfer, respectively. Finite element method with penalty technique has been applied to obtain the solution of governing equations. Results are obtained through numerically and displayed in terms of streamlines, heat flux lines , isotherms, velocity, temperature, entropy, Nusselt number and average Bejan number against the extensive range of bi-viscosity β=0.002-1 and thermal radiation N_R=0-5, at fixed Rayleigh Ra=〖10〗^5 and Prandtl number Pr=10. It is observed that there exist a direct relation between bi-viscosity parameter and convection heat transfer due to buoyancy-driven flow. Moreover, the dominant entropy generation has been reported through heat transfer in the lower region of the cavity with and without thermal radiation.

Entropy generation optimization of unsteady radiative hybrid nanofluid flow over a slippery spinning disk

Entropy generation investigation of hybrid nanofluidic transport over an unsteady spinning disk is reported in this analysis. The magnetic influence, velocity slips, and thermal radiative effects are included within the flow. Ferrous oxide (Fe3O4) and graphene oxide (GO) are used as tiny nano ingredients, and water (H2O) is the base medium. The dimensional leading equations are settled to dimensionless nonlinear ordinary differential equations (ODEs) by significant similarity transformations. Then, classical RK-4 scheme with a shooting process has been initiated to execute the numerical simulation. The software MAPLE-18 is used to run the entire simulation with an indispensable accuracy rate. Several streamlines, graphs, and requisite tables are executed to divulge the parametric impact on the nanofluidic stream. Entropy generation–related figures are depicted for diverse parameters, and parametric effects on Bejan number are also analyzed. Moreover, the corresponding physical consignments like the measure of the frictional hindrance, heat transport are calculated and reviewed. The entropy generation augments for higher magnetic value but reduces for velocity slip, radiation, and nanoparticle concentration. Hybrid nanofluid gives a lower magnitude in entropy production as compared to the usual nanofluid. Magnetic parameter reduces the Bejan number, while slip factor and nanoparticle concentration amplify such effects. Heat transfer ultimately seems to increase for nanoparticle volume fraction, and the increase rate is 4.01685 for usual nanofluid, but it is 6.7557 for hybrid nanofluid. Also, the numerical fallouts address the possibility of using magnetized spinning disks in space engines and nuclear propulsion, and such a model conveys significant applications in heat transport improvement in so many industrial thermal management equipment and renewable energy systems.