Lattice-Boltzmann numerical simulation of double-diffusive natural convection and entropy generation in an n-shaped partially heated storage tank

Energy and mass storage in various single-phase fluid flows is of particular interest, as the world currently faces energy challenges. Double-diffusive natural convection in an n-shaped storage tank is numerically studied which can be a general guideline to maintain a storage tank with higher exergy. Lattice-Boltzmann's approach in an in-house computational code is used to simulate the problem. To display the results, it is considered that the Rayleigh number lies between 103 and 105, and the Lewis number in the range of 0.1 and 10. The average Nusselt and Sherwood number, as well as entropy generation, showing the energy loss, are illustrated. It is observed that the average Nusselt and Sherwood number rises with increasing Rayleigh number and buoyancy ratio. Further, the average Sherwood number boosts by increasing the Lewis number. The most promising parameter in increasing the heat and mass transfer are found to be Rayleigh and Lewis number, respectively, with a maximum 300 percent improvement. The flow friction can be regarded as the main source of entropy generation, with a share of 90 percent. The Rayleigh number increment from 103 to 105 leads to the rise in the total entropy generation by approximately fivefold

Laminar Mixed Convection of Al 2 O 3 -Water Nanofluid in a Three-Dimensional Microchannel

Abstract The fluid flow and heat transfer in a three-dimensional microchannel filled with Al 2 O 3 -water nanofluid is numerically investigated. The hybrid scheme is used to discretize the convection terms and SIMPLER algorithm is adopted to couple the velocity and pressure field in the momentum equations. The temperature fields, variation of horizontal velocity along the centre line of the channel, average Nusselt number and the thermal resistance in different aspect ratios are presented. It is observed that aspect ratio mainly affected the temperature gradient as well as heat transfer. Analyzing the results of numerical simulations indicates that with increasing aspect ratio, horizontal velocity along the centre line increased and then, average Nusselt number and the inlet and outlet thermal resistance decrease in the microchannel. JNS All rights reserved Article history

Hybridized power-hydrogen generation using various configurations of Brayton-organic flash Rankine cycles fed by a sustainable fuel: Exergy and exergoeconomic analyses with ANN prediction

This paper investigates different configurations of organic Rankine flash cycles combined with a Brayton cycle by performing thermodynamic, exergy, and exergoeconomic analyses. The thermal energy of the cycle is produced through burning gaseous methane generated via gasification of biomass. A systematic analysis of these configurations is conducted to enhance the exergy efficiency of the cycles. Additionally, the reutilization of the thermal energy that would otherwise be wasted in the Brayton cycle contributes to a notable enhancement in the overall thermal efficiency of the combined cycle. A range of working fluids, namely m-Xylene, o-Xylene, p-Xylene, toluene, and ethylbenzene are analyzed for the organic Rankine cycle. Predictions using an artificial neural network (radial base function) are also carried out. The results indicate that the p-Xylene increases exergy efficiency more than other working fluids. Further, the improved organic Rankine cycle mitigates exergy destruction by 10 %. Although applying double flash evaporators improves the exergy efficiency by 3 %, it increases the unit cost of power generated by more than 10 %. The application of a data-driven model to predict various configurations of combined organic Rankin cycle with a Brayton cycle fed by biomass has rarely been investigated