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In the present study, natural convection heat transfer is investigated in a porous cavity filled with Cu/water nanofluid and equipped with horizontal fins. Optimization and sensitivity analysis of the fin's geometry, porous medium and nanofluid properties to maximize heat transfer rate is the aim of this work. To achieve this purpose, a design space is created by input parameters which include length, number of fins, distance between fins, porosity, Darcy number and volumetric fraction of the nanoparticles. Several tools have been used to implement optimization methods including the Taguchi method (TM) for design points generation, sensitivity analysis of design variables by using signal-to-noise ratio (SNR) and analysis of variance (ANOVA), response surface method (RSM) for interpolation and regression by using nonparametric regression, and genetic algorithm (GA) for finding optimum design point. The double multi-relaxation time lattice Boltzmann method (MRT-LBM) is used to analyze and simulate the flow field and heat transfer in each design point. The results show that the optimal configuration leads to an average Nusselt number of 5.56. This optimal configuration is at the length of fins L/2, the number of fins 2, the distance between fins L/12, porosity 0.8, Darcy number 0.1, and the volumetric fraction of the nanoparticles 0.02. By using the SNR results, the Darcy number and the number of fins have the most and the least effect in maximizing the average Nusselt number, respectively. The ANOVA results and global sensitivity analysis (GSA) findings further validated this conclusion. [ABSTRACT FROM AUTHOR]

The present study has been examined the effect of the heating system position in a cubic cavity on the heat transfer rate. Also, the effects of adding the nanoparticles to the based fluid for the various heating system positions have been considered. Double multi-relaxation time lattice Boltzmann method has been used in this study as the numerical method. The position of the heating system has been varied from the bottom to the top of the room with H/4 interval ( z HW = 0 , H 4 , H 2 , H ). Cu/water nanofluid has been used to consider the effects of nanoparticle. Results have been presented for the various parameters such as Rayleigh number (103 < Ra < 105) and volume fraction of nanoparticle (0% < φ < 4%). The results show that the present numerical method is a proper method for simulating the internal heat transfer. In addition, by adding the nanoparticles, heat transfer rate increases and the amount of this augmentation depends on the position of the heating system as the maximum increment has been observed when the heating system is fixed on H 4 < z HW < H 2 . Also, the best position for the heater is H 4 < z HW < H 2 with respect to heat transfer rate. The results of the present study will be beneficial for the designing of the future optimal heating systems with high energy-saving capabilities. [ABSTRACT FROM AUTHOR]

New numerical approach has been selected for simulating magnetic force and radiation influences on alumina transportation within a permeable medium. To enhance characteristics of working fluid, we choose Al2O3–water with various shapes of nanoparticles. Various amounts of radiation, magnetic force and buoyancy have been considered to show their impacts on nanoparticles transportation. Brownian motion influences on working fluid thermal conductivity and viscosity were involved. Outcomes prove that convection decreases with augment of magnetic forces. Considering radiation can increase Nusselt number. [ABSTRACT FROM AUTHOR]

In this paper, lattice Boltzmann simulation of turbulent natural convection with large-eddy simulations (LES) in a square cavity which is filled by water/copper nanofluid has been investigated. The present results are validated by experimental data at Ra = 1.58×10 9. This study is conducted for high Rayleigh numbers (Ra = 10 7–10 9) and volume fractions of nanoparticles (0 ≤ Φ ≤ 0.06). In this research, the effects of nanoparticles are displayed on streamlines and isotherms counters, local and average Nusselt numbers. The average Nusselt number is enhanced by the augmentation of nanoparticle volume fraction in the base fluid while the manner has an erratic trend toward different Rayleigh numbers. [ABSTRACT FROM AUTHOR]