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In this paper Double Multi Relaxation Time Lattice Boltzmann method (DMRT-LBM) is utilized to investigate the particle motion in a modeled room for the first time. The effect of indoor heating system location has been considered on both particle deposition and convective heat transfer so six different positions have been selected for the heating system. Results are shown for two Rayleigh numbers (104 and 105) and different particle sizes (1 μ m and 10 μ m). To study the particle motion, after the flow reaches steady state, 50 000 particles are randomly injected to the room and the number of deposited particles on the walls has been reported for 100 s. Considering the present results, when the heating system is in the middle of the wall, the maximum heat transfer rate is seen for both Rayleigh numbers. Also, the number of deposited 1 μ m particles on the walls for all locations of the heating system is zero for R a = 104, so the number of suspended particles is the maximum. For both Rayleigh numbers and 10 μ m particles, the number of deposited particles is maximum when the heating system is fixed on the top of the wall. It is also concluded that when the heating system is located on the top of the wall, the number of suspended 1 μ m particles for R a = 105 reaches its maximum value. [ABSTRACT FROM AUTHOR]

Highlights • Interaction effects of an inclined magnetic field and nanofluid on the forced convection heat transfer and the flow irreversibility in a duct with an inclined FFS are studied. • The Hartmann number and the magnetic field inclination angle have the reverse effects on the heat transfer rates, whiles their influence on the flow irreversibility is increasing. • Nanoparticles volume fraction has an increasing effect on the heat transfer rates and the flow irreversibility. Abstract This research examines the interaction effects of an inclined magnetic field and nanofluid on forced convection heat transfer and flow irreversibility in a duct with an abrupt contraction. This contraction is created by an inclined forward facing step and is simulated using the Blocked region method. To analysis the flow irreversibility, the entropy generation number is calculated based on the second law of thermodynamics. The effects of Hartmann number H a = 0 - 100 , magnetic field inclination angle β = 0 Â ° - 90 Â ° and nanoparticles volume fraction ϕ = 0 - 0.06 on the values of friction coefficient, Nusselt number and entropy generation number are shown graphically. The results present that the Hartmann number and inclination angle of the magnetic field have the reverse effects on the heat transfer rate, whiles their influences on the flow irreversibility is significantly increasing. Also, total entropy generation number and average Nusselt number increase as the volume fraction of nanoparticles enhances from 0 to 0.06. [ABSTRACT FROM AUTHOR]

This research simulates the conduction-radiation problem in a complex enclosure for the gray/ non-gray assumptions with the presence of scattering influences to improve energy efficiency of thermal systems. The enclosure bottom wall includes an inclined recess with two diagonal walls. To convert these diagonal surfaces to the regular rectangular surfaces in Cartesian coordinates, the Blocked-off method is used. The air containing 10% CO 2 and 20% H 2 O is regarded as participating medium in the enclosure. The absorption coefficient of this mixture is obtained across the spectrum using the information of HITRAN2008 database. Simulating the non-gray medium is done by employing the full-spectrum k-distribution (FSK) approach, whilst the gray medium simulation is performed utilizing the Planck mean absorption coefficient. The finite volume and discrete ordinates methods are respectively applied to calculate the energy and radiation transport equations. Impacts of surface emissivity on conductive, radiative and total heat fluxes are examined in details. [ABSTRACT FROM AUTHOR]

• Forced convection in the Exhaust problem are simulated using SLW and gray models. • Difference between the gray and SLW models in calculating the magnitudes of N u c ¯ decreases with enhancing the RC and ɛ w parameters. • Difference between gray and SLW models in computing the magnitudes of N u t ¯ increases with enhancing the RC parameter. In this work, influences of thermal radiation on forced convection in the Exhaust problem are effectively simulated by application of the spectral line-based weighted sum of gray gases (SLW) model. The Exhaust problem includes an abrupt contraction in a horizontal channel. The working fluid of this problem is an air mixture with 10% CO 2 and 20% H 2 O mole fractions. This mixture is regarded as an emitting, absorbing and non-scattering medium. In addition, the gray model is utilized to simulate the radiative medium based on total emissivity. Then, the findings of this model are compared with the results of SLW model as the main case to attain the error rate of gray model in simulating the Exhaust problem. The results clearly show the differences between the gray and SLW models to simulate the thermal behaviors are strongly dependent on the radiation-conduction parameter (25 ≤ RC ≤ 50) and wall emissivity (0 ≤ ɛ w ≤ 1). In this regards, the gray model is unable predict the real results in many cases. [ABSTRACT FROM AUTHOR]

This study deals with the analysis of the interacting influences of Lorentz force and bleeding on the hydrothermal behaviors of magnetohydrodynamic (MHD) nanofluid flow and entropy generation in a trapezoidal recess. This trapezoidal recess is created by two inclined steps in a horizontal channel. The Lorentz force is appeared due to the existence of a magnetic field in the flow domain. The Brownian motion influences on the effective characteristics of CuO -water nanofluid are considered to have more accuracy. The effects of bleeding coefficients (−0.005 ≤ V w ≤ + 0.005), Hartmann number (0 ≤ Ha ≤ 60) and concentration of solid nanoparticles (0 ≤ ϕ ≤ 0.04) on the flow characteristics, heat transfer and flow irreversibility rates are investigated. The results show that the trends and values of friction coefficient, Nusselt number and entropy generation number can be different at the various magnitudes of Ha and V w , whereas the ϕ parameter only increases the values of them. These differences are related to the variations of streamlines contours against the Ha , V w and ϕ parameters. [ABSTRACT FROM AUTHOR]

In this work numerical simulation of magneto hydrodynamics (MHD) natural convection in a three-dimensional cubic cavity with sinusoidal temperature distribution on one side wall has been considered. New means of the Lattice Boltzmann method with double Multi-Relaxation-Time (MRT) model has been applied utilizing cu/water nanofluid. D3Q19 and D3Q7 models have been used to solve the momentum and energy equations, respectively. Different Rayleigh numbers (Ra = 10 3 _ 10 5 ) and various Hartmann numbers (Ha = 0–100) for volumetric fraction of the nanoparticles (Ø) between Ø = 0 and 12% have been investigated. Also, phase deviation varied from θ = 0 to π with interval π/2. The magnetic field is considered horizontally and the results have been shown at different planes and lines of the 3-D enclosure. Based on the results, the double MRT-LBM method is a proper method for simulating the 3-D flows with complex boundary conditions. The results show that augmentation of the Hartmann number decreases the heat transfer rate whereas the increase of the Rayleigh number and nanoparticles’ volumetric fraction enhance the heat transfer rate. The highest effect of magnetic field is obtained at Ra = 10 4 and the lowest effect is seen at Ra = 10 3 . Also, the greatest effect of Rayleigh number is captured at Ha = 0 for all volumetric fraction of the nanoparticles. [ABSTRACT FROM AUTHOR]