• Energy Research

Abstract In this paper, an analysis of three-dimensional squeezing flow of carbon nanotubes (CNTs) based nanofluids in a rotating channel with a permeable fixed bottom wall by taking into account the effect of thermal radiation has been presented. The partial differential equations (PDEs) governing the problem were converted to ODEs and then solved using numerical method. The effects of changes in the values of various parameters on linear and angular velocity, temperature, skin friction coefficient, and local Nusselt number profiles have been investigated and for various nanofluids composed of SWCNT and MWCNT as nanoparticles and ethylene glycol as the base fluid. The most important results obtained from these figures are the oscillating behavior of the horizontal linear velocity profile due to the changes in the rotation parameter, the reverse flow in the central areas of the channel, the reduction of the temperature profile caused by increasing the radiation parameter, the direct relationship between the Eckert number and the heat transfer rate in the upper channel wall, and their reverse relationship in the lower wall of the channel.

In this paper, two-phase Nanofluid condensation and heat transfer analysis over a vertical plate under gravity and between two parallel plates under magnetic force are investigated respectively using Least Square Method (LSM) and numerical method. After presenting the governing equations and solving them by LSM, the accuracy of results is examined by fourth order Runge–Kutta numerical method. Modeling results show that the condensate film thickness after condensation is reduced and therefore, the rate of heat transfer is enhanced by the addition of nanoparticles to the regular fluid. Effect of different nanoparticles and constant numbers on the temperature/velocity/concentration profiles as well as Nusselt number and boundary layer thickness, are also investigated. For instance, it was found that TiO2 and Ag have maximum boundary layer thicknesses and Nusselt number, respectively. By considering the magnetic field effect, it is also found that nanoparticles concentration can be controlled by changing the Hartmann number which, in turn, leads to different condensation and heat transfer properties.

This paper presents a new algorithm for production planning, thermal units called so-called economic dispatch. The selected problem for algorithm implementation is a bounded and non-linear optimization problem. In the present paper, it has been tried to reduce the production costs, as well as the polluting gases emitted while generating energy. The proposed algorithm is based on multi-objective optimization algorithm of Genetic Algorithm, which is a meta-heuristic algorithm. In this paper, an idea is suggested to improve the efficiency of the multi-objective optimization algorithm. After implementation and comparing the results obtained for the multi-objective standard algorithm with the previous works, it was observed that the proposed algorithm can obtain better results. To investigate the results, a 3-generator system with and without considering the losses was used. However, in each state, 3 different demands for energy was considered and the algorithm was implemented on this system. The proposed algorithm, find answers with less than 0.15% improvement in production costs, as well as on average 0.30% improvement on the find answers with less contaminant. Keywords: Economic load dispatch, Emission dispatch, Multi-objective optimization, Multi-objective optimization algorithm based on GA (NSGA II)

In this study, three highly accurate and simple analytical methods, Differential Transformation Method (DTM), Collocation Method (CM) and Least Square Method (LS) are applied for predicting the temperature distribution in a porous fin with temperature dependent internal heat generation. The selected porous fin’s materials are Si3N4 and AL and generated heat varies linearly with temperature. The heat transfer through porous media is simulated using passage velocity from the Darcy’s model. Results reveal that DTM, CM and LS are very effective and accurate in comparison with the numerical results. Moreover the temperature distribution is depended to the Darcy and Rayleigh numbers. In addition the results show that using the AL as a porous fin’s substrate leads to higher value of temperature than Si3N4 element. A higher heat generation rate leads to higher fin temperatures since more amount of heat is dissipated to the surrounding.

Abstract The main aim of this study is to obtain an optimum design point for fin geometry, so that heat transfer rate reaches to a maximum value in a constant fin volume. Effect of fin thicknesses ratio (τ), convection coefficient power index (m), profile power parameter (n), base thickness (δ) and fin material are evaluated in the fin optimization point for heat transfer rate, effectiveness and efficiency. It’s assumed that the thickness of longitudinal fins varies with length in a special profile, so four different shapes (rectangular, convex, triangular and concave) are considered. In present study, temperature-dependent heat generation, convection and radiation are considered and an analytical technique based on the least square method is proposed for the solution methodology. Results show that by increasing the fin thicknesses ratio, maximum heat transfer rate decreases and Copper among the other materials has the most heat transfer rate in a constant volume.

Abstract In this paper, forced-convection boundary-layer of MHD Al2O3–water nanofluid flow over a horizontal stretching flat plate is investigated using Homotopy Analysis Method (HAM) and fourth order Runge–Kutta numerical method. Comparison between HAM and numerical method shows that HAM is an exact and high efficient method for solving these kinds of problems. The influence of the nanofluid volume fraction (φ) and magnetic parameter (Mn) on non-dimensional temperature and velocity profiles is investigated. As an important outcome, by increasing Mn number, thermal boundary layer thickness significantly increased but increasing the nanofluid volume fraction hasn't very sensible effect on it.

Abstract In this paper, after a short review of waste heat recovery technologies from diesel engines, the heat exchangers (HEXs) used in exhaust of engines is introduced as the most common way. So, a short review of the technologies that increase the heat transfer in HEXs is introduced and the availability of using them in the exhaust of engines is evaluated and finally a complete review of different HEXs which previously were designed for increasing the exhaust waste heat recovery is presented. Also, future view points for next HEXs designs are proposed to increase heat recovery from the exhaust of diesel engines.

In this paper, flow analysis for a third grade non-Newtonian blood in porous arteries in presence of magnetic field is simulated analytically and numerically. Blood is considered as the third grade non-Newtonian fluid containing nanoparticles. Collocation Method (CM) and Optimal Homotopy Asymptotic Method (OHAM) are used to solve the Partial Differential Equation (PDE) governing equation which a good agreement between them was observed in the results. The influences of the some physical parameters such as Brownian motion parameter, pressure gradient and thermophoresis parameter, etc. on temperature, velocity and nanoparticles concentration profiles are considered. For instance, increasing the thermophoresis parameter (Nt) caused an increase in temperature values in whole domain and an increase in nanoparticles concentration near the inner wall.

In the present paper, numerical investigations of the magnetohydrodynamics forced convection of CNT-water nanofluid inside a square enclosure with one inlet and one outlet were performed. The analysis was carried out for a wide range of Reynolds number (100 <= Re <= 1000), Hartmann number (0 <= Ha <= 60), inclination angle of the magnetic field (0 degrees <= gamma <= 90 degrees), elasticity of the bottom and left walls of the enclosure (10(4) <= E <= 10(7)), location of the center of the hexagonal body in horizontal directions (0.3 <= x(0)/L <= 0.7) and in normal directions (0.25 <= y(0)/L <= 0.75), size of the internal hexagonal body (0.1 <= a/L <= 0.3), and, finally, the volume fraction of the nanoparticles (phi = 0 and 0.1). For the flexible walls of the enclosure, a series of coupled fluid-structure interaction (FSI) analyses were accomplished by utilizing the Arbitrary Lagrangian-Eulerian formulation. It has been revealed that the bottom wall of the enclosure is very sensitive to the elastic wall, while the Nusselt number on the top wall increases with Hartmann number no matter which wall is elastic. It is also the most contributor to the heat transfer at Reynolds numbers of Re = 100 and 500, while the contribution of other walls changes with Reynolds number.