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Garoosi F.,Semnan University | Garoosi F.,Islamic Azad University | Hoseininejad F.,Islamic Azad University | Rashidi M.M.,Shanghai Key Laboratory of Vehicle Aerodynamics and Vehicle Thermal Management Systems | Rashidi M.M.,ENN Group
Applied Thermal Engineering | Year: 2016

This article presents a numerical study of natural convection heat transfer in a heat exchanger filled with nanofluid. Walls of the enclosure are insulated and constant temperature conditions are given for hot (Th ) and cold (Tc ) pipes (Th >. Tc ). The effects of pertinent parameters such as; Rayleigh number, temperature of the nanofluid, diameter and type of the nanoparticles on the heat transfer rate are examined. Moreover, the influence of design parameters such as; arrangement and orientation of the hot and cold pipes, location and number of the hot pipe, internal and external cooling and heating on the flow field, temperature distributions and the heat transfer rate are also investigated. The results show that, the total Nusselt number enhances with increasing the nanoparticle volume fraction up to an optimal particle loading at which the heat transfer rate within the enclosure has a maximum value. In addition, the results indicated that, the heat transfer rate and the optimal particle loading enhances by increasing the average temperature of the nanofluid. Finally, the numerical results demonstrate that, location, arrangement and number of the hot and cold pipes have a significant impact on the heat transfer rate across the heat exchanger. © 2016 Elsevier Ltd.

Rashidi M.M.,Shanghai Key Laboratory of Vehicle Aerodynamics and Vehicle Thermal Management Systems | Rashidi M.M.,ENN Group | Parsa A.B.,Islamic Azad University | Shamekhi L.,Islamic Azad University | Momoniat E.,University of Witwatersrand
Thermal Science | Year: 2015

The similar solution on the equations of the revised Cheng-Minkowycz problem for natural convective boundary layer flow of nanofluid through a porous medium gives (using an analytical method), a system of non-linear partial differential equations which are solved by optimal homotopy analysis method. Effects of various drastic parameters on the fluid and heat transfer characteristics have been analyzed. A very good agreement is observed between the obtained results and the numerical ones. The entropy generation has been derived and a comprehensive parametric analysis on that has been done. Each component of the entropy generation has been analyzed separately and the contribution of each one on the total value of entropy generation has been determined. It is found that the entropy generation as an important aspect of the industrial applications has been affected by various parameters which should be controlled to minimize the entropy generation.

Uddin M.J.,Bangladesh American International University | Rostami B.,Islamic Azad University | Rashid M.M.,Shanghai Key Laboratory of Vehicle Aerodynamics and Vehicle Thermal Management Systems | Rashid M.M.,ENN Group | Rostami P.,Isfahan University of Technology
Alexandria Engineering Journal | Year: 2016

This paper deals with an analytical solution of free convective flow of dilatant nanofluid past a vertical cone/plate. A two-phase mixture model is used for nanofluid in which the Brownian motion and thermophoretic diffusivities are the important slip mechanisms between solid and liquid phases. The governing transport equations along with physically realistic thermal and mass convective boundary conditions are reduced to similarity equations using relevant similarity transformations before being solved by homotopy analysis method. The effects of the governing parameters (Brownian motion, thermophoresis, convection-conduction, convection-diffusion, Lewis number, buoyancy ratio, and power-law) on the dimensionless velocity, temperature and nanoparticle volume fraction, friction and heat transfer rates are plotted and discussed. It is found that friction factor decreases with the increase in Le and Nr for both vertical plate and cone. The local Nusselt number decreases with the increase in the thermophoresis and Brownian motion parameters for both the plate and cone. The local Sherwood number increases with the Brownian motion parameter and decreases for thermophoresis parameter. The results have been compared with the published ones and an excellent agreement has been noticed. © 2015 Faculty of Engineering, Alexandria University. Production and hosting by Elsevier B.V.

Sarwar S.,COMSATS Institute of Information Technology | Rashidi M.M.,Shanghai Key Laboratory of Vehicle Aerodynamics and Vehicle Thermal Management Systems
Waves in Random and Complex Media | Year: 2016

This paper deals with the investigation of the analytical approximate solutions for two-term fractional-order diffusion, wave-diffusion, and telegraph equations. The fractional derivatives are defined in the Caputo sense, whose orders belong to the intervals [0,1], (1,2), and [1,2], respectively. In this paper, we extended optimal homotopy asymptotic method (OHAM) for two-term fractional-order wave-diffusion equations. Highly approximate solution is obtained in series form using this extended method. Approximate solution obtained by OHAM is compared with the exact solution. It is observed that OHAM is a prevailing and convergent method for the solutions of nonlinear-fractional-order time-dependent partial differential problems. The numerical results rendering that the applied method is explicit, effective, and easy to use, for handling more general fractional-order wave diffusion, diffusion, and telegraph problems. © 2016 Taylor & Francis

Garoosi F.,Semnan University | Rohani B.,University of Technology Malaysia | Rashidi M.M.,Shanghai Key Laboratory of Vehicle Aerodynamics and Vehicle Thermal Management Systems | Rashidi M.M.,ENN Group
Powder Technology | Year: 2015

Steady state mixed convection heat transfer of nanofluid in a two-sided lid driven cavity with several pairs of heaters and coolers (HACs) inside is investigated numerically using two-phase mixture model. The governing equations have been discretized using the finite volume method while the SIMPLE algorithm has been introduced to couple the velocity-pressure. The influences of volume fraction, diameter and type of the nanoparticles, Richardson number, number of the Heaters and Coolers (HACs), external and internal heating and moving direction of the cavity walls on flow structure, the heat transfer rate and distribution of nanoparticles are investigated. The results of this investigation illustrate that, at low Richardson number by increasing number of the HACs, the heat transfer rate increases. On the other hand, at high Ri, a saturated number of HACs exists which beyond that the value of mean Nusselt number does not changes significantly. In addition, the results reveal that by reducing the diameter of the nanoparticles and Ri, the heat transfer rate increases. It is also observed that at high Richardson numbers, distribution of nanoparticles with dp≥145nm is fairly non-uniform while at low Richardson numbers particle distribution remains almost uniform. Moreover, it is found that by changing direction of the moving walls the heat transfer rate changes significantly. © 2015 Elsevier B.V.

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