Houman B. Rokni

Effect of magnetic field on Cu–water nanofluid heat transfer using GMDH-type neural network

Heat transfer of Cu–water nanofluid over a stretching cylinder in the presence of magnetic field has been investigated. The group method of data handling (GMDH) type neural networks (NNs) is used to calculate Nusselt number formulation. Results indicate that GMDH-type NN in comparison with fourth-order Runge–Kutta integration scheme provides an effective means of efficiently recognizing the patterns in data and accurately predicting a performance. The effects of nanoparticle volume fraction, magnetic parameter and Reynolds number on Nusselt number are studied by sensitivity analyses. The results show that Nusselt number is an increasing function of Reynolds number and volume fraction of nanoparticles while it is a decreasing function of magnetic parameter. As volume fraction of nanoparticles increases, the effect of this parameter on Nusselt number also increases, but opposite behavior is obtained for magnetic parameter and Reynolds number.

Magnetic nanofluid flow and convective heat transfer in a porous cavity considering Brownian motion effects

In the present article, the improvement of nanofluid heat transfer inside a porous cavity by means of a non-equilibrium model in the existence of Lorentz forces has been investigated by employing control volume based finite element method. Nanofluid properties are estimated by means of Koo-Kleinstreuer-Li. The Darcy-Boussinesq approximation is utilized for the nanofluid flow. Roles of the solid-nanofluid interface heat transfer parameter Nhs, Hartmann number Ha, porosity e, and Rayleigh number Ra were presented. Outputs demonstrate that the convective flow decreases with the rise of Nhs, but it enhances with the rise of Ra. Porosity has opposite relationship with the temperature gradient.

Approximate traveling wave solutions for coupled Whitham-Broer-Kaup shallow water

Homotopy Perturbation Method (HPM) was used for computing the Coupled Whitham-Broer-Kaup Shallow Water. Then HPM solution verified against exact one and compared with another approximate solution, the Homotopy Analysis Method (HAM). The existent error of the methods computed and convergence of the HPM solution has presented. Results reveal that HPM is an effective and powerful in solving the non-linear systems in mechanic, analytically.

Flow of Microencapsulated Phase Change Material Slurry through Planar Spiral Coil

ABSTRACT Forced convection cooling is an effective method in thermal management that relies mainly on dissipating heat by pumping heat transfer fluid (HTF) through the heat source. In this paper, we investigate the thermal properties enhancement of dielectric water as the HTF. To enhance the properties of the HTF, microencapsulated phase change materials (MPCM) will be added to the base fluid. The MPCMs are composed of phase change material (PCM) encapsulated with shell materials. The PCM inside the capsules may undergo a phase change. This leads to a significant heat gain and release. The numerical model is developed to solve for continuity, momentum, and heat transfer equations using the finite volume method. The behavior of the MPCM slurry in curved channels, generates unique patterns due to different viscosity values and the centrifugal forces. Our preliminary numerical data on MPCM slurry through planar spiral coil heat exchangers show the new patterns of velocity and heat transfer curves. The current paper studies the steady condition of laminar flow at different boundary conditions. The velocity and temperature profiles, heat transfer data with different mass fractions of MPCM additives to the base fluid, and their heat removal capabilities are quantified and discussed in detail.

Convective Electronic Device Cooling Using Microencapsulated Phase Change Material Slurry in Planar Spiral Coil

The current trend in miniaturization of electronic devises requires more effective thermal management techniques to remove the heat to ensure the maximum performance of the devise. Among all available thermal management techniques for electronic cooling, convective heat transfer cooling has gained attentions due to low cost and maturity in the market. The single-phase convective heat removal technique suffers from the low heat carrying capacity since there is no phase change occurs during the process. On the other hand, Microencapsulated phase change materials (MPCMs) are gaining attention due to their high heat carrying capacity. MPCMs are composed of phase change material (PCM) as the core material that is encapsulated with micrometer size shell materials. The PCM inside the capsules may undergo a phase change as the temperature varies around the melting and freezing temperature points of the PCM. This leads to a significant heat gain/release due to the phase change of the PCM.In this paper, we are performing a numerical modeling on the performance of MPCMs mixed with single-phase base fluid when pumped through planar spiral coils. From electronic thermal management point of view, it is ideal to have an enhanced coolant that maintain the operating temperature under an allowable level uniformly. The behavior of MPCM slurry when pumped through planar spiral coils reveals unique patterns due to the centrifugal forces. The available data on MPCM slurry through spiral coil heat exchangers show the new patterns of velocity and heat transfer curves that require further investigation and scientific explanations. The current paper studies the steady conditions of flows under laminar regimes at different boundary conditions. A CAD model of a planar coil heat exchanger is developed in SolidWorks. The model is meshed and discretized in order to apply the governing equations into the model. ANSYS Fluent package is used to solve the fluid flow and heat transfer equations inside the geometry. The velocity and temperature profiles along the coil are studied and discussed to quantify the roles of different forces in such flows. The ultimate goal of this study to evaluate the efficacy of utilizing such formulated microencapsulated PCM slurry at different mass concentrations on electronic thermal management considering the cost associated to the added pressure drop when using MPCM slurry.Copyright