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Books by Ehsan M Languri

Over the past few decades there has been a prolific increase in research and development in area ... more Over the past few decades there has been a prolific increase in research and development in area of heat transfer, heat exchangers and their associated technologies. This book is a collection of current research in the above mentioned areas and describes modelling, numerical methods, simulation and information technology with modern ideas and methods to analyse and enhance heat transfer for single and multiphase systems. The topics considered include various basic concepts of heat transfer, the fundamental modes of heat transfer (namely conduction, convection and radiation), thermophysical properties, computational methodologies, control, stabilization and optimization problems, condensation, boiling and freezing, with many real-world problems and important modern applications. The book is divided in four sections : "Inverse, Stabilization and Optimization Problems", "Numerical Methods and Calculations", "Heat Transfer in Mini/Micro Systems", "Energy Transfer and Solid Materials", and each section discusses various issues, methods and applications in accordance with the subjects. The combination of fundamental approach with many important practical applications of current interest will make this book of interest to researchers, scientists, engineers and graduate students in many disciplines, who make use of mathematical modelling, inverse problems, implementation of recently developed numerical methods in this multidisciplinary field as well as to experimental and theoretical researchers in the field of heat and mass transfer.

Papers by Ehsan M Languri

The two-dimensional fluid flow and heat transfer in a circular tube heat exchanger with two ellip... more The two-dimensional fluid flow and heat transfer in a circular tube heat exchanger with two elliptic obstacles at the back is studied numerically. The computational domain consists of a circular tube and two elliptic obstacles that are situated after the tube, such that the angle between their centerlines and the direction of free coming flow is 45 degrees. The numerical solution is achieved by numerical integration of full Navier-Stokes and energy equations over the computational domain, using finite volume method. The fluid flow is assumed to be laminar, incompressible and steady-state with constant thermo-physical characteristics. In this study major thermo-fluid parameters such as temperature, pressure and velocity fields as well as Nusselt number and friction factor variations are computed and some results are presented in the graphs. It is shown that using of elliptic obstacles leads to an increase in the average Nusselt number and also pressure. .

A solar flat plate air collector was manufactured in the north of Iran, and connected to a room a... more A solar flat plate air collector was manufactured in the north of Iran, and connected to a room as the model to study the possibility of using such solar heating systems in the northern parts of Iran. This collector was tested as a solar air heater to see how good it could be for warming up the test room during the winter. The experimental data obtained through accurate measurements were analyzed using second law approach to find the optimum mass flow rate, which leads to the maximum exergy efficiency. It was found that for the test setup at the test location, a mass flow rate of 0.0011 kg/s is the optimum mass flow rate for tested conditions which leads to the highest second law efficiency.

A theoretical model for the 1-D flow of a resin-like liquid in the naturalfiber fiber mats of res... more A theoretical model for the 1-D flow of a resin-like liquid in the naturalfiber
fiber mats of resin transfer molding (RTM) mold is proposed. After assuming the
porosity and the permeability to vary only a function of time, a theoretical formula for the
front location is proposed after employing an altered form of continuity equation (which
takes into account both the liquid absorption and the fiber swelling) and the Darcy’s law for
the single-phase flow. A comparison of the theoretical predictions with the experiments
reveals that the variable permeability model offers a better match viv-a-vis the fixed
permeability

Variational iteration method (VIM) and homotopy perturbation method (HPM) have been used to evalu... more Variational iteration method (VIM) and homotopy perturbation method (HPM) have been
used to evaluate the efficiency of straight fins with temperature-dependent thermal
conductivity and to determine the temperature distribution within the fin. These methods
are useful and practical for solving the nonlinear heat diffusion equation, which is
associated with variable thermal conductivity condition. VIM and HPM provide an
approximate analytical solution in the form of an infinite power series. The fin efficiency
of the straight fins with temperature-dependent thermal conductivity has been obtained as
a function of thermo-geometric fin parameter and the thermal conductivity parameter
describing the variation of the thermal conductivity. It has been observed that the thermal
conductivity parameter has a strong influence over the fin efficiency. The data from the
present solutions has been correlated for a wide range of thermo-geometric fin parameter
and the thermal conductivity parameter. The resulting correlation equations can assist
thermal design engineers for designing of straight fins with temperature-dependent
thermal conductivity.

Permeability is fundamental to an accurate simulation of mold-filling in liquid composite molding... more Permeability is fundamental to an accurate simulation of mold-filling in liquid composite
molding (LCM) technologies (such as RTM) that are used for manufacturing polymer composites. In this paper,
unit cells representing the micro-structure of a biaxial stitched fiber mat are used by the 3D finite element based
CFD simulation to estimate numerical permeability. Stokes and Brinkman equations are employed to model the
saturated flow in the inter- and intra-tow regions, respectively, of the non-crimp fiber mat with a dual-scale pore
structure. Two different unit cells are identified for the mat: one bigger and true to the mat architecture, and the
other smaller but inaccurate, though including the essence of tow distribution. The experimental permeability of
the mat is measured using the 1D flow experiment. A comparison of the numerical and experimental
permeabilities reveals that the permeability estimated using the big (true) unit cell is less close to the real value
as compared to the permeability estimated using the small (apparent) unit cell. Explanations such as nesting
between the plies, tow deformation, and overlooking of stitches in the flow simulation, can be used to explain the
larger error witnessed in the numerical permeability obtained from the geometrically accurate, big unit-cell. CFD
simulation in the small unit cell is shown to be a quicker, less difficult, and paradoxically more accurate way of
estimating the mat permeability.

In this article, the problem of two-dimensional flow of a micropolar fluid in a porous channel is... more In this article, the problem of two-dimensional flow of a micropolar fluid in a porous channel is presented, and the homotopy perturbation method (HPM) is employed to compute an approximation to the solution of the system of nonlinear differential equations governing the problem. Comparisons are made between the numerical solution and the results of the HPM. The results reveal that this method is very effective and simple and can be applied to other nonlinear problems.

In this paper, He’s variational iteration method (VIM) and homotopy perturbation method (HPM) are... more In this paper, He’s variational iteration method (VIM) and homotopy perturbation method (HPM) are implemented for solving analytically two systems of ordinary differential equations that often appear in chemical applications. In both methods, the initial approximations can be freely chosen with possible unknown constants which can be determined by imposing the boundary and initial conditions. The solution procedure is of utter simplicity, and the obtained solution is of high accuracy.

Instead of finding a small parameter for solving nonlinear problems through perturbation method, ... more Instead of finding a small parameter for solving nonlinear problems through perturbation method, a new analytical method called
He’s variational iteration method (VIM) is introduced to be applied to solve nonlinear Jaulent–Miodek, coupled KdV and coupled
MKdV equations in this article. In this method, general Lagrange multipliers are introduced to construct correction functionals for
the problems. The multipliers can be identified optimally via the variational theory. The results are compared with exact solutions

Fluid flow and heat transfer exist in our daily life as well as usual industrial problems. Simple... more Fluid flow and heat transfer exist in our daily life as well as usual industrial problems. Simple examples of such common phenomena are the flowing water in a riverbed, flying airplanes above the earth, boiling water for making tea, etc. Such simple phenomena can be modeled mathematically by means of Partial Differential Equations (PDEs). Most of the natural PDEs in the life are nonlinear due to the complexity of the problem and the number of variables involved in the problem. There are several ways to tackle such problems—such as ...

International Communications in Heat and Mass …, Jan 1, 2010

This paper offers theoretical results for fully developed slip-flow forced convection through a m... more This paper offers theoretical results for fully developed slip-flow forced convection through a microchannel of semicircular cross-section. Numerical results are also presented to study the developing region. Velocity slip and temperature jump boundary conditions are applied at the uniformly heated walls. The results from the two different sources are cross validated and those pertaining to the limiting case of no-slip flow are found to be in good agreement with those available in the literature.

International Communications in Heat and Mass …, Jan 1, 2010