Begell House Inc.
Heat Transfer Research
HTR
1064-2285
43
1
2012
NONEQUILIBRIUM DIFFUSION COMBUSTION OF LIQUID FUEL DROPLETS AND SPRAYS MODELING
1-17
Nickolay N.
Smirnov
M. V. Lomonosov Moscow State University, Moscow 119992, Russia ; Scientific Research Institute for System Analysis of the Russian Academy of Sciences, Moscow 117218, Russia
V. F.
Nikitin
M. V. Lomonosov Moscow State University, Moscow 119992, Russia ; Scientific Research Institute for System Analysis of the Russian Academy of Sciences, Moscow 117218, Russia
V. V.
Tyurenkova
M. V. Lomonosov Moscow State University, Moscow 119992, Russia ; Scientific Research Institute for System Analysis of the Russian Academy of Sciences, Moscow 117218, Russia
A mathematical model is developed for simulating the non-equilibrium combustion of a single droplet surrounded by a diffusion microflame. The model takes into account non-equilibrium phase transitions. The formulas obtained for droplet burning out are used to simulate spray injection into a heated chamber. It is demonstrated that a scenario of fuel spray injection and self-ignition in a heated air inside the combustion chamber has three characteristic stages.
ENTROPY GENERATION DUE TO NATURAL CONVECTION COOLING OF A HORIZONTAL HEAT SOURCE MOUNTED INSIDE A SQUARE CAVITY FILLED WITH NANOFLUID
19-46
Mina
Shahi
Department of Mechanical Engineering, Faculty of Engineering, Semnan University, Semnan, Iran ; R & D Department of Semnan Water & Waste Water Company, Semnan, Iran
Amir Houshang
Mahmoudi
Department of Mechanical Engineering, Faculty of Engineering, Semnan University, Semnan, Iran ; R & D Department of Oghab Afshan Company, Semnan, Iran
Farhad
Talebi
Department of Mechanical Engineering, Faculty of Engineering, Semnan University, Semnan, Iran
The objective of this paper is to investigate the natural convection cooling of a heat source mounted inside a square cavity with special attention being paid to entropy generation. The cavity is filled with copper−water nanofluid; the right vertical wall is kept at a constant temperature, while other walls are adiabatic ones. The numerical scheme is based on the finite volume method with the SIMPLE algorithm for pressure−velocity coupling.
In this study, the influence of some effective parameters such as the Rayleigh number, location of the heat source, and solid concentration are studied; then, entropy generation due to the heat transfer irreversibility and fluid friction irreversibility as a function of Ra and solid concentration and heat source location is studied. The result shows that location of the heat source is an important parameter affecting the flow pattern and temperature field and variation of the entropy generation. Consequently the optimum case is selected since the thermal system could have the least entropy generation and the best heat transfer rate.
VOF MODELING AND ANALYSIS OF FILMWISE CONDENSATION BETWEEN VERTICAL PARALLEL PLATES
47-68
Zhenyu
Liu
Shanghai Jiao Tong University, 800 Dong Chuan Rd. Minhang District, Shanghai 200240, China
Bengt
Sunden
Division of Heat Transfer, Department of Energy Sciences, Lund University, P.O. Box 118,
SE-22100, Lund, Sweden
Jinliang
Yuan
Department of Energy Sciences, Lund University, Box 118, SE-22100 Lund, Sweden
In this study, a computational model has been developed to predict condensation heat transfer between vertical parallel plates. Transient simulations of filmwise condensation in a small two-dimensional parallel plate passage are performed. The Volume of Fluid (VOF) method is used to track the vapor−liquid interface. The Geometric Reconstruction Scheme, which is a Piecewise Linear Interface Calculation (PLIC) method, is employed to keep the interface sharp. The governing equations and the VOF equation with relevant source terms for condensation are solved explicitly. The surface tension is taken into account in the modeling and it is evaluated by the Continuum Surface Force (CSF) approach. Different methods to evaluate the source terms in the VOF and energy equations are summarized based on previous studies. The simulation is performed using the CFD software package, Ansys Fluent, and an in-house developed code. This in-house code is specifically developed to calculate the source terms associated with phase change, which are deduced from the Hertz−Knudsen equation based on the kinetic gas theory. The predicted results show that a laminar regime exists at the top of the wall, where the film is the thinnest. A wavy regime appears as a series of regular ripples/waves of condensate moving downwards under the action of both gravity and shear stress in the interface area. As a further step, the simulations have been run under different surface tension, wall temperature, and inlet velocity conditions. The predictions also indicate that the wave peak height decreases with increasing surface tension and decreases with increasing inlet velocity. This has an effect on the heat transfer characteristics of the condensation process. The condensation heat transfer increases sharply by increasing the temperature difference between the wall and saturation temperature of the inlet steam.
INFLUENCE OF HEAT AND CHEMICAL REACTIONS ON HYPERBOLIC TANGENT FLUID MODEL FOR BLOOD FLOW THROUGH A TAPERED ARTERY WITH A STENOSIS
69-94
Noreen Sher
Akbar
DBS&H, CEME, National University of Sciences and Technology, Islamabad, Pakistan
Sohail
Nadeem
Department of Mathematics, Quaid-i-Azam University 45320, Islamabad 44000, Pakistan
Mohamed
Ali
King Saud University, College of Engineering, Mechanical Engineering Department, P. O. Box 800, Riyadh 11421, Saudi Arabia
In the present article, the blood flow through a tapered artery with a stenosis is analyzed by considering axially nonsymmetric but radially symmetric mild stenosis on blood flow characteristics in the presence of heat and mass transfer, assuming the flow is steady and blood is treated as hyperbolic tangent fluid. The solution of the nonlinear equations have been obtained by employing a regular perturbation technique. Perturbation solutions have been evaluated for velocity, temperature, concentration, resistive impedance, wall shear stress, and shearing stress at the stenosis throat. The quantitative behavior of the power law index m, Weissenberg number We, stenosis shape n, Brinkman number Br, Soret number Sr and maximum height of the stenosis δ for different types of tapered arteries (i.e., converging tapering, diverging tapering, nontapered artery) has been examined through graphs.