Begell House Inc.
Heat Transfer Research
HTR
1064-2285
43
3
2012
NUMERICAL APPROACH TO MAGNETOHYDRODYNAMIC VISCOELASTIC FLUID FLOW AND HEAT TRANSFER OVER A NONISOTHERMAL STRETCHING SHEET
187-206
Talla
Hymavathi
School of Mathematical & Information Sciences, Adikavi Nannaya University, Rajahmundry, Andhra Pradesh, India
The paper deals with the study of the flow of an incompressible electrically conducting viscoelastic fluid referred to as Walter's liquid B over a nonisothermal stretching sheet with radiation using a quasi-linearization technique adopting a numerical approach. The speed of the sheet is assumed to be proportional to the distance from the origin. The velocity and temperature profiles are obtained numerically and these are displayed by graphs for diverse values of the Prandtl number, viscoelastic, magnetic, source/sink, wall temperature, wall heat flux, and thermal radiation parameters. The results are compared with those available in the literature obtained by analytical procedures and are seen to be in good agreement.
ENHANCEMENT OF HEAT TRANSFER OF LAMINAR FLOW OF VISCOUS OIL THROUGH A CIRCULAR TUBE HAVING INTEGRAL AXIAL RIB ROUGHNESS AND FITTED WITH HELICAL SCREW-TAPE INSERTS
207-227
Sujoy
Saha
WBUT & AICTE
Suvanjan
Bhattacharyya
Department of Mechanical Engineering, MCKV Institute of Engineering, Liluah, Howrah − 711204, West Bengal, India
G. L.
Dayanidhi
Mechanical Engineering Department, Bengal Engineering and Science University Shibpur, Howrah 711 103, INDIA
The experimental friction factor and Nusselt number data for laminar flow through a circular duct having integral axial rib roughness and fitted with helical screw-tape inserts have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the helical screw-tape inserts in combination with integral axial rib roughness perform better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of the fin parameter.
INCREASE IN RATES OF KINETIC PROCESSES INSIDE THE BIMODAL HYPERSONIC SHOCK WAVE
228-236
M. M.
Kuznetsov
Moscow Regional State University, Russia
Yu. D.
Kuleshova
Moscow Regional State University, Russia
The problem on the influence of nonequilibrium (non-Maxwell) translational energy distributions over freedom degrees of molecules upon the velocity of inelastic binary collisions with activation threhold energy in the hypersonic shock wave is considered. The method is based on the bimodal Tamm−Mott−Smith approximation of the distribution function of molecules as applied to the analysis of rates of barrier chemical processes. Based on this model the expressions are obtained in explicit form for the distribution function of molecule pairs and frequencies of inelastic binary collisions with energy threshold that allow for the effect of translational nonequilibrium in the hypersonic shock wave. These expressions take into account the anisotropy of a temperature field in the hypersonic shock wave. This fact is of importance for a physical experiment where in the course of numerical calculations the influence of the temperature anisotropy on chemical reaction constants was only estimated. It is shown that in one-component, polyatomic gases with inelastic collisions in the high-velocity "tail" of the bimodal Tamm−Mott−Smith distribution function of molecule pairs, earlier known as the "overlapping" effect, i.e., the excess of the number Nneq of high-velocity pairs inside the wave front over the number Neq in the translational equilibrium zone behind the front, has a maximum in the relative quantity Nneq /Neq</sub dependent on the compression degree inside a strong shock wave.
NONLINEARITY EFFECT OF TRANSPORT PROPERTIES ON COMBUSTION OF VOLATILE ORGANIC PARTICLES
237-257
Mehdi
Bidabadi
Department of Mechanical Engineering, Department of Energy Conversion, Combustion and
Heat Transfer Modeling Laboratory, Iran University of Science and Technology, Tehran, Iran
Seyed Alireza
Mostafavi
School of Mechanical Engineering, Department of Energy Conversion, Iran University of Science and Technology
Payam
Asadollahzadeh
School of Mechanical Engineering, Department of Energy Conversion, Iran University of Science and Technology, Narmak, 16887, Tehran, Iran
This paper presents the structure of laminar, one-dimensional, and steady-state flame propagation in a uniform cloud of volatile organic particles. In this model, it is assumed that particles vaporize to yield a gaseous fuel. In order to study the effects of thermal conductivity and thermal diffusion on combustion of organic particles, an asymptotic analysis, based on the large Zeldovich number or high rate of reaction, is used. In the preheat zone, the rate of chemical reaction is small, and transfer phenomena play a significant role in temperature and mass distributions. Therefore, according to the kinetic theory of gases, thermal (conductivity (λ) and diffusion coefficient (D) are considered to be proportional to T 1/2 and T 3/2, respectively. Finally, flame characteristics for different equivalence ratios of solid mixture for different Lewis numbers are reported. Results show that both flame temperature and burning velocity increase with rise in the Lewis number.
INVESTIGATING THE NATURAL CONVECTION HEAT TRANSFER FROM TWO ELLIPTIC CYLINDERS IN A CLOSED CAVITY AT DIFFERENT CYLINDER SPACINGS
259-284
Seyyed Mohammad Ali
Noori Rahim Abadi
University of Pretoria
Arian
Jafari
School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
A numerical investigation is presented to survey the laminar natural convection heat transfer around two elliptic cylinders with different vertical spacings relative to each other in a closed cavity. The numerical model used in this paper is based on a 2D Navier-Stokes incompressible flow momentum and energy equations solver on an unstructured grid. Discretization of the governing equations that include the continuity, momentum, and energy equations is achieved through a finite element scheme based on the Characteristic Based Split (CBS) algorithm. The working fluid is assigned a Prandtl number of 0.71 (air) and assumed to be incompressible with constant physical properties. The radiation, viscous dissipation, and pressure work are also assumed to be negligible throughout this investigation. Fluid flow and heat transfer characteristics are examined in the range of the Rayleigh number, cylinders spacing, and cylinders' orientation such that: 103 ≤ Ra ≤ 106, 1 ≤ s/a ≤ 4, and b/a = 0.67, 1.5. It is also assumed that cylinders' location can be changed vertically along the square cavity centerline. The local and average Nusselt numbers streamlines, and isotherms are presented for various relevant dimensionless groups. The obtained results reveal that the Rayleigh number and cylinders' position would change magnitude and patterns of streamlines and isotherms.