Begell House Inc.
Heat Transfer Research
HTR
1064-2285
46
8
2015
NUMERICAL SOLUTION FOR THE BLASIUS FLOW IN A CASSON FLUID WITH VISCOUS DISSIPATION AND CONVECTIVE BOUNDARY CONDITIONS
689-697
MUHAMMAD
QASIM
COMSATS Institute of Information Technoogy,Islamabad-Pakistan
B.
Ahmad
Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science,
King Abdulaziz University, Jeddah 21589, Saudi Arabia
Effects of thermal radiation and viscous dissipation on the Blasius flow in a Casson fluid have been investigated. The statements of the problems are given in terms of convective boundary conditions. A numerical solution to the resulting problems is presented. The influences exerted by the involved emerging flow variables are analyzed. A comparison with the previous study is made. It is noticed that the temperature increases with an increase in the Eckert number. Moreover, the temperature is also an increasing function of the Biot number.
NUMERICAL SOLUTIONS OF TELEGRAPH EQUATIONS USING AN OPTIMAL HOMOTOPY ASYMPTOTIC METHOD
699-712
Shaukat
Iqbal
Department of Computer Science, COMSATS Institute of Information Technology, Sahiwal, Pakistan
Muhammad Sadiq
Hashmi
Department of Computer Science, COMSATS Institute of Information Technology, Sahiwal, Pakistan
Nargis
Khan
Department of Mathematics, The Islamia University of Bahawalpur, Pakistan
M.
Ramzan
Department of Mathematics, The Islamia University of Bahawalpur, Pakistan
Amir H.
Dar
Department of Electrical Engineering, COMSATS Institute of Information Technology, Islamabad, Pakistan
A telegraph equation is solved by employing an optimal homotopy asymptotic method (OHAM) when considering the propagation of electric signals in a cable of transmission line and wave phenomena. The method use simple computations with quite acceptable approximate solutions that agree closely with exact solutions. To illustrate the efficiency and reliability of the method, some examples are given. Finally, a comparison with the existing results reveals that the OHAM performs extremely well in terms of accuracy and simplicity.
SLIP EFFECT ON FREE CONVECTION FLOW OF SECOND GRADE FLUIDS WITH RAMPED WALL TEMPERATURE
713-724
Dumitru
Vieru
Department of Theoretical Mechanics, Technical University of Iasi 700050, Romania
M. A.
Imran
Department of Mathematics, University of Management and Technology Lahore, Pakistan
A.
Rauf
Abdus Salam School of Mathematical Sciences, GC University Lahore, Pakistan
The unsteady free convection flow of an incompressible second-grade fluid near a vertical plate is considered on the assumption that the fluid moves with a slip at the heated wall. The relative velocity of the fluid is assumed to be proportional to the shear rate at the wall. The exact expressions for temperature and velocity are determined by means of the Laplace transform with respect to the temporal variable t. The velocity fields corresponding to both the slip and no-slip conditions for second-grade and Newtonian fluids are obtained in the general case where the vertical plate is moved with the velocity Uof(t). Two particular cases, namely translation with a constant velocity and sinusoidal oscillations of the wall are discussed. Some physical aspects of the two flows are illustrated graphically. The influence of the slip coefficient on the velocity is also studied.
MAGNETOHYDRODYNAMIC VISCOUS FLOW OVER A SHRINKING SHEET IN A SECOND-ORDER SLIP FLOW MODEL
725-734
Tahir
Mahmood
Department of Mathematics, The Islamia University of Bahawalpur, Pakistan
S. M.
Shah
Department of Mathematics, The Islamia University, Bahawalpur, Pakistan
Ghulam
Abbas
Department of Mathematics, COMSATS Institute, of Information Technology, Sahiwal, Pakistan
In this paper, we investigate a magnetohydrodynamic viscous flow over a permeable shrinking surface by means of a second-order slip flow model. We have obtained a closed form of exact solution for the Navier−Stokes equations by using the similarity variable technique. The effects of slip, suction, and magnetic parameters have been investigated in detail. The results show that there are two solution branches, namely, a lower solution branch and an upper solution branch. The behavior of velocity and shear stress profiles at different values of slip, suction, and magnetic parameters has been discussed through graphs.
AN INVERSE HEAT CONDUCTION MODEL FOR DETERMINING THE CASTING/CHILL INTERFACIAL HEAT TRANSFER COEFFICIENT
735-749
Liqiang
Zhang
College of Mechanical and Electrical Engineering, Central South University of Forestry and Technology, Changsha, 410004, Hunan, P. R. China; State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha, 410082
Luoxing
Li
State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha, 410082, Hunan, P. R. China
The interfacial heat transfer coefficient (IHTC) is required for accurate simulation of the casting process. However, it cannot be easily obtained simply by using either experimental or theoretical methods. Using measured temperature data, an inverse method can be used to predict the IHTC. However, the latent heat released during the solidification of a molten metal complicates the associated temperature and IHTC calculations. To overcome this difficulty, an equivalent specific heat method is applied in this study to calculate the IHTC for the casting process. It is found that the identified IHTC varies with time during castings solidification. The IHTC values calculated for an aluminum alloy casting of simple geometry cast on a steel chill vary from 1200 to 3500 W·m−2·K−1. Application of the indentified IHTC in the forward heat conduction model with the same boundary condition allows comparison between numerically calculated and experimentally obtained results for validation of the method. The results show that the numerically calculated temperatures are in good agreement with those measured experimentally. This confirms that the proposed method is a feasible and effective tool for determining the casting-mold IHTC. Additionally, the characteristics of the time−varying IHTC have also been discussed.
HEAT TRANSFER CHARACTERISTICS OF THE WICKLESS JACKET-TYPE RADIAL HEAT PIPE
751-763
Yonggang
Jiao
Department of Energy and Environmental Engineering, Shĳiazhuang Tiedao University,
Shĳiazhuang 050043, China
Guodong
Xia
Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124, China
Suge
Huang
Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124, China
This paper presents a theoretical investigation of the behavior of the jacket-type radial heat pipe in a transient regime. We used a simple, rapid mathematical model to calculate the unsteady-state startup process of the jacket-type radial heat pipe. We also developed a computer simulation program based on the method that estimates the temperature of the heat pipe as well as the time needed to reach a steady-state condition. This paper presents an analysis of the startup performance of the heat pipe with variation of the input heat power. Experiments were focused on defining the influence of the input heat power on the steady-state heat transfer characteristics of the jacket-type radial heat pipe. The simulation results are in good agreement with experimental data. Other favorable outcomes were: the locations near the orifice have good temperature uniformity in the inner tube; an increasing Reynolds number results in a decreasing Nusselt number on a smooth surface, and the total thermal resistance of the heat pipe decreases with increase in the input heat power and filling ratio.
NATURAL CONVECTION HEAT TRANSFER IN A DIFFERENTIALLY HEATED ENCLOSURE WITH ADIABATIC PARTITIONS AND FILLED WITH A BINGHAM FLUID
765-783
Karim
Ragui
Laboratoire des Phenomenes de Transfert, Faculte de Genie Mecanique et de Genie des Procedes, Universite des Sciences et de la Technologie Houari Boumediene BP, 32 El Alia, 16111 Bab Ezzouar, Algiers, Algeria
Youb Khaled
Benkahla
Faculté de Génie Mécanique et de Génie des Procédés, Université des Sciences et de la Technologie Houari Boumediene USTHB, B.P. 32, El-Alia Bab-Ezzouar, 16111 Algiers, Algeria
Nabila
Labsi
Laboratoire des Phenomenes de Transfert, Faculte de Genie Mecanique et de Genie des Procedes, Universite des Sciences et de la Technologie Houari Boumediene BP, 32 El Alia, 16111 Bab Ezzouar, Algiers, Algeria
Abdelkader
Boutra
Laboratoire des Phenomenes de Transfert, Faculte de Genie Mecanique et de Genie des Procedes, Universite des Sciences et de la Technologie Houari Boumediene BP, 32 El Alia, 16111 Bab Ezzouar, Algiers, Algeria
The present numerical study deals with two-dimensional natural convection in a differentially heated square enclosure, with centrally located partitions and offset partitions. The cavity is considered to be completely filled with a yield fluid obeying the rheological model of Bingham. The governing equations were solved using a code based on the finite volume method. The code has been validated for both cases of a Newtonian and non-Newtonian fluid, after comparison between the present results and those given in the literature.
In order to investigate the effect of a set of parameters, i.e., the partitions height and thickness, on heat and flow behaviors, the Prandtl number is taken equal to 20, the Rayleigh number is fixed at 106, and the Bingham number covers the range from 0 to 20. The results show, on the one hand, that the average Nusselt number is a decreasing function of the Bingham number and that all parameters related to geometrical dimensions of partitions exert a crucial effect on the flow field and heat transfer, on the other hand. Moreover, it has been pointed out that the position of such partitions has an important effect on both fluid flow and heat transfer and that the partitions thickness enhanced heat transfer.