Begell House Inc.
Heat Transfer Research
HTR
1064-2285
47
5
2016
ANALYTICAL STUDY OF THE THREE-DIMENSIONAL TEMPERATURE FIELD OF A KDP CRYSTAL IRRADIATED BY A SQUARE WAVE MODULATED LASER
423-431
Yingcong
Zhang
Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094, China
Hua
Shen
Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094, China
Rihong
Zhu
Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094, China
A general analytical expression for a transient temperature field of a KDP crystal irradiated by a square wave modulated laser is obtained by the integral transform method, based on the heat conduction equation for an orthotropic material. The influence of the radius, power, and frequency of the laser and the heat transfer coefficient on the transient temperature field of the KDP crystal is simulated by Matlab. The results show that the temperature of the material has a ladder-type distribution with time, which shows periodical stable distribution after some time, and it increases with a decrease in the laser radius and increase in the laser power. The temperature of the surface will decrease with increase in the heat transfer coefficient. The above results provide a theoretical basis for the photothermal displacement technology used in measurement of the optothermal parameters of the KDP crystal.
NUMERICAL STUDY OF WALL PROTECTION BY THE EVAPORATION OF LIQUID FILM OF ETHYLENE GLYCOL
433-447
Hicham
Meftah
CORIA, University of Rouen, France; Ibn Zohr University, GEMS Laboratory, ENSA, B.P 1136, Agadir-Morocco
M'barek
Feddaoui
Laboratory of Energy Engineering, Materials and Systems, ENSA, Ibn Zohr University, Morocco
Wall protection by evaporation of an ethylene glycol liquid film along a vertical channel is considered. The numerical method applied solves the coupled governing equations together with the boundary and interfacial conditions. The systems of equations obtained by using an implicit finite difference method are solved by the TDMA method. The solution technique is based on a variational procedure for determining the temperature at the gas−liquid interface. Parametric computations were performed to investigate the effect of the inlet liquid temperature and inlet liquid mass flow rate on the efficiency of wall protection. The results indicate that the most important factor for the protection of walls is the thickness of the liquid film that acts as an insulator.
NUMERICAL OPTIMIZATION OF THE THERMAL PERFORMANCE OF A SOLAR AIR CHANNEL HAVING DISCRETE MULTI V-RIB ROUGHNESS ON THE ABSORBER PLATE
449-469
Anil
Kumar
School of Mechanical and Civil Engineering, Shoolini University, Solan 173229; Himalayan Center of Excellence in Nanotechnology, Shoolini University, Solan 173229
R. P.
Saini
Alternate Hydro Energy Centre, IIT, Roorkee, Uttarakhand-247667, India
J. S.
Saini
Mechanical and Industrial Engineering Department, IIT, Roorkee, Uttarakhand-247667, India
Rib roughness and different obstructions used in the path of the air passage in a solar air channel are used to increase the thermal performance by breaking the laminar sublayer or by increasing turbulence in the channel passage for air flow. This work is concerned with optimization of rib parameters of solar air channel based on thermal efficiency. The roughness produced on the absorber plate forms the wetted side of the upper broad wall of the rectangular solar air channel. The following quantities varied as: e/D from 0.022 to 0.043, Gd/Lv from 0.24 to 0.80, g/e from 0.5 to 1.5, α from 30° to 75°, P/e from 6.0 to 12.0, and W/w from 1.0 to 10.0. A methodology has been developed for predicting the thermal efficiency. A program was also developed in MATLAB for calculating the thermal efficiency. Based on the values of thermal efficiency, optimization has been carried out to determine the set of values of rib parameters that correspond to the maximum thermal efficiency for the given values of operating parameters of the channel. It was observed that the maximum values of the thermal efficiency and enhancement factor are 0.043 for e/D, 0.69 for Gd/Lv, 1.0 for g/e, 60° for α, 8.0 for P/e, and 6.0 for W/w. Finally, discrete multi v-rib shape solar air channel has been found to have better thermal efficiency as compared to other rib shapes of the solar air channel investigated by other researchers under similar numerical conditions.
EFFECTS OF AXIAL MAGNETIC FIELD AND THERMAL CONVECTION ON A COUNTERROTATING VON KARMAN FLOW
471-488
Lyes
Bordja
Faculte des Sciences et Technologie, Dept. Genie Mecanique, Universite Cheikh Larbi Tebessi, Tebessa-12002, Algeria
Emilia
Crespo del Arco
Departamento de Fisica Fundamental, U.N.E.D., Apdo. Correos 60.141, 28080 Madrid, Spain
Eric
Serre
Aix-Marseille Universite, CNRS, Ecole Centrale Marseille, Laboratoire M2P2, Marseille,
France
Rachid
Bessaih
L.E.A.P, Dept. Genie Mecanique, Universite Mentouri de Constantine, Route d'Ain El Bey, 25000 Constantine, Algeria
The effects of thermal convection and of a constant axial magnetic field on a von Karman flow driven by the exact counterrotation of two lids are investigated in a vertical cylinder of aspect ratio Γ(= height/radius) = 2 at a fixed Reynolds number Re(= Ω R2/v) = 300. Direct numerical simulations are performed when varying separately the Rayleigh and Hartmann numbers in the range [0, 1800] and [0, 20], respectively, in the limit of the Boussinesq approximation and of a small magnetic Reynolds numbers, Rem << 1. Without a magnetic field, the base flow symmetries of the von Karman flow are broken by thermal convection that becomes dominant in the range of Ra [500, 1000]. Three-dimensional solutions are characterized by the occurrence of a steady, m = 1, azimuthal mode exhibiting a cat's eye vortex in the circumferential plane. When increasing the Rayleigh number in the range [500, 1000], the vortex pulsates in an oscillatory manner, due to variations of the flow intensity. Otherwise, increasing the axial magnetic field intensity stabilizes the flow, and the oscillatory motion can be inhibited. Numerical solutions show that the critical Rayleigh number for transition increases linearly with the Hartmann number. Finally, results show that when varying the Rayleigh number, the structure of the electric potential can be strongly modified by thermal convection. Such an observation suggests new induction mechanisms in the case of small nonzero values of the magnetic Reynolds number.
EFFECTS OF VARIABLE VISCOSITY AND INCLINED MAGNETIC FIELD ON PERISTALTIC MOTION OF FOURTH-GRADE FLUID WITH HEAT TRANSFER
489-503
Tasawar
Hayat
Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000, Pakistan; Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science,
King Abdulaziz University, P.O. Box 80257, Jeddah 21589, Saudi Arabia
Z. Ali
Bhatti
Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000, Pakistan
Fahad M.
Abbasi
Department of Mathematics, COMSATS, Institute of Information Technology, Islamabad, Pakistan
B.
Ahmad
Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science,
King Abdulaziz University, Jeddah 21589, Saudi Arabia
Ahmed
Alsaedi
Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, P. O. Box. 80257,
Jeddah 21589, Saudi Arabia
The effect of variable viscosity on the peristaltic flow of fourth-grade fluid is investigated. The concept of inclined magnetic field is employed in mathematical simulation. Heat transfer analysis is carried out in the presence of viscous dissipation. The peristaltic waves propagating along the channel walls with different amplitudes and phase induce asymmetry in the flow. Numerical solutions are obtained for the stream function, longitudinal velocity, temperature and pressure gradients. Numerical integration is performed for the pressure rise per wavelength. Pumping and trapping phenomena are analyzed.
EXPERIMENTAL-COMPUTATIONAL ANALYSIS OF HIGH-SPEED INTERACTION OF A SOLID WITH WATER BARRIERS
505-518
S. A.
Afanasyeva
Research Institute of Applied Mathematics and Mechanics, National Research Tomsk State University, Tomsk, Russia
V. V.
Burkin
National Research Tomsk State University, Tomsk, Russia
A. S.
D'yachkovskii
National Research Tomsk State University, Tomsk, Russia
A. N.
Ishchenko
National Research Tomsk State University, Tomsk, Russia
M. V.
Khabibullin
National Research Tomsk State University, Tomsk, Russia
The stress−strain state of projectiles is investigated when a high-speed projectile enters water and interacts with barriers protected by a water layer. Experimental investigations are carried out using a high-speed ballistic setup. Calculations are performed within the framework of the mechanics of continuous media for an elastoplastic model of a solid with allowance for fracture and a hydrodynamic water model. Depending on the projectile speed, different stress−strain state regimes are observed: from little deformed one at a speed of about 1 km/s to a fractured one at a speed of about 2 km/s. The calculation technique allows the distances in water to be determined at which a metal barrier can be punched in the inertial model.