Begell House Inc.
Computational Thermal Sciences: An International Journal
CTS
1940-2503
9
4
2017
EXOTHERMICALLY REACTING OF NON-NEWTONIAN FLUID FLOW OVER A PERMEABLE NONLINEAR STRETCHING VERTICAL SURFACE WITH HEAT AND MASS FLUXES
283-296
Mohamed R.
Eid
Department of Mathematics, Faculty of Science, New Valley Branch, Assiut University,
Al-Kharga, Al-Wadi Al-Jadid 72511, Egypt
S. R.
Mishra
Department of Mathematics, I.T.E.R., Siksha 'O' Anusandhan University, Bhubaneswar,
Odisha 751030, India
This paper reports the mathematical model of the heat and mass transfer in a non-Newtonian fluid flow through
a permeable nonlinear stretching vertical wall in the presence of such effects as exothermically reacting, heat generation/absorption, thermal radiation, and heat and mass fluxes. A similarity transformation is used to reduce the
controlling partial differential equations (PDEs) into ordinary ones, which are solved numerically by an efficient numerical shooting technique with a fourth-fifth order Runge–Kutta method. Numerical results for the temperature and concentration profiles as well as for the local skin friction, Nusselt number, and Sherwood number are obtained and depicted graphically for different parametric conditions to illustrate interesting aspects of the solution. It is found that the source parameter enhances the distribution at all points, and heavier species cause a lower concentration level near the concentration boundary layer.
NUMERICAL SIMULATION OF MELTING AND SOLIDIFICATION OF DIFFERENT KINDS OF PHASE CHANGE MATERIALS (PCM) ENCAPSULATED IN SPHERICAL NODULES IN A WATER FLOW
297-310
Khouiled
Rachedi
ETAP Laboratory, Department of Mechanical Engineering, University of Tlemcen, B.P. 230,
Tlemcen 13000, Algérie
Abdel Illah Nabil
Korti
ETAP Laboratory, Department of Mechanical Engineering, University of Tlemcen, B.P. 230,
Tlemcen 13000, Algérie
The objective of this work is to carry out a computational study on the thermal behavior of two different phase change
materials (PCMs), inside aluminum spherical capsules, in both charging and discharging modes. Water is used as
heat transfer fluid (HTF) at constant temperature. The thermal and dynamical behavior of both PCM, i.e., PCM1
and PCM2, put in two capsules, is detailed at the beginning of this study. The results indicate that natural convection
dominates heat transfer during the chargingmode. The solidification phase is conduction-dominated in the discharging mode. Moreover, these same results suggest that the PCM1-PCM1 configuration is preferable when the application requires the storage of a small latent energy (latent heat) and a long discharge time. Whereas configuration PCM2-PCM2 is preferred when the application requires the storage of a large latent heat energy and a short discharge time. However, the configuration PCM1-PCM2 is more desirable when the application requires the storage of an average latent heat energy with a long discharge time. Moreover, for the height velocity of water flow, the latent heat energy packed by two different PCM without thermal interaction is the arithmetical addition between them. Whereas, from v = 10-5, the thermal interaction between two different PCM cannot be neglected and the energy stored is not the arithmetic addition. The thermal interaction appears clearly in the discharging mode. Thus, the thermal interaction has accelerated the discharging of PCM2. Whereas, the discharging of PCM1 is prolonged by this thermal interaction.
MELTING OF NANOPARTICLE-ENHANCED PHASE CHANGE MATERIAL IN A SHELL-AND-TUBE LATENT HEAT STORAGE UNIT HEATED BY LAMINAR PULSATING FLUID FLOW
311-334
Radouane
Elbahjaoui
Cadi Ayyad University, Faculty of Sciences Semlalia, Department of Physics, P.O. 2390, Fluid
Mechanics and Energetic Laboratory, Marrakesh, Morocco
Hamid
El Qarnia
Cadi Ayyad University, Faculty of Sciences Semlalia, Department of Physics, Fluid Mechanics
and Energetic Laboratory (affiliated to CNRST, URAC 27), Marrakesh, Morocco
The aim of this paper is to investigate the effect of the laminar pulsating heat transfer fluid (HTF) flow on the melting of nanoparticle-enhanced phase change material (NEPCM) inside a shell-and-tube latent heat storage unit (LHSU). The shell space is filled with n-octadecane as a base phase change material (PCM) dispersed with copper nanoparticles. A heat transfer fluid (HTF: water) flows in the inner tube and transfers heat to NEPCM. In order to evaluate the effect of the use of both pulsating flow and NEPCM instead of a stationary flow and a base PCM on the storage performance, a mathematical model based on the energy conservation equations has been developed and validated by experimental, numerical, and theoretical results. Numerical simulations were conducted to investigate the effect of the volumetric fraction of nanoparticles, pulsating frequency, Reynolds number, and Stefan number on the thermal behavior and performance of the storage unit. Calculations were performed in the following control parameter ranges: the volumetric fraction of nanoparticles from 0 to 7%, dimensionless pulsating frequency from 0.01 to 3, Reynolds number from 100 to 2000, and Stefan number ranges from 0.155 to 0.402. The results showed that the dispersion of copper nanoparticles in base PCM enhances the thermal performance of the LHSU. For a volumetric fraction of nanoparticles of 7%, a reduction up to 14.4% in the melting time (at dimensionless pulsating frequency of 1, Reynolds number of 500, and Stefan number of 0.155) was achieved. The results also showed that the pulsating frequency affects the heat transfer rate to NEPCM, and the small melting time is obtained for a low pulsating frequency. It was also revealed that high Reynolds and Stefan numbers highly reduce the time required for the complete melting.
A NUMERICAL APPROACH TO INVERSE BOUNDARY DESIGN PROBLEM OF COMBINED RADIATION-CONDUCTION WITH DIFFUSE SPECTRAL DESIGN SURFACE
335-349
Mohamad
Omid Panah
Mechanical Engineering Department, School of Engineering, Shahid Bahonar University of
Kerman, Kerman, Iran
S. A. Gandjalikhan
Nassab
Mechanical Engineering Department, School of Engineering, Shahid Bahonar University of
Kerman, Kerman, Iran
S. M. Hosseini
Sarvari
Mechanical Engineering Department, School of Engineering, Shahid Bahonar University of
Kerman, Kerman, Iran
In the present work, an optimization technique is applied for inverse boundary design problem of radiative-conductive
heat transfer in a square cavity. All the boundary walls except the design surface are gray. The main goal is to verify the effect of spectral behavior of the design surface on the solution of an inverse problem. The conjugate gradient method is used to find the unknown temperature distribution over the heater surface, which is located along the top wall, to satisfy the prescribed temperature and heat flux distributions over the design surface. The variation of emissivity with respect to the wavelength is approximated by considering a set of spectral bands with constant emissivity, and then the radiative transfer equation is solved by the discrete ordinates method for each band. The sensitivity problem is obtained by differentiation of all governing equations and related boundary conditions with respect to the unknown variable (heater temperature). The performance of the present method is evaluated by comparing the results to those obtained by considering a diffuse gray design surface. Finally, an attempt is made to investigate the spectral behavior of the design surface on the calculated temperature distribution over the heater surface. For the direct problem, the present numerical results are compared to theoretical findings in literature and a good consistency is found.
PREDICTION OF THERMODYNAMIC STABILITY LIMITS AND CRITICALITY CONDITIONS FOR BINARY HYDROCARBON SYSTEMS
351-361
Fahad M.
Al Sadoon
Department of Chemical Engineering, American University of Sharjah, P.O. Box 26666,
Sharjah, UAE
Muhammad
Qasim
Department of Chemical Engineering, American University of Sharjah, P.O. Box 26666,
Sharjah, UAE
Naif A.
Darwish
Department of Chemical Engineering, American University of Sharjah, P.O. Box 26666,
Sharjah, UAE
Thermodynamic stability (spinodal) limits are determined for several binary hydrocarbon mixtures of N-methyl-α-pyrrolidone, NMP(1), with alkanes(2). Using the NRTL model, rigorous criteria for both intrinsic stability and criticality
conditions are derived and solved numerically using MATLAB. In addition, the spinodal and binodal data are
tested for compliance with the critical universality theory. Results indicate that the binary liquid systems of NMP
with the considered alkanes represent a universal class such that the binodal and spinodal information for other binary
mixtures of NMP within the same class can be predicted using simple power law models. Spinodal and miscibility
gaps for binary liquid mixtures of NMP with alkanes not included in the database are predicted and found to be in
excellent agreement with those obtained from the developed thermodynamic criteria and the experimental binodal data.
The developed simple power law model is very helpful in easy and quick estimation of liquid-liquid equilibrium data.
NUMERICAL PREDICTION OF 3D THERMOSOLUTAL NATURAL CONVECTION AND ENTROPY GENERATION PHENOMENA WITHIN A TILTED PARALLELEPIPEDIC CAVITY WITH VARIOUS ASPECT RATIOS
363-382
Fakher
Oueslati
Al-Baha University, Physics Department, Faculty of Science, 6543 Al-Baha, Kingdom of Saudi
Arabia; University of Tunis El-Manar, Laboratory of Physics of Fluids, Physics Department, Faculty of Science of Tunis, 2092 El-Manar 2, Tunis, Tunisia
Brahim
Ben-Beya
University of Tunis El-Manar, Laboratory of Physics of Fluids, Physics Department, Faculty of
Science of Tunis, 2092 El-Manar 2, Tunis, Tunisia
Three-dimensional (3D) thermosolutal natural convection and entropy generation within an inclined enclosure is
investigated in the current study. A numerical method based on the finite volume method and a full multigrid technique
is implemented to solve the governing equations. Effects of various parameters, namely, the aspect ratio (Az), buoyancy ratio (N) and inclination angle (γ) on the flow patterns and entropy generation are predicted and discussed. The
numerical outcome of the present study shows that, the thermal and solutal isosurfaces exhibit a central stratification that significantly strengthens as the aspect ratio is augmented. It is also found that decreasing the aspect ratio value Az leads to weakening the total entropy generation and reducing the 3D effects exhibited within the cavity. Moreover, the distribution of total entropy generation is found to decrease by further enhancing the buoyancy ratio value for all Az investigated. Especial attention is attributed to analyze the periodic flow pattern that appears for Ra = 104, Az = 2, and the inclination angle γ = 75 deg. In terms of irreversibility criterion at the oscillatory regime, total entropy generation (Stot) and Bejan number (Be) are seen to oscillate with the same frequency but in opposing phases and with different amplitudes. Furthermore, the heat and mass transfer rates at the equilibrium state present a maximum and a minimum at the specific inclination values γ = 30 deg and γ = 75 deg. A comparison of 2D and 3D models at normal
situation γ = 0 deg is conducted when N varied in the transition range −2 ≤ N ≤ −0.6 demonstrating that the 2D
assumption can be adopted for the 3D flows when −0.5 ≤ N ≤ 0.