Begell House Inc.
Heat Transfer Research
HTR
1064-2285
49
2
2018
MIXED CONVECTION FLOW OF Al2O3–WATER NANOFLUID IN A TWO-SIDED LID-DRIVEN CAVITY WITH WAVY WALLS
91-102
10.1615/HeatTransRes.2017014257
Hasan
Karabay
Mechanical Engineering Department, Engineering Faculty, Kocaeli University, Kocaeli, 41380,
Turkey
mixed convection
nanofluid
wavy wall
Richardson number
lid-driven cavity
In the present work, fluid flow and heat transfer characteristics of Al2O3–water nanofluid in a two-sided lid-driven cavity with wavy walls is investigated numerically. The top and bottom flat walls of the cavity are driven in opposite directions,
while the vertical wavy walls are maintained at different temperatures. The influence of the geometric parameters such as the amplitude of a wave and the number of undulations together with the Richardson number and volume fraction of the nanofluid in fluid flow and heat transfer is studied. The results demonstrated that both flow and temperature distributions are sensitive to the geometric parameters. It is also shown that introducing nanoparticles to the base fluid enhances heat transfer considerably for all Richardson numbers considered in this study.
NUMERICAL INVESTIGATION OF HEAT TRANSFER TO SUPERCRITICAL WATER IN A 2 × 2 ROD BUNDLE WITH TWO CHANNELS
103-118
10.1615/HeatTransRes.2017019599
Ibrahim
Tahir
Department of Nuclear Engineering, Pakistan Institute of Engineering and Applied Sciences
(PIEAS), Nilore, Islamabad 45650, Pakistan
Waseem
Siddique
Department of Mechanical Engineering, Pakistan Institute of Engineering and Applied Sciences
(PIEAS), Nilore, Islamabad 45650, Pakistan
Inam ul
Haq
Department of Nuclear Engineering, Pakistan Institute of Engineering and Applied Sciences
(PIEAS), Nilore, Islamabad 45650, Pakistan
Kamran
Qureshi
Department of Mechanical Engineering, Pakistan Institute of Engineering and Applied Sciences
(PIEAS), Nilore, Islamabad 45650, Pakistan
Anwar Ul Haq
Khan
Department of Polymer and Process Engineering, University of Engineering and Technology,
Lahore, Pakistan
computational fluid dynamics
heat transfer
supercritical water
In the present study, a numerical investigation was made using the ANSYS Fluent code to analyze the heat transfer to
supercritical water in a 2 × 2 rod bundle. The geometry consists of two channels separated by a solid body. Water moves downward in the first channel and then moves upward in the second channel, which is connected through U-turns. This results in cooling of the rod bundle, which is stationed in the second channel. The outer diameter of the heated rod is 10 mm. Two turbulence models, i.e., k–ε (RNG) and k–ω (SST), were benchmarked against the experimental data. It was found out that the k–ω (SST) model gives the best prediction for heat transfer as well as for the wall temperature distribution in supercritical water with an error maximum of up to 6.8% for the heat transfer coefficient. A parametric study was carried out by the variation in the wall heat flux, mass flux, and operating pressure to study their effects on heat transfer. The results show that the heat transfer phenomenon is similar to that found in a simple tube. A comparison of the heat transfer
coefficient with the Dittus–Boelter equation was made and was used for normalizing the predicted heat transfer coefficient. Three heat transfer regimes were observed, namely: normal heat transfer, enhanced heat transfer, and deteriorated heat transfer. The onset of heat transfer deterioration was predicted for a mass flux of 350 kg/m2·s, which shows lower values of the heat transfer coefficient ratio. It was observed that the effect of buoyancy was prominent near the pseudocritical region, after which its effect faded out.
HEAT AND MASS TRANSFER BOUNDARY-LAYER FLOW OVER A VERTICAL CONE THROUGH POROUS MEDIA FILLED WITH A Cu–WATER AND Ag–WATER NANOFLUID
119-143
10.1615/HeatTransRes.2017016247
Patakota Sudarsana
Reddy
Department of Mathmetatics, Rajeev Gandhi Memorial College of Engineering & Technology,
Nandyal-518501, AP, India
P.
Sreedevi
Department of Mathematics, Rajeev Gandi Memorial College of Engineering and Technology,
Nandyal-518501, AP, India
Ali J.
Chamkha
Faculty of Engineering, Kuwait College of Science and Technology, Doha District, Kuwait;
Center of Excellence in Desalination Technology, King Abdulaziz University, P.O. Box 80200,
Jeddah 21589, Saudi Arabia; Mechanical Engineering Department, Prince Sultan Endowment for Energy and
Environment, Prince Mohammad Bin Fahd University, Al-Khobar 31952, Saudi Arabia; RAK Research and Innovation Center, American University of Ras Al Khaimah, P.O. Box
10021, Ras Al Khaimah, United Arab Emirates
Ali F.
Al-Mudhaf
Manufacturing Engineering Department, The Public Authority for Applied Education and Training, P. O. Box 42325, Shuweikh, 70654 Kuwait
heat and mass transfer
Cu–water and Ag–water nanofluid
MHD
thermal radiation
chemical reaction
finite element method
In this paper, we have described the influence of thermal radiation and chemical reaction on boundary-layer flow, heat and mass transfer of two different nanofluids in a porous medium over a vertical cone with heat generation/absorption. In the present study, we have considered two varieties of nanofluids, namely, Cu–water and Ag–water nanofluids (with volume fraction 10% and 30%). The similarity variables are used to transform conservation equations for the nanofluid into a set of ordinary differential equations and are solved numerically subject to the boundary conditions using well-organized, extensively authorized, variational finite element method. The correctness of the present numerical code is validated with previously published data, and the results are found to be in good agreement. The sway of important nondimensional parameters of velocity, temperature, and nanoparticle concentration fields as well as the skin friction coefficient, Nusselt number, and Sherwood number are examined in detail, and the results are shown graphically and in a tabular form to illustrate the physical importance of the problem. The thermal boundary-layer thickness is raised in the entire flow region as the volume fraction of nanoparticles increased from 10% to 30%, and this rise in the temperature profiles is more in the Ag–water nanofluid than in the Cu–water nanofluid.
CHARACTERISTICS OF WATER EVAPORATION ON A NANOPATTERNED SURFACE FABRICATED BY UV NANOIMPRINT LITHOGRAPHY
145-156
10.1615/HeatTransRes.2017015899
Noriyuki
Unno
Department of Mechanical Engineering, Tokyo University of Science, Yamaguchi, 1-1-1 Digakudo-ri, Sanyo-onoda, Yamaguchi, 756-0884 Japan
Motoharu
Asano
Department of Applied Electronics, Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo, Japan
Yuki
Matsuda
Department of Applied Electronics, Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo, Japan
Shin-ichi
Satake
Department of Applied Electronics, Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585 Japan
Jun
Taniguchi
Department of Applied Electronics, Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585, Japan
evaporation
nanoimprint
UV curable resin
transparent
antireflection
We investigated the behavior of water droplet evaporation on a nanopatterned surface. The nanopattern was fabricated by
ultraviolet nanoimprint lithography (UV-NIL) on a transparent film using an UV curable resin. In this study, a moth-eye structure, which is used for anti-reflection, on a glassy carbon substrate was used as a master mold. Furthermore, a nanopattern made of the UV curable resin via UV-NIL was also used as a replica mold, and we succeeded in fabrication of a second generation nanopatterned film. Using both obtained transparent films with nanopattern, the evaporation characteristics of a water droplet were investigated. As a result, it became clear that the speed of evaporation on the first and second generation films was improved, compared to the substrate without the nanopattern. Moreover, the nanopatterned surface has a lower reflectance ratio than the planar surface. Consequently, the obtained film can be a multifunctional transparent film to prevent the light reflection and improve the evaporation rate of water droplet.
NUMERICAL INVESTIGATION OF NATURAL CONVECTION IN AN ENCLOSURE WITH A CONDUCTING SOLID BODY
157-172
10.1615/HeatTransRes.2017016351
Bengisen
Pekmen
TED University
heat transfer
natural convection
conducting solid body
DRBEM
In this study, heat transfer characteristics in the presence of a conducting body placed in an enclosure are investigated
by using the dual reciprocity boundary element method (DRBEM). The governing dimensionless equations in terms
of stream function, temperature, and vorticity are solved numerically, and the effect of different thermal conductivity ratios, sizes, shapes, locations, and numbers of the solid bodies and of the Rayleigh number on heat transfer is observed by isotherms and average Nusselt number. A way to determine the stream function boundary condition around solid body is also proposed.
PULSATING HYBRID NANOFLUIDS DOUBLE SLOT JETS IMPINGEMENT ONTO AN ISOTHERMAL WALL
173-188
10.1615/HeatTransRes.2017015650
Fatih
Selimefendigil
Department of Mechanical Engineering, College of Engineering, King Faisal University, Al Ahsa
31982, Saudi Arabia; Department of Mechanical Engineering, Manisa Celal Bayar University, Manisa, Turkey
hybrid nanofluids
pulsating impinging jet
heat transfer enhancement
In the present work, a numerical study of oscillating rectangular double slot jets subjected to Alsub>2O3−Cu–water hybrid
nanofluid is conducted. The unsteady governing equations are solved by a finite volume based commercial solver. The
effects of pulsating frequency, Reynolds number in the laminar flow regime on the heat transfer characteristics are
numerically investigated. It is observed that both in the steady flow and pulsating flow case, the stagnation point
Nusselt number increases with the Reynolds number. More recirculation bubbles are formed on the bottom wall and
on the top wall, and their complicated interactions cause the fluctuation of the local peak in the Nusselt number for
the lowest frequency in the pulsating flow case. At f = 0.5 Hz, heat transfer enhancements of 7.76%, 5.75%, and 6.52% are obtained in pulsating flow compared to the steady flow case for a Reynolds number of 250, 500, and 750,
respectively.