Begell House Inc.
Heat Transfer Research
HTR
1064-2285
50
7
2019
NUMERICAL INVESTIGATION OF A COPPER—WATER NANOFLUID FLOWING IN A PARALLEL PLATE CHANNEL
617-632
Saeb
Ragani
Department of Mechanical and Aerospace Engineering, University at Buffalo, State University of New York, Buffalo, NY 14214, USA
Arian
Bahrami
Department of Mechanical Engineering, Eastern Mediterranean University, G. Magosa, TRNC
Mersin 10, Turkey
Heat transfer behavior of a Cu-water nanofluid flowing in a laminar mode in a parallel plate channel was investigated numerically. The governing continuity, momentum, and energy equations were discretized using the finite volume approach and solved with the SIMPLE algorithm. The thermal conductivity of the nanofluid was determined by the model proposed by Patel et al. and the Brinkman model was used to calculate the effective viscosity. The study was conducted for a wide range of Reynolds numbers from 10 to 1500, and for solid volume fractions between 0% and 5%. Top and bottom walls were considered for the cases of constant temperature and constant wall heat flux, while results for both uniform and parabolic entrance velocities were considered for each case. It was observed that the rate of heat transfer increases with increase in solid volume fraction as well as with increase in flow rate. Moreover, higher heat transfer was observed for uniform entrance velocity compared to that of a channel with parabolic inlet velocity.
EMISSIVITY MODEL OF STEEL 316L AT 800–1100 K DURING OXIDE LAYER GROWTH ON THE SPECIMEN SURFACE
633-647
Deheng
Shi
College of Physics and Material Science, Henan Normal University, Xinxiang 453007, China
Shan
Sun
College of Physics and Material Science, Henan Normal University, Xinxiang 453007, China
Zunlue
Zhu
College of Physics and Material Science, Henan Normal University, Xinxiang 453007, China
Jinfeng
Sun
College of Physics and Material Science, Henan Normal University, Xinxiang 453007, China
This work strived to study the variation in the spectral emissivity of steel 316L specimens with wavelength at a certain temperature. The spectral emissivity and radiances from the specimen surface were measured by multispectral radiation thermometry at wavelengths of 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, and 2.1 μ;m and at temperatures from 800 to 1100 K in increments of 20 K. The specimen was heated and kept at a certain temperature in air for 6 h. The temperature of the specimen surface was measured by two thermocouples, which were symmetrically welded onto the front surface of the specimens near the measuring area for accurate monitoring of the surface temperature. The average of their readings was regarded as the real temperature. Variation in the spectral emissivity with wavelength was studied at different temperatures and different heating times. Effect of surface oxidation on the fitting accuracy of the emissivity models was evaluated. Two favorite models were determined. With the radiant values measured by thermometry and in combination with the least-squares fitting technique, two favorite models were examined. On the whole, both the five-parameter LLWE and LWE models could yield the best overall temperature prediction and could farthest relieve the effect of surface oxidation on the accuracy of temperature prediction over the present wavelength and temperature ranges.
NUMERICAL STUDY OF MOMENTUM AND HEAT TRANSFER OF MHD CARREAU NANOFLUID OVER AN EXPONENTIALLY STRETCHED PLATE WITH INTERNAL HEAT SOURCE/SINK AND RADIATION
649-658
Majeed Ahmad
Yousif
Faculty of Science, Department of Mathematics, University of Zakho, Kurdistan Region, Iraq
Hajar Farhan
Ismael
Faculty of Science, Department of Mathematics, University of Zakho, Kurdistan Region, Iraq
Tehseen
Abbas
Department of Mathematics, University of Education Lahore, Faisalabad Campus, Faisalabad
38000, Pakistan
Rahmat
Ellahi
Center for Modeling & Computer Simulation, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran-31261, Saudi Arabia; Department of Mathematics and Statistics, FBAS, IIUI, Islamabad, Pakistan
In this article, the magnetohydrodynamic (MHD) thermal boundary layer of a Carreau flow of Cu-water nanofluids over an exponentially permeable stretching thin plate is investigated numerically. Internal heat source/sink is also taken into account. After gaining the system of leading equations, the appropriate transformations have been first employed to come across the fitting parallel conversions to alter the central governing equations into a suit of ODEs and then the renovated system of ODE along with appropriate boundary conditions is numerically solved by the shooting method with fourth-order Runge-Kutta technique. The consequences of the relevant factors of physical parameters on velocity and temperature of merging water (H2O) and nanoparticles (Cu) have been exemplified through graphs.
HEAT LOSS ANALYSIS AND OPTIMIZATION OF HOUSEHOLD SOLAR HEATING SYSTEM
659-670
Jieyuan
Yang
Western China Energy and Environment Research Center, Lanzhou University of Technology,
Lanzhou 730050, China; Key Laboratory of Complementary Energy System of Biomass and Solar Energy, Lanzhou 730050, China
Jinping
Li
Western China Energy and Environment Research Center, Lanzhou University of Technology,
Lanzhou 730050, China; Key Laboratory of Complementary Energy System of Biomass and Solar Energy, Lanzhou 730050, China
Rong
Feng
Shaanxi Key Laboratory of Industrial Automation, Shanxi University of Technology, Hanzhong
723001, China
Renewable energy sources have the leverage of unlimited availability and environmental friendliness, therefore, they are the optimal alternation for fossil fuel. Among all renewable energy sources, solar energy is the most signifi cant due to the safety and sustainability. Based on this fact, utilization of solar thermal energy has increased sharply mainly for heating and cooling applications. In order to analyze and optimize the heat loss associated with the household solar heating system, an experimental model was built and tested in Minqing County, Gansu Province, China. In this work, the multiple linear regression method is considered to address the outcomes. The relationship between the environmental factors (such as wind speed, ambient temperature, and the temperature of the heating water tank) and the indoor temperature is identifi ed. The experimental results indicate that the convection heat loss of the tank accounted for more than 86% of the heat loss at night. Changes in the supply mode for the night time heating can save about 685.38 kg of standard coal, 0.47 tons of CO2, 11.31 kg of SO2, and 10.69 kg of NOx emissions, which are equivalent to an annual value of more than 1028.07 yuan. A shift to the use of renewable energy has clear economic, energy-saving, and environmental benefits.
NUMERICAL INVESTIGATION OF TURBULENT NANOFLUID FLOW AND TWO-DIMENSIONAL FORCED-CONVECTION HEAT TRANSFER IN A SINUSOIDAL CONVERGING-DIVERGING CHANNEL
671-695
Davood Semiromi
Toghraie
Department of Mechanical Engineering, Khomeinishahr Branch, Islamic Azad University,
Khomeinishahr, Iran
Omid Ali
Akbari
Young Researchers and Elite Club, Khomeinishahr Branch, Islamic Azad University, Khomeinishahr, Iran
Ali
Koveiti
Department of Mechanical Engineering, Khomeinishahr Branch, Islamic Azad University, Khomeinishahr, Iran
Ramin
Mashayekhi
Young Researchers and Elite Club, Khomeinishahr Branch, Islamic Azad University, Khomeinishahr, Iran
The purpose of this research is to numerically simulate turbulent flow and forced-convection heat transfer of a water/CuO nanofluid in a sinusoidal converging-diverging channel. In the present study, the effects of some parameters such as Reynolds number in the range 4000 ≤ Re ≤ 20,000, volume fraction of nanoparticles in the range 1% ≤ φ ≤ 4%, and the wavelength in the range 0.2 m ≤ λ ≤ 1 m on velocity, temperature, and pressure contours, Nusselt number, friction factor, and also the velocity and temperature profiles in various cross sections of the channel have been investigated. The simulations were done by the finite volume method in a 2D space in Cartesian coordinates. The obtained results indicate that on increase of the volume fraction of solid nanoparticles with the use of wavy walls, the heat transfer rate rises significantly. The presence of sinusoidal walls compared with flat ones is accompanied by a higher friction factor and pressure drop. By increasing the Reynolds number, the axial velocity of flow increases 5 times, the Nusselt number increases by 94%, and the friction factor reduces by almost 2.5 times. By increasing the wavelength from 0.2 to 1 m, the heat transfer area is reduced and the conduction heat transfer coefficient is reduced due to the reduced flow velocity and temperature gradient on the channel walls as the thickness of the velocity and thermal boundary layers rises resulting in reduced Nusselt number and heat transfer rate. Based on the contours of the axial flow velocity at the end of the converging section of the channel, the flow distribution is no longer uniform and the flow velocity is continuously changing and at the center of the channel (channel neck), when the volume fraction is raised from 1 to 4%, the flow velocity increased by 25%. By increasing the wavelength of the wall, the axial velocity of flow and Nusselt number are reduced by almost 85% and 91%, respectively. Also, by increasing the volume fraction of nanoparticles, the axial velocity of flow and Nusselt number are increased nominally.
EFFECT OF LORENTZ FORCES ON NANOFLUID FLOW INSIDE A POROUS ENCLOSURE WITH A MOVING WALL USING VARIOUS SHAPES OF CuO NANOPARTICLES
697-715
Zhixiong
Li
School of Engineering, Ocean University of China, Qingdao 266110, China; School of Mechanical, Materials, Mechatronic and Biomedical Engineering, University of Wollongong, Wollongong, NSW 2522, Australia
Mohsen
Sheikholeslami
Department of Mechanical Engineering, Babol Noshirvani University of Technology, Babol, Iran
M. M.
Bhatti
Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai
200072, China
Forced convection of a nanofluid in a permeable enclosure with a moving wall is presented under the effect of Lorentz forces. The mathematical modeling is formulated with the help of a stream function. The control volume finite element method (CVFEM) has been used to determine the solutions of nonlinear coupled differential equations. Shape effects of nanoparticles (NPs) with Brownian motion impact are taken into account in the present flow problem. Graphical results are demonstrated for multiple values of Darcy number, CuO-water volume fraction, Reynolds number, and Hartmann number, respectively. Computational results depict that platelet-shaped nanoparticles have a higher rate of heat transfer. Convective heat transfer augments with increase in the Darcy and Reynolds numbers while it is reduced with increase of a magnetic field.