Begell House Inc.
Heat Transfer Research
HTR
1064-2285
47
9
2016
RADIATION EFFECT ON MHD STAGNATION-POINT FLOW OF A NANOFLUID OVER A NONLINEAR STRETCHING SHEET WITH CONVECTIVE BOUNDARY CONDITION
797-816
10.1615/HeatTransRes.2016007840
Muhammad Imran
Anwar
Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia; Department of Mathematics, Faculty of Science, University of Sargodha UOS, Sargodha, Punjab, Pakistan
Sharidan
Shafie
Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia
81310 UTM Johor Bahru, Johor, Malaysia
Abdul Rahman M.
Kasim
Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia JB, 81310 Skudai, Johor, Malaysia
Mohd Zuki
Salleh
Applied and Industrial Mathematics Research Group, Faculty of Industrial Sciences & Technology, Universiti Malaysia Pahang, 26300 UMP Kuantan, Pahang, Malaysia
nanofluid
radiation effect
MHD flow
stagnation-point
convective boundary condition
nonlinear stretching sheet
The effect of radiation on the MHD stagnation-point flow of a nanofluid over a nonlinear stretching sheet with convective boundary condition is investigated numerically. A small magnetic Reynolds number and Rosseland approximation are also assumed in this study where the sheet is stretched with a power law velocity in the presence of a nonuniform magnetic field applied in the y direction normal to the flow on the sheet. A highly nonlinear problem is modeled using the modified Bernoulli equation for an electrically conducting nanofluid. The momentum, thermal, and concentration boundary-layer thicknesses are intensified with increasing values of the velocity ratio parameter. By using appropriate similarity transformation, the system of nonlinear partial differential equations is reduced to ordinary differential equations. These equations subjected to the boundary conditions are solved numerically using the Keller-box method. Numerical results are plotted and discussed for pertinent flow parameters. A comparison with previous results given in the literature is also made.
THERMAL RADIATION EFFECT ON TURBULENT FORCED CONVECTION FLOW OVER A BACKWARD FACING STEP IN THE PRESENCE OF PARTICIPATING MEDIA
817-838
10.1615/HeatTransRes.2016008178
Amir
Asghari
Mechanical Engineering Department, School of Engineering, Shahid Bahonar University,
of Kerman, Kerman, Iran
Seyed Abdolreza Gandjalikhan
Nassab
Mechanical Engineering Department, School of Engineering, Shahid Bahonar University of
Kerman, Kerman, Iran
radiation
turbulent forced convection
discrete ordinate method
The effect of radiation on turbulent forced convection flow over a two-dimensional duct with a sudden expansion was studied numerically. The medium is treated as a gray, absorbing, emitting, and scattering. The two-dimensional Reynolds-averaged Navier-Stokes equations, coupled with the energy equation and the turbulence kinetic energy equations, as well as their dissipation rates are solved numerically by the computational fluid dynamics (CFD) techniques to obtain the velocity and temperature distributions in the channel. The AKN low-Reynolds-number model is employed for computation of turbulence fluctuations. The finite volume method is adopted to solve the governing equations, while the integro-partial differential radiative transfer equation is solved by the discrete ordinates method (DOM). The SIMPLE algorithm is used for pressure-velocity decoupling. Along a benchmark problem, the numerical results are compared with some experimental data and good agreement is found. Results are presented for the distributions of bulk temperature and Nusselt numbers by varying the controlling parameters, i.e., radiation-conduction parameter (RC), optical thickness, single scattering albedo, and wall emissivity. Two different thermal boundary conditions are considered and results show that the gas radiation has a significant effect on the heat transfer.
EFFECT OF PERIODICALLY ALTERNATING WALL TEMPERATURE ON NATURAL CONVECTION HEAT TRANSFER ENHANCEMENT IN A SQUARE CAVITY FILLED WITH Cu-WATER NANOFLUIDS
839-854
10.1615/HeatTransRes.2016011093
Xi
Meng
College of Architecture and Urban-Rural Planning, Sichuan Agricultural University,
Chengdu 610065, P.R. China
Yan
Wang
Institute for Disaster Management and Reconstruction, Sichuan University, Chengdu 610065, P.R. China
Jun
Wang
College of Architecture and Environment, Sichuan University
Enshen
Long
Institute for Disaster Management and Reconstruction, Sichuan University, Chengdu 610065, P.R. China
nanofluids
natural convection
periodic alternation
numerical simulation
Natural convective heat transfer of copper--water nanofluids in a square enclosure with sinusodally alternating temperature at one vertical wall, relatively low temperature at the opposite sidewall, and adiabatic at the other walls is investigated. The transport equations are solved numerically by finite volume approach using the SIMPLEC algorithm. Calculations are performed for the Rayleigh number from 104 to 106, nanoparticle volume fractions from 0 to 0.2, dimensionless amplitude from 0 to 1.0, and dimensionless frequency from 0.1 to 200. The fluctuating behaviors are found for the flow fields and temperature fields as a result of the alternating temperature. The utilization of nanoparticles enhances heat transfer especially at high Rayleigh numbers, and the percentage increase in the time-averaged Nusselt number is 37.61%, when the solid volume fraction is increased from 0 to 0.2. In addition, the alternating temperature amplitude and frequency affect heat transfer of nanofluids. When the dimensionless amplitude is increased from 0 to 1, the percentage increase in the time-averaged Nusselt number is 12.24%. The double-humped resonance phenomenon of nanofluids heat transfer is observed for variation of the temperature oscillation frequency.
OBSERVATION OF HEAT TRANSFER IN OSCILLATING FLOW WITHIN A CIRCULAR CHANNEL
855-863
10.1615/HeatTransRes.2016010434
Ke
Tang
Institute of Refrigeration and Cryogenics, Zhejiang University, Hangzhou 310027, China
Jiale
Huang
Institute of Refrigeration and Cryogenics, Zhejiang University, Hangzhou 310027, China
Wentao
Tang
Institute of Refrigeration and Cryogenics, Zhejiang University, Hangzhou 310027, China
Juan
Yu
Institute of Refrigeration and Cryogenics, Zhejiang University, Hangzhou 310027, China
Tao
Jin
Institute of Refrigeration and Cryogenics, Zhejiang University, Hangzhou 310027, China
heat transfer
oscillating flow
maximum Reynolds number
Peclet number
Nusselt number
A periodical reversion of velocity direction distinguishes an oscillating flow from a common unidirectional steady flow. This study focuses on heat transfer in oscillating flow within a circular channel. An experimental apparatus operating at a frequency of 0.3-1.1 Hz and at a near atmospheric pressure has been built for measuring the heat transfer rate. Typical experimental data on the oscillating pressure, velocity, temperature difference (between the central fluid and the channel wall), on the heat flux at the channel wall are presented. A zero-order Nusselt number is used to characterize the time-averaged heat transfer of the oscillating flow. A marked increase in the zero-order Nusselt number with increase in the Peclet number is observed, which indicates that the raised frequency can effectively enhance heat transfer in oscillating flow.
EVAPORATION HEAT LOSS IN THE FLAMELET MODEL FOR DILUTE SPRAY FLAMES
865-884
10.1615/HeatTransRes.2016014017
Jing
Chen
Department of Thermal Science and Energy Engineering, University of Science and Technology of China, Hefei 230027, P.R. China
Minming
Zhu
Department of Thermal Science and Energy Engineering, University of Science and Technology of China, Hefei 230027, P.R. China
Minghou
Liu
Department of Thermal Science and Energy Engineering, University of Science and Technology of China, Hefei 230027, P.R. China
Yiliang
Chen
Department of Thermal Science and Energy Engineering, University of Science and Technology of China, Hefei 230027, P.R. China
spray combustion
evaporation heat loss
flamelet model
large eddy simulation
The motivation of this paper is to extend the flamelet/progress variables (FPV) approach used successfully in gaseous flames to spray combustion. To consider the evaporation heat loss effect in the FPV approach, two new methods are proposed. One is to correct the gaseous temperature in the flamelet calculation, and the other is to couple this heat loss into the CFD process. To evaluate their performance, the piloted ethanol-air spray flames are simulated by LES in the Eulerian-Lagrangian framework. The simulation results using these two methods and some other existing models are compared with experimental data. It is shown that both methods give lower gaseous temperature compared to the conventional FPV approach and the mean gaseous temperature is closer to the experimental data especially downstream and near the centerline. As to other statistical results (e.g., the mean velocities and rms velocities and SMD), these methods show similar profiles which are all in good agreement with experimental data. The conclusion is that our models can give a good account of the evaporation heat loss. Meanwhile, much lower computational costs are needed compared to the method of solving the enthalpy equation.
EXPERIMENTAL AND NUMERICAL ANALYSIS OF HEAT TRANSFER IN AN ATTIC-SHAPED ENCLOSURE
885-892
10.1615/HeatTransRes.2016014504
Francesco
Corvaro
Dipartimento di Ingegneria Industriale e Scienze Matematiche (DIISM), Università
Politecnica delle Marche, Ancona, Italy
Giorgia
Nardini
DIISM, Dipartimento di Ingegneria Industriale e Scienze Matematiche, Università Politecnica delle
Marche, Via Brecce Bianche - 60131 Ancona, ITALY
Massimo
Paroncini
DIISM, Dipartimento di Ingegneria Industriale e Scienze Matematiche, Università Politecnica delle
Marche, Via Brecce Bianche - 60131 Ancona, ITALY
Raffaella
Vitali
DIISM, Dipartimento di Ingegneria Industriale e Scienze Matematiche, Università Politecnica delle
Marche, Via Brecce Bianche - 60131 Ancona, ITALY
fluid flow
natural convection
Particle Image Velocimetry
triangular
attic-shaped
An experimental and numerical investigation of natural convection in an attic-shaped triangular cavity in winter or nighttime conditions was carried out. The cavity had three isothermal, aluminum walls and a Plexiglas wall. The experimental method used was Particle Image Velocimetry and Fluent 12.1.4 was the numerical software employed. The range of Rayleigh numbers analyzed was from 5·105 to 1·107. The isotherms, velocity maps, and streamlines produced were examined and studied. The results show that for Ra < 6.0·106 two main vortices develop in the enclosure while for Ra > 6.0·106 a third vortex begins to form.