Begell House Inc.
Computational Thermal Sciences: An International Journal
CTS
1940-2503
8
3
2016
THE EFFECT OF HOMOGENEOUS NUCLEATION IN SUPERSONIC CONDENSING SUBMILLIMETER SCALED JETS
209-232
10.1615/ComputThermalScien.2016012508
Miah Md. Ashraful
Alam
Institute of Ocean Energy (IOES), Saga University, 1, Honjo-machi, Saga 840-8502, Japan
Toshiaki
Setoguchi
Institute of Ocean Energy (IOES), Saga University, 1, Honjo-machi, Saga 840-8502, Japan
Shigeru
Matsuo
Department of Advance Technology Fusion, Saga University, Japan
M.
Takao
Department of Mechanical Engineering, Matsue National College of Technology, Japan
Heuy Dong
Kim
Department of Mechanical Engineering, Andong National University, Andong 760-749, Korea
compressible
homogeneous condensation
nonequilibrium
shock wave
supersonic
two-phase flow
A numerical work is reported of the effect of nonequilibrium homogeneous condensation in the underexpanded supersonic condensing jets issuing from the submillimeter scaled nozzles. Moist air as working gas is used to simulate the condensing jets. The classical nucleation rate and droplet growth equations are used to model the nonequilibrium nucleation phenomena. A TVD numerical method is applied to solve the time dependent Reynolds- and Favre-averaged Navier-Stokes equations that coupled the rate equation of liquid phase production. The influence of size of the nozzle exit diameter on the aerodynamic features of jets is investigated. The shock structure is investigated under different operating conditions−pressure ratios and initial relative humidities. Special attention is given to the effect of homogeneous condensation on the thermo-fluid dynamic features of the jets. The present computational model is validated through comparison of the predicted results with the experimental data.
HARTMANN FLOW AND HEAT TRANSFER OF COUPLE STRESS FLUID IN A POROUS MEDIUM BETWEEN TWO PARALLEL PLATES WITH PERIODIC SUCTION AND INJECTION
233-247
10.1615/ComputThermalScien.2016012067
Odelu
Ojjela
Department of Applied Mathematics, Defence Institute of Advanced Technology (Deemed University), Pune−411025, India
N. Naresh
Kumar
Department of Applied Mathematics, Defence Institute of Advanced Technology (Deemed University), Pune−411025, India
MHD
porous medium
couple stress fluid
temperature distribution
skin friction
periodic suction and injection
In the present article, we consider the two-dimensional unsteady incompressible flow and heat transfer of an electrically conducting couple stress fluid in a porous medium between two parallel plates with the periodic injection and suction at the lower and upper plates, respectively. Assume that the plates are maintained at different temperatures changing periodically with time. The governing partial differential equations are reduced to nonlinear ordinary differential equations using suitable similarity transformations, then solved numerically by a quasilinearization technique. The effects of various fluid and geometric parameters on velocity components and temperature distribution are studied and shown graphically. In addition, the coefficient of skin friction and heat transfer rate at the lower and upper plate are discussed in detail and presented in the form of tables. The present results have good agreement with the published work.
A MODEL TO CALCULATE HEAT LOSS OF FLOWING SUPERHEATED STEAM IN PIPE OR WELLBORE
249-263
10.1615/ComputThermalScien.2016016880
Zhanxi
Pang
MOE Key Laboratory of Petroleum Engineering, Beijing, China
Lushan
Wang
China University of Petroleum, Beijing, China
X. C.
Lv
China University of Petroleum, Beijing, China
superheated steam
heat loss
specific enthalpy
specific volume
pipeline
wellbore
Aiming at the flowing of superheated steam in a horizontal pipe and vertical wellbore, an improved model of heat loss was established to calculate physical properties of superheated steam along a pipeline or wellbore. Based on the basic theory of mass conservation, momentum conservation, and energy conservation, the model comprehensively considered the physical properties of water at different states, the structure of the pipeline and wellbore, friction loss, and heat conduction and heat convection during flowing. The test data of the oilfield verified that the model could give high-accuracy results about temperature and pressure levels. The results showed that the optimum steam flow rate was 25−35 t/h for a surficial horizontal pipeline with inner diameter of 0.1 m and the optimum steam flow rate should be chosen 3.5−7.5 t/h for a vertical wellbore with inner diameter of 0.076 m.
NUMERICAL ANALYSIS OF COHERENT STRUCTURES IN BIDIRECTIONAL SWIRL COMBUSTION CHAMBER
265-289
10.1615/ComputThermalScien.2016016209
V.
Aghakashi
Center of Excellence in Energy Conversion (CEEC), School of Mechanical Engineering, Sharif University of Technology, Tehran, 11155-9567, Iran
P. M.
Keshavarz
Center of Excellence in Energy Conversion (CEEC), School of Mechanical Engineering, Sharif University of Technology, Tehran, 11155-9567, Iran
Mohammad Hassan
Saidi
Center of Excellence in Energy Conversion (CEEC), School of Mechanical Engineering, Sharif
University of Technology, P.O. Box 11155-9567, Tehran, Iran
bidirectional swirl combustor
coherent structures
swirl flow
swirl intensity
vortex cham¬ber
Analysis and identification of vortex structures and their formation, particularly in swirl flows, have received widespread interest among researchers in the field of fluid mechanics. Due to the importance of vortex structures and their applications in combustion chambers, a special type of combustion chamber, which is called a "bidirectional swirl combustor", has been investigated in this work. The dependence of vortex structures on the combustion chamber geometry and fuel injection location in cold flow, the effect of hot flow on coherent structures, and the difference between vortex structures in hot and cold flows have been studied as well. A common characteristic which is in combustion chambers and cyclones alike and that has not yet been exactly surveyed is swirl intensity and its variation along the length of the combustion chamber In this study, the velocity profiles obtained from the numerical simulation have been used to determine swirl intensity profiles along the combustion chamber axis for various models. Numerical solutions have been performed via OpenFOAM software. The results show that the mean vortex intensity increases while the combustion chamber length decreases. Also, comparison of the reactive flow with the nonreactive flow shows that the vortex intensity in the hot chamber is approximately half of its value for the cold flow. Unlike the cold chamber model, there is no opportunity to form small recirculation zones in the hot model due to the heat release and increment of the axial momentum.
FLOW AND HEAT TRANSFER SIMULATION OF THREE DIFFERENT NANOFLUIDS IN A CAVITY WITH SINUSOIDAL BOUNDARY CONDITIONS UNDER THE INFLUENCE OF AN INCLINED MAGNETIC FIELD USING LBM: A PHASE DEVIATION APPROACH
291-308
10.1615/ComputThermalScien.2016017026
Amir Javad
Ahrar
Department of Mechanical Engineering, Faculty of Sadooghi, Yazd Branch, Technical and Vocational University (TVU), Yazd, Iran
Mohammad Hassan
Djavareshkian
Ferdowsi University of Mashhad, Iran
magneto-hydro-dynamics
nanoparticle volume fraction
magnetic field intensity and direction
In the present study, a nanofluid-filled cavity with sinusoidal temperature boundary condition under the influence of an inclined magnetic field was investigated numerically. The lattice Boltzmann method (LBM) was applied to simulate the nanofluid flow with water as the carrier fluid and for three different nanoparticle types: Al2O3, Cu, and TiO2. More than 1100 individual tests were carried out in this work to show the combined effect of the nanoparticles and magnetic field situations. It goes without saying that nanoparticles are meant to improve the heat transfer rate, because unlike the magnetic field they are not present in any system on their own, but they're added manually to enhance the Nusselt number. However, it is seen that in some magnetic situations (field intensity and direction) adding the volume fraction of nanoparticles cannot help the heat transfer increment. The flow and heat transfer behavior of these three nanofluids were observed for different Rayleigh numbers (103−106), Hartmann numbers (0−80), nanoparticle volume fraction (0−6%), magnetic field direction θ = 0−90°, and temperature boundary condition phase deviation γ = 0−90°. The results indicated that the influence of nanoparticles for this geometry and boundary conditions is highly dependent on the Rayleigh and Hartmann numbers. Although the magnetic field direction plays an unimportant role in lower Rayleigh numbers, the effects will become most significant for moderate Rayleigh numbers like 105.