Begell House Inc.
Computational Thermal Sciences: An International Journal
CTS
1940-2503
9
3
2017
INFLUENCE OF LATERAL ANGLE ON FILM COOLING PERFORMANCE OVER ASYMMETRICAL TURBINE BLADE
183-193
Mustapha
Benabed
Aeronautical Laboratory and Propulsive Systems, Faculte de Genie-Mecanique, Universite des Sciences et de la Technologie d'Oran, B.P. 1505 El-Mnouar, Oran, Algeria
A numerical investigation was performed to determine the effect of the lateral angle injection on film cooling effectiveness over a turbine blade. The rows are located in the vicinity of the stagnation line. One row is located on the suction side and the other one is on the pressure side. The predicted pressure field for various blowing ratios (M = 0.5, 1.1, and 1.5) is compared to available experimental results at the design condition. Moreover, the effect of three lateral angles 30, 45, and 60 deg at three blowing rates is investigated by analyzing the results of both laterally averaged and area-averaged values of adiabatic film cooling effectiveness. The outcomes of the numerical results indicate that the thermal protection of the blade can be strongly influenced by the lateral angle. The coolant structure flow is characterized by a dominant single asymmetric vortex on both sides. Lateral injection at angle γ = 60 deg significantly improves film cooling effectiveness. From γ = 30 to 45 deg, overall, no appreciable improvement could be noted in cooling performance except for the lower blowing ratio M = 0.5. At suction side, the increase of blowing ratio has an adverse effect on the blade thermal protection.
CFD MODELING OF NON-PREMIXED COMBUSTION OF PULVERIZED COAL IN A FURNACE
195-211
Moode Praveen Kumar
Naik
Mechanical Engineering Department, National Institute of Technology-Raipur (CG), India
Satish Kumar
Dewangan
NIT Raipur (CG) - INDIA
Coal continues to be one of the main sources of energy, even in the present scenario, for power generation and process
industries. A 2D blast furnace (duct) with air as inlet (two inlets with different velocities at same temperature) has been considered for modeling of non-premixed combustion of coal particles being injected as the high-velocity stream with air being supplied from the top and bottom inlets. ANSYS Fluent CFD code (version 12) has been used for modeling. Considering the symmetric geometry, only one-half of the domain is considered. Validation and mesh independent
study has been done for a group of coal particles (10 discrete particles with different diameters that follow Rosin-Rammler size distribution law) considering the total heat transfer rate as our main concern. Furthermore, results
of the total heat transfer rate have been obtained for different bottom air inlet velocities. Dimensionless length versus parameters (such as static temperature, burnout, and mean mixture fraction) have been plotted by considering different sections along the height of the furnace for different bottom air velocities. Results show that as bottom air inlet velocity increases the peak temperature inside the furnace decreases, the furnace length occupied for burnout increases, the peak value of mean mixture fraction decreases, and the total heat transfer rate decreases and then increases.
OPTIMIZATION OF SECONDARY COOLING PERCENTAGE DURING SEMI-CONTINUOUS COPPER CASTING PROCESS
213-225
Amar H.
Hameed
Mechanical Engineering Department, KTO Karatay University, Konya, Turkey
Sufficient cooling is essential to reduce casting defects and to get high productivity in semi-continuous casting of copper billet. On the other hand, low rate solidification is desired in order to develop coarser grain size and softer metal for less energy losses and metal discards in extrusion. Cooling intensity and percentage in both primary and secondary cooling stages was inspected to optimize microstructure and quality of billets. A three-dimensional steady-state numerical model was developed including solidification behavior of copper through mushy zone. Solid shell thickness, pool length, and mushy zone thickness are monitored during the reduction of the cooling rate in the mold region. Adequate primary cooling range is concluded, as a function of mold inlet water temperature, to be between 43 and 63°C. For moderate pool length according to solidification time, not reduced total heat removal, a cooling rate with less available inequality along the billet, and at the range of adequate primary cooling, perfect secondary cooling percentage sets at the range of 52−67%. At this range and for a specified speed of casting, melt at the core needs between 600 and 750 s to start solidification and solidification needs between 125 and 225 s to complete.
HEAT TRANSFER ENHANCEMENT OF UNIFORMLY/LINEARLY HEATED SIDE WALL IN A SQUARE ENCLOSURE UTILIZING ALUMINA−WATER NANOFLUID
227-241
Saritha
Natesan
School of Mechanical Engineering, VIT University, Vellore, India
Senthil Kumar
Arumugam
School of Mechanical Engineering, VIT University, Vellore, India
Sathiyamoorthy
Murugesan
Department of Mathematics, Government Thirumagal Mills College, Gudiyatham, Vellore,
India
Ali J.
Chamkha
Department of Mechanical Engineering, Prince Sultan Endowment for Energy and
Environment, Prince Mohammad Bin Fahd University, Al-Khobar 31952, Kingdom of Saudi
Arabia; RAK Research and Innovation Center, American University of Ras Al Khaimah, United Arab Emirates, 10021
A numerical study is carried out on natural convection flow of Al2O3-water nanofluid in a square cavity when the left wall is uniformly (or) linearly heated and the right wall is cooled whereas the top and bottom walls are well insulated. A computational code is developed based on the SIMPLE algorithm, and the finite volume method is used to solve the discretized equations. The Maxwell-Garnett and the Brinkman models are used to evaluate the nanofluid thermal conductivity and dynamic viscosity, respectively. Numerical results are presented in terms of the velocity profiles, stream functions, and isotherm contours, and the local and average Nusselt numbers for a wide range of the Rayleigh number Ra = 104 − 106 and the solid volume fraction (0 ≤ φ ≤ 0.2) at the Prandtl number Pr = 6.2. It is found that, for both cases of boundary conditions, the average Nusselt number increases as the volume fraction increases at a given Rayleigh number. That is, the heat transfer rate performance is improved by the addition of alumina nanoparticles in water. However, the overall heat transfer rate at the left wall for the linearly heated case is less than that for the uniformly heated case with the corresponding values of Ra and φ.
EXPERIMENTAL AND NUMERICAL INVESTIGATIONS OF BUBBLING FLUIDIZED BED APPARATUS TO INVESTIGATE HEAT TRANSFER COEFFICIENT FOR DIFFERENT FINS
243-255
Masoud
Farzinpour
Department of Mechanical Engineering, Khomeinishahr Branch, Islamic Azad University,
Khomeinishahr, Iran
Saeed
Rasouli
Department of Mechanical Engineering, Khomeinishahr Branch, Islamic Azad University,
Khomeinishahr, Iran
Davood Semiromi
Toghraie
Department of Mechanical Engineering, Khomeinishahr Branch, Islamic Azad University,
Khomeinishahr, Iran
In this study, a bubbling fluidized bed apparatus was designed and constructed to investigate heat transfer coefficients from rectangular, triangular, and circular fins, which all have the same heat transfer area. After constructing the apparatus and fins, several experiments (approximately 100) were conducted, and the heat transfer coefficients of the fins were obtained, compared, and analyzed. Reynolds particles are limited, ranging from 2.22 to 4.81. Furthermore, the input air speed is equal to 0.17−0.22 m/s, the diameter of the fluid bed is equal to 12 cm, and the horizontal immersed tube of the fin is 6 cm long and has a 2 cm diameter in the bubbling fluidized bed. The results revealed that the diameter of solid particles and the rate of inlet airflow to the apparatus are among the parameters affecting the heat transfer coefficients. Moreover, the temperatures of triangular and rectangular fins were compared to each other in numerical
and experimental methods. We found that these temperatures are relatively similar.
BOUNDARY LAYER FLOW OF VISCOELASTIC NANOFLUID OVER A WEDGE IN THE PRESENCE OF BUOYANCY FORCE EFFECTS
257-267
Madhu
Macha
Kuvempu University
Naikoti
Kishan
Osmania University, Hyderabad, India
In this paper, we investigate incompressible flow of a viscoelastic nanofluid past a wedge in the presence of buoyancy force effects. The momentum, energy and mass equations are reduced to coupled non-linear ordinary differential equations by using suitable similarity transformations. The coupled ordinary non-linear equations are solved by using variational finite element method. The profiles of velocity, temperature and nanoparticle volume fraction are presented through graphs for various values of physical parameters also the skin-friction co-efficient and local Nusselt number are calculated.
PERFORMANCE ANALYSIS OF DIFFERENT SOLVERS FOR COMPUTING THE RADIATIVE TRANSFER EQUATION IN COMPLEX GEOMETRIES USING FINITE VOLUME METHOD AND BLOCK STRUCTURED GRIDS
269-282
Flavia
Cavalcanti Miranda
Institute of Energy and Power Plant Technology, TU Darmstadt, Darmstadt, Germany
F.
di Mare
Department of Reactive Flows and Diagnostics, TU Darmstadt, Darmstadt, Germany
Amsini
Sadiki
Institute of Energy and Power Plant Technology, Technische Universität Darmstadt, 64287 Darmstadt, Germany
Johannes
Janicka
Institute of Energy and Power Plant Technology, TU Darmstadt, Jovanka-Bontschits-Strasse 2, 64287 Darmstadt, Germany; Darmstadt Graduate School of Excellence Energy Science and Engineering, TU Darmstadt,
Jovanka-Bontschits-Strasse 2, 64287 Darmstadt, Germany
The finite volume method (FVM) is adopted to solve the radiative transfer equation in complex 3D geometries using
block structured grids. In the standard solution algorithm, the discrete set of algebraic equations in the FVM is solved
using the Gauss-Seidel method with the mesh sweeping algorithm. This algorithm gives an optimal order in which the control volumes are visited and the calculations are performed. However by dealing with radiation in industrial size problems and complex geometries, this procedure may not be the most efficient option to be employed. This paper investigates the performance of the sweeping algorithm and several other alternative solutions to point out the best strategy to be followed when dealing with heat radiation and large-scale industrial problems using FVM and block structured grids. For this purpose, a real combustion chamber with two block structured grids is studied after a successful verification on three simple tests. While a temperature distribution was fixed inside and at the boundaries of the chamber, the radiative heat source term was calculated and the computational time required for each solver was measured. The results show that the cyclic reduction method with SSOR preconditioner performs better than the sweeping algorithm for cases with black walls and slightly reflecting walls.