Begell House Inc.
Heat Transfer Research
HTR
1064-2285
48
1
2017
IDENTIFICATION IN STOCHASTIC THERMODIFFUSION PROBLEMS
1-8
Andrzej
Sluzalec
Technical University of Czestochowa, 42-200 Czestochowa, ul. Akademicka 3, Poland
Stochastic identifi cation of material parameters in the thermodiff usion process is presented. The numerical solutions for deterministic as well as stochastic direct and inverse problems have been described. The discretization of the fi eld equations through the use of the fi nite element approximation is applied. The inverse problem is solved by the use of gradient-based methods and a sensitivity analysis. The proposed direct and inverse formulation describes probabilistic distributions of material data. A one-dimensional axisymmetrical problem of a cylindrical element with random material parameters is solved as an example. The stochastic solutions are obtained by application of the Monte Carlo method.
FREE CONVECTION IN NON-NEWTONIAN POWER-LAW FLUIDS ALONG A VERTICAL PLATE WITH VARIABLE VISCOSITY AND THERMAL STRATIFICATION IN THE PRESENCE OF INTERNAL HEAT GENERATION
9-22
M. B. K.
Moorthy
Department of Mathematics, Institute of Road and Transport Technology, Erode − 638316,
Tamil Nadu, India
Kannan
Thangavelu
SASTRA University
K.
Senthilvadivu
Department of Mathematics, K. S. Rangasamy College of Technology, T. Gode − 637215,
Tamil Nadu, India
An investigation has been carried out to discuss the effects of variable viscosity and thermal stratification in the presence of internal heat generation on free convection flow along a nonisothermal vertical plate. The plate is semi-infinite and embedded in a porous medium which is saturated with a non-Newtonian power-law fluid. The governing equations of continuity, momentum, and energy are transformed into nonlinear ordinary differential equations using similarity transformations. The Runge−Kutta−Gill method and shooting technique are employed to solve the resulting equations. For the nonisothermal plate, the heat transfer rate increases as θc → 0 for liquids, whereas it decreases for gases as θc → 0 due to the thermal stratification in the presence of internal heat generation. The velocity decreases near the plate and increases away from the plate as θc → 0 for gases. In the case of liquids, the result is reversed. The obtained results are depicted graphically for different parameters involved.
MODELING THE INFLUENCE OF INCLINATION ANGLE ON NATURAL CONVECTION AROUND AN EVACUATED TUBE SOLAR COLLECTOR
23-34
Dardan
Klimenta
Faculty of Technical Sciences, University of Pristina in Kosovska Mitrovica, Kneza Milosa 7, Kosovska Mitrovica 38220, Serbia
The main purpose of this paper is to propose a procedure for modeling heat transfer by natural convection for both laminar and turbulent flows around an evacuated tube collector at inclination angles of 0−90°. Using the experimental results obtained by Heo and Chung (2012) for different cylinders and inclinations, the heat transfer correlations based on the fundamental dimensionless number for natural convection have been derived. Their experiments included measurements for solid circular cylinders having diameters of 0.01, 0.034, and 0.067 m, and lengths of 0.1, 0.25, and 0.45 m, as well as for a Prandtl number of 2094 in either laminar or turbulent conditions. Introducing the correlations based on the fundamental dimensionless number for natural convection, the studies performed on inclined cylinders were generalized for the whole range of Prandtl numbers. A modified Nusselt number, which represents the mean of the heat transfer correlations based on the cylinder diameter and on the cylinder length, was introduced and applied to estimate the heat transfer coefficients for natural convection on the outer surface of an evacuated tube collector surrounded by air. The results obtained by applying the proposed correlations were also compared to the results obtained using existing ones for various Prandtl numbers.
MHD EFFECTS ON THERMOCAPILLARY-BUOYANT CONVECTION IN AN ANNULAR TWO-LAYER SYSTEM
35-47
Xiaoming
Zhou
Institute of Engineering Thermal Physics, Chinese Academy of Sciences, Beijing, 100190, China
Xiulan L.
Huai
Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, China;
School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China
Hulin
Huang
College of Astronautics, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing 210016, China
Effects of various magnetic fields on thermocapillary-buoyant convection in an annular pool are investigated by three-dimensional numerical simulation, where the outer and inner walls are differentially heated. The computational results show that, under horizontal magnetic field, the number of azimuthal wave decreases with magnetic field intensity increase, and the induced electric current forms two closed circuits under a magnetic field of B0 = 0.5 T. Under an axial magnetic field, the azimuthal wave pattern shrinks to the vicinity of the inner wall gradually with increase in the magnetic field intensity, and the induced electric current forms one circular closed circuit under an axial magnetic field of B0 = 0.5 T. In general, the damping effect of an axial magnetic field is stronger than that of a horizontal magnetic field.
RELIABLE ONE-DIMENSIONAL MODEL APPLIED TO AN INSULATED RECTANGULAR DUCT CONSIDERING THERMAL RADIATION
49-67
Ho-Chiao
Chuang
College of Mechanical and Electrical Engineering, National Taipei University of Technology,
Taipei 10608, Taiwan
Shih-Shih
Ku
College of Mechanical and Electrical Engineering, National Taipei University of Technology,
Taipei 10608, Taiwan
King-Leung
Wong
Kun-Shan University
The heat-transfer characteristics of an insulated long rectangular duct, considering thermal radiation, are analyzed by using the one-dimensional Plane Wedge Thermal Resistance (PWTR) model and Plate Thermal Resistance (PTR) model in this study. It is found that the errors generated by the PWTR model are all positive and the errors generated by the PTR model are all negative. Thus, the Combined Plate Wedge Thermal Resistance (CPWTR) model generated by paralleling PWTR and PTR models with the proportion factors 0.6 vs. 0.4 (64-CPWTR model) or 0.7 vs. 0.3 (73-CPWTR model) can neutralize the positive and negative errors and yield very accurate results in comparison with the two-dimensional numerical solutions analyzed by a CFD software. The 64-CPWTR model returns better results for practical sizes and practical insulated thickness, and the errors are mostly within 2%; on the contrary, the 73-CPWTR model returns better results for practical sizes and a very cold duct with very large insulated thickness. For the results obtained by the same method as the present study except neglecting thermal radiation, it is found that neglecting the thermal radiation effect is likely to produce very large errors in noninsulated and quite large errors in thinly insulated ducts under conditions of low external convection effect introduced by ambient air and higher surface emissivity. The 73-CPWTR model, without considering thermal radiation, can also generate acceptable results in situations of a very cold rectangular duct with thicker insulation, even when an insulated surface is actually with ε = 0.8.
THERMAL WAVE SCATTERING BY TWO SUBSURFACE SPHERES INCLUDING NON-FOURIER EFFECTS
69-80
Xiao-Bo
Ma
School of Mechanical Engineering, Tongji University, Shanghai 201804, China
Sheng-Lin
Ye
School of Mechanical Engineering, Tongji University, Shanghai 201804, China
Qing-Qing
Wang
School of Mechanical Engineering, Tongji University, Shanghai 201804, China
De-Zhen
Chen
School of Mechanical Engineering, Tongji University, Shanghai 201804, China
In this paper, a general solution for the temperature field induces by the modulated heating of an opaque semi-infinite solid with two subsurface spheres was presented based on the non-Fourier equation of heat conduction. Multiple scattering of thermal waves from the subsurface spheres in the solid was investigated by using the wave function expansion method and the virtual image method. A series solution to hyperbolic equations of heat conduction and a matrix formulation to solve the scattering coefficients are used. The temperature at the frontal surface of the solid at different parameters was calculated and illustrated graphically. The analytical method and numerical results would be applied to thermal wave imaging, physical inverse problem, and the evaluation of subsurface defects in materials.
NUMERICAL AND EXPERIMENTAL INVESTIGATION OF THE SHELL SIDE CHARACTERISTICS OF THE TREFOIL-HOLE BAFFLE HEAT EXCHANGER
81-95
Dan
Wang
Key Laboratory of Process Heat Transfer and Engergy Saving of Henan Province, Zhengzhou University, No.97 Wenhua Rd. Jinshui District, Zhengzhou City, Henan 450002, China
Ke
Wang
China University of Petroleum-Beijing, 18 Fuxue Road, Changping, Beijing 102249, China; Royal Institute of Technology (KTH), Albanova University Center, Roslagstullsbacken 21, Stockholm
10691, Sweden
Yongqing
Wang
Key Laboratory of Process Heat Transfer and Engergy Saving of Henan Province, Zhengzhou University, No.97 Wenhua Rd. Jinshui District, Zhengzhou City, Henan 450002, China
Caipeng
Bai
Key Laboratory of Process Heat Transfer and Energy Saving of Henan Province, Zhengzhou
University, Zhengzhou 450002, China
Minshan
Liu
Key Laboratory of Process Heat Transfer and Engergy Saving of Henan Province, Zhengzhou University, No.97 Wenhua Rd. Jinshui District, Zhengzhou City, Henan 450002, China
The shell-and-tube heat exchanger with a trefoil-hole baffle in the shell side is extensively used at nuclear power stations. In the present work, a periodic flow unit duct was taken as a simplified model to numerically investigate the thermal-hydraulic performance of the trefoil-hole baffle heat exchanger. Based on the numerical results, the empirical correlations for the Nusselt number and pressure drop were derived, and the relative errors of the two empirical correlations are all less than 10%. The detailed characteristics of fluid flow and heat transfer for the fully developed section in the shell side of the trefoil-hole heat exchanger were analyzed. The fluid flow experiments for the trefoil-hole baffle heat exchanger were carried out. The flow velocities at special points in the shell side of a heat exchanger were measured by using a Laser Doppler Velocimeter (LDV). It can be concluded that the relative errors of the axial velocity Vz for all measured points between simulation and experiment are within 20%. The validity and accuracy of the numerical simulation results are verified.