Begell House Inc.
Heat Transfer Research
HTR
1064-2285
32
7&8
2001
Complex Heat Transfer in Furnaces with a Circulating Fluidized Bed
6
K.
Breitholtz
Chalmers Technological University, Goteborg, Sweden
B.
Leckner
Department of Energy Conversion, Chalmers University of Technology, S-412 96 Goteborg, Sweden
A. P.
Baskakov
Ural State Technical University, Ekaterinburg
Intensity of heat transfer to screen surfaces in the furnaces with a circulating fluidized bed (CFB) is determined by both radiation and convection of particles. Due to the formation of a thermal boundary layer near the screens the role of radiation decreases and that of convection increases with an increase in concentration of particles in the furnace. Generalization of the data obtained in pilot-full-scale and industrial furnaces with a CFB allowed one to obtain a simple empirical dependence of the furnace-mean coefficient of heat transfer α (W/(m2·K) on the volumetric-mean concentration of particles c (kg/m3): α = 85·c0.3.
Experimental Study of Pulse Characteristics of Turbulent Tube Flow of a Gas with Solid Particles
7
Aleksey Yur'evich
Varaksin
Joint Institute for High Temperatures (JIHT) of the Russian Academy of Sciences, Izhorskaya Street, 13, Building 2, 125412, Moscow, Russia
Yury V.
Polezhaev
Department of Heat Transfer, Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya 13/19, Moscow 127412, Russia
Anatoly F.
Polyakov
Department of Heat Transfer, Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya 13/19, Moscow 127412, Russia
Distributions of longitudinal and transverse components of the intensity of velocity fluctuations of a carrying air in the presence of a disperse phase in the form of solid particles are obtained for the case of realization of a weakly dusted nonequilibrium flow in a vertical tube. The distributions showed that the presence of particles in the flow results in a decrease of turbulent fluctuations of velocity. The effect of suppression of fluctuations increases with an increase in concentration of particles, a distance from the tube wall and with a decrease in time lag of particles.
Study of Large-Scale Vapor Explosions in Interaction of Fusible Metals with Water
7
G. A.
Kapinos
State Scientific Center of Russian Federation - "A. I. Leipunskii Physico-Energetical Institute", Obninsk, Russia
Yu. P.
Meleshko
State Scientific Research Institute of Scientific Production Association "Luch" Obninsk, Russia
V. I.
Nalivaev
State Scientific Research Institute of Scientific Production Association "Luch" Obninsk, Russia
O. V.
Remizov
State Scientific Center of Russian Federation - "A. I. Leipunskii Physico-Energetical Institute" Obninsk, Russia
S. R.
Kharitonov
State Scientific Center of Russian Federation - "A. I. Leipunskii Physico-Energetical Institute" Obninsk, Russia
Experimental data on thermal interaction between metal melts (lead, bismuth) and water are presented. The bench LAVA-P, methodical problems of experiments, results of measurements of pressure pulses in vapor explosions are described. Test data on vapor explosions are analyzed, a number of special features which are caused by the specifics of the nature of thermal interaction in the melt-water system, the type of the melt-water contact, and the type of the experimental setup are noted.
Wall-Temperature Control in Free Convection
8
A.K.
Alekseev
"Energiya" Rocket-Space Corporation, Korolev, Moscow Region, Russia
The problem of determining the temperature on the lower boundary of a volume of viscous liquid which ensures the prescribed distribution of temperature or velocity is considered. The flow parameters were calculated by means of finite differences using three-dimensional nonstationary Navier-Stokes equations in Boussinesq form. An adjoint problem is used for fast calculation of discrepancy gradient with the calculation time as for a forward problem. The same finite difference method is used for both forward and adjoint problems. The optimization was performed using the conjugate gradient method.
Numerical Modeling of Convective Heat Transfer in a Compressible Turbulent Boundary Layer under Extremely High Cooling
9
I. A.
Bassina
Russian Scientific Center "Applied Chemistry", St. Petersburg, Russia
Michael Kh.
Strelets
New Technologies & Services St-Petersburg 197198, Russia
V. K.
Shikov
Institute for High Temperatures, Russian Academy of Sciences, Moscow, Russia
A systematic comparison of numerical predictions by different turbulence models with experimental data published recently for a compressible turbulent boundary layer of a high-enthalpy air flow (Te up to 6700 K, Pe up to 5 atm, Me up to 3.5) is performed. It is shown that conclusions about suitability of some turbulence models previously made for moderate cooling are not justified under the conditions of very high cooling (enthalpy factor 0.01−0.1) in combination with flow compressibility and variability of gas properties.
Heat and Mass Transfer in a Boundary Layer in Evaporation and Combustion of Ethanol in a Turbulized Air Stream
6
Boris Fedorovich
Boyarshinov
Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
The influence of the dynamic properties of external flow on mass transfer in a boundary layer was investigated experimentally. The air stream turbulence was changed from 1% to 26% with the aid of lattices. The edges of height up to 15 mm were installed at the beginning of the boundary layer. The influence of viscosity was evaluated from comparison of experimental data for cases with combustion and without it. It is revealed that the extremes of mass transfer parameters exist for certain combination of the main stream turbulence level and the height of the edge. Without combustion it is a maximum of evaporation rate. With combustion - the flame breakdown main stream velocity maxima, and also it is the minimum of burning rate. In both cases the multiple changes of mass transfer intensity are noted. The reasons of their appearance are analyzed.
Turbulent Gas Flow Structure under Unsteady Hydrodynamic Conditions
9
V. B.
Bukharkin
Moscow State Aviation Institute (Technical University), Moscow, Russia
Guenrikh A.
Dreitser
Department of Aviation-Space Thermal Techniques,
Moscow Aviation Institute, Volokolamskoe shosse, 4, Moscow, 125993, Russia
V. M.
Kraev
Moscow State Aviation Institute (Technical University), Moscow, Russia
The data obtained on the structure of a turbulent circular tube gas flow in the case of hydrodynamic unstable influence of averaged velocity longitudinal and radial components fields, their pulsations and correlations. These are supplemented with the data on the influence of stationary conditions on the turbulent coefficient and heat transfer coefficient. The existence of the zone of greatest changes in the structure parameters is confirmed. It is found that the flow nonisothermicity enhances the influence of hydrodynamic instability. Under nonisothermal boundary conditions, after the removal of the effect, the return of structure characteristics to the stationary influence slow down considerably. A new dimensionless criterion of hydrodynamic instability is suggested.
Heat Transfer in Instrumentation Modules of Spacecrafts with the Systems of Heat Control on the Basis of Heat Pipes
7
A. N.
Kozlobrodov
Scientific-Research Institute of Applied Mathematics and Mechanics at the Tomsk State University, Tomsk, Russia
S. F.
Sandu
Scientific-Research Institute of Applied Mathematics and Mechanics at the Tomsk State University, Tomsk, Russia
G. V.
Kuntsevich
Scientific-Research Institute of Applied Mathematics and Mechanics at Tomsk State University, Tomsk, Russia
The process of heat transfer in an instrumentation module of a spacecraft with the systems of heat control on the basis of low-temperature heat pipes is studied numerically. Special attention is paid to an analysis of heat transfer due to internal reirradiation and operation of heat pipes. A multi-dimensional character of heat propagation in the structure of the instrumentation module and the possibility of construction of these design-arrangement schemes which could provide stable operation of instrument panels under extremum conditions of heat transfer are shown. It is found that a number of heat pipes and their arrangement exert a substantial effect on the distribution of temperature fields of all the panels of the module and an account for internal re-emission leads to leveling of them.
Heat Transfer Processes in High-Temperature Flows of Two-Phase Media
7
M. I.
Osipov
Bauman Moscow State Technical University, Moscow, Russia
K. A.
Gladoshchuk
Bauman Moscow State Technical University, Moscow, Russia
A. N.
Arbekov
N. E. Bauman Moscow State Technical University, Moscow, Russia
The results of an experimental study and theoretical analysis of specific features of heat transfer in inner and outer supersonic high-temperature turbulent flows of heterogeneous flows are presented. The experiment is conducted on a high-temperature setup by means of laser diagnostics which allowed one to obtain fluctuation characteristics of the flow and also to determine substantial enhancement of heat transfer within a range of 10−85% with an increase in particle concentration from 3 to 15%. It is shown that the presence of solid particles with a diameter of 40−50 μ;m in a supersonic flow leads to an increase of the degree of turbulence and to a substantial change in the structure of a wall surface.
Heat Exchange and Magnetic Hydrodynamics of the Core of the Earth
5
V. K.
Bulgakov
Khabarovsk State Technical University, Khabarovsk, Russia
S. V.
Solov'ev
Khabarovsk State Technical University, Khabarovsk, Russia
We consider natural-convective heat exchange of electrically conducting liquid in a spherical interlayer in the Boussinesq approximation. Free-fall acceleration is directed to the center of the sphere. For the ranges of magnetic interaction S and Reynolds magnetic number Rem 1.5·10−5 ≤ S ≤ 1.5·10−2 and 1.5·10−8 ≤ Rem ≤ 1 we found the critical number (S/Rem) ~ 450, in passing over which the direction of meridional circulation of liquid undergoes a change in the core of the Earth.
Heat Transfer and Hydraulic Resistance in Rod Bundles of Tubes with Counter Wire-Winding in Longitudinal Flow
10
Benediktas B.
Cesna
Lithuanian Energy Institute, Kaunas, Lithuania
The paper presents the results of experimental investigation of hydraulic resistance, mixing, and heat transfer of rod bundles consisting of 85 counter wire-wound rods in an axial air flow. The rods were spaced by means of two- and four-wire counter coils. The pitch-to-diameter ratio P/d = 1.23 was used. For the bundle with opposite wire-winding 43 rods were with 4-wire coils and 42 rods were with 2-wire coils. The left direction of wire winding was used for 4-wire coils and the right direction for 2-wire coils. The helical-lead-to-rod-diameter ratio was T/d = 20 for rods with 4-wire coils and T/d = 10 for rods with 2-wire coils. Experiments were performed in an air flow within the range 4.3·103 4.
Experimental Study of the Transition and Developed Turbulent Flow Regimes in Free Convection Boundary Layer Near a Vertical Heated Surface
5
The results of an experimental study of a free-convective boundary layer formed on a vertical isothermally heated plane surface are presented. Three regimes of flow are studied: laminar, turbulent, and a laminar-turbulent transient flow, which is given a considerable amount of attention. The free-convective flow is generated by a vertical aluminum plate 90 cm in width and 4.95 m in height. The large height of the plate gave the possibility to obtain all three flow regimes such as laminar, transient, and a developed turbulent one. The study of the boundary-layer properties is based on the measurements of the average and fluctuational temperature and velocity components. When measuring the velocity characteristics, two components of velocity (streamwise and normal) are determined. Attention is specially paid to the near-wall flow region, in particular, to the measurement of the heat flux and the wall stress. New empirical dependences of these values within a wide range of the Grash of numbers are obtained, including three flow regimes: laminar, transient, and turbulent. Some features of the flow in the transient region which are appropriate only for a free-convective flow are described. Various criteria of the beginning and end of the transient region are analyzed. In the present work a fluctuational flow is analyzed in detail in a laminar-turbulent transient region. The results of the measurements of different boundary-layer characteristics (intensity of temperature and longitudinal velocity fluctuations) are presented. The results of the present study are compared in detail with the data given in other references.
Efficiency of Heat Transfer Enhancement in Heat Exchangers
9
Guenrikh A.
Dreitser
Department of Aviation-Space Thermal Techniques,
Moscow Aviation Institute, Volokolamskoe shosse, 4, Moscow, 125993, Russia
A method of evaluating the efficiency of heat transfer enhancement in channels of heat exchangers is presented. The method allows one to evaluate any technique of heat transfer enhancement without detailed calculations of heat exchangers. A method of calculating the efficiency of heat transfer enhancement for any ratio between heat transfer coefficients on hot and cold sides of heat exchangers is given.
Convective Heat and Mass Transfer for Nonuniform Heat Generation in Twisted Rod Bundles
9
Boris V.
Dzyubenko
Moscow Aviation Institute (State Technical University), 4 Volokolamskoe Highway, Moscow, 125993, Russia
Guenrikh A.
Dreitser
Department of Aviation-Space Thermal Techniques,
Moscow Aviation Institute, Volokolamskoe shosse, 4, Moscow, 125993, Russia
The results of experimental and theoretical studies of steady and unsteady convective heat and mass transfer in twisted rod bundles are presented. New generalizing relations are derived to calculate effective turbulent transfer coefficients used to close a system of equations describing thermal and hydraulic processes in such rod bundles. The physical phenomena that characterize the specific features of heat and mass transfer for different types of unsteadiness are considered. The developed empirical method for closing a system of equations is based on both the hypothesis for local similarity of transfer and mathematical formalism in solving the problems.
Efficiency of Heat Transfer Surfaces Using the Method of Effective Parameters
8
R. I.
Yakimenko
Moscow State Aviation Institute (Technical University), Moscow, Russia
Boris V.
Dzyubenko
Moscow Aviation Institute (State Technical University), 4 Volokolamskoe Highway, Moscow, 125993, Russia
We present the results of analysis of thermohydraulic efficiency of different types of heat transfer surfaces obtained by means of the Method of Effective Parameters. It is found that for the range of Reynolds numbers typical for Heat Exchangers (HE) of Food Industry the most effective heat transfer surface is the formed by a bundle of twisted tubes. This is due to augmentation of heat and mass exchange as a result of flow swirling by twisted tubes. On the basis of this analysis a compact HE of twisted tubes has been developed for champagne type wine cooling. The mass of these HE are several times less than the mass of plane tubes HE designed previously for the same food product flow rate.
Thermal Boundary Layer in the Presence of Upper Bypass Transition
10
Eleonora Ya.
Epik
Institute of Engineering Thermophysics of National Academy of Sciences of Ukraine (IET NASU), 2a Zhelyabov Str., 03057, Kyiv, Ukraine
V. A.
Grigorenko
Institute of Technical Thermophysics, National Academy of Sciences of Ukraine, Kiev, Ukraine
The results of experimental investigation of heat transfer are presented for the case of origin of the "upper" bypass laminar-turbulent transition. On the basis of an analysis of integral and local characteristics of hydrodynamic and thermal boundary layers a method is proposed for calculation of heat transfer enhancement in terms of turbulent viscosity at the outer edge of the hydrodynamic boundary layer. The substantiations of the calculation method using coefficients of longitudinal intermittency are developed. The promise of this method for hydrodynamic intermittency and necessity of its further revision for thermal one is shown.