Begell House Inc.
Heat Transfer Research
HTR
1064-2285
35
3&4
2004
PROMINENT SCIENTISTS
3
Vladimir Isaakovich Timoshpolskii
(On his 50th birthday)
Statistical Characteristics of Temperature in a Turbulent Flow in a Granular Bed
6
B. V.
Perepelitsa
Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
The results of an experimental investigation of the statistical characteristics of a temperature field in a water and air flow in a near-wall cell of a closely packed granular bed are presented. Measurements were made for Reynolds numbers ranging from 100 to 5000. The range corresponds to flow regimes from a laminar to a developed turbulent one. The temperature distribution, the root-mean-square temperature values, and the behavior of turbulent temperature fluctuations in a flow were measured as functions of the spatial location along the flow and of the Prandtl number.
Condensation Heat Transfer of Ethylacetate and Water Vapors in a Vertical Tube
7
Oleg Anatolievich
Lonshchakov
Kazan State Technological University (KSTU), K. Marx Str. 68, 420015, Kazan, Russia
V. G.
Dyakonov
Kazan State Technological University (KSTU), K. Marx Str. 68, 420015, Kazan, Russia
The results of experimental studies of the influence of mass fraction on the intensity of condensation heat transfer of ethylacetate-water vapor mixtures in a vertical tube are presented. Experimental data are compared with theoretical dependences obtained for pure liquids. The results demonstrate that application of these calculation formulas to mixtures gives a 40-50% overestimate. The results obtained are correlated as Nu = f(Pe, We, Ku).
Heat and Mass Transfer of a Bubble in the Volume of Chemically Reacting and Inert Solutions
13
V. A.
Nemtsev
Joint Institute of Power and Nuclear Research of the National Academy of Sciencies of Belarus, 99 Krasin Str., Minsk, 220109, Belarus
A. M.
Cherkashin
Institute of Radiative Physicochemical Problems, National Academy of Sciences of Belarus, Minsk, Belarus
A mathematical model for the dynamics of a vapor bubble in chemically reacting solution has been formulated and numerically realized on a computer with due account of the kinetics of chemical reactions and phase transitions for the cases of a stationary bubble in the liquid volume and floating up under the effect of lifting forces. The model describes the bubble dynamics in the chemically inert liquids and solutions under limited transitions. The results of numerical investigation on growth and collapse of vapor bubbles in the volume of chemically reacting and inert liquids are presented. The comparison of the mathematical model with the available experimental data shows good agreement.
Combined Regimes of Self-Excited Oscillations in Condensation Inside Tubes
12
Sergey I.
Lezhnin
Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk
State University, Novosibirsk, 630090, Russia
Nikolay A.
Pribaturin
Kutateladze Institute of Thermophysics, Acad. Lavrentiev ave., 1, Novosibirsk, Russia; Nuclear Safety Institute, Novosibirsk Branch, Acad. Lavrentiev ave., 1, Novosibirsk, Russia
S. B.
Samoilenko
Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Vladimir A.
Fedorov
Research and Innovation Joint-Stock Company "Turbocon", Kaluga Turbine Plant, 255, Moskovskaya Street, Kaluga, 248021, Russia; Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
A model of the dynamics of vapor-bubble collapse in a channel, which takes into account hydraulic damping in a condensate flow, is developed. Numerical results are compared with experimental data. At a high rate of condensation, the numerical experiments show that high-frequency self-excited oscillations, such as the so-called "chugging" oscillations, could be obtained. Moreover, possible combinations of different types of self-excited oscillations which occur in condensation inside tubes are considered.
The Hazen-Dupuit-Darcy Model for Investigation of Viscous Dissipation Effects on Thermal Development of a Liquid-Metal Flow in a Porous Medium: Circular Tube with Uniform Wall Temperature
10
A. A.
Ranjbar-Kani
Mechanical Engineering Department, Faculty of Engineering, Mazandaran University, PO Box 484, Babol, Iran
Kamel
Hooman
Mechanical Engineering Department, Persian Gulf University, Bushehr 75168, Iran
An exact solution is presented to investigate the effects of viscous dissipation on the thermal development of a liquid-metal fluid flowing in a circular tube with a uniform wall temperature filled by a saturated porous medium. The Hazen-Dupuit-Darcy model is employed. The analysis leads to expressions for the local Nusselt number, as a function of the dimensionless axial coordinate Peclet and Brinkman numbers.
Numerical Investigation of Flow and Heat Transfer of a Liquid Metal in a Compact Heat Exchanger
10
A. A.
Ranjbar-Kani
Mechanical Engineering Department, Faculty of Engineering, Mazandaran University, PO Box 484, Babol, Iran
Kamel
Hooman
Mechanical Engineering Department, Persian Gulf University, Bushehr 75168, Iran
The paper presents a numerical solution for laminar fluid flow and heat transfer of a liquid metal in the entrance region of a rectangular channel with solid fins which are arranged on the top and bottom isothermal walls in a periodically staggered way. This arrangement simulates a compact heat exchanger. The governing equations are solved by a power-law scheme. The velocity and pressure terms of the momentum equation are solved by the SIMPLER method. The results demonstrated that the fins interrupt the boundary later and cause a detachment from the wall forming a recirculation zone in front of the fin, thus leading to a reattachment point with a relatively high Nusselt number. It is observed that increasing the fin height affects the heat exchanger design in two opposing ways, namely, a higher Nusselt number and increasing the pressure drop. It is also understood that the location of the periodically fully developed region is sensitive to both the Reynolds number and the Peclet number.
Using a Porous Segment to Increase Thermal Efficiency by Converting Gas Enthalpy to Thermal Radiation in High-Temperature Industrial Furnaces: Exact Solution
8
Kamel
Hooman
Mechanical Engineering Department, Persian Gulf University, Bushehr 75168, Iran
A. A.
Ranjbar-Kani
Mechanical Engineering Department, Faculty of Engineering, Mazandaran University, PO Box 484, Babol, Iran
Arash
Ejlali
Reservoir Research Center, Azarab Co.; and Reactor-Saz Co., Engineering Deptartment, Tehran, Iran
Based on the concept of local thermal equilibrium an exact solution is reported to investigate effects of a porous segment at the outlet of a high-temperature one-dimensional duct modeled as an industrial furnace. Since the enthalpy of a high-temperature gas is converted to thermal radiation by means of this porous segment, thermal efficiency increases. The two-flux method is taken into account for this problem.
Special Features of Liquid Boiling in Horizontal Annular Channels
6
A. V.
Ovsyannik
P. O. Sukhoi Gomel State Technical University, Gomel; and A. V. Luikov Heat and Mass Transfer Institute, National Academy of Sciences of Belarus, Minsk, Belarus
The results of the experimental study of the process of boiling of liquids on smooth and longitudinally ribbed surfaces in a horizontal annular channel are presented. The investigations showed the effect of a pressurized vapor-liquid mixture on the intensity of the boiling process resulting in an increase of the mixture turbulence and heat-transfer coefficient and a decrease of temperature head.
Determination of the Boundaries of a Two-Phase Liquid-Metal Flow in the Loop with Natural Circulation
10
D. E.
Martsinyuk
State Scientific Center of the Russian Federation - Physical and Power Engineering Institute, Obninsk, Russia
A. P.
Sorokin
State Scientific Center of the Russian Federation - Physical and Power Engineering Institute, Obninsk, Russia
The experimental study of liquid metal boiling under atmospheric pressures is carried out and analyzed. The description of the experimental loop and experiments on boiling of sodium-potassium coolant in the model of a fast-reactor fuel assembly under the conditions of natural circulation is presented.
Investigation of the Vicinity of the Front of Change of Boiling Regimes
6
M. O.
Lutset
S. S. Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
The results of experimental investigation of heat transfer processes in the vicinity of border between the areas of nucleate and film boiling are given. The experiment is carried out in liquid nitrogen on a sapphire plate with sprayed platinum gauges of temperature. The distributions of temperature and heat fluxes in the liquid along a heater axis are obtained during the process of propagation of the film-boiling site. The front site instability is found. The instability is a consequence of film boiling. The heat fluxes into the liquid realized in a transient area turned out to be much larger than the critical heat flux.
Transient Regimes of Boiling
13
Aleksandr N.
Pavlenko
Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences,
Novosibirsk, Russia
Irina P.
Starodubtseva
IT SB RAS
The dynamics of development of 1D and 2D sites of film boiling is simulated numerically. While analyzing the boundary conditions at the front of change of boiling regimes, we introduce the dimension-less parameter ε which characterizes the ratio of the temperature gradient at the front to the linear scale of capillary force action. Here we show the effect of the nonstationary coefficient of heat transfer in various zones of the front on the values of equilibrium density of the heat flux and the velocity of propagation of the film boiling boundary.
Robust Predictive Control of a Humidifying Process by Using the Kautz Model and LMI Approach
20
A.
Mbarek
Unité de Recherche ATSI, Ecole Nationale d'Ingénieurs de Monastir, Rue Ibn EL Jazzar 5019 Monastir, Tunisia
K.
Bouzrara
Ecole Nationale d'Ingenieurs de Monastir (ENIM) Rue Ibn El Jazzar, 5019 Monastir-Tunisia
T.
Garna
Unité de Recherche ATSI, Ecole Nationale d'Ingénieurs de Monastir, Rue Ibn EL Jazzar 5019 Monastir, Tunisia
Hassani
Messaoud
Research Unit ATSI, National School of Engineers of Monastir, University of Monastir, Rue Ibn El Jazzar, 5019 Monastir, Tunisia
This paper proposes a new robust predictive control algorithm based on the Kautz model the coefficients of which belong to an uncertainty domain. Two performance criteria (l1 and l∞) are optimized with respect to constraints resulting from boundedness measurements and those due to parameter uncertainties. The optimization problem is solved by using the LMI approach to provide the optimal future control sequence. The proposed algorithm is used to regulate the humidity inside a drying blower.
Numerical Simulation of Natural Convection in a Horticultural Greenhouse Heated from Below (by Using CFD)
34
Tadj
Nacima
University Center of Bechar Institute of Exact Sciences, BP 417 08000 Bechar, Algeria
The analysis of the possibility of determining climate under a greenhouse confronts us with a very complex system composed at least of three components (culture, substrate or soil, and air) and of exchange of energy, steam, and CO2 between them. The recent advance of greenhouse surfaces in the Mediterranean basin puts in the forefront the problem of air-conditioning whose solution will improve production at least as far as the quality is concerned. This work is concerned with numerical simulation of natural convection in a laminar regime in closed greenhouses (tunnel greenhouse and single span greenhouse) of length 25 m, width 6 m, and height 3.5 m, intended for planting vegetation for the table with soil heated by a flux of 100 W. The walls of a single span greenhouse are adiabatic, the roof is maintained at a temperature of 280 K in both greenhouses. For all the walls of the two greenhouses and the soil in them the conditions of adhesion hold: u = v = w = 0 m/sec. The model suggested represents the equation of motion associated with an energy equation; it is solved by means of a Computational Fluid Dynamic software (CFD2000) based on the PISO algorithm. The results are represented in the form of streamlines, isotherms, and velocity profiles. The results obtained allow one to characterize the general flow of air in a greenhouse. It is also shown that for the conditions of flux application to soil (heating by means of a buried tube), the circulation of air is characterized by two recirculation cells rotating in the opposite directions. Therefore, this study will permit one to improve thermal designs of greenhouses and positioning of air-conditioning systems.