Begell House Inc.
Heat Transfer Research
HTR
1064-2285
34
3&4
2003
Pulverized Lignite Combustion in Swirl Burners. A Mathematical Model
12
Aleksandar
Saljnikov
Faculty of Mechanical Engineering, University of Belgrade, Belgrade 11000, Serbia and Montenegro
Simeon N.
Oka
Laboratory for Thermal Engineering and Institute of Nuclear Sciences — VINCA, Belgrade 11001, Serbia and Montenegro
M.
Radovanovic
Faculty of Mechanical Engineering, University of Belgrade, 27. marta 80, Belgrade, Serbia, Serbia and Montenegro
M.
Sijercic
Institute of Nuclear Sciences - VINCA, Laboratory for Thermal Engineering and Energy PO. Box 522, 11001 Belgrade, Serbia and Montenegro
Premature Burnout
9
V. V.
Ovchinnikov
Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
B. P.
Avksentyuk
Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
A unified mechanism for the occurrence of premature burnout in forced convection boiling and in pool boiling is suggested. A region of the regime parameters at which premature burnout in subcooled forced convection boiling may occur is determined. The equation for the computation of the lower limit of premature burnout is suggested.
Length of Condensation Zone in Tubes with Supply of a Concurent Gas Jet into Nitrogen and Hydrogen Flows
11
V. A.
Bershadskii
Moscow 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. P.
Firsov
Moscow Aviation Institute (Technical University), Moscow, Russia
I. V.
Antyukhov
Moscow Aviation Institute (Technical University), Moscow, Russia
The size of a nonequilibrium condensation region in a tube flow of cryogenic liquids (nitrogen, hydrogen) under subcooled conditions with axial supply of a gas jet in the direction of flow is investigated. Experiments were conducted in the visual test sections of the diameter of 95 and 140 mm which were made of quartz glass and were located in a low-pressure chamber. The axial input of gas flow was executed through a jet injector of the diameter of 6 and 8 mm. The experiments on the condensation zone length were generated using the representations about the predominance of turbulent splitting and condensation of steam bubbles. Generalizing relations for calculation of dimensionless lengths of the condensation zone in the flow of liquid nitrogen and hydrogen were obtained for the concurrent input of gas into the flow.
Heat Exchange during Production of Particles in the Process of Impact Atomization
6
A. S.
Kalinichenko
Belarusian State Polytechnic Academy, Minsk, Belarus
A. N.
Abramenko
Belarusian State Polytechnic Academy, Minsk, Belarus
Yu. K.
Krivosheev
Belarusian State Polytechnic Academy, Minsk, Belarus
E. A.
Voronin
Belarusian State Polytechnic Academy, Minsk, Belarus
The method of impact atomization of melt is one of the up-to-date processes for producing spherical particles. An atomization unit must provide extraction of constant heat flux and maintain a stable tooth temperature. The original unit designed is based on the evaporation-condensation cycle. The method of calculation of the thermal parameters of the unit was developed just as its technical documentation. The pilot unit was manufactured and tested successfully.
Heat and Mass Transfer in Evaporative Cooling of Water Films on Two Vertical Plates
14
V. V.
Antonik
"Belenergo" Belorussian State Power Engineering Concern, Minsk, Belarus
Alexey I.
Petruchik
A. V. Luikov Heat and Mass Transfer Institute, National Academy of Sciences of Belarus, Minsk, Belarus
A. D.
Solodukhin
A. V. Luikov Heat and Mass Transfer Institute, National Academy of Sciences of Belarus, 15 P. Brovka Str., Minsk, 220072, Belarus
N. N.
Stolovich
A. V. Luikov Heat and Mass Transfer Institute, National Academy of Sciences of Belarus, 15 P. Brovka Str., Minsk, 220072, Belarus
Sergey P.
Fisenko
A. V. Luikov Heat and Mass Transfer Institute, National Academy of Sciences of Belarus, Minsk, Belarus
A mathematical model of evaporative cooling of water films on vertical plates is developed. The model is a boundary-value problem for a system of four ordinary nonlinear differential equations. Using the model, we performed calculations and compared them with the data obtained on a commercial cooling tower. It is established that at small and average densities of irrigation the model allows one to adequately describe the parameters of vapor–air mixture above the plates and the temperature of the water cooled. The comparison of experimental and calculated data also shows that at a nominal hydraulic load the contribution of film currents is not less than 50% in a cooling tower.
Efficiency of Vapor Generating Facilities Based on the Use of Twisted and Transit Flows
11
E. A.
Boltenko
Elektrogorsk Scientific Research Center of Safety of Nuclear Power Stations, Elektrogorsk, Russia
The paper presents the assessment of the efficiency of the augmentation method which consists in simultaneous use of twisted and transit flows moving along the gap formed by concave and convex surfaces of the annulus and along the convex heat transfer surface, respectively. It has been shown that, as compared to a smooth channel or a twisted flow channel, the simultaneous use of twisted and transit flows allows heat removal rate and critical heat flux to be significantly increased on both heat transfer surfaces.
Waves on the Surface of Metal Melt in a Melt–Water System
6
Natalya Nikolaevna
Avakimyan
Kuban' State Technological University, Krasnodar, Russia
N. I.
Vasil'ev
Kuban' State Technological University, Krasnodar, Russia
V. V.
Guguchkin
Kuban’ State Technological University, Krasnodar, Russia
I. V.
Tereshchenko
Kuban’ State Technological University, Krasnodar, Russia
A. S.
Trofimov
Kuban’ State Technological University, Krasnodar, Russia
Results of the experimental investigation of the processes of interaction of molten metal with evaporating liquid are presented. A series of successive photographs (in 10–4 sec) of the process of development of perturbations on the melt surface are given. The scale and the velocity of motion of a wave on the melt surface are evaluated. A model of the increase in the wave amplitude, which is a consequence of instability of the melt surface in the vapor layer that separates liquid from the melt, is suggested.
Concerning the Theory of the Incipience of the Two-Phase Mushy Zone in Solidification of Binary Melts
8
Dmitri V.
Alexandrov
Urals State University, Ekaterinburg, Russian Federation
The well-known problem of incipience of a mushy zone for binary melt solidification processes is solved with the aid of the Laplace transform in a laboratory coordinate system. The integral relations for the rate of solidification and the time of incipience of the mushy zone are derived when crystallization proceeds near a cooling wall. The last assumption is confirmed by numerical calculations and by the relations obtained. In other words, a mush appears ahead of the solidification front at the initial stage of crystallization (when the front moves toward the binary melt near the cooling wall). Thus, the time when the classical description of crystallization by means of the Stefan thermodiffusion model becomes incorrect and when the mushy region appears due to the concentrational (constitutional) supercooling is found.
Absorption of Electromagnetic Waves under Heat and Mass Transfer Conditions in Nonequilibrium Media
5
P. V.
Nikitin
Stavropol Branch of the Rostov Military Institute, Stavropol, Russia
V. A.
Loshkarev
Stavropol Branch of the Rostov Military Institute, Stavropol, Russia
An analysis of the interaction between electromagnetic waves and heat protection materials under thermal destruction conditions is made. Incident radiation is absorbed by the inhomogeneities occurring as a result of stability loss in nonequilibrium conditions. Nonlinear effects and dissipation create solutions which participate in dispersion of electromagnetic radiation.
Numerical Simulation of Heat and Mass Transfer during the Process of Convective Drying in Stagnant and Fluidized Beds
13
M. B.
Stakic
Laboratory for Thermal Engineering and Energy, Institute of Nuclear Sciences "Vinca", Belgrade, Yugoslavia
Numerical simulation of the process of drying actual wet materials in stagnant and fluidized beds is presented. A mathematical model describing simultaneous unsteady heat and mass transfer between a gas phase and a solid phase during the process of convective drying in a stagnant and a fluidized bed has been developed. A two-phase fluidization model of a fluidized bed was used. New definition of the drying equation is introduced. Transport phenomena inside and outside dried material is discussed separately, because there are two types of resistance during convective drying of any actual material. An original technique based on experimental investigation of the kinetics of drying of an elementary stagnant bed of a given material was used for defining the coefficients of mass transfer inside the material dried. The mathematical model was tested on the available experimental data and very successfully varified.
Translation of Heat Transfer Measurements from Laboratory CFBs to the Conditions of CFB-Boilers
17
C.
Breitholtz
Department of Energy Conversion, Chalmers University of Technology, S-412 96 Goteborg, Sweden
B.
Leckner
Department of Energy Conversion, Chalmers University of Technology, S-412 96 Goteborg, Sweden
The aim of this work is to find a method for translation of heat transfer data from cold laboratory units to boiler conditions. From a compilation of existing data on heat transfer to walls in hot and cold circulating fluidized beds it is concluded that the results can be translated approximately by compensating for changes in the thermal conductivity of the gas and thermal radiation. A more general methodology is developed by deriving the criteria for thermal similarity. The only criterion that was added to those for fluid-dynamic similarity was the ratio of heat capacity of gas and particles. The thermal scaling is tested by comparing heat transfer measurements in a boiler with measurements in a scaled laboratory model. The results show that the Nusselt numbers were not the same in the boiler and the scaled model, which can be a result of the characteristic length-scale chosen, a too low heat capacity of the scaled particles or a failure to scale the local fluid-dynamics at the wall.
Scaling Formula for Heat-Transfer Optimal Gas Velocity in a Fluidized Bed
6
A. V.
Smirnov
Military Engineering-Technical University, St. Petersburg, Russia
Yu. V.
Yuferev
Military Engineering-Technical University, St. Petersburg, Russia
A. D.
Gol'tsiker
Military Engineering-Technical University, St. Petersburg, Russia
V. E.
Kravchenko
Military Engineering-Technical University, St. Petersburg, Russia
The advantages of the scaling form of computational relations for the processes of hydrodynamics and optimal heat transfer in fluidized-bed apparatuses as against the dimensionless form are shown. A scaling formula is proposed for heat transfer with optimal gas velocity in a fluidized bed which is more justifiable and convenient for usage in practical calculations.
An Exact Solution for Fully Developed Temperature Distribution in Laminar Steady Forced Convection Inside Circular Tubes with Uniform Wall Temperature
11
Kamel
Hooman
Mechanical Engineering Department, Persian Gulf University, Bushehr 75168, Iran
In this paper the fully developed temperature distribution in laminar steady forced convection inside circular tubes with uniform wall temperature has been obtained using an exact analytical procedure. Up to now, the procedure for obtaining the temperature profile was a trial and error method. Kakac, Shah, and Aung [1], have reported an unpublished paper that proposed the solution in the form of a power series (cited in [1]). Any of the above processes seems quite sufficient to find the Nusselt number. However, a strictly exact analytical procedure does not exist. The aim of the present paper is to fill this gap in the literature. A numerical solution is also reported here. To achieve this goal a finite difference backward scheme with the truncation error of O(0.001) is utilized. It is observed that the results agree perfectly with those found by analytical solution. The agreement between the results of these two methods — numerical and analytical — left no suspicion that our analytical solution is the correct answer of the problem published for the first time.
Heat and Mass Transfer During Destruction of Materials under the Action of a Heterogeneous Flow With a High Concentration of Particles
11
Genii V.
Kuznetsov
National Research Tomsk Polytechnic University, Institute of Power Engineering, Tomsk,
634050, Russia
N. N.
Alekseenko
Scientific-Research Institute of Applied Mathematics and Mechanics at the Tomsk State University, Tomsk
T. N.
Nemova
Scientific-Research Institute of Applied Mathematics and Mechanics at the Tomsk State University, Tomsk
A. I.
Tkachev
Scientific-Research Institute of Applied Mathematics and Mechanics at the Tomsk State University, Tomsk, Russia
A mechanism of the destruction of steel under the influence of a high-temperature supersonic heterogeneous jet with a high mass concentration of particles is studied experimentally. Analysis and generalization of experimental results are used to create a more precise physical model — the model of thermomechanical destruction of metals.