Begell House Inc.
Heat Transfer Research
HTR
1064-2285
37
2
2006
Influence of Nonisothermicity on the Heat Transfer from a Bank of Finned Tubes in the Presence of Coating on the Outside Surface
93-102
V. G.
Gorobets
Institute of Engineering Thermophysics, National Academy of Sciences of Ukraine, Kiev, Ukraine
The results of solution of the conjugated heat transfer problem for a staggered bank of finned tubes in the presence of a weakly conducting coating on the outside surface are given. The characteristics have been determined and the basic laws governing heat transfer and the influence of coatings on the conditions of conjugated heat transfer have been studied. The results of solution of conjugated problems were compared with the data of calculations obtained with the aid of simplified models that ignore the influence of the surface nonisothermicity or employ averaged values of the heat transfer coefficients. The differences between the local and integral characteristics of heat transfer of the objects under study found in conjugated and simplified statements of the problem are found.
Heat Transfer and Aerodynamic Drag of Banks of Smooth Tubes with Surfaces of Different Geometries in a Crossflow
103-112
V. T.
Buglaev
Bryansk State Technical University, Bryansk, Russia
A. A.
Anisin
Bryansk State Technical University, Bryansk, Russia
A. K.
Anisin
Bryansk State Technical University, Bryansk, Russia
The possibility of enhancing heat transfer from a symmetrical inline 1.45 × 1.45 bank of smooth tubes with the outer diameter d1 = 11 mm in a crossflow with smooth cylindrical turbulizing rods of diameter d2 = 1.2−4.5 mm disposed inside the bank successively at the centers of squared tubular cells is analyzed. The implementation of the proposed arrangement of tubular elements in the form of a combined heat-transfer surface of tube banks of different outer diameters d1 = 11 mm and d2 = 6 mm with a triangular one with d1 = 11 mm and d2 = 8 mm with a linear arrangement and experimental thermal and aerodynamic characteristics obtained on their basis point to the expediency of practical application of the proposed approach to heat transfer enhancement and increase of the energy efficiency of tubular heat exchanging apparatus and facilities. Various variants of the design of a tubular surface in a crossflow are presented.
Simulation of the System Stabilizing Film Cooling of Turbine Blades Based on Blank Damping Cavities
113-122
N. N.
Kovalnogov
Ul'yanovsk State Technical Universtiy, Ul'yanovsk, Russia
D. A.
Buinov
Ul'yanovsk State Technical Universtiy, Ul'yanovsk, Russia
A mathematical model of film cooling of turbine blades under the conditions of the formation of a film on a punched surface having blank damping cavities is suggested. Based on numerical investigation with the use of the proposed model, the possibility of a substantial increase (under the analyzed conditions ensuring a decrease in the adiabatic wall temperature by 200 K) in the efficiency of film cooling due to partial laminarization of a turbulent boundary layer on the punched surface has been revealed.
The Results of Experimental Investigation into Rational Intensification of Convective Heat Transfer in Rectangular Channels with Protrusions and Grooves Having a Smoothly Rounded Two-Dimensional Cross Section
123-134
Victor Ya.
Vasiliev
Department of Mechanical Engineering, Astrakhan State Technical University, Astrakhan 414025, Russia
Experimental investigation of heat-transfer enhancement in short rectangular air-flow channels with transverse protrusions and grooves of 15 specially manufactured gilled-tube water-air-flow radiators (heat exchangers) has been carried out (the channel characteristics are: l'/d = 0.183−1.695 and d*/d = 0.813−0.953). The process of rational heat-transfer enhancement is implemented in the channels; it is controlled by the l'/d and d*/d characteristics. It has been proven that the results of heat transfer enhancement in short channels are somewhat worse than those for long ones. This makes it possible to reduce the mass and volume of the radiator core (matrix) by a factor of 1.4 in comparison with short smooth channels under the same conditions.
Study of the Thermal Resonance in Multidimensional Irregular Thermal Fields that is Initiated by the Nonlinear Boundary Conditions
135-148
A. V.
Kotovich
N. E. Bauman Moscow State Technical University, Moscow, Russia
G. A.
Nesenenko
N. E. Bauman Moscow State Technical University, Moscow, Russia
A method for obtaining approximate analytical solutions of nonlinear boundary-value problems of irregular heat conduction has been proposed and substantiated. The regions, where solutions can be found by the suggested method, can have a random shape and nonlinear conditions can be specified on their boundaries. The developed "geometrical-optical" asymptotic method allows one to find approximate analytical solutions in the form of asymptotic Poincare expansions whose coefficients are calculated explicitly. The report gives as an example the results of analytical-numerical parametric analysis of irregular (i.e., singularly perturbed) temperature fields in a boundary layer on the side of the rectangle on which nonlinear boundary conditions are specified. Two types of nonlinear boundary conditions are discussed, viz., exponential (Arrhenius) type and Stefan-Boltzmann type. A set of parameters has been found for which the initial Gaussian-type distribution results, in the boundary layer, in a local nonlinear enhancement of the thermal field, i.e., in "thermal resonance".
Quasistatic Thermoelastic Fields in a Half-Space Heated by a Circular Surface Heat Source
149-164
V. A.
Pinsker
Open Joint-Stock Company "Drilling Techniques" of United Heavy Machinery, Moscow, Russia
An accurate analytical solution of a classical problem, related to unbound thermoelasticity in a homogeneous and isotropic linearly-elastic half-space has been obtained in a closed integral form. Important partial cases, when the expressions for temperature and stresses take a simpler form, have been analyzed. The asymptotics of the found solutions have been investigated at small and large values of dimensionless time near the heat source and at a distance from it. The fields of isotherms and isobars have been studied. Unapparent properties of spatial inversion of both temperature and thermal stresses have been found. Maximum values of all components of the thermoelastic field at different values of the Poisson ratio have been found. For steady-state heating, a general solution, expressed in terms of a set of elliptical integrals, has been constructed in an explicit form. It has been shown that only compression stresses are possible in a steady-state mode in a semibounded body. The deformation profile of a free boundary has been determined. Possibility of mechanical destructions in the heated half-space has been analyzed. The graphs illustrating the spatial distribution and the time evolution of thermoelastic fields are given. The constructed solution can serve as a Green function for a set of other problems, having similar geometrical and boundary conditions.
Investigation of Processes in Melting Accumulators with a Heat-Conducting Packing and Development of Computational Methods for Their Optimization
165-174
E. A.
Lesyuk
Elekrostal Polytechnic Institute, Branch of the Moscow Institute of Steel and Alloys, Elektrostal, Russia
Heat transfer processes in accumulators of cold with a liquid-solid body phase transition, with due account of a heat-conducting packing in the form of a porous body with open pores are studied. The results of optimization and experimental studies of the accumulator of cold with such packings are given.
Improving Technological Effectiveness of Computational Techniques of the Applied Thermomechanics by Their Computerization
175-182
Yu. S.
Postolnik
Dneprodzerzhinsk State Technical University, Dneprodzerzhinsk, Ukraine
I. A.
Pavlyuchenkov
Dneprodzerzhinsk State Technical University, Dneprodzerzhinsk, Ukraine
N. V.
Andrianov
Republican Unitary Enterprise "Belarusian Metallurgical Plant", Zhlobin, Belarus
Based on the previously obtained [1, 2] approximate solutions of all classes of nonlinear problems of thermomechanics (heat conduction and thermoelasticity), Postolnik and Ogurtsov [3, 4] presented respective techniques for computation of temperatures and stresses, given nonlinearities of the 1st (temperature dependence of thermophysical characteristics of the material), 2nd (radiative heat transfer), and 3rd (melting-solidification phase transformations) kinds. For the purpose of increasing the technological effectiveness of the computation process, most of these techniques are supported by computerized programs. Here, we present an example of a block diagram for computation of the temperature and thermally stressed state of massive bodies of the basic shape (BBS) under the conditions of radiative heating.
Analytical Solution of the Problem of Heat Conduction of a Semi-Bounded Body with an Envelope and Its Application to Control and Identification of Heat Transfer Processes
183-189
N. M.
Lazuchenkov
Institute of Technical Mechanics, National Academy of Sciences of the Ukraine, Ukraine
D. N.
Lazuchenkov
Institute of Technical Mechanics, National Academy of Sciences of the Ukraine, Ukraine
The problem of heat conduction of a uniformly heated semi-bounded body, instantaneously coming in an ideal thermal contact with a thin envelope of a different initial temperature, has been discussed. The analytical solution of the problem was used to build a simple mathematical model of the product heating in a continuous lamination device, allowing effective control of the technological process. The possibility of application of the analyzed heat conduction problem for assessing the levels of single pulsed thermal impacts on the solid body surface has been justified.