Modeling of heat transfer in an isotropic velocity field in the presence of a transverse temperature gradient

Known second-order models are verified in a test problem of an isotropic velocity field with a constant temperature gradient.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 1, pp. 14–20, January, 1988.     

Clustering of charged particles in isotropic turbulence

A statistical model is given of the formation of ordered structures (clusters) in a homogeneous isotropic turbulent field. The suggested model is based on the kinetic equation for the probability density function of relative velocity of a pair of particles. The solution of the problem is treated for a steady-state rarefied system of dispersed particles in view of pair interaction.Translated from Teplofizika Vysokikh Temperatur, Vol. 42, No. 6, 2004, pp. 908–916.Original Russian Text Copyright © 2004 by V. M. Alipchenkov, L. I. Zaichik, and O. F. Petrov.     

Clustering of low-inertia particles in isotropic turbulence

A statistical model is given for describing the clustering of small heavy particles in homogeneous isotropic turbulence. The suggested model is based on the kinetic equation for the probability density function of distribution of relative velocity of two particles. Analysis is performed of the phenomenon of clustering of low-inertia particles at high values of the Reynolds number.     

Nonlinear properties of the temperature gradient in problems of wave heat transfer with moving boundaries

High-intensity thermal phenomena for one-dimensional and self-similar two-dimensional versions are the object of investigation. The effect of the velocity of motion of the boundaries and the degree of nonstationarity of the thermal process on the behavior of the temperature gradient is considered. The conditions for the appearance of a gradient catastrophe on the boundary of a moving two-dimensional region are analyzed.     

Turbulent heat transfer of rotating disk at constant temperature or density of heat flux to the wall

Conclusions 1. The approximation of the velocity and temperature profiles [8-10], used in this study, enabled us to obtain an expression for the Nusselt number which agrees with the experimental data atq _w = const andT _w = const much better than the well-known Dorfman formula (4). 2. The difference between the solution obtained and formula (4) increases with the deviation of the exponent in the wall temperature distribution (1) from the value n * = 2 toward negative values. 3. The obtained solution makes it possible to vary the exponent on the number Re_ω. A comparison with the data with the exponent 0.83 [7] revealed good agreement of these results with the obtained solution.     

Conductive-convective heat transfer in disperse systems with suspended particles

A film model of heat transfer between a disperse medium and a macrosurface under conditions of an ascending gas flow is suggested. Model equation (11) for the coefficient α_c-c as a function of the governing factors is obtained. It is used for generalization of experimental data in various systems: a fludized bed, a circulating fluidized bed, vertical pneumotransport — described by formulas (12), (13), (15), and (16).     

Radiative-conductive heat transfer in a semitransparent composite with microspherical particles

A mathematical model for calculating the temperature field in a semitransparent composite material that includes a polymethyl methacrylate matrix and quartz microspheres is suggested. In calculating the optical properties of the composite material, use was made of the optical properties of the matrix and of the interacting quartz microspheres at different filling factors which characterize the volume concentration of particles in the matrix. Allowance for the interaction between the composite components is made following the Maxwell–Garnett approximation. Data on the complex refractive index of the composite were used for calculating the coefficients of absorption, scattering, and attenuation of packed particles by the Mie theory. The temperature fields in a layer of the material are found from solving the boundary-value problem for the energy equation and a system of radiation transfer equations with the use of these coefficients.     

Analysis of the processes of heat transfer with periodic intensity with allowance for temperature fluctuations in the heat carrier

A previously developed method of analysis of the processes of heat transfer with periodic intensity is generalized to the case of simultaneous fluctuations of the temperatures of the wall and the liquid. A final expression for the dependence of the coefficient of conjugation on the generalized parameter of the problem is obtained. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 2, pp. 250–254, March–April, 2000.     

On the effectiveness of porosity on unsteady flow between parallel plates of a viscoelastic fluid under constant pressure gradient with heat transfer

The unsteady flow in a porous medium of an incompressible non-Newtonian viscoelastic fluid between two parallel horizontal non-conducting porous plates is studied with heat transfer. A sudden uniform and constant pressure gradient and uniform suction and injection through the surface of the plates are applied. The two plates are kept at different but constant temperatures, while the Joule and viscous dissipations are taken into consideration. Numerical solutions for the governing momentum and energy equations are obtained using finite difference approximations. The effect of the porosity of the medium, the parameter describing the non-Newtonian behavior, and the velocity of suction and injection on both the velocity and temperature distributions is examined.     

Effects of plasma flow structure on heat transfer with powder particles

Measurements have been made on the heat transfer to granular material in a plasma reactor having a multijet mixing chamber. The temperature distribution over the cross section has been measured by a spectral method and by calorimetry. The granular-material flow rate affects the heat flux to the walls. The measurements are fitted to an equation in dimensionless parameters.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 58, No. 5, pp. 824–828, May, 1990.     

低螺纹管的冷凝换热分析

管壳式冷凝器是制冷空调、石油化工行业中应用广泛的一种换热器。在制冷工程中常用低螺纹管作为换热管,使其具有更好的换热特性。本文对低螺纹管的膜状冷凝换热进行了分析计算,建立了低螺纹管基本换热单元面积计算和低螺纹管在基管、翅片及翅顶上的凝结换热模型以及管簇对冷凝换热的影响模型,并对影响其换热的结构参数和运行参数进行了分析探讨。模型对观客换热器得失优化设计和运行分析具有重要的理论价值和实际应用意义。     

定热流状态下圆管内层流冰浆流体传热特性的数值模拟

在对冰浆流体的换热情况提出一系列假设前提下,建立等效比热容模型,用于描述冰晶粒子融化吸收潜热。运用有限差分的方法,对所得的差分方程组进行求解,从而得到定热流状态下圆管内层流冰浆流体的传热特性。计算结果表明,随着含冰率的增大和Ste的减小,平均Nu增大,换热性能得到加强。     

Analytical study of the heat transfer in a longitudinal flow past cylindrical bodies of small radius at constant temperature

We obtain over a wide range of curvature parameters the analytical dependence of the heat transfer in a longitudinal flow past cylindrical bodies of small radius at constant temperature.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 25, No. 5, pp. 785–791, November, 1973.     

Characteristics of radiative heat transfer in multizone systems taking account of isotropic scattering

A procedure for calculating heat-transfer characteristics in absorbing and isotropically scattering media is developed and tested by applying it to internally fired furnaces.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 31, No. 3, pp. 463–470, September, 1976.     

Effect of a temperature gradient on the heat transfer during laminar natural convection along a vertical wall

Results are shown of calculations and of an experimental study concerning the heat transfer during laminar natural convection along a vertical wall, in the general case when the temperature excess varies along the wall height according to an arbitrary law.     

Direct simulations of aggregates in homogeneous isotropic turbulence

We study aggregation in turbulent flow by means of particle-resolved, direct numerical simulations. Mono-sized spheres with an attractive square-well potential are released in homogeneous, isotropic turbulence generated through linear forcing. Typical cases have a solids volume fraction of 0.08 and a ratio of the Kolmogorov scale over the primary sphere radius of O(0.1). The latter implies that the flow around the primary spheres is inhomogeneous. The simulations show the continuous formation and breakage of aggregates as a result of the turbulence and the attractive potential. The average size of the aggregates is a pronounced function of the strengths of turbulence and interaction potential. Fractal dimensions of the aggregates are in the range 1.4–1.8 for the cases studied.     

Experimental study of the transient heat transfer between metal balls and a stream of liquid at constant temperature

The article describes a method of determining the transient heat-transfer coefficient and a study of the transient heat transfer between metal balls and a stream of liquid. It is shown here how the heat flux and the heat-transfer coefficient depend on a number of parameters. The relation is then generalized for a transient heat flux at a surface.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 18, No. 1, pp. 12–20, January, 1970.     

One-dimensional model of heat transfer in cryogenic vacuumshield thermal insulation with radiant heat sources

The heat-transfer problem in an insulation consisting of layers which receive heat from external source through radiation is numerically solved in the one-dimensional approximation.Notation T temperature - x coordinate in the direction normal to the stack - stack thickness - thermal conductivity of the vacuum-shield thermal insulation along the x-coordinate - q_v amount of heat released in a unit volume of vacuum-shield thermal insulation as a result of the incidence of radiation on the face of the shield layers - emissivity - B density of effective radiant flux - Stefan-Boltzmann constant - N number of surfaces - S_ins surface of a vacuum-shield thermal insulation stack - d_di-dj angular coefficient between elementary areas i and j of a surface - Q_o thermal flux through the insulation without a hole - Q_T thermal flux through the insulation with a hole Q_rad thermal flux through the insulation with radiative heat transfer to the bottom base of the hole - Q_s thermal flux reaching the insulation with a hole - Q_rad thermal flux through the insulation with radiative heat transfer to the bottom base of the hole - Q_s thermal flux reaching the stack face by radiative heat transfer through the hole (channel) - x thickness of the i-th insulation layer including one or more shields - _eff effective emissivity of the gap face - q_rad amount of heat reaching a unit area of the bottom base of the hole - T₀ and T₀ boundary temperatures - length of the gap between layers of the insulation stack and the length of the vacuum-shield thermal insulation stack - h width of the gap between layers of the insulation stack - longitudinal thermal conductivity of the vacuum-shield thermal insulation Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 1, pp. 78–85, January, 1982.