Incompressible fluid flow and heat transfer through a nonsaturated porous medium

This work studies a nonsaturated flow and the heat transfer associated phenomenon of a newtonian fluid through a rigid porous matrix, using a mixture theory approach in its modelling. The mixture consists of three overlapping continuous constituents: a solid (porous medium), a liquid and an inert gas, included to account for the compressibility of the system as a whole. A set of four nonlinear partial differential equations describe the problem whose hydrodynamical part is approximated by means of a Glimm's scheme combined with an operator splitting technique.     

Experimental investigation of heat transfer through porous media in superfluid helium

An experimental investigation of heat transfer through porous media in superfluid helium has been conducted in the framework of the development of porous electrical insulations for superconducting magnet cables cooled by superfluid helium. Several types of porous media with different characteristics were tested and, in particular, samples with pore size diameters of 0.1 μm, 1 μm, 2 μm, 10 μm and 20 μm. Temperature and pressure were measured between an insulating inner bath and the cryostat bath, communicating only through the porous medium. The cryostat bath is held constant all along the measurement and, for each sample, the tests are performed for bath temperature from 1.4 K to 2.1 K with 0.1 K increment. Depending on the porous medium average pore size diameter, different flow regimes are observed: for porous media with a pore diameter of 0.1 and 1 μm, only the Landau regime is observed whereas for porous media with a pore diameter of 2 μm, we observed the Landau regime and the Gorter-Mellink regime. For samples with a pore diameter of 10 and 20 μm, measurements only permitted to detect the Gorter-Mellink regime. In the laminar regime, the permeability of the samples was determined and it was found that the permeability is constant for bath temperature above 1.9 K whereas it increases as the bath temperature decreases from 1.8 K to 1.4 K. For samples with a pore size diameter of 10 and 20 μm, measurement permits only to observe the turbulent regime and the analysis exhibits a constant average tortuosity for each samples, independently of the bath temperature.     

Experimental investigation of the special features of heat transfer through glass packets

We consider experimental procedures for determining the thermal resistances of certain types of commercial glass packets based on investigation of thermal and temperature fields on the outer packet surfaces at a stationary temperature head (∼40°C), which corresponds to extreme climatic conditions of the middle belt. We evaluate the inhomogeneity of thermal losses over the glass-packet area coused by edge effects. The error in measuring the thermophysical parameters does not exceed ±3%. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 2, pp. 209–213, March–April, 2000.     

Effect of anisotropic permeability on convective heat transfer through a porous river bed underlying a fluid layer

A study is made of convective heat transfer through packed porous beds which consist of a horizontal fluid layer (river bed) and a porous zone with anisotropic permeability and underlaid by a surface heated to a constant temperature $T_1$ . The free surface of the fluid layer overlying the horizontal porous layer is heated isothermally at temperature $T_2$ ( $>T_1$ ). Using the Navier–Stokes model for the fluid layer and the generalized Brinkman-extended Darcy model for the porous zone, an exact solution is found for a fully developed system of forced convective flow through the superposed layers. The Beavers–Joseph condition is applied at the interface between the two layers. The influence of hydrodynamic anisotropy on the convective phenomenon is investigated analytically. It is shown that the anisotropic permeability ratio $K^*$ , the inclination angle of the principal axes $\varphi $ of the porous medium, and the thickness of the porous lining $\epsilon $ have a strong influence on the convective flow and the heat transfer rate. This analysis helps to predict environmental aquatic behavior.     

Experimental investigation of heat transfer in the evaporator of a water heat pipe

The applicability of Gilmour's correlation equation in describing the heat transfer in the evaporator of a low-temperature heat pipe was experimentally confirmed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 33, No. 2, pp. 250–254, August, 1977.     

复合材料夹芯结构非线性热传导分析

针对复合材料夹芯结构温度场分布的特点, 提出一种用于复合材料夹芯结构热传导精细分析的有限单元模型。这种单元模型为三维六面体模型, 单元模型厚度方向的插值函数在芯层和面板交界节点处温度值是连续的, 但温度变化率是不连续的, 而芯层内部节点处沿厚度方向温度值和温度变化率都是连续的。在考虑材料热传导参数随温度变化的情况下, 基于这种有限单元模型建立的复合材料夹芯结构瞬态温度场分析有限元方程为非线性方程。在求解此瞬态热传导非线性有限元方程时, 改进了常用的动力学平衡方程的解法, 改进后的动力学平衡方程解法避免了迭代运算, 提高了求解非线性动态平衡方程的效率。数值算例结果显示了该分析模型的有效性和可靠性。      

Radiative heat transfer in a flow of rheologically complex fluid

The problem of complex radiative and convective heat transfer in steady-state generalized Couette flow of a nonlinear viscoplastic fluid is examined.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 3, pp. 491–497, September, 1980.     

On heat transfer to pulsatile flow of a viscoelastic fluid

Summary A study is made of a problem of heat transfer to pulsatile flow of a viscoelastic fluid between two parallel plates of which the upper one is at a temperature higher than the lower one. The solutions for the steady and the fluctuating temperature distributions are obtained. The rate of heat transfer at the plates is also calculated. Numerical solutions are discussed with graphical representations. It is shown that the elasticity of the fluid significantly increases the temperature in the boundary layers near the plates. The magnitude of heat transfer at the plates is also greatly affected by the elasticity of the fluid and the Eckert number.     

An experimental investigation of heat transfer in a pebble bed

An experimental investigation is performed of heat transfer under conditions of longitudinal flow of water moving in a bed of glass pebbles past a flat heated wall. Experiments involving the flow of single-phase liquid are performed in the ranges of variation of filtration velocities from 6 to 60 mm/s and of heat fluxes from 40 to 140 kW/m²; in the case of wall boiling, the experiments are performed in the ranges of variation of filtration velocities from 2 to 50 mm/s and of heat fluxes from 27 to 86 kW/m². The temperature distribution is measured over the height of the heated wall and over the cross section (depth) of the channel at the outlet from the pebble bed. The experimental data are processed for single-phase flow using numerical optimization techniques. The values of the coefficient of “turbulent” thermal conductivity in the pebble bed are obtained as a function of the process parameters     

An investigation of convective heat transfer in a closed space

An empirical formula is obtained fot the convection coefficient in a closed parallelepiped.     

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.     

Stagnation point flow and heat transfer for a viscoelastic fluid impinging on a quiescent fluid

A theoretical study is made in the region near the stagnation point when a lighter incompressible viscoelastic fluids impinges orthogonally on the surface of another quiescent heavier incompressible viscous fluid. Similarity solutions of the momentum balance equations for both fluids are equalized at the interface. It is noted that an exact boundary layer solution is obtained for the lower lighter fluid. The velocity of the lower fluid is independent of lateral interface velocity but the velocity of the upper viscoelastic fluid increases with increasing lateral interface velocity. It is observed that lateral interface velocity increases with increasing viscoelastic parameter for fixed values of density and viscosity ratio of the two fluids. The convective heat transfer is investigated base on the similarity solutions for the temperature distribution of the two fluids. The interface temperature increases with increasing viscoelastic parameter of the upper viscoelastic fluid.     

Schlieren investigation of the natural-convection heat transfer of a rotating sphere

The results of an experimental investigation are presented. A formula is obtained for estimating the effect of rotation. The schlieren method has been used to investigate the thermal boundary layer.     

Unsteady heat transfer by radiation in a system of coaxial cylinders

An investigation has been made on a non-linear analog computer of unsteady heat transfer by radiation in a system of coaxial cylinders simulating the heating of the load component, the muffle, and the lining of a vacuum induction furnace.     

Calculation of heat transfer through a porous multilayer vacuum insulation

A system of differential equations describing heat and mass transfer under steady-state conditions in porous vacuum insulations is obtained and the method of their solution is discussed. The effect of various factors on heat transfer by gases in such porous media is shown.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol.19, No.2, pp.276–282, August, 1970.     

A new method of solving the integral equations of radiation heat transfer

We present a method for calculating the radiation heat transfer between bodies and a new approach to the solution of the corresponding integral equations. We show, in fact, that the first approximation describes the solution of these equations with sufficiently high accuracy and is, in some cases, exact.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 6, pp. 1031–1040, December, 1986.     

Unsteady heat transfer in a micropolar fluid flowing in a plane channel

Heat transfer in a micropolar fluid flowing in a plane channel following an abrupt change in the wall temperature is investigated. The obtained results indicate that in several cases the fluid microstructure has a considerable effect on the main heat-transfer characteristics.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 37, No. 6, pp. 994–999, December, 1979.     

乙烷槽道低温热管冷量传输性能及启动特性试验研究

为适应空间红外探测系统中低温光学对160—200 K温区的冷量传输需求,研制了乙烷工质的槽道热管作为传热单元。采用模拟冷板和真空低温试验系统对乙烷槽道热管在160—200 K温区的传热能力进行了测试,试验结果表明:在10 W@200 K时、8 W@180 K、8 W@165 K工况下,传热温差分别为1.12 K、2.91 K和4.23 K。说明乙烷热管具有良好的传热能力,且在200 K时传热性能最佳。对乙烷热管的启动特性进行了试验研究,对试验过程中遇到的热管启动异常现象进行了分析,试验结果验证了启动异常原因分析的合理性。     

Natural convection heat transfer of a viscous fluid in a vertical porous channel

Approximate analytic solutions to second-order nonlinear systems arising in natural convection flow and heat transfer in vertical porous channels are obtained via the Galerkin–Legendre Spectral Method. Furthermore, existence, uniqueness, and concavity results are established using Green’s functions and degree theory. We find that an increase in either the Darcy number or the quadratic density temperature variation results in an increase in the velocity and the temperature of a Newtonian fluid. Finally, parametric zones for the occurrence of reverse flow are considered, and the resulting influences on the obtained approximate solutions are analyzed.