Influence of turbulence on the thermal radiation transfer in diffusion hydrogen flames

The effect of the turbulent fluctuations of the temperature and concentrations in a diffusion hydrogen flame on its thermal radiation has been quantitatively estimated. The numerical investigations were carried out using the data on the laser probing of this flame. The coefficients of the radiation-transfer equation were determined by averaging instantaneous temperatures and concentrations, which made it possible to eliminate the errors introduced by model distribution functions. It is shown that the effect of the turbulence of a flame on its radiation determines, to a large extent, the formation of the thermal radiation fields of the flame.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 77, No. 6, pp. 146–151, November–December, 2004.     

The effect of thermal radiation on the propagation of temperature waves in a semitransparent medium

The propagation of temperature waves arising as a result of periodic external thermal stimulation is investigated in a plane layer of semitransparent absorbing and radiating medium without scattering. The classification of temperature waves on the basis of two dimensionless parameters is suggested. It is rigorously demonstrated that not more than two temperature waves may simultaneously exist in a gray semi-infinite medium. The relative contribution of radiation to complex heat transfer is estimated. The system of equations of radiative-conductive heat transfer is reduced to a single integral equation on the boundary. The effect of reflection on the boundary is discussed.     

Taking account of the effect of turbulent pulsations on the thermal radiation of a medium in a quadratic approximation

An expression is obtained for the mean heat-radiation intensity of a plane layer, taking account of turbulent pulsations.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 37, No. 3, pp. 405–411, September, 1979.     

Inverse thermal effect of displaced liquid in a porous medium

The inverse thermal effect of the liquid displaced in a porous medium is investigated, with the effect occurring because of the fact that, with the thermal conductivity being neglected, temperature jumps move with the speed of convective heat transfer. In piston displacement, the front moves with a true velocity which several times exceeds those of filtration and of convective heat transfer. Due to the faster advance of the displacement front, a special zone is formed, in which the process of inverse thermal effect of the displaced liquid on the displacing one is observed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 4, pp. 139–145, July–August, 2006.     

Effect of radiation heat transfer on thermal diffusivity measurements

Experimental data on thermal conductivity and thermal diffusivity of a semitransparent material generally include an error due to the radiation heat transfer. This error varies in accordance with the experimental conditions such as the temperature level of the sample and the measuring method. In this paper, research on the influence of radiation heat transfer on thermal diffusivity are reviewed, and as an example, the method to correct the radiation component in the apparent thermal diffusivity measured by the stepwise heating technique is presented. The transient heat transfer by simultaneous thermal conduction and radiation in a semitransparent material is analyzed when the front surface is subjected to stepwise heating. The apparent thermal diffusivity, which includes the radiation component, is calculated for various parameters.Paper presented at the Second U.S.-Japan Joint Seminar on Thermophysical Properties, June 23, 1988, Gaithersburg, Maryland, U.S.A.     

Longitudinal radiation transfer in movement of a dust containing medium in a plane channel

The article presents the solution of the problem of radiative and convective heat exchange in stabilized flow of a scattering medium in a plane channel, with the longitudinal radiative fluxes taken into account.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 3, pp. 402–406, September, 1985.     

Investigation of MHD Go-water nanofluid flow and heat transfer in a porous channel in the presence of thermal radiation effect

In this paper, flow and heat transfer of MHD Go-water nanofluid between two parallel flat plates in the presence of thermal radiation are studied. One of plates is externally heated and cooled by coolant injection through the other plate, which also expands or contracts with time. A similarity transformation is used to transmute the governing momentum and energy equations into non-linear ordinary differential equations with the appropriate boundary conditions. The obtained non-linear ordinary differential equations are solved by Duan–Rach Approach (DRA). This method allows us to find a solution without using numerical methods to evaluate the undetermined coefficients. This method modifies the standard Adomian Decomposition Method by evaluating the inverse operators at the boundary conditions directly. The impacts of various parameters such as the Reynolds number, the expansion ratio, the magnetic parameter, the power law index, the solid volume fraction and the radiation parameter are investigated on the velocity and temperature. Furthermore, the value of the Nusselt number is calculated and presented through figures. The results indicate that the temperature profile and the Nusselt number have a direct relationship with the solid volume fraction and have an inverse relationship with the radiation parameter. In addition, the limiting cases are gained and found to be in an excellent agreement with the previous works.     

A model of averaged radiation transfer in two-phase heterogeneous medium

Presently employed for describing the radiation transfer in heterogeneous media is the radiation transfer equation (RTE) which is rigorously validated only for homogeneous media, although the hypothesis of the validity of one and the same model for both homogeneous and heterogeneous media is questionable. The local intensities of radiation in different phases of heterogeneous medium may significantly differ; therefore, the only averaged radiation intensity employed in the RTE model is insufficient. A model of radiation transfer is obtained for two-phase heterogeneous medium in the geometrical optics limit, which consists of two transfer equations for partial radiation intensities averaged in each phase separately. These equations resemble ordinary RTEs but include the exchange of radiation between the phases; therefore, they are referred to as the vector model of RTE. This model reduces to ordinary RTE if one of two phases is nontransparent or one phase prevails in the volume. It is demonstrated that the vector model of RTE in these two extreme cases does not contradict the known results of calculations by the ray optics and Monte-Carlo methods, as well as the experimental data. The suggested vector model is necessary if both phases are transparent or semitransparent and their volume fractions are comparable, because no adequate mathematical models are available in this case. The vector model describes the known results of Monte-Carlo simulation of packed beds of semitransparent spheres. The use of the vector model of RTE for experimental identification of the radiative properties is illustrated with the example of normal-directional reflectance of packed bed of semitransparent SiC particles. The results of numerical calculations confirm the general experimentally observed tendency for increase in reflectance with increasing angle of reflection. The main contribution to the error is made by the boundary conditions for vector RTEs; therefore, detailed analysis of the suggested model in boundary regions is required.     

The effect of thermoacoustic waves on heat transfer in a layer of compressible medium

The problem on heat transfer in a layer of perfect gas in view of thermoacoustic convection is solved numerically in a one-dimensional approximation. Analysis is made of the effect of heating (cooling) intensity on the solution of the problem.     

Evolution of homogeneous turbulence in a density-stratified medium. 1. Analysis in far field

The equations presented in [1] for the evolution of homogeneous turbulence in a density-stratified medium are investigated analytically. The problem involves the small parameter ε = Fr². Applying variants of the small-parameter method, it is possible to calculate the frequency of internal waves and a number of asymptotic regimes in the development of turbulent velocity and scalar fields over time. The so-called far field of evolution, i.e., the field of large values of τ (τ ≫ 1, is considered, in which the differential order of the initial system of equations is lowered. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 1, pp. 30–39, January–February, 1997.     

The evolution of homogeneous turbulence in a density-stratified medium. 3. Analysis of the near region

Development of a turbulent perturbation in a homogeneous flow moving within a medium that is linearly density-stratified across the direction of flow motion is described. The initial region of the evolution of turbulence with a large turbulent Reynolds numberR _λ is considered. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 3, pp. 393–403, May–June, 1997.     

The effect of rotating cylinder on the heat transfer in a square cavity filled with porous medium

The heat transfer in a square cavity filled with clear fluid or porous medium is numerically investigated in the present study. To change the heat transfer in the cavity a rotating circular cylinder is placed at the centre of the cavity. The ratio of cylinder diameter to cavity height is chosen as 0.8. Depending on the angular velocity of the cylinder the convection phenomena inside the cavity becomes natural, mixed, and forced. To keep the number of data low the Grashof number, Gr, is set to 10⁶, while the parameter defining the convection regime in the cavity, Gr/Re², is changing from 0.0625 to 10². The Darcy number in the cavity is set to 10⁻², 10⁻³, and 10⁻⁴. Galerkin finite element method is used to solve the Navier–Stokes equations with Brinkman–Forcheimer extended Darcy’s law, and energy equation in 2-D non-dimensional form. The solution methodology is compared and validated with the literature for a similar problem, and good agreement is achieved. The results are presented in terms of Nusselt numbers, velocity profiles and temperature contours. The results show that rotation is more effective in the forced convection regime than in mixed and natural convection regimes, and at high spin velocities the heat transfer is almost independent from the Darcy number.     

Finite element method for the effect of various injection parameter on heat transfer for a power-law non-Newtonian fluid over a continuous stretched surface with thermal radiation

An analysis is carried out to study the effect of suction and injection on heat transfer for a power-law, non-Newtonian fluid. The flow in a boundary layer includes the effects of radiation and a cooled surface temperature. The resultant governing boundary-layer equations, highly non-linear and a coupled form of partial differential equations, have been solved by employing a numerical, finite element technique. A parametric study of all involved parameters is conducted, and a representative of the results for the temperature profile as well as the Nusselt number is illustrated graphically to elucidate interesting features of the solutions.     

Forced-convection heat transfer in porous medium with Joule-Thomson effect

The heat-conduction effect on the thermal field of the throttle effect is investigated close to the boundary of a porous medium at low pressure gradients.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol.31, No.1, pp. 42–46, July, 1976.     

Grid-generated turbulence in two-phase flow: The effect of parameters of the carrier medium and particles

Results are given of an experimental investigation of the initial region of decay of grid-generated turbulence in a downward two-phase flow of the “gas-solid particles” type. Optical diagnostic methods are used to obtain the distributions of the dynamic parameters of two-phase flow, namely, averaged and fluctuation velocities of gas, and the curves of decay of turbulence along the flow axis are constructed for grids with square meshes sized 4.8, 10, and 16 mm. The investigation results demonstrate that solid particles 700 μm in size have varying effect on the degree of decay of turbulence. In the case of grids with small mesh sizes of 4.8 and 10 mm, the presence of such particles leads to additional generation of turbulence; in the case of a grid with mesh size of 16 mm, vice versa, the particles suppress the turbulence. Investigations reveal that these tendencies become still more pronounced with increasing concentration of particles. In addition, the investigation of the effect of velocity phase slip reveals that the generation of turbulence increases with the difference between phase velocities. In so doing, variation of the pattern of the effect of particles on turbulence is observed for a grid with large meshes, namely, the suppression of turbulence at low values of velocity slip and generation of turbulence with increasing slip. Based on the results of analysis of experimental data, a criterional parameter is suggested, which defines the effect of particles on the turbulence of two-phase flow, i.e., the ratio of the Reynolds number of particle to the turbulence Reynolds number for gas.     

Interaction of holmium laser radiation and cortical bone: ablation and thermal damage in a turbid medium

The ablation of cortical bone by holmium laser radiation is described by experimental values of the ablation rate, the depth of tissue damage, and the tissue temperature. An ablation model is presented on the basis of photon diffusion in a turbid medium. When this model is compared with experimental results for the ablation rate, the penetration depth is determined. The expansion of the laser-induced heat can be explained by a point heat source located in a distance beneath the surface equal to the ablation depth. The accumulation of heat as a function of the repetition rate of the laser leads to a limitation of the repetition rate. In order to avoid traumatic heat accumulation, a maximum repetition rate should not be exceeded.     

Regular thermal regime in a multi-layer medium

Regular thermal regime is examined for a multi-layer medium with perfect and imperfect contact. Possible experimental methods of investigating such a system are determined.     

Nonstationary heat transfer in a heterogeneous medium

We consider heat transfer in the displacement of a hot interstitial liquid from an artificially cracked region formed by a camouflet explosion.     

Solution of the boundary-value problem for the equation of radiation transfer in a limited volume of a dispersion medium with a linear scattering indicatrix

We propose a method for solving the boundary-value problem for the equation of radiation transfer with a linear indicatrix, with the boundary conditions being exact in the formulation of this problem. The results of the numerical experiments based on the solution of the radiation-transfer problem are presented. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 2, pp. 27–34, March–April, 2006.