Simulation of the heat transfer of a lithospheric platform in the subduction zone. II. Method of solution and results of calculations

Based on the control volume method, a numerical algorithm is developed for solving the problem of natural convective heat exchange in the earth's upper mantle. Part I was published in Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 1, pp. 16–25 (1996). Khabarovsk Polytechnic Institute, Khabarovsk, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 2, pp. 261–271, March–April, 1996.     

Analysis of the working process in a reciprocating expander in the region of wet vapor

By means of a numerical experiment with the example of methane, we analyze the features of the working process of a reciprocating expander with heat release associated with condensation, friction, and external heat exchange. The influence of the technical characteristics of expanders and inlet gas parameters is also considered. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 3, pp. 524–529, May–June, 2008.     

Nonstationary crisis of nucleate boiling under the conditions of an electrically controlled heat load

Experimental data on the nonstationary heat exchange under a controlled heat load are presented. Investigations were carried out with cut plates specially formed to shape, on which the distribution of the heat-flow density is near-exponential (from the periphery to the center). Empirical dependences of the critical density of a heat flow and the heat-transfer coefficient on the rate of heating have been obtained. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 6, pp. 126–130, November–December, 2005.     

Effects of Mg,Fe, Be additions and solution heat treatment on the π-AlMgFeSi iron intermetallic phase in Al–7Si–Mg alloys

The presence of magnesium in Be-free Al–7Si–Mg alloys results in the formation of an undesirable iron-intermetallic known as the π-AlMgFeSi phase. The effect of Mg, Fe, and Be on the formation of this phase in both unmodified and Sr-modified Al–7Si–xMg–yFe alloys containing 0.4–0.8-wt% Mg and 0.1–0.8-wt% Fe has been investigated at a dendrite arm spacing of 65 μm. A qualitative microstructural examination was carried out to study the effect of solution heat treatment (540 °C/8 h) on the decomposition of the π-AlMgFeSi phase (“π-phase”) in Al–7Si–xMg–0.1Fe alloys containing 0.4–1.0-wt% Mg. The results indicate that increasing the Mg and Fe content increases the amount of the π-AlMgFeSi phase formed. Quantitative measurements revealed a reduction in the surface fraction of the π-phase after solution heat treatment. Different levels of decomposition of the π-phase into needles of β-Al₅FeSi iron intermetallic phase (“β-phase”) were observed at 0.4-, 0.6-, and 0.8-wt% Mg, after solution heat treatment.     

Influence of natural and forced convection on the characteristics of heterogeneous combustion of a carbon particle

The little-studied problem of the effect of natural and forced convection on the stationary (combustion) and critical (ignition and extinction) high-temperature states of a carbon particle with account for radiative heat exchange with the cold walls of the processing setup is considered. The effect of molecular and convective heat and mass exchange of a carbon particle with a gas on the critical diameter of the particle d_e at which the particle is spontaneously extinguished (a jumpwise transition from combustion to oxidation) is analyzed. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 6, pp. 1050–1055, November–December, 1998.     

Averaging of the heat-transfer coefficient in the processes of heat exchange with periodic intensity

This work presents a proof of the inequality that determines the relation between two values of the heat-transfer coefficient averaged by different procedures in processes of heat exchange with periodic intensity. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 3, pp. 654–658, May–June, 2000.     

Investigation of regimes of thermogravitational convection of a fluid between coaxial semicylinders with a heat-conducting shell in the presence of a local energy source

A numerical analysis has been made of the thermodynamic regimes of natural convection of a Newtonian fluid satisfying the Boussinesq approximation in the gap between coaxial semicylinders with finitely-thick walls in the presence of the heat-release source under the conditions of convective heat exchange with the environment. A mathematical model has been formulated in the dimensionless variables current function–velocity vorticity vector–temperature in polar coordinates. Streamlines and velocity and temperature fields reflecting the influence of the Prandtl number Pr = 0.7 and 7.0, the nonstationarity factor 0 < τ ≤ 300, the dimensions of the energy source, and of the relative thermal conductivity on the flow regimes and heat transfer have been obtained.     

Thermal fatigue crack propagation in massive cylinders during their cyclic heating

Processes that reduce the level of maximum unsteady stresses during thermal fatigue crack propagation in massive bodies during their convective cyclic heating are considered. It is shown that during crack propagation, the stress intensity factor K₁ increases initially to a certain limit K _1max and then decreases. The factor K _1max depends on the initial and boundary conditions of heat exchange as well as on the rates of decrease in the maximum stresses during thermal fatigue crack propagation. It is shown that the asymmetry of boundary and initial conditions of heat exchange can contribute to either acceleration or retardation of crack propagation depending on the material properties and heating conditions. Deceased. Institute of Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 4, pp. 68–80, July–August, 1999.     

Mathematical models of radiative-conductive heat exchange in heat-shield materials of shuttle space transportation systems

A system of mathematical models of radiative-conductive heat exchange in partially transparent porous heat-shield materials is considered. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 1, pp. 11–25, January–February, 2000.     

Enhancement of the generating power in Cu/Bi–Te/Cu composite thermoelectric devices

The voltage ΔV and electric current ΔI of the p- and n-type Cu/Bi–Te/Cu composite thermoelectric devices were measured as a function of ΔT for four regions of the intrinsic Bi–Te compound, Cu/Bi–Te and Bi–Te/Cu interfaces and Cu/Bi–Te/Cu composite using thermocouples set at intervals of s = 2 and 6 mm, where the lengths of Bi–Te compound and copper are 4 and 5 mm, respectively. ΔV and ΔI of all regions tended to increase linearly with an increase of ΔT. The resultant α was obtained from the relation ΔV/ΔT. The resultant α values of regions including the interface are much higher in absolute value than those of the intrinsic Bi–Te compounds, so that the barrier thermo-emf is found to occur in the forward-bias direction. It indicates that the barrier thermo-emf appears even in the semiconductor-metal junction, as in the case of the p–n junctions. The resultant α of Cu(T _H)/Bi–Te interface rich in the heat flow increases with an increase of ΔT, while that of Bi–Te/Cu(T _C ) interface poor in the heat flow decreases with an increase of ΔT. The ΔT-dependence of α of the interfaces is entirely opposite at the hot and cold sides. As a result, the resultant α of the p- and n-type Cu/Bi–Te/Cu composites remained little varied with changes of ΔT, so that the present composites have a thermal stability superior to the intrinsic Bi–Te compounds.The generating powers ΔW _Bi-Te and ΔW _Cu/Bi-Te/Cu for the p- and n-type intrinsic Bi–Te compounds and Cu/Bi–Te/Cu composites increased parabolalically with an increase of ΔT, and the ratios of ΔW _{Cu/Bi–Te/Cu} to ΔW _Bi–Te reached great values of 1.41 and 1.45 for the p- and n-type composites, respectively. It was thus found that the enhancement in the resultant α of the composite materials results in a significant improvement in the conversion efficiency for generators.     

Hemodynamics and heat transfer in controlled whole-body hyperthermia: modeling of processes

The possibilities of describing structural couplings between the organs of a human being subjected to a treatment procedure of controlled whole-body hyperthermia at 43–44°C are considered. The requirements on a model that characterizes changes in the hemodynamics have been formulated, and the interrelations between the models of hemodynamics and heat transfer are shown. As an example of the implementation of the proposed approaches, a system of equations is given that describes heat exchange between an organism and a heat carrier, numerical simulation in the Matlab, toolbox Simulink medium is carried out, and the results of simulation are presented. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 6, pp. 1188–1197, November–December, 2008.     

Free-convective heat transfer within a differentially heated vertical plane during additional heat supply through a bottom wall

This work presents results of a numerical investigation of the structure of flow and heat exchange in a vertically closed interlayer with various relative heights A = H/L = 4–16 during variation in heat supply to its bottom. The vertical walls were isothermic; top wall, bottom wall, heat flow was supplied uniformly. The nonstationary Navier-Stokes equations were solved numerically in the two-dimensional formulation for the laminar flow. At small Rayleigh numbers (Ra ≈ 10³), when conductive heat transfer prevails within the interlayer, the effect of heat supply from below results in a change of heat transfer only in an immediate vicinity of the bottom. As the Rayleigh number and supplied heat increase, flow destabilization is observed, which results in strong heterogeneity of the density of heat flow along the wall height. At the same time, the heat flow at the hot vertical wall at defined Rayleigh numbers and heating from below may change the sign to the opposite one.     

Computation of phonon dynamics of Mg<Subscript>70</Subscript>Zn<Subscript>30</Subscript> metallic glass

In the present paper, the computation of the phonon dynamics of binary Mg₇₀Zn₃₀ metallic glass is reported using the well-recognized model potential of Gajjar et al. The present study includes the phonon dispersion curves (PDC), elastic and thermodynamic properties such as longitudinal sound velocity υ_L, transverse sound velocity υ_T, Debye temperature θ_D, isothermal bulk modulus B _T, modulus of rigidity G, Poisson’s ratio σ and Young’s modulus Y and specific heat capacity C _V of the glass. Three theoretical models given by Hubbard–Beeby (HB), Takeno–Goda (TG) and Bhatia–Singh (BS) are used to compute the PDC. Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru–Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are employed for the first time to study the effect of exchange and correlation in the aforesaid properties. The pseudo-alloy-atom (PAA) model is applied for the first time instead of Vegard’s Law.     

Influence of Optical and Thermophysical Characteristics of Biological Tissue on Its Thermal Conditions Under Laser Irradiation

On the basis of the developed analytical method of solving the heat conduction equation in a multicomponent biological tissue, its thermal conditions under laser irradiation have been investigated. Quantitative data on the temperature fields under a wide variation of the optical and thermophysical parameters in the tissue in the 400– 700-nm range of wavelengths are given. The steady-state regime of the field in the tissue at various depths has been investigated. Estimates of the possible use of the time dependence of temperature under tissue cooling to solve the inverse problem — determine the heat-conductivity coefficient, the parameter of heat exchange with the medium, and the depth attenuation coefficient of light — are given. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 3, pp. 15–21, May–June, 2005.     

Thermoelastic state of a thermosensitive hollow sphere under the conditions of convective-radiant heat exchange with the environment

The solution of the nonstationary problem of heat conduction is constructed for a thermosensitive hollow sphere in the process of convective-radiant heat exchange with media kept at constant temperatures. In this case, it is assumed that the heat-transfer and emissivity coefficients of the surfaces are functions of temperature. We study the influence of the thermal sensitivity of the material of the sphere on the intensity and character of distribution of temperature and the components of the stress-strain state. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 6, pp. 39–48, November–December, 2006.     

Simulation of thermal and moisture-content conditions on the upper layer of peat soils

The problem of two-dimensional interrelated heat- and moisture-transfer in the upper layer of soil is formulated taking into account exchange by heat and moisture with the ground-level air layer. On its basis a difference scheme was constructed and algorithms and a program were developed to calculate the processes of heat and moisture transfer. We evaluated the effect of various meteorological and hydrological factors and the composition of organogenic rocks on the change in the temperature and moisture-content conditions of peat deposits and soils. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 5, pp. 999–1005, September–October, 2000.     

A new approach to heat and moisture regeneration in the ventilation system of rooms. I. Laboratory prototype of the regenerator

We propose a new heat-and-mass transfer device that permits simultaneous heat and moisture regeneration in the ventilation system, provides anti-icing at the heat-exchanger outlet, and maintains comfortable humidity in a room. In this device, ahead of the heat-accumulating medium acting as a heat regenerator, a fine-grained adsorbent that controls the humidity of air flows is located. In the first part of the work, we have investigated the cyclic process of heat exchange (in the absence of adsorbent) and conducted its optimization for attaining maximum regeneration of heat. It has been shown that the regeneration efficiency can exceed 90%. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 3, pp. 143–150, May–June, 2006.     

Influence of the concentration of a dispersed phase and of the magnetic field on the attenuation of ultrasonic waves in magnetic fluids

The regularities of the propagation of elastic waves of ultrasonic range in magnetic fluids have been experimentally established. The influence of relaxation processes — nonlocal heat exchange and viscous dissipation — on the coefficient of attenuation of sound has been revealed and a comparison to the existing theoretical data has been made. The dependences (anisotropic in form) of the attenuation of the wave’s amplitude on the value and direction of the magnetic field have been determined and an interpretation of the results obtained has been proposed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 5, pp. 133–140, September–October, 2007.     

Estimation of the thermohydraulic efficiency of swirlers at small Reynolds numbers

To estimate the thermohydraulic efficiency of different types of swirlers of heat exchange in pipes, we have generalized the experimental data, which has made it possible to determine the optimal range of Reynolds numbers and the optimal geometric sizes of swirlers. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 23–30, January–February, 2009.     

Phonon dispersion and specific heat in <Emphasis Type="Italic">trans</Emphasis> 1,4, poly (2,3-dimethylbutadiene)

A comprehensive study of the normal modes and their dispersion for trans 1,4-poly (2,3 dimethylbutadiene) is described in the reduced zone scheme using Wilson’s GF matrix method as modified by Higg’s for an infinite polymeric chain. Urey Bradley force field is obtained by least square fitting of the observed IR and Raman bands. Optically active frequencies corresponding to the zone center and zone boundary are identified and discussed. Some of the characteristic features of dispersion curves are repulsion accompanied by exchange of character and Von Hove type singularities. The evaluation of normal modes and their dispersion has been taken to logical conclusion by calculating the heat capacity as a function of temperature. Specific heat has been obtained from dispersion curves via density of states in the range 10–400 K using Debye’s relation. The predictive values of specific heat show a typical variation for an one dimensional polymeric system.