Investigation of the Behavior of Reflected Particles under Conditions of Heterogeneous Flow past Blunt Bodies

The results are given of an experimental investigation of the velocity of large particles of glass in the vicinity of a blunt body subjected to a heterogeneous flow. The particle inertia varies from Stk _f = 10.5 to Stk _f = 82. The velocity distribution is obtained for particles of different forms, such as incident, reflected from the model, reprecipitating on the surface, and so on. The dependence of the size of the region of existence of reflected particles on the inertia of the dispersed phase is determined.     

Simultaneous measurement of aerodynamic and heat transfer data for large angle blunt cones in hypersonic shock tunnel

Aerodynamic forces and fore-body convective surface heat transfer rates over a 60° apex-angle blunt cone have been simultaneously measured at a nominal Mach number of 5.75 in the hypersonic shock tunnel HST2. An aluminum model incorporating a three-component accelerometer-based balance system for measuring the aerodynamic forces and an array of platinum thin-film gauges deposited on thermally insulating backing material flush mounted on the model surface is used for convective surface heat transfer measurement in the investigations. The measured value of the drag coefficient varies by about ± 6% from the theoretically estimated value based on the modified Newtonian theory, while the axi-symmetric Navier-Stokes computations overpredict the drag coefficient by about 9%. The normalized values of measured heat transfer rates at 0‡ angle of attack are about 11% higher than the theoretically estimated values. The aerodynamic and the heat transfer data presented here are very valuable for the validation of CFD codes used for the numerical computation of flow fields around hypersonic vehicles.     

Influence of stefan flow on heat and mass transfer and kinetics of chemical reactions of a carbon particle in air

With account taken of Stefan flow, an analysis of the interrelated heat and mass transfer of a carbon particle in parallel reactions on its surface is performed.Notation T temperature, K - t time, sec - density, kg/m³ - c specific heat, J/(kg·K) - d diameter - R particle radius, m - thermal conductivity coefficient, W/(m·K) - particle emissivity - v Stefan flow velocity, m/sec - r radial coordinate - C _j relative mass concentration of the jth component - µ _j molar weight, kg/mole - k ₁,k ₂ constants of the first and the second reaction rates, m/sec - k ₀₁ andk ₀₂ preexponents - E ₁,E ₂ activation energies, J/mole - D diffusion coefficient, m²/sec - =v _RR/D dimensionless value of the Stefan flow velocity - Q _x surface power of heat release, W/m² - Q _st density of the heat flux via heat conduction and Stefan flow, W/m² - Q _r density of the heat flux via radiation - j _j mass flux density - W rate of the heterogeneous chemical reaction in O₂, kg/(m²·sec). Indexes - 1 particle - 2 gas - w wall - st Stefan - infinitely distant - in initial - R on the particle surface - by heat conduction - r by radiation - j 1, O₂ - j 2, CO₂ - j 3, CO - j 4, N₂ Odessa State University. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 4, pp. 576–582, July–August 1995.     

The Distribution of Phase Velocities of Heterogeneous Flow in the Neighborhood of the Stagnation Point of a Blunt Body

The paper gives the results of experimental investigation of the velocities of both phases of heterogeneous flow in the neighborhood of the stagnation point of a blunt body with a hemispherical end face. The distribution of the velocities of pure air, of incident particles, and of particles reflected from the body is measured. The resultant data are necessary for constructing mathematical models of flows of gas with solid particles which intensively interact both with the model surface and with one another.     

Controlled Heat Transfer in a Laminar Boundary Layer along the Penetrable Surface of a Blunt Body

The problem on the determination of distributed forced injection from the surface of a blunt body subjected to flow for attaining preassigned characteristics of heat transfer is treated within the framework of the model of laminar boundary layer.     

Investigation of the behavior of reflected particles under conditions of heterogeneous flow past a blunt body: Experiment and calculation

The behavior of solid particles in the neighborhood of a blunt body subjected to a heterogeneous flow is investigated experimentally and theoretically. A laser Doppler anemometer is used to measure the velocity of the dispersed phase. The particle dynamics are measured within the Lagrangian (trajectory) approach. As a result of physical and numerical simulation, the velocity distribution is obtained for particles of different types such as incident, reflected from the model, and re-precipitating on the surface. The size of the region of existence of the phase of reflected particles is determined, as well as the velocity of particles repeatedly interacting with the model.__________Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 2, 2005, pp. 317–320.Original Russian Text Copyright © 2005 by T. F. Ivanov, and A. Yu. Varaksin.     

Oxide Protection of Materials in Melts of Lead and Bismuth

Corrosion and mass transfer in lead–bismuth flow circuits proceed in the range of concentrations of dissolved oxygen of 5·10^–7–10^–12 mass %. We have developed and implemented a technology of continuous oxide protection of materials against corrosion in lead–bismuth nonisothermal flow circuits with the heat carrier mass up to 70 tons, the surface area of steels up to 2000 m², and temperatures up to 650°C under conditions of control, regulation, and maintenance of the oxidation potential of a heat carrier in flow circuits.     

Heat transfer from a cylindrical,heavily finned surface

The transfer of heat from a strongly heated, heavily finned surface is examined. The material of the surface and of the fins has high thermal conductivity (copper), while the heat transfer fluid has comparatively low thermal conductivity (oil). Under these conditions, increase in the number of fins and reduction of the distance between them makes possible a high value of the coefficient of heat transfer from the heated surface to the fluid.Notation R₂ and r₁ radii of cylindrical surface at tip and base of fins, respectively - r, z coordinate axes - angle between planes of adjacent slots - x slot width - b anda coordinates of tip and base of fin - thermal conductivity of fin material - t fin temperature - u mean fluid temperature over slot width - coefficient of heat transfer from fin surface to fluid - c specific heat of fluid - v fluid velocity (since the viscosity is considered constant over the flow, v is also constant) - q density of heat flux through base of fin - specific weight of fluid - ¯t, ¯u Laplace transforms - p Laplace transform parameter, s-auxiliary quantity determined from equation (13) - I, K, J, Y Bessel functions - u⁰ mean fluid temperature over height of slot     

Enhancement of Heat Transfer to a Steam-Water Mixture in the Postcritical Region with the Aid of Spherical Cavities

The paper describes the experimental stand and the procedure for investigation of heat transfer from a surface with spherical cavities under conditions of boiling of water in the postcritical region. The experimental section is provided by a 14/10 mm round channel 590 mm long, whose replaceable inner pipe is smooth or covered with spherical cavities 3.8 mm in diameter and 1.0 mm deep. The arrangement of cavities is in-line, with a longitudinal step of 6 mm and a transverse step of 6.3 mm. Experiments are performed at a mass velocity ranging from 300 to 500 kg/(m² s) and a pressure of 17.7 and 21.7 MPa in a wide range of relative enthalpy. The results of comparison of the values of heat-transfer coefficient for a surface with cavities with the values of for a smooth surface (obtained by us and other researchers) reveal a considerable enhancement of heat transfer thanks to cavities: an increase in by a factor of 1.5–4 and a decrease in the pipe wall temperature by 100–200 K.     

Tape-cast ceramic membranes for microfiltration application

Alumina membrane filters in the form of thin (0.3–0.8 mm) discs of 25–30 mm diameter suitable for microfiltration application, have been fabricated by the tape-casting technique. Their pore size could be varied in the range 0.1–0.7 m and porosity in the range 25%–55% through optimization of experimental parameters. The most important factor which determines the pore size, is the initial particle size of ceramic powders used for this purpose. Temperature of firing, and also the soaking time are crucial parameters which determine the porosity. Water permeability under suction conditions varies in the range 110–900 lm^–2h^–1 depending on porosity, pore size and thickness of the membrane. Most of these membranes, particularly those with pore sizes less than 0.5 m, are found to be suitable for complete removal of bacteria from water and are also reusable after cleaning by acid or heat sterilization.     

Heat transfer in the flow of low-density air in narrow channels

Results are given from measurements on air flow in narrow channels; relationships in dimensionless terms are derived for the heat transfer over a wide range in speed (1–120 m/sec) and in pressure (1 · 10⁵ > P > 1.33 · 10³) N/m².Notation V volume flow rate of air - N total number of buret divisions - P₀ pressure in measuring tank - l length of measuring section of buret - t time of oil column rise to the height h_i - n number of buret division corresponding to_i - _o, _m specific weights of oil and mercury - c scale division of buret - h₂ height of oil drop in measuring cylinder - v₀ total volume of system from needle throttle to heat exchanger inlet - P_p pressure at heat exchanger inlet - T_p, T₀ temperature at heat exchanger inlet and of surrounding air - G flow rate in mass terms - c_p mean specific heat of air - t temperature variation over measuring section - Nu, Re Nusselt and Reynolds numbers - l, d length and diameter of channel Translated from Inzhenerno-Fizicheskii Zhurnal, vol. 20, No. 5, pp. 879–883, May, 1971.     

Analytic study of the temperature change in the flowing molten metal in sand casting

A system of differential equations is given for the heat transfer in the flow of a liquid alloy in the channels in casting sand, and a formula is derived for the temperature of the alloy at any given point at an arbitrary instant.Notation c₁ specific heat of liquid alloy, J/kg · deg - ₁ density of alloy, kg/m³ - heat transfer coefficient, W/m² · deg - ₁ effective heat transfer coefficient, W/m² · deg - P channel cross-section circumference, m - F cross-section of channel - t_g temperature at inner channel surface, °K - w flow velocity, m/sec - R half-thickness of channel, m - t₂ temperature of mold wall, °K - _sta time from start of alloy flowing in channel, sec - ₂ thermal conductivity of mold material, W/m · deg - t₀ initial mold temperature, °K - c₂ specific heat of mold material, J/kg · deg - ₂ density of mold, kg/m³ - a₂ thermal diffusivity, m₂/sec - km, b_a coefficients of heat accumulation by mold and alloy, W/sec^1/2/m² · deg - t_in temperature of alloy at inlet, °K Translated from Inzhenerno-Fizicheskii Zhurnal, vol. 20, No. 5, pp. 872–878, May, 1971.     

Free convective flow on a vertical plate with a constant heat flux in the presence of one or more steps

We carried out an experimental investigation of free convective heat transfer on a vertical plate subjected to a constant heat flux in the presence of one or several rectangular steps. Temperature fields were investigated with the help of a Mach-Zehnder interferometer. During the experiment the Rayleigh number changed from zero to Ra=2.8·10³. The flow was observed by the method of track visualization by means of a laser knife. Durectly behind a step we observed a circulating free convective flow having the shape of two oppositely rotating vortices.Academic Scientific Complex A. V. Luikov Heat and Mass Transfer Institute of the Academy of Sciences of Belarus, Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 67, Nos. 3–4, pp. 190–196, September–October, 1994.     

Problem of heat-flux screening in the radiative-convective heating of bodies over which a high-enthalpy gas flows

The results are presented on a calculated theoretical investigation of the radiativeconvective heat exchange and the screening properties of the gaseous products of the ablation of heat-shield materials in hypersonic flow over the front surface of a smooth blunt body.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 46, No. 1, pp. 77–85, January, 1984.     

Heat Exchange on the Front Surface of a Blunt Body in a High‐Speed Flow Containing Low‐Inertia Particles

The method and results of an experimental investigation of the heat exchange on the front surface of a sphere in a supersonic flow containing particles of diameter d = 0.12–2.4 m and hollow particles of d = 160 m are presented. It has been revealed that in the case where even very small particles of d = 0.15 m are contained in an undisturbed flow and their concentration is low (of the order of a percent), the heat flux in the region of the critical point of the model markedly increases. A comparison of the experimental data with the data of calculations of the heat exchange in the region of the forward critical point which are based on the theory of a twophase laminar boundary layer has been made. A glow near the surface of the model was observed in the experiments conducted in total darkness.     

Experimental Study of Subcooled Flow Boiling Heat Transfer on a Smooth Surface in Short-Term Microgravity

The flow boiling heat transfer characteristics of subcooled air-dissolved FC-72 on a smooth surface (chip S) were studied in microgravity by utilizing the drop tower facility in Beijing. The heater, with dimensions of 40 × 10 × 0.5 mm³ (length × width × thickness), was combined with two silicon chips with the dimensions of 20 × 10 × 0.5 mm³. High-speed visualization was used to supplement observation in the heat transfer and vapor-liquid two-phase flow characteristics. In the low and moderate heat fluxes region, the flow boiling of chip S at inlet velocity V =?0.5 m/s shows almost the same regulations as that in pool boiling. All the wall temperatures at different positions along the heater in microgravity are slightly lower than that in normal gravity, which indicates slight heat transfer enhancement. However, in the high heat flux region, the pool boiling of chip S shows much evident deterioration of heat transfer compared with that of flow boiling in microgravity. Moreover, the bubbles of flow boiling in microgravity become larger than that in normal gravity due to the lack of buoyancy Although the difference of the void fraction in x-y plain becomes larger with increasing heat flux under different gravity levels, it shows nearly no effect on heat transfer performance except for critical heat flux (CHF). Once the void fraction in y-z plain at the end of the heater equals 1, the vapor blanket will be formed quickly and transmit from downstream to upstream along the heater, and CHF occurs. Thus, the height of channel is an important parameter to determine CHF in microgravity at a fixed velocity. The flow boiling of chip S at inlet velocity V =?0.5 m/s shows higher CHF than that of pool boiling because of the inertia force, and the CHF under microgravity is about 78–92% of that in normal gravity.     

Analysis of heat transfer in the furnace of the P-67 boiler P-67 furnace and improvement of its design

The results of experimental study of heat transfer in the furnace of the P-67 boiler (under the Russian trademark) burning Kansk-Achinsk coal are presented. Means of improving the design of the furnace device are proposed.Notation N energy unit power, MW - _fur furnace air excess coefficient - r gas recirculation degree - q_in incident radiation flux density, kW/m² - a spacing between the combustion chamber walls, m - b_b burner width, m - n number of the burner row, starting from below - and inclination angles of the burners located in front of and behind the combustion chamber axis - d diameter of the conventional circumference, tangential to which the burners are directed, m - q_ch heat-stress of the radiant heat absorbing surface of the active combustion zone, MW/m² - furnace-mean thermal efficiency of deflecting walls Krasnoyarsk Institute of Non-Ferrous Metals, Siberian Branch of the All-Union Heat Engineering Institute, Krasnoyarsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 64, No. 3, pp. 275–278, March, 1993.     

Heat transfer between liquid3He and sintered metal heat exchangers

A new model to explain the unexpectedly large heat transfer between liquid³He and sintered metal heat exchangers is described and evaluated. The heat transfer results from a direct coupling of³He quasiparticles in the pores to vibrational modes of the sintered metal powder. It is proposed that for a range of temperatures below 20 mK the dominant vibrational modes of the sinter are localized oscillations involving a few powder particles with frequencies distributed over a constant density of states. The³He is then treated as a Fermi gas in a set of boxes corresponding to the pores in the sinter. The vibrating or shaking boxes transfer energy to the³He quasiparticles inside the box. The calculated heat transfer between liquid³He and the vibrational modes of sintered metal heat exchangers isQ/(VT)4×10 ^–15 T/d ³ W m^–3 K^–1, where Q is the heat flow for a temperature differenceT, V is the volume of the sinter (metal and helium), andd is the powder particle diameter in meters; this has the observed linear temperature dependence, and in magnitude is larger than or comparable to published results from several laboratories. The heat transfer between the vibrational modes and the electron gas in the metal sinter that is needed to complete the heat path can also be described by the same model with the result that the electron-phonon coupling is significantly larger than the³He-phonon coupling. When the model is applied to heat transfer between liquid³He-⁴He mixtures and sinter the calculated results are again comparable to or larger than those measured. The postulated localized oscillator modes give a specific heat, linear in temperature, that is in reasonable agreement with measurements for pressed powder by Pohl and Tait.     

Investigation of the evaporation process and sonic limits in sodium heat pipes

The maximum heat fluxes in the heating zone and the sonic limits of power transfer in sodium heat pipes and vapor chambers with composite (channel) wicks are investigated experimentally.Notation P vapor pressure - T temperature - density - molecular weight - L latent heat of vaporization - q specific heat flux in heating zone - Q specific heat transfer along heat pipe - G mass flow of vapor in pipe cross section - W average vapor flow velocity in pipe - surface porosity of wick - R universal gas constant - f coefficient of evaporation - momentum-flux coefficient - coefficient of friction - d_v diameter of heat pipe vapor channel Indices 0 liquid surface - v vapor at liquid surface - w wall surface - in entrance to heating zone - so critical cross section Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 33, No. 5, pp. 832–837, November, 1977.     

Influence of radiation on the limits of heterogeneous combustion of a particle in two parallel reactions on its surface

The influence of radiation on critical parameters of heterogeneous ignition and extinction of a carbon particle in air is analyzed with allowance for two heterogeneous reactions.Notation Q _chem surface power of heat release through chemical reactions, W/m² - Q _h overall density of heat flux by molecular convectionQ _m.c. and radiationQ _i, W/m² - d particle diameter, m - t time, sec - T ₁,T ₂,T ₂,T _w particle gas, and reaction chamber wall temperature respectively, K - ₁, ₂ particle and gas density, kg/m³ - c ₁,c ₂ specific heat of particle and gas, J/(kg·K) - n _ox relative mass concentration of oxidant in the gaseous medium - q _i thermal effect of the first (i=1, C+O₂=CO₂) and the second (i=2, 2C+O₂=2CO) chemical reactions, J/kg - _i stoichiometric coefficient - E activation energy, J/mole - k _0i preexponential factor, m/sec - R universal gas constant, J/(mole·K) - Nu Nusselt number - ₂ thermal conductivity coefficient of gas, W/(m·K) - D ₂ diffusion coefficient of gas, m²/sec - ₂₀, ₂₀,D ₀ density, thermal conductivity, and diffusion coefficients of gas atT ₀ - emissivity coefficient - Stefan-Boltzmann constant, W/(m²·K⁴) - , heat- and mass-transfer coefficients, W/(m²·K), m/sec. Indexes: 1, particle - 2 gas - ign ignition - ext extinction - w wall - st steady - cr critical - in initial - c combustion - m maximum - lim limiting I. I. Mechnikov Odessa State University. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 3, pp. 466–473, 1995.