Determination of average heat-transfer coefficients by means of built-inα-calorimeters

The article describes an approximate method for determining the average heat-transfer coefficient on a surface upstream from a built-in-calorimeter, on the basis of temperature measurements on the wall, as well as measurements of the local heat-transfer coefficient and the local flow velocity at the point of installation of the-calorimeter.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol.19, No. 2, pp. 236–242, August, 1970.     

On the solution of nonstationary heat-conduction problems with variable heat-transfer coefficient

The article describes an exact method for calculating the temperature field in solids when they are heated in a medium with a variable heat-transfer coefficient and a nonuniform initial temperature distribution.Notation temperature - L thickness of plate - x space coordinate - a thermal diffusivity - thermal conductivity - heat-transfer coefficient - t time - X=x/L dimensionless coordinate - Fo=at/L² Fourier number - Bi(Fo)=(Fo)L/ Biot number Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 20, No. 5, pp. 921–924, May, 1971.     

Spatial nonstationary heat-conduction problem for a prism with a coordinate-dependent heat-transfer coefficient

We present an efficient method for the determination of three-dimensional nonsteady-state fields of bodies of simple shapes, when the heat-transfer coefficient from their surface changes locally.Notation t temperature field - dimensionless temperature field - x, y, and z dimensional coordinates - X, Y, and Z dimensionless cordinates - time - thermal conductivity - a thermal diffusivity Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 1, pp. 133–137, January, 1982.     

Simulation of temperature distributions in vacuum

A method is presented for simulating the temperature distribution in an object when there is no convective heat transfer. Similarity of boundary conditions is ensured by a heat shield with a controlled temperature serving as a free parameter.Notation surface emissivity - thermal conductivity - radiative heat-transfer coefficient - l characteristic linear dimension - c length scale for the model - P power - T_iob T_ia, T_is, T₀ temperatures of the object, the model, the shield, and the environment - Stefan-Boltzmann constant Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 20, No. 5, pp. 925–927, May, 1971.     

Analytic solutions of parabolic and hyperbolic heat-transfer equations for nonlinear media

New classes of analytic solutions are obtained which describe unsteady temperature distributions and take account of the temperature dependence of the thermophysical properties of the material. The concept of a solution of the boundary layer transition type is introduced for the generalized heat-transfer equation.Notation T temperature - x Cartesian coordinate - t time - c volumetric heat capacity - thermal conductivity of medium - heat-transfer (heat flux) relaxation period - q_v internal heat source strength - new argument - auxiliary function Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 40, No. 3, pp. 510–517, March, 1981.     

Estimation of the unknown parameters in the melt-spinning process

The free-surface temperature history of the melt spinning of copper measured by Tenwick and Davies [3] is compared with those calculated using a thermokinetic model assuming different parameters. The heat-transfer coefficient, nucleation temperature and the crystal-growth kinetics were thus estimated for the melt spinning of copper at a wheel speed of 35 ms^–1 as follows: heat-transfer coefficient during liquid cooling stage HL=1.0 × 10⁷ W m^–2K^–1, heat-transfer coefficient after solidification finished HS=1.0 × 10⁵ W m^–2K^–1, heat-transfer coefficient during solidificationH= 1.0 x 10⁷- 1.2 x 10¹¹ (t-t _n) (W m^–2K^–1), the nucleation temperatureT _n 1233 K and the crystal-growth kinetic lawV=4.0 × 10^–3 T^1.1 (ms^–1).     

The thermal boundary layer of a non-fourier power-law fluid on a plate with a variable surface temperature

The equation for the thermal boundary layer of a non-Fourier powerlaw fluid on a flat plate with an exponential distribution of surface temperature is reduced to an ordinary equation and solved by the method of finite differences. The effect of the exponent on the temperature profile and on the heat-transfer coefficient is determined. It is demonstrated that the asymptotic solutions of the equation for large are nearly exact.     

Heat transfer and the combustion temperature of coke particles in a fluidized bed

The temperature of carbon particles undergoing combustion in a fluidized bed is measured. Heat-transfer laws are ascertained.Notation a diffusivity of air - c heat capacity of air - D diffusion coefficient of oxygen in air - d₀, d initial and running diameters of carbon sphere - d_i diameter of inert particles - k rate constant for carbon monoxide combustion - q calorific value of carbon oxidation to CO₂ - T temperature difference between burning particle and fluidized bed - X, X_n oxygen concentration in the fluidized bed and on the surface of the burning particle - Z, Z_n running concentration of carbon monoxide and concentration on the surface of the burning particle - heat-transfer coefficient between fluidized bed and burning particle - _m maximum heat-transfer coefficient between fluidized bed and a stationary body submerged in the bed - masstransfer coefficient between fluidized bed and burning particle - thermal conductivity of air - kinematic viscosity of air - ₀, gr, ₄ density of oxygen, air, and inert material - relative thickness of burning gas layer - relative thickness of diffusion boundary layer Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 1, pp. 21–27, January, 1982.     

Localization of vibrations of shrouded turbomachine rotor blading

We study the influence of the nature of the circumferential distribution of the blade frequencies on the localization of the vibrations of shrouded blade rings. It is shown that the most favorable configuration (with regard to both the level of the vibratory stresses and the scatter of the resonant amplitudes of the vibrations) for the shrouded blade rings with mistuning of the blade frequencies is the sawtooth arrangement of the frequencies around the circumference of the disk, while the most unfavorable configuration is the arrangement with two or three neighboring blades with the same or similar frequencies. We propose a technique for studying the localized vibrations of the subject systems, making it possible to significantly simplify the solution of the problem.This work was performed under the State Research Program Improving the Reliability and Service Life and Eliminating Catastrophic Failures of Gas Turbine Transport Engines,Translated from Problemy Prochnosti, No. 7, pp. 53–61, July, 1994.     

Nonstationary process of heat transfer in a tube with longitudinal fins

An analytical solution to the problem of nonstationary thermal interaction of a flow of a heat-transfer agent and a thin-walled tube with longitudinal fins is constructed for variable parameters of heat transfer.Notation u, temperatures of the fins - ,w temperatures of the tube walls - temperature of the flow of the heat-transfer agent - _i ,i= coefficients of heat transfer from the ambient medium to the fins and the tube walls, respectively - _i ,i= temperature distributions for the ambient medium - coefficients of heat transfer from the flow of the heat-transfer agent to the tube walls - q _i density of the heat flux to the corresponding portions of the tube - heat capacity, thermal conductivity, density, and thickness of the fin and tube material - c _p , ,G, F heat capacity, density, and flow rate of the heat-transfer agent, cross-sectional area of the tube - dimensions of the tube Bauman Moscow State Technical University. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 6, pp. 673–680, June, 1994.     

Investigation of heat exchange in the water-spray cooling of high-temperature metal surfaces

A method is described and certain results presented of an experimental study of local heat exchange in the forced cooling of metal surfaces heated to high temperatures.Notation l distance from nozzle to heated surface - x, y horizontal and vertical coordinates in the field of the jet, read from the geometric center of the jet - V volumetric flow rate of water through the nozzle - p excess pressure of the water in front of the jet - F₀ area of sprayed surface of specimen - F_c area of unsprayed surface of working part of specimen - t temperature of sprayed surface of specimen - t_w temperature of the water entering the nozzle - N, N_c power required to heat the working part of the specimen to a given temperature with and without the spraying of water onto the surface, respectively - g local spraying density - local heat-transfer coefficient Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 2, pp. 315–322, August, 1980.     

Influence of heat flux and pressure on heat transfer associated with fully developed nucleate pool boiling

Heat transfer in the pool boiling of helium is investigated experimentally. The dependence of the heat-transfer coefficient on the heat flux and pressure is determined for the fully developed nucleate boiling regime.Notation q heat flux, W/m² - T temperature differential, °K - heat-transfer coefficient, W/m²·°K - P pressure, N/m² - P_cr critical pressure, N/m² - P_* reference pressure, N/m² - n a power exponent - C a proportionality factor - , F₁ special functions Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 33, No. 5, pp. 828–831, November, 1977.     

Heat transfer in hydrocarbon fuel boiling under conditions of natural convection

Data on the heat-transfer coefficient in boiling of five jet fuels, two automotive gasolines, and a diesel fuel are presented over a wide range of regime parameters. The obtained results are described by a unified similarity equation.Notation heat-transfer coefficient, W/(m²·K) - P _s pressure, MPa - q heat flux density, W/m² - V volume, m³ - T _s temperature, K - ₁ and ₂ density of the liquid and vapor phases, kg/m³ - thermal conductivity, W/(m·K) - viscosity of the liquid, m²/sec - surface tension, N/m - C _p heat capacity, J/(kg·K) - r vaporization heat, J/kg - Nu Nusselt number - P Pecklet number.l=C _p T _{s 1}/(r₂)² serves as a governing dimension Kazan' State Techological University. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 3, pp. 438–443, May–June, 1995.     

Passive acoustic emissions from particulates in a V-blender

Context: Regulatory agencies are recommending the development of process analytical technologies (PAT) to improve the efficiency and product quality during pharmaceutical manufacturing.

Objective: The objective of the research was to investigate the potential application of passive acoustic emission monitoring of a V-blender.

Materials and methods: Trials were conducted with sugar spheres, lactose or MCC in a V-blender. Vibrations from acoustic emissions were measured using PCB Piezotronics accelerometers with ICP signal conditioners.

Results and discussion: A wavelet filter was applied to the measured acoustic emissions to remove vibrations from the tumbling motion of the V-shell, allowing a focus on information about particle motion and interactions within the V-shell. The ideal sensor location was determined to be the lid of one of the V-shell arms due to the impact of the tumbling particles on the lid and transmission of the vibrations from other particle motion within the V-shell. The amplitude of vibrations increased with particle size due to larger particle momentum before a collision. The fill level and the V-shell scale also influenced the measured vibrations as particle motion was affected which in turn affected momentum. Changes in particle flowability could be detected through variations in the measured acoustic emissions.

Conclusion: The measured vibrations from passive acoustic emissions reflected particle motion and interactions within a V-blender demonstrating potential as a monitoring method.     

Investigation of the Crisis of Heat Transfer under Conditions of Boiling on an Inclined Surface Facing Downward

An experimental investigation is performed of the crisis of heat transfer under conditions of boiling on an inclined extended (1 to 2 m) surface facing downward and immersed in a large pool of water. The effect of water subcooling on the value of critical heat flux (CHF) is investigated for the plate slopes of 8, 12, and 16° at a pressure close to atmospheric. The experimental results indicate that the critical heat flux increases with the surface slope. An anomaly in the dependence of the CHF on subcooling t is revealed, namely, the existence of a minimum of the CHF under conditions of water subcooling of 20(±10)°. Such a nonmonotonic dependence of the CHF on subcooling was previously observed under conditions of subcooled water boiling in pipes at relatively high values of the circulation rate. No such effect was previously described in the literature for the conditions of pool boiling of liquid. Based on the hypothesis on the effect of water subcooling on the velocity of the steam-liquid layer formed at the surface being heated and intensifying the precritical boiling of the liquid, an explanation is suggested of such a nonmonotonic pattern of the dependence of the CHF on subcooling. A theoretical model which makes it possible to include the effect of the orientation of the heat-transfer surface, of subcooling, and of pressure is used to derive the correlation for the CHF which generalizes the experimental data.     

Quantitative phase analysis of metastable structure in a laser melted Fe-C alloy

Quantitative X-ray diffraction phase analysis was utilized to investigate the structure of a Fe-3.5 wt% C alloy after laser melting. The measurements were taken on surfaces modified by a series of equidistant laser tracks with overlappings k = 0.25, 0.50 and 0.75, and the results were extrapolated to the non-interfering tracks. On the same samples, the microstructure was observed by scanning electron microscopy. The structure of the rapidly solidified surface layers consists of -Fe (ferrite and martensite), -Fe (retained austenite) and cementite. The results of X-ray diffraction point to a very high amount of carbide indicating a non-stoichiometric composition of cementite. Besides, the volume fraction of -Fe increases with increasing coefficient of overlapping k. At the same time, the volume fraction of cementite decreases while the content of -Fe remains nearly constant. The changes are attributed to decomposition of the metastable carbide due to tempering of the former tracks by the following laser passes. This thermal effect was quantified on the base of the heat-transfer model of moving Gaussian beam.     

Heat transfer to He I and He II in pulsed thermal loading

Results are given on the effects of a pulsed thermal load on a copper specimen immersed in He I and He II. Estimates are made of the mean heat-transfer coefficient _p for He I, He II, and He I with T _l s.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 40, No. 3, pp. 389–393, March, 1981.     

Convective Heat Transfer at an Annular Jet Impingement on a Flat Blockage

The experimental results on heat transfer of an annular impinging jet have been. The Reynolds numbers Re = (1.2–3.6) × 10⁴, the distance S from the nozzle to a blockage, S/d₀ = 2, 4, 6, and the circular slit height d₂/d₀ = 0.51 and 0.71, where d₀ and d₂ are the internal and external nozzle diameters, have been varied. It is shown that at the same air mass flow rate, replacement of a round nozzle with an annular one results in heat-transfer intensification (up to 70% at the stagnation point). The maximum heat transfer gain occurs at a small nozzle–wall distance (S/d₀ = 2). The heat-transfer increase is accompanied by an increase in the thermal pulsation intensity. The degree of intensification of the heat exchange depends on the height of the circular slit and the nozzle–wall distance.     

Specific heat of disordered and amorphous rare-gas solids: Quench-condensed pure and binary films

We report measurements of the low-temperature specific heatC of crystalline pure rare-gas films (Ne, Ar, Kr, Xe) and amorphous rare-gas mixtures (Ne-Xe, Ar-Xe) condensed at low temperatures (T6 K). For both the crystalline and the amorphous films a large contribution toC linear inT (0.5 mJ/mol K²) is found at very low temperatures (T<1 K), which is attributed to tunneling states. Annealing strongly decreases this contribution. At higher temperatures an enhancement ofC with respect to bulk samples is observed, which is explained by surface vibrations arising from the porous structure of the films. For the crystalline films, this contribution is reduced upon annealing, while only a slight annealing effect is found for the amorphous mixtures.