Investigation of the process of liquid evaporation from a porous metal under vacuum conditions

The method and results of an investigation of the evaporation of water into a vacuum are described. The steady-state regime of evaporation in a porous metal is examined. The dependence of the evaporation rate on the parameters of the porous metal and the heat flux density has been experimentally determined. The temperature distribution in the porous plate is determined theoretically.     

Features of Heat Transfer in the Granulation of Sulfur

The influence of the temperature regimes of the granulation of sulfur in an aqueous medium on the qualitative characteristics of the granules obtained has been experimentally investigated. The admissible range of change in the operating parameters of an apparatus for granulation of sulfur with the use of water has been determined and a dimensionless quantity defining this range has been derived. The influence of the heattransfer regimes on the formation of the internal structure of sulfur granules has been numerically investigated and the reasons for the dependence of the qualitative characteristics of the granules on the temperature conditions of their production have been revealed.     

Theoretical study of hydrodynamics and heat transfer by free convection of non-Newtonian fluids near a cooled surface with regard for variable viscosity

We have made a theoretical study of the hydrodynamics and heat transfer of non-Newtonian fluids near a cooled isothermal surface by laminar free convection with regard for the change in the fluid viscosity with temperature. A power rheological model has been used. The solutions to the systems of differential equations for the boundary layer have been obtained numerically. It has been shown that the strongest influence in the considered kinds of convection is produced by the relative viscosity. Moreover, of great importance is the nonlinearity index of the medium. With increasing rheological parameter the influence of variable viscosity decreases. Criteria equations for calculating the local and mean Nusselt numbers and friction coefficients have been obtained. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 6, pp. 49–56, November–December, 2006.     

On the long-term deformation process in viscoelastic composites around an elliptical hole

This paper deals with the dependence of stress redistribution around an elliptical hole in a composite on viscoelastic properties of the composite components. The results are obtained for composites with elastic and viscoelastic reinforcement. It is shown that the stress on a surface of the hole can change non-monotonically for the case of viscoelastic reinforcement, i.e., there can be maxima on the stress–time diagrams during the lifetime of the composite.     

Computational optimization of characteristics for composites of viscoelastic components

The problem of describing of the viscoelastic properties of composite materials that consist of more than one viscoelastic component is studied. It is supposed that the viscoelastic properties of the components are known. The difficulty in the application of the mixture theory arises in the cases when the properties are described by integral operators with different integral kernels. This difficulty is avoided by the approximations of the viscoelastic operators in the stress–strain relations. A method is proposed to obtain appropriate approximations that reduce all the viscoelastic operators to a general kernel using rational approximations of their Laplace transforms. The proposed method allows for the reduction of the approximation error for related operators. Examples are given for the adjustment of viscoelastic functions in the cases of increase and decrease of functions parameter.     

A current source with an inductive energy storage for measuring pulse impedances of grounding connections

A pulse generator with an inductive energy storage for measuring pulse impedances of grounding connections is developed. The generator produces current pulses with a rise time of 200–300 ns and an amplitude of up to 8 A. In contrast to the capacitive storage sources, it is fully controllable, allows one to adjust the amplitude, and ensures a constant current-pulse shape regardless of the load parameters. The different operation modes of the source are described. The experimental load-current waveforms are presented.     

Characteristics of the new YAlO3:Ce compared with BGOand GSO

The characteristics of YAlO₃:Ce (YALO) used as a fast scintillation detector with high density (5.35 gm/cm³) and high light yield were investigated and compared with those of other scintillation materials. The decay of the scintillation light could be described by the sum of two exponentials with decay constants of 31 ns and 246 ns and contributing 98% and 2% to the total light yield, respectively. The light yield of 19700 photons/MeV was measured by comparing the number of photoelectrons produced in YAlO in BGO under the same conditions. The energy resolution at a gamma ray energy of 511 keV was 6.7% for a 4.0×8.0×25.0 mm³ sample. The FWHM of a timing measurement using two YAlO crystals detecting annihilation quanta (with 200 keV threshold) was 1.1 ns. Monte Carlo simulations showed that the crystal depth for the absorption of 90% of 511 keV gamma quanta is 51.8 mm in YAlO (compared with 25.2 mm in BGO)