Home – Home – Jornals – Advanced Search

In the second part of review, we have considered the problems related to momentum and heat transfer in nanofluids. Results on hydrodynamic friction, forced and free convection in the laminar and turbulent flows are analysed; heat transfer at boiling is considered. The available models describing heat transfer intensification and suppression in nanofluids are studied. It is shown that for some problems on convective heat transfer there is a contradiction in data of different authors; possible reasons for this contradiction are analysed

Experimental heat-transfer data for a small-diameter hot wire have been obtained and generalized in a wide range of Reynolds numbers typical of hot-wire anemometry. The experiments were carried out using an IRVIS-TA5 digital hot-wire anemometer and standard critical nozzles used for regulating the flow in the test section of the Eiffel chamber in which the hot-wire sensor was installed. Approaches to carrying out hot-wire anemometric measurements without a labor-consuming calibration procedure for the hot-wire sensor are substantiated.

Time dependences of temperature distributions in a thin metal wall were studied experimentally under two conditions of convective heat transfer in a tank model. In the first case, the vertical working wall was heated from within due to a convective heat flux from the opposite wall heated monotonously, and it was cooled due to heat transfer to the ambient medium. Dependence of the temperature field on a thin wall at the stage of convective flow development was retraced with the help of the thermographic camera and thermocouple sensors. In the second case, the tank wall was heated uniformly by IR radiation from the outside, and nonstationary convective flow and volumetric liquid heating were formed inside. Time dependence of temperature distribution over the wall height is studied. It is shown that the flow structure and convective heat transfer in a fuel layer with free boundary are subjected not only to the buoyancy force, but also to the thermocapillary effect. The local features of the flow affect temperature distribution in a thin wall.

The dynamics of phase fronts in a hydrothermal solution filtering through the fluid-conductor pores upwards to the earth surface was investigated on the basis of the model of volcanogenic orthomagmatic fluid systems. The problem was solved with regard for the rise and gradual extinction of the source of a fluid related to the crystallization of water-saturated basite magma in a shallow intrusion chamber. The influence of the porosity and permeability of supra-intrusion rocks as well as the heat-exchange conditions at their boundaries on the evolution of the orthomagmatic fluid system was investigated.

Density of low-temperature eutectic in magnesium−lead system (83.06 at. % Pb) has been measured by gamma-raying of the samples with narrow beam from cesium-137 isotope over the temperature range 293−1000 K of solid and liquid states. Approximation density dependences have been obtained and data of this work and other authors have been compared. Reference tables of temperature dependences of the alloy thermal properties have been compiled for the entire range of measurements and their errors estimated. It is shown that differences in the values of volumetric changes obtained during melting and crystallization are bound with the metastable β′-phase formation.

The process of heating a moving medium by an electromagnetic radiation in high-frequency range is considered in the presence of heat exchange with the ambient medium in the approximation of a thermally thin layer. The existence of temperature profiles in the form of auto-waves is established. The analytic and numerical solutions are compared.

The one-phase Stefan problem was simulated numerically in a layer of semitransparent medium with different emissivity factors at the right moving boundary. The effect of optic properties of irradiated surface on formation of temperature fields and radiation flux densities was demonstrated.

The dynamics of planar one-dimensional shock waves applied to the available experimental data for the water−Freon system is studied on the basis of the theoretical model of the bubbly liquid refined with regard for a possible hydrate formation. A scheme is proposed for considering the fragmentation of bubbles in the shock wave, which is one of the main factors of the intensification of the hydrate formation process with the growth of the shock wave amplitude.

Fundamental potential of single-stage processing of ilmenite concentrate to synthetic rutile of commercial quality has been shown experimentally and by thermodynamic computations. The method has its origins in selective chloridation of iron and impurity of magnesium, chrome, manganese, sulphur, and vanadium by chlorine with no use of any reducer. Possibility to extract vanadium without reduction smelting and without loss of titanium and other target ingredients of the concentrate was revealed for high-titanium titanomagnetite concentrate. The other target ingredients can be later isolated by the reduction chlorination. It has been found that the great bulk of iron and vanadium can be extracted from titanium concentrates for 10 min at a temperature of 1373 K and under atmospheric pressure.

Principal tendencies of variation in crude oil composition and properties during thermolysis under laboratory conditions have been studied by the example of heavy, high-viscosity crude oils from Usinsk and Lyaokhe oil fields. The experiments were conducted in an autoclave of periodic action in a range of temperatures 200-350 ^oC with addition of water and with application of a mineral admixture to study the nature of the influence of oil-bearing rock. Thermolysis products are represented by gases, insoluble carbonisation products, and converted oil. It has been found that the content of nitrogen, sulphur in liquid products of thermolysis differs from that for initial crude oils, the content of asphaltenes grows, the proportion of resins and oils decreases. Proportion of nitrogen bases, aromatic and oxygen-containing structural fragments in the composition of aquathermolysis products increases, amides appear in it. Specific absorption index of oils and their fractions at a wavelength of 500 nm tangibly change together with individual composition of alkanes and naphthalenes. Tendencies of variation in key parameters of composition during the aquathermolysis of Usinsk oil and crude oil from Lyaokhe oil field are quite opposite. The effect of mineral admixture on the results of thermolysis manifests itself only at the level of liquid yield, of their elemental, group, and functional (according to IR spectra) compositions and it is imperceptible at the level of functional group composition and at the level of individual composition of compounds that were identified in these oils