Calculation of Free‐Convective Heat Transfer on a Vertical Semiinfinite Plate

Selfsimilar problems of freeconvective heat transfer on a vertical flat semiinfinite plate for high Prandtl numbers and three types of thermal boundary conditions (an adiabatic surface, a constant temperature, and a constant heat flux on the surface) are solved by the method of internal and external expansions on the basis of the equations of a laminar boundary layer in the Boussinesq approximation. Asymptotic relations are found for the main characteristics. The results obtained are compared with the data of other authors.     

Influence of Water on the Total Heat Transfer in ‘Evacuated’ Insulations

The impact of water vapor on the thermal conductivity of vacuum insulation panels (VIPs) filled with fumed silica kernels was investigated and found to be surprisingly large. Besides thermal transport by water vapor within the pore space, the question was whether water in the adsorbed phase also contributed significantly to the total heat transfer. In order to quantify these effects, several series of thermal conductivity measurements were performed in an evacuable guarded-hot-plate. The fumed silica specimens were first investigated in the dry state. Then water vapor was added into the vacuum system in different quantities (valves closed and no pumping), yielding water content in the VIP-kernel of up to 4% by mass. Most of the water is adsorbed in the specimens; smaller amounts are to be found in the gas phase. The parameter varied was the temperature; accordingly, the partial pressure of water vapor changed. An empirical equation is presented that describes the influence of water vapor and adsorbed water on the total heat transfer.     

Heat and Mass Transfer in Condensation of Harmful Air‐Polluting Substances on the Phytocenosis Surface

A mathematical model for the condensation of harmful airpolluting substances on the phytocenosis surface is formulated. Results of a numerical study of the problem of heat and mass transfer are presented. The temperature and concentration fields, the time dependence of the condensation rate, and the distribution of the condensate film over the phytocenosis surface are obtained.     

Research on Marangoni Condensation Modes for Water–ethanol Mixture Vapors

In this paper the condensation experiments for water–ethanol vapors were carried out at different vapor pressures over a wide range of ethanol concentration. The condensation modes were observed and quantitatively analyzed in order to clarify the condensation phenomenon and dropwise condensation mechanisms. The cycle time of dropwise condensation, affected by vapor-to-surface temperature difference, ethanol concentration and vapor pressure, was approximate 0.2 s to 2 s. The quantity proportion of drops with the diameter less than 1 mm was more than 70% in all drops for all mixture vapors. The peak values of the maximum departing diameters increased with the ethanol vapor concentration, and were weakly affected by the vapor pressure, and the values were about 1.5 mm to 5 mm. The rivulet condensation mode was usually observed as a transition state appeared when the drop mode changed to film mode. The maximum distance between rivulets was sensitive to the ethanol vapor concentrations and little dependent on the vapor-to-surface temperature difference.     

Self-Organization of Detonation-Diamond Particles on a Substrate in Carbon Condensation from the Vapor–Gas Phase

Technical Physics Letters - Processes in which the island structure is ordered occur in composite carbon films produced by preliminary population of an amorphous substrate with a detonation-diamond...     

Molecular Dynamics Simulation of Pervaporation of an Ethanol–Water Mixture on a Hybrid Silicon Oxide Membrane

A molecular-statistical method for simulating the process of pervaporation on hybrid silicon oxide membranes is proposed. This method is a development of the control volume method. Models of three membrane samples with different densities and pore sizes were obtained. These samples were used for the molecular-dynamics simulation of pervaporation of a 95 mol % aqueous solution of ethanol at a temperature of 343 K. It is shown that the membrane is selective with respect to water; the component flow is found to exponentially depend on the pore size.     

Experimental Study on the Hydrodynamics and Mass Transfer Characteristics of Airlift Loop Reactors（ALR）

The promoting effect of ultrasonic wave on the hydrodynamics and mass transfer characteristics of the airlift loop reactor was studied．The effect of the airlift reactor and ultrasonic wave on the reactor’s gas holdup,liquid circulation velocity,mixing time and overall volumetric mass transfer coefficient respectively with and without the presence of ultrasonic wave is empathetically examined and compared．The experiment has proven that the incorporation of ultrasonic wave has no effect on the gas holdup but has the tendency to gradually decrease the liquid circulation velocity and increase the overall volumetric mass transfer coefficient; the effect on the mixing time is relatively complex．At low gas velocity,low powered ultrasonic wave promotes the radial mixing of fluid;with the increase of ultrasonic power,ultrasonic vibration obstructs the radial mixing of fluid．Therefore,there exists an optimal ultrasonic power．Moreover,the effect of ultrasonic wave on the mixing time gradually decreases with the increase of the superficial gas velocity．Correlations were also proposed for the hydrodynamics and mass transfer characteristics of the reactor．     

Influence of Water Vapor on the Isothermal Oxidation Behavior of Thermal Barrier Coatings

The oxidation of specimens with thermal barrier coating (TBC) consisted of nickel-base superalloy, low-pressure plasma sprayed Ni-28Cr-6AI-0.4Y (wt pct) bond coating and electron beam physical vapor deposited 7.5 wt pct yttria stabilized zirconia (YSZ) top coating was studied at 1050℃ respectively in flows of 02, and mixture of O2 and 5%H2O under atmospheric pressure. The thermal barrier coating has relatively low oxidation rate at 1050℃ in pure O2. Oxidation rate of thermal barrier coating in the atmosphere of O% and 5%H2O is increased The oxidation kinetics obeys almost linear law after long exposure time in the presence of 5% water vapor. Oxide formed along the interface between bond coat and top coat after oxidation at 1050℃ in pure O2 consisted of Al2O3, whereas interfacial scales formed after oxidation at 1050℃ in a mixture of O2 and 5%H2O were mainly composed of Ni(AI,Cr)2O4,NiO and AI2O3. It is suggested that the effect of water vapor on the oxidation of the NiCrAlY coating may be attributed     

Specific Features of Peroxide Precipitation of Uranium from Acid Water–Ethanol Solutions

Radiochemistry - Effect of acidity and hydrogen peroxide and ethanol concentrations on the degree of precipitation of uranium peroxide in solutions of various compositions was studied. The...     

Kinetic Study of Cementation of Copper on Zinc Metal in Ethanol-Water Mixtures

The cementation reaction of copper on zinc metal in solutions of different concentrations ofcopper sulphate, at 25℃, has been studied and it is found to be a first order reaction. Moreover,the rates of this reaction at 0.15 mol'L-1 copper sulphate solution have been measured in a varietyof ethanol-water media at temperatures from 20℃ to 40℃. The correlation between the masstransfer coefficient and the dielectric constant has been investigated. Also, the thermodynamicparameters of activation have been calculated. The isokinetic relationship reveals the existenceof compensation effect, where the solute-solvent interactions play an important role.     

Investigation of the Ice–Water Vapor Equilibrium Along the Sublimation Line

An accurate knowledge of the thermodynamic properties of water at low temperature plays an important role in atmospheric processes, chemical physics, and metrological applications. Preliminary investigations of the water vapor?Cice equilibrium along the sublimation line have been carried out at Istituto Nazionale di Ricerca Metrologica (INRIM). The measurements covered the temperature range from ?50?°C to 0?°C, corresponding to a saturation vapor pressure from about 4?Pa to 611?Pa. The measurements were performed using a small gold-plated cell kept in a liquid bath at a constant temperature with millikelvin stability. The sample cell was connected to a manifold where the pressure was measured using two capacitive diaphragm pressure gauges. The paper reports the water sample preparation, measuring method, and measurement corrections. Measurement results are discussed and uncertainty sources estimated. The resulting expanded relative uncertainty (k = 2) varies from 0.038 % at 0?°C to 0.70 % at ?50?°C.     

Preliminary Study on Corrosion Behaviour of Carbon Steel in Oil–Water Two-Phase Fluids

The corrosion behavior of type 1045(AISI) carbon steel(CS) in oil-water fluids was investigated by considering the surface wetting state as the breakthrough point.The surface water wetting percentage(SWWP)and corrosion weight loss of CS in different oil-water fluids were measured.The morphology and composition of the corrosion films were detected via scanning electron microscopy,electron-probe facescanning technology and Fourier-transform infrared spectroscopy.The results indicated that the corrosion weight loss of CS in the oil-water fluids corresponded with SWWP and that the corrosion process was influenced by the participation of oil.     

Distinctive Features of Water–Dimethyl Sulfoxide Mixtures: Dielectric Spectra Revisited

Broadband dielectric spectra (1 MHz to 80 GHz) are reported for dimethyl sulfoxide–water mixtures in the complete composition range. The spectra are evaluated in order to yield information about the underlying relaxation time distribution, the principal relaxation time, and the static permittivity of the liquids. With a view of gaining insights into the structure and microdynamics of water in its different states of interaction, these parameters are compared to such for mixtures of water with other protic and aprotic dipolar liquids as well as with non-polar substances. Also used for information about structure fluctuations are ultrasonic spectra of the dimethyl sulfoxide–water system (0.2 MHz to 2.75 GHz). A notable result is the composition dependence of the principal dielectric relaxation time. In conformity with the wait-and-switch model, it increases at low DMSO content and thus reflects the decrement in the concentration of hydrogen-bonding sites. The decreasing relaxation time at high DMSO content is clearly a result of the reduced association due to the reduced concentration of hydrogen-donating sites.     

Effect of the Shape of Pulses on Heat Transfer at the Stagnation Point of a Nonstationary Axisymmetric Impact Gas–Droplet Jet

Journal of Engineering Physics and Thermophysics - A numerical investigation was carried out to study the influence of the shape of pulses (rectangular, triangular, and sinusoidal) on heat transfer...     

Surface Reaction of TiAl with Water Vapor and Oxygen

The interaction of water vapor and oxygen with TiAI-based alloy has been studied with Auger electron spectroscopy and X-ray photoelectron spectroscopy. The results indicate that both surface reactions initiate at a very short exposure (about 6×10-7 Pa·s) and the oxides Al2O3 and TiO2 form in the surface reactions. In the oxidizing reaction, the water vapor reacts firstly with Al, and then reacts with Ti after certain exposure. The surface reaction of Al with water vapor may be responsible for the environmental embrittlement at room temperature in TiAI-based alloy.