Specific features of heat transfer at the stagnation point of an impact axisymmetric jet at low Reynolds numbers

The average and pulsating thermal characteristics at the stagnation point of a plate at inflow of an impact axisymmetric air jet have been studied. The influence of the Reynolds number (100 < Re < 12000) on heat transfer has been investigated for a jet flowing from a long tube (diameter d = 5 mm, relative length h/d = 200) with the output located at a distance h/d = 20 from the obstacle. The measurements have been carried out using a heat-flow sensor with high spatial and temporal resolutions. A nonmonotonic change in heat transfer having a maximum is found in the range Re < 4000 (in contrast to the known monotonic increase in heat transfer). A significant increase (200–600%) in the Nusselt number is observed for outflow from a tube in comparison with jet outflow from a nozzle. At Re > 4000, the difference in heat transfers for two cases of jet formation (from a tube and a nozzle) decreases asymptotically.     

Startup of the Proton Radiographic Facility at the U-70 accelerator

The first results of Proton Radiographic Facility operation on the beam with energies of 50–70 GeV extracted from the U-70 synchrotron at the Institute for High Energy Physics are presented. This facility is capable of forming proton radiographic images of samples with an optical thickness as large as 450 g/cm² and a field of view of 220 mm or more.     

Measuring the depth of conducting coatings with gap and substrate-conductivity detuning

The problem of measuring the depth of nonmagnetic conducting coatings on nonmagnetic substrates with simultaneous detuning of the gap and substrate conductivity is considered. It is shown that the gap can be detuned by introducing a compensating voltage with a fixed phase and an amplitude that is adjusted proportionally to the high-frequency channel signal.     

Catalytic hydrodechlorination of chlorinated hydrocarbons in a medium of sodium hydroxide solutions. I: Conversion of carbon tetrachloride

Carbon tetrachloride, classified as an ozone-depleting substance in the Montreal Protocol, is formed as a byproduct in the production of chlorinated hydrocarbons (chloromethanes, perchloroethylene, etc.). To develop a rational method of CCl₄ utilization (an alternative to burning), in this work we study the liquid-phase catalytic hydrodechlorination of CCl₄ with the formation of useful products such as sodium formiate, hexachloroethane, and perchloroethylene in the presence of aqueous sodium hydroxide solutions. Experiments are performed in a 300-mL autoclave at pressures of up to 1.5 MPa within a temperature range of 80–120°C on a Pd catalyst on sibunite (5 fractions, 0.1 to 1.6 mm). The dependences of the CCl₄ conversion and the selectivities with respect to the principal reaction products on the initial concentrations of CCl₄ and NaOH, the temperature, the partial pressure of hydrogen, the size of catalyst particles, and the palladium content in a catalyst are studied. Using the obtained data as a basis, we propose a process flowsheet, make some recommendations on the process conditions (depending on the specified composition of products), and determine the optimum catalyst characteristics: 1.5 wt % Pd on sibunite with a grain size of 0.315–0.63 mm. The proposed process allows us not only to solve the problem of recycling CCl₄-containing wastes, but also to provide the production of three marketable products.     

Application of pressure transducers subjected to large vibrations

Conclusions The application of the above system for protecting the means of measurement from appreciably destabilizing effects ensures that the required statistical measurement precision is obtained, trustworthy information about the dynamic processes (in measuring relatively high pressures) which occur over periods exceeding 0.03 sec is provided, and a higher reliability for the normal functioning of a measurement channel is ensured with its possible future utilization for controlling the working objects with a speed of operation exceeding that of existing control systems.In principle the above system for protecting pressure transducers from destabilizing effects can be extended to the measurement of lower pressures and processes with characteristic durations down to 0.01 sec. This entails reducing the pipeline length and preserving at the same time the vibration properties of the system.Translated from Izmeritel'naya Tekhnika, No. 10, pp. 23–25, October, 1969.     

Thermal oxidation of V2S5/InP heterostructures in oxygen

X-ray emission and IR spectroscopy data are used to elucidate the mechanism of thermal oxidation of V₂S₅/InP structures in oxygen. The substrate-activator interaction is shown to have a significant effect on the oxidation mechanism and to improve the engineering performance of the structures.