Yu. L. Shekhter

Visualization of boiling of subcooled water

Data of high-speed photography of boiling of subcooled water on stainless steel foil at atmospheric pressure, heat flowrate relative to 6 MW/m2, subcooling of up to the saturation temperature of 45–75°C, and water flow velocities of 0.4 m/s are presented.

The nature of microbubble emission under subcooled water boiling

Under boiling of highly subcooled water at high heat flow rates, several authors have observed emission of numerous small (10–80 μm) bubbles. This phenomenon has been called as “microbubble emission.” In this paper we make an attempt to explain this phenomenon by emission on the surface and in the near-surface liquid layer of the residual air that has not been removed in the course of the water deaeration (degassing).

Behavior of air bubbles during subcooled water boiling

The data of video filming of the behavior of air bubbles near the heating surface during boiling of subcooled water are presented. The effects the regime parameters (heat flow rate and water subcooling relative to the saturation temperature) have on the characteristics of the vapor-air-water mixture are described.

Use of combined-cycle power units at cogeneration plants

Indices of reconstructed and new cogeneration plants (CPs) using combined cycle units (CCPUs) are considered. The conclusions that follow from the necessity of retention of the heat capacity of a CP under reconstruction and limited possibilities of CCPUs as to heat output are given.

Generalization of experimental data on heat transfer in permeable shells made of porous reticular materials

Heat transfer from six samples of porous reticular material to cooling gas (air) at small Reynolds numbers is experimentally studied. The specific features pertinent to heat transfer essentially affected by longitudinal heat conductivity along gas flow are analyzed. The experimental results are generalized in the form of dimensionless empirical relations.

Microbubble boiling: Mechanism of the process, objectives and methods of investigations

Results are given of analysis of experimental studies devoted to the mechanism of subcooled liquid boiling under conditions of forced flow and, in particular, to its extreme case realized under high heat fluxes, i.e., microbubble boiling. The problems are formulated which are associated with experimental investigation of structural characteristics and dynamics of microbubble boiling. The description is given of the experimental stand and diagnostic system for solving the problems set.

Investigation of Pyrolysis of Methane under Conditions of Filtering through a Heated Porous Medium

An unsteady-state one-dimensional mathematical model is used to perform a theoretical analysis of the process of thermal decomposition of methane under conditions of filtering through a heated porous medium formed by granules of commercial-grade carbon. A scheme of the process kinetics is developed. The effect of the basic characteristics of commercial-grade carbon and of the operating conditions on the efficiency of the process is treated. Laboratory experiments are performed in support of the commercial-scale technology of production of granular pyrocarbon. A comparison of the calculation results with experimental data demonstrates their good agreement.

Experimental data on the mechanism of subcooled water boiling: high-speed video shooting

The article provides statistical data on the characteristics of subcooled liquid boiling and behavior of vapor and air bubbles resulted from high-speed shooting. The authors have described a number of new phenomena going along with water boiling.

The hydraulic characteristics of porous materials for a system of transpiration cooling

As a result of laboratory and numerical experiments, data on hydraulic drag and structure of flow are obtained for the first time in samples of sheet porous material prepared using the ingenious technology of two-way strain cutting. The study is aimed at developing an efficient system of transpiration cooling with tangential injection of cooling gas onto a microrough surface.

Simulation of Porous Transpiration Cooling of the Leading Semicylindrical Edge of a Streamlined Body

Experiments are carried out for simulating the efficiency of cooling the leading edge of a blunt streamlined body made of porous reticular material with an impermeable insert placed along the stagnation zone. Satisfactory results are obtained that make it possible to recommend the proposed method of organizing transpiration porous cooling of the leading edge of the blades used in high-temperature gas turbines for implementation.