Mathematical Modeling of the Evaporation of a Water Drop from a Heated Surface.

This paper presents the results of mathematical modeling of the evaporation of a single water drop from the surface of a copper substrate using a new model, which does not require special experiments to close the system of equations and the corresponding boundary conditions with empirical constants. On the basis of the results of mathematical modeling, it was found that convective currents that occur in a small water drop (≤1 mm in diameter) do not significantly affect the characteristics or conditions of heat and mass transfer processes occurring in a liquid drop heated on a copper substrate. The results of numerical simulation showed that during the initial period of droplet heating, the latter undergoes a rapid transformation of the flow field. Five seconds after the beginning of the thermal action, a quasi-stationary regime of flows in the drop sets in. The model is tested on known experimental data. The theoretical analysis of temperatures at the characteristic points of a water drop and the surface on which the drop is located is carried out in ranges of thermal loads quite typical for practice, conditions for transferring heat and water vapor to the environment. According to the results of mathematical modeling, the possibility of using the developed model in the analysis of the state of cooling of surfaces heated to high temperatures, in cases typically used, is substantiated.

Emissions from the combustion of high-potential slurry fuels.

Slurry fuels based on wood and coal processing and petroleum refinery waste are an environmentally friendly and economically feasible alternative to the conventional solid fuel-coal. As part of this experimental research, we compared a set of fuels (coal and coal-water slurries with and without petrochemicals) by normalizing and calculating the specific concentrations of pollutants from their combustion. The pollutant concentrations were normalized with respect to the mass of burnt fuel, the thermal energy released by combustion, specific mass emissions per unit time, specific maximum mass emissions, and specific mass emissions per 1 kg of fuel equivalent or 1 MJ of thermal energy. The key objective of this research was to develop a method for comparing composite fuels in terms of their relative environmental friendliness. As part of the research, coal combustion was notable for the peak emissions of gaseous pollutants irrespective of the fuel mass and combustion chamber temperature. When slurries were burnt, CO2, SO2, and NOx concentrations were 12-90% lower as compared to coal. The research findings established that the most promising fuel of all the slurries under study is the one based on coal slime and sawdust due to its high environmental indicators.