PARAMETRIZATION OF THE HEAT AND MASS EXCHANGE PROCESS IN THE SURFACE ATMOSPHERIC LAYER

When constructing numerical models of the atmosphere and the surface atmospheric layer (PAS) interacting with it, the “parametrization” approach is used, that is, the representation of processes with scales smaller than the scale of the cells of the computational grid intended for modeling processes of larger scales.

MATHEMATICAL MODELING OF THERMOGRAVITATIONAL AND THERMOCA-PILLARY CONVECTION IN GAS-LIQUID PROCESSES

. The interaction of gas and liquid phases in some cases is accompanied by the spontaneous occur-rence of convective flows and turbulent pulsations at the phase boundary and in adjacent areas. Hy-drodynamic instability allows to accelerate the interfacial transfer of matter and leads to an increase in mass transfer coefficients. Research in this field is not only theoretical, but also practical, since sur-face convection can be artificially created in apparatus for intensifying the mass exchange process.

The Role of Discrete Capillary Rings in Mass Transfer From the Surface of a Drying Capillary Porous Medium

The mass exchange between the surface of a model capillary porous medium and the adjacent gas-side boundary layer is studied in the limiting condition of isothermal, slow drying. In order to quantify the role and significance of liquid films in the mass exchange process, three-dimensional pore network Monte Carlo simulations are carried out systematically in the presence and absence of discrete capillary rings. The pore network simulations performed with capillary rings show a noticeable delay in transition from the capillary-supported regime to the diffusion-controlled regime. These simulation results differ significantly from the predictions of classical pore network models without liquid films, and they appear to be more consistent with the experiments conducted with real porous systems. As compared to classical pore network models, the pore network model with rings seems to predict favorably the spatiotemporal evolution of wet and dry patches at the medium surface as well as of their relative contributions to the net mass exchange rate. This is apparent when the analytical solution of the commonly used Schlünder’s model is examined against the numerical simulations conducted using classical and ring pore network models.

Simulation of the growth of sucrose crystals in a sugar-containing solution

Crystallization is one of the most important steps in the technological flow of commodity sugar. By its nature, it develops in a fairly wide temperature range, conditions of varying concentration of the solution, its peptization and other mass-exchange process of formation and growth of sugar crystals in a sugar solution by diffusion transfer in it sucrose molecules. To this it is necessary to add such complicating physical and mathematical formalization phenomena, affecting crystallization, such as the shape of the crystal, purity, viscous properties and surface tension of the solution, the presence of non-sugars, etc. Therefore, among the factors that determine the whole process, the factors usually take place, keeping among them only priority and most important from the point of view of the study. The article, unlike known analogues, provides justification and quantitative analysis of the kinetics of the sucrose crystallization process, taking into account the features of the crystal shape and diffusion properties of the solution. From the point of view of classical diffusion theory, the phenomenon of crystallization is interpreted as molecular with infinite rate of perilation from the source of diffusion transfer in the solution of sucrose molecules, so that the concentration in the sugar-containing liquid system is also supposed to change instantly at each point. However, since in the real world this effect is not observed, in order to resolve this contradiction, introduce the concepts of the indignant and unperturbed, separated by the diffusion front of the concentration of the regions of these phase states. Using the kinematic characteristics of the front, determine the time of the crystallization process in general in both phases. This allows us to calculate the processing period of the solution with greater accuracy than the results obtained on the basis of classical theory.

Experimental studies of unsteady processes of cryogenic liquid evaporation in rocket tank model

The program and the methodology of the experiment and the results of the experiment have been developed. The experimental bench and metrological support have been created, liquid nitrogen (LN) has been considered as a model liquid. A database of heat and mass exchange process parameters (pressure, temperature) under the modes of tank inflation with helium gas up to 2 atm., given external thermal loading, pressure relief after reaching 4 atm. up to 1 atm. The technique of processing the results of pressure and temperature measurements with the assumptions and limitations is given.

INFLUENCE OF VARIOUS FACTORS ON RADIANT AND CONVECTION HEATING OF GREENHOUSE

The traditional heating of greenhouses (based on liquid or air) lacks efficiency, when it concerns energy-saving or economic expenditures. The agricultural industry is therefore inter-ested in the innovative approach to the power supply of greenhouses. The use of geothermal sources, biofuel, heating pumps and other conventional greenhouse heating methods is not al-ways reasonable, as their application depends on location of an object, ecological factors and others. This research investigates a complex heating, when convection heating of the green-house territory is maintained by temperature using ceiling infrared radiators. The aim of the paper is to study the influence of the outdoor air temperature, thermal prop-erties of the perimeter walls and soil surface absorbing capacity on the heating power of a greenhouse within the proposed method of radiant and convection heating. A system of complex heatand material-balance equations is used to calculate the greenhouse perimeter walls and the soil surface. The research results show the dependency of the total heating power when calculated with regard to the outdoor temperature, heat resistance properties of the perimeter walls and the soil surface absorbing capacity. The results obtained can be used to justify the efficiency of the radiant and convection heat-ing of the greenhouse in specific climatic conditions. The scientific novelty of the paper is the proposed method of calculating which accounts of multiple heater reflection, the influence of the mass-exchange process inside the greenhouse as well as the absorbing soil properties.