Mathematical Simulation of the Heat and Mass Transfer in the Movement of Liquid Droplets in a Gas Medium Under the Condi
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Journal of Engineering Physics and Thermophysics, Vol. 93, No. 5, September, 2020
HEAT TRANSFER IN PHASE TRANSFORMATIONS MATHEMATICAL SIMULATION OF THE HEAT AND MASS TRANSFER IN THE MOVEMENT OF LIQUID DROPLETS IN A GAS MEDIUM UNDER THE CONDITIONS OF THEIR INTENSE PHASE TRANSFORMATIONS D. V. Antonov, G. V. Kuznetsov, and P. A. Strizhak
UDC 536.4
A physical and mathematical model of the movement of a liquid droplet in a high-temperature air flow has been formulated with regard for the main factors of this movement: the inertia of the droplet, its viscous friction, the surface tension of the liquid in it, the air drag, the gravity, lift, and Magnus forces acting on the droplet, its turbophoresis and thermophoresis, the convective heat flows inside the droplet, the turbulence and compressibility of the carrying medium, the concentration of the dispersed phase in it, the nonstationarity of the movement of the droplet, its phase transformations, the collisions of the droplet with the neighboring liquid droplets in the gas flow, the partial fragmentation of the droplet, and its breakdown. Numerical and experimental investigations of the influence of the indicated factors on the velocity of movement, the heating, and the intensity of evaporation of a liquid droplet in a high-temperature gas medium have been performed. The results of these investigations were generalized for determining the possible applications of the model developed. Keywords: heat and mass transfer, gas medium, liquid droplet, phase transformations, high-temperature heating, mathematical simulation. Introduction. Vapor–gas flows with liquid droplets heated to a high temperature (higher that 600 K) occur in the extinguishing of fires, in the thermal purification of liquids, in contact heat exchangers, and in different technological processes [1–5]. The optimum parameters of plants, units, systems, and apparatus operating with such flows are determined empirically as a rule [6] because the concentration of the dispersed phase (droplets) in these flows is fairly difficult to reliably estimate on the basis of the modern theory of heat and mass exchange and phase transformations, especially at temperatures of 500–1500 K. The number and sizes of droplets in a gas–vapor medium can change substantially under the action of different forces and as a result of their coagulation or breakage in the process of collisions of them with each other [7, 8]. The development of the theory of the processes occurring in vapor–gas flows including liquid droplets under the conditions of their rapid heating to high temperatures was complicated until recently by the lack of experimental data on the concentration of the liquid phase in such flows, the velocity of movement of droplets in them, the heating of the droplets, and their evaporation. In [9–17], experiments on the recording of the characteristics of movement of liquid droplets in high-temperature gas flows have been conducted with the use of the optical investigation methods PIV, Stereo PIV, Micro PIV, Tomo PIV, PTV, IP
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