scholarly journals Investigation of Regularities of Heat and Mass Transfer and Phase Transitions during Water Droplets Motion through High-Temperature Gases

2014 ◽  
Vol 6 ◽  
pp. 865856 ◽  
Author(s):  
Roman S. Volkov ◽  
Olga V. Vysokomornaya ◽  
Genii V. Kuznetsov ◽  
Pavel A. Strizhak
Keyword(s):  
Mass Transfer ◽  
Phase Transitions ◽  
High Temperature ◽  
Heat And Mass Transfer ◽  
Water Droplet ◽  
Small Neighborhood ◽  
Droplet Evaporation ◽  
Optical Methods ◽  
Water Droplets ◽  
Two Phase

The macroscopic regularities of heat and mass transfer and phase transitions during water droplets motion through high-temperature (more than 1000 K) gases have been investigated numerically and experimentally. Water droplet evaporation rates have been established. Gas and water vapors concentrations and also temperature values of gas-vapor mixture in small neighborhood and water droplet trace have been singled out. Possible mechanisms of droplet coagulation in high-temperature gas area have been determined. Experiments have been carried out with the optical methods of two-phase gas-vapor-droplet mixtures diagnostics (“Particle Image Velocimetry” and “Interferometric Particle Imaging”) usage to assess the adequateness of developed heat and mass transfer models and the results of numerical investigations. The good agreement of numerical and experimental investigation results due to integral characteristics of water droplet evaporation has been received.

scholarly journals Influence of radiative heat and mass transfer mechanism in system “water droplet-high-temperature gases” on integral characteristics of liquid evaporation

2015 ◽  
Vol 19 (5) ◽  
pp. 1541-1552 ◽  
Author(s):  
Dmitrii Glushkov ◽  
Genii Kuznetsov ◽  
Pavel Strizhak
Keyword(s):  
Mass Transfer ◽  
High Temperature ◽  
Heat And Mass Transfer ◽  
Water Droplet ◽  
Radiative Heat ◽  
Transfer Mechanism ◽  
Water Droplets ◽  
Mass Transfer Mechanism ◽  
Integral Characteristics ◽  
Liquid Evaporation

Physical and mathematical (system of differential equations in private derivatives) models of heat and mass transfer were developed to investigate the evaporation processes of water droplets and emulsions on its base moving in high-temperature (more than 1000 K) gas flow. The model takes into account a conductive and radiative heat transfer in water droplet and also a convective, conductive and radiative heat exchange with high-temperature gas area. Water vapors characteristic temperature and concentration in small wall-adjacent area and trace of the droplet, numerical values of evaporation velocities at different surface temperature, the characteristic time of complete droplet evaporation were determined. Experiments for confidence estimation of calculated integral characteristics of processes under investigation - mass liquid evaporation velocities were conducted with use of cross-correlation recording video equipment. Their satisfactory fit (deviations of experimental and theoretical velocities were less than 15%) was obtained. The influence of radiative heat and mass transfer mechanism on characteristics of endothermal phase transformations in a wide temperature variation range was established by comparison of obtained results of numerical simulation with known theoretical data for ?diffusion? mechanisms of water droplets and other liquids evaporation in gas.

scholarly journals Modelling of Heat and Mass Transfer for Wire-Based Additive Manufacturing Using Electric Arc and Concentrated Sources of Energy

2018 ◽  
Vol 7 (4.38) ◽  
pp. 741
Author(s):  
Dmitriy Trushnikov ◽  
Anatoly Perminov ◽  
Shengyong Pang ◽  
K. P. Karunakaran ◽  
Vladimir Belenkiy ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Phase Transitions ◽  
Additive Manufacturing ◽  
Heat Source ◽  
Heat And Mass Transfer ◽  
Initial Temperature ◽  
Fluid Motion ◽  
Density Variation ◽  
Phase Region ◽  
Two Phase

The paper presents a model developed by the authors and aimed to describe heat and mass transfer during wire-based additive manufacturing, when electron beam, plasma or arc are used as energy sources in case of non-consumable electrode welding. The model describes non-stationary and non-equilibrium conjugated processes of heat and mass transfer in free-surface liquid metal. The solution of differential equations of viscous fluid motion (Navier-Stokes), with convective terms and at laminar flow, has become the model base. Melting and crystallization of the metal is recognized by heat release in a two-phase region. The material density variation during phase transitions of the first and the second order can be described by introducing a certain dependence on temperature. The model is able to consider the use of preliminary and additional induction heating by changing the initial temperature and establishing an additional distributed bulk heat source. Variables for the simulation of heat and mass transfer during additive formation are the intensity and type of the heat source, the plate initial temperature, the power density distribution, the intensity of the additional bulk heating, the dependence of material thermal and physical characteristics on temperature, the characteristics of the phase transitions, the motion velocity of the heat source, the rate of wire feeding. 

Water Droplet With Carbon Particles Moving Through High-Temperature Gases

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Roman S. Volkov ◽  
Maxim V. Piskunov ◽  
Genii V. Kuznetsov ◽  
Pavel A. Strizhak
Keyword(s):  
High Temperature ◽  
Water Droplet ◽  
Solid Particles ◽  
Optical Methods ◽  
Solid Inclusion ◽  
Two Phase ◽  
Carbon Particles ◽  
Liquid Evaporation ◽  
Liquid Flows ◽  
Particle Imaging

An experimental investigation was carried out on the influence of solid inclusions (nonmetallic particles with sizes from a few tens to hundreds of micrometers) on water droplet evaporation during motion through high-temperature gases (more than 1000 K). Optical methods for diagnostics of two-phase (gas and vapor–liquid) flows (particle image velocimetry (PIV) and interferometric particle imaging (IPI)) were used. It was established that introducing foreign solid particles into the water droplets intensifies evaporation rate in high-temperature gas severalfold. Dependence of liquid evaporation on sizes and concentration of solid inclusion were obtained.

Modelling of Combined Heat and Mass Transfer of Water Droplets in Thermal Technology Equipment

2011 ◽  
Author(s):  
Gintautas Miliauskas ◽  
Stasys Sinkunas ◽  
Kristina Norvaisiene ◽  
Kestutis Sinkunas
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Gas Flow ◽  
Thermal State ◽  
Droplet Evaporation ◽  
Heat Transfer Process ◽  
Droplet Surface ◽  
Convective Heating ◽  
Two Phase ◽  
Balancing Energy

Water droplet evaporation process is numerically modelled under various heat and mass transfer conditions. Regularities of heat transfer process interaction are examined. Modelling in this work was performed using the combined analytical–numerical method to investigate heat and mass transfer in the two-phase droplets-gas flow system. The influence of forced liquid circulation on the thermal state of droplets is taken into account by the effective coefficient of thermal conductivity. Calculating the rate of droplet evaporation and the intensity of convective heating, the influence of the Stefan’s hydrodynamic flow is taken into account. Balancing energy fluxes in the droplet to within one hundredth of a percent and using the fastest sinking the droplet surface temperature is determined.

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