Conditions of Intensive Evaporation of Heterogeneous Water Droplet in High Temperature Gas Environment

2015 ◽  
Vol 32 (3) ◽  
pp. 349-355 ◽  
Author(s):  
O. V. Vysokomornaya ◽  
G. V. Kuznetsov ◽  
P. A. Strizhak
Keyword(s):  
Numerical Simulation ◽  
Mass Transfer ◽  
High Temperature ◽  
Water Droplet ◽  
Sufficient Conditions ◽  
Solid Inclusion ◽  
Necessary And Sufficient ◽  
Heating Up ◽  
System Water ◽  
High Temperature Gas

AbstractThe results of a numerical simulation of heat and mass transfer during evaporation of a water droplet with solid inclusion in air at temperature as high as 1000K are presented. Typical heating steps of droplet until it reaches the conditions of intensive evaporation (i.e.the interface “solid inclusion – liquid” reaches the boiling temperature) are described. The roles played by the external air temperature and by the main properties of inclusion are detailed. The droplet size, the relation between the sizes of inclusion and a liquid layer during the heating up is determined. The necessary and sufficient conditions of intensive evaporation in the system “water droplet with solid inclusion in high-temperature air” are pointed out.

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.

Numerical Simulation of Accident Scenario in High Temperature Gas Cooled (Pebble Bed) Nuclear Reactors

2012 ◽  
Author(s):  
Geoffrey J. Peter
Keyword(s):  
Numerical Simulation ◽  
High Temperature ◽  
Boundary Conditions ◽  
Nuclear Reactors ◽  
Numerical Study ◽  
Packed Bed ◽  
Pebble Bed ◽  
Accident Scenario ◽  
Set Up ◽  
High Temperature Gas

The accident scenario resulting from blockages due to the retention of dust in the coolant gas or from the rupture of one or more fuel particles used in the High Temperature Gas Cooled (Pebble Bed) Nuclear Reactors considered for the next generation of Advanced High Temperature Reactors (AHTR), for nuclear power production, and for high-temperature hydrogen production using nuclear reactors to reduce the carbon footprint is examined in this paper. Blockages can cause local variations in flow and heat transfer that may lead to hot spots within the bed that could compromise reactor safety. Therefore, it is important to know the void fraction distribution and the interstitial velocity field in the packed bed. The blockage for this numerical study simulated a region with significantly lower void than that in the rest of the bed. Finite difference technique solved the simplified continuity, momentum, and energy equations. Any meaningful outcome of the solution depended largely upon the validity of the boundary conditions. Among them, the inlet and outlet velocity profiles required special attention. Thus, a close approximation to these profiles obtained from an experimental set-up established the boundary conditions. This paper presents the development of the elliptic-partial differential equation for a bed of pebbles, and the solution procedure. The paper also discusses velocity and temperature profiles obtained from both numerical and experimental setup, with and without effect of blockage. In addition, the paper compares the results obtained from the experimental set-up with numerical simulation using a commercially available code that uses finite element techniques.

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