scholarly journals Analysis the dynamics formation of a vapor supersonic jet under outflow from thin nozzle

2021 ◽  
Vol 2103 (1) ◽  
pp. 012219
Author(s):  
R Kh Bolotnova ◽  
V A Korobchinskaya ◽  
E A Faizullina
Keyword(s):  
Supersonic Jet ◽  
Mach Disk ◽  
Point Explosion ◽  
Water Mixture ◽  
Evaporation And Condensation ◽  
Mass Transfer Processes ◽  
Barrel Shock ◽  
Model Equations ◽  
Thin Nozzle ◽  
Account Heat

Abstract The dynamics formation of a vapor jet with near-critical state parameters outflowing from a high-pressure vessel through a thin nozzle is studied. The numerical modeling of this process, by using a system of model equations for gas-vapor-liquid mixture, which include conservation laws of mass, momentum, and energy of phases in accordance with one-pressure, one-velocity and two-temperature approximations, was conducted, taking into account heat and mass transfer processes of evaporation and condensation under conditions of equilibrium state with modified reactingTwoPhaseEulerFoam solver of open package OpenFOAM. The process of barrel shock formation in supersonic boiling jet with shaping Mach disk is shown. It was found that the process of boiling fluid outflow is accompanied by formation of vortex zones near axis of symmetry and leads to generation of acoustic wave pulses series preceding the main jet flow, which are the source of pulsations, observed in experiments. The justification of applied numerical method reliability is shown by comparing the computational and analytical solutions for Sedov’s problem of a point explosion in gas-water mixture at the plane case.

scholarly journals Experimental and numerical investigation of an axisymmetric supersonic jet

2001 ◽  
Vol 426 ◽  
pp. 177-197 ◽  
Author(s):  
B. MATÉ ◽  
I. A. GRAUR ◽  
T. ELIZAROVA ◽  
I. CHIROKOV ◽  
G. TEJEDA ◽  
...  
Keyword(s):  
Rotational Temperature ◽  
Supersonic Jet ◽  
High Sensitivity ◽  
Mach Disk ◽  
Low Velocity ◽  
Barrel Shock ◽  
Global Agreement ◽  
Temperature Maps ◽  
Subsonic Region ◽  
Subsonic Part

A comprehensive study of a steady axisymmetric supersonic jet of CO2, including experiment, theory, and numerical calculation, is presented. The experimental part, based on high-sensitivity Raman spectroscopy mapping, provides absolute density and rotational temperature maps covering the significant regions of the jet: the zone of silence, barrel shock, Mach disk, and subsonic region beyond the Mach disk. The interpretation is based on the quasi-gasdynamic (QGD) system of equations, and its generalization (QGDR) considering the translational–rotational breakdown of thermal equilibrium. QGD and QGDR systems of equations are solved numerically in terms of a finite-difference algorithm with the steady state attained as the limit of a time-evolving process. Numerical results show a good global agreement with experiment, and provide information on those quantities not measured in the experiment, like velocity field, Mach numbers, and pressures. According to the calculation the subsonic part of the jet, downstream of the Mach disk, encloses a low-velocity recirculation vortex ring.

Theoretical Considerations of Combined Thermal and Mass Transfer From a Vertical Flat Plate

1956 ◽  
Vol 23 (2) ◽  
pp. 295-301
Author(s):  
E. V. Somers
Keyword(s):  
Mass Transfer ◽  
Flat Plate ◽  
Fluid Motion ◽  
Practical Case ◽  
Forced Circulation ◽  
Evaporation And Condensation ◽  
Mass Transfer Processes ◽  
Convective Thermal ◽  
Theoretical Considerations ◽  
Vertical Flat Plate

Abstract In free-convective processes involving both thermal and mass transfer, since the driving force for the fluid motion has its source solely in the density difference from ambient, it is necessary to consider the thermal and mass-transfer processes simultaneously in solving any given problem. The present problem involves evaporation and condensation phenomena associated with free-convective thermal and mass transfer from a wetted isothermal vertical flat plate to a gas at an ambient temperature and mass concentration different from that on the plate. This problem presents itself in the practical case of vaporization cooling of equipment without forced circulation of the ambient gas.

scholarly journals Identification of heat and mass transfer processes in bread during baking

2005 ◽  
Vol 9 (2) ◽  
pp. 73-86 ◽  
Author(s):  
Ivanka Zheleva ◽  
Vesselka Kambourova
Keyword(s):  
Partial Differential Equations ◽  
Moisture Content ◽  
Differential Equations ◽  
Moisture Transfer ◽  
Partial Differential ◽  
Linear Partial Differential Equations ◽  
Mass Transfer Processes ◽  
Model Equations ◽  
Heat And Moisture ◽  
Simultaneous Heat

A mathematical model representing temperature and moisture content in bread during baking is developed. The model employs the coupled partial differential equations proposed by Luikov. Dependences of mass and thermal properties of dough on temperature and moisture content are included in the model. Resulting system of non-linear partial differential equations in time and one space dimension is reduced to algebraic system by applying a finite difference numerical method. A numerical solution of the model equations is obtained and simultaneous heat and moisture transfer in dough during baking is predicted. The changes of temperature and moisture content during the time of the process are graphically presented and commented.

Parallel DSMC Simulation of a Single Under-Expanded Free Orifice Jet From Transition to Near-Continuum Regime

2005 ◽  
Vol 127 (6) ◽  
pp. 1161-1170 ◽  
Author(s):  
J.-S. Wu ◽  
S.-Y. Chou ◽  
U.-M. Lee ◽  
Y.-L. Shao ◽  
Y.-Y. Lian
Keyword(s):  
Flow Structure ◽  
Three Dimensional ◽  
Direct Simulation Monte Carlo ◽  
Mean Free Path ◽  
Mach Disk ◽  
Orifice Diameter ◽  
Axial Distance ◽  
Free Jet ◽  
Barrel Shock ◽  
Dynamic Domain Decomposition

This paper describes the numerical analysis of the flow structure of a single underexpanded argon free jet issuing into a lower-pressure or vacuum environment using the parallel three-dimensional direct simulation Monte Carlo (DSMC) method employing dynamic domain decomposition. Unstructured and tetrahedral solution-based refined mesh depending on the local mean free path is used to improve the resolution of solution. Simulated Knudsen numbers of the stagnation conditions based on orifice diameter, Reynolds numbers based on the conditions at the orifice exit, and stagnation-to-background pressure ratios are in the range of 0.0005–0.1, 7–1472, and 5-∞, respectively, where “∞” represents vacuum condition in the background environment. Results show that centerline density decays in a rate proportional to the inverse of the square of the axial distance (z−2) from the orifice for all ranges of flow in the current study. The more rarefied the background condition is, the longer the z−2-regime is. In addition, a distinct flow structure, including barrel shock, Mach disk and jet boundary, is clearly identified as the Knudsen number reaches as low as 0.001. Predicted location and size of Mach disk in the near-continuum limit (Kn=0.001,0.0005) are found to be in reasonable agreement with experimental results in the continuum regime.

Investigation of Vortex Structures for Supersonic Jet Interaction Flowfield

2015 ◽  
Vol 798 ◽  
pp. 546-550 ◽  
Author(s):  
Asel Beketaeva ◽  
Amr H. Abdalla ◽  
Yekaterina Moisseyeva
Keyword(s):  
Stokes Equations ◽  
Pressure Ratio ◽  
Supersonic Jet ◽  
Three Dimensional ◽  
Horseshoe Vortex ◽  
Bow Shock ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Trailing Vortices ◽  
Barrel Shock

The three-dimensional supersonic turbulent flow in presence of symmetric transverse injection of round jet is simulated numerically. The simulation is based on the Favre-averaged Navier-Stokes equations coupled with Wilcox’s turbulence model. The numerical solution is performed using ENO scheme and is validated with the experimental data that include the pressure distribution on the wall in front of the jet in the plane symmetry. The numerical simulation is used to investigate in detail the flow physics for a range of the pressure ratio . The well-known primary shock formations are observed (a barrel shock, a bow shock, and the system of λ-shock waves), and the vortices are identified (horseshoe vortex, an upper vortex, two trailing vortices formed in the separation region and aft of the bow shock wave, two trailing vortices that merge together into one single rotational motion). During the experiment the presence of the new vortices near the wall behind the jet for the pressure ratio is revealed.

An investigation of two-phase grain-fluid model on the development process of debris flow fan

2021 ◽  
Author(s):  
Hock Kiet Wong ◽  
Ching-Yuan Ma ◽  
Chi-Jyun Ko ◽  
Yih-Chin Tai
Keyword(s):  
Debris Flow ◽  
Fluid Model ◽  
Fluid Flows ◽  
Deposition Process ◽  
Sediment Concentration ◽  
Water Mixture ◽  
Flume Experiments ◽  
Two Phase ◽  
Terrain Following ◽  
Model Equations

<p>The movement of a debris flow is channelized by the mountain topography. It slows down and begins to deposit, forming the so-called debris-flow fan, when the slope is gentle. Since the flow body is composed of solid grains with interstitial fluid, the solid fraction may vary and plays a crucial role in the deposition process. In the present study, an entrainment-deposit law together with the two-phase model for grain-fluid flows (Tai et al., 2019) is proposed for describing the development of a debris flow fan. The model equations are derived in a terrain-following coordinate system, in which the coordinates are in coincidence with the topographic surface and the deposition/erosion is treated as the sub-topography. Numerical validation is performed against flume experiments (Tsunetaka et al., 2019), where the sediment-water mixture is released from a channel and merging into a gentle inclined flat plain via a steady water inflow. In this study, we shall illustrate the impacts of the sediment concentration on the evolution of the debris-flow fan, such as the location, distribution, geometry of debris-flow fan as well as the flow paths. </p>

scholarly journals Mathematical modelling of solid desiccant systems

2018 ◽  
Vol 23 ◽  
pp. 00029
Author(s):  
Anna Pacak ◽  
Demis Pandelidis ◽  
Sergey Anisimov
Keyword(s):  
Heat Exchanger ◽  
Humidity Ratio ◽  
Desiccant Wheel ◽  
Transfer Processes ◽  
Mass Transfer Processes ◽  
System 2 ◽  
Model Equations ◽  
System 1 ◽  
The Mathematical Model ◽  
Method Show

In this study, the mathematical model equations for solid desiccant system integrated with indirect evaporative coolers with Maisotsenko - Cycle are presented. The authors chose the modified ε–NTU method to describe heat and mass transfer processes in regenerative indirect evaporative cooler and desiccant wheel. The models based on the ε–NTU method show satisfactory agreement with experimental results. That is why this method allows to analyze and develop the performance of solid desiccant systems. In this study, the models allowed to prove that solid desiccant system with an additional heat exchanger before the desiccant wheel (System 1) obtains higher thermal COP values, higher humidity ratio drop and lower supply airflow temperatures in comparison to system with only one heat exchanger after the desiccant wheel (System 2).

scholarly journals Liquid Ring Vacuum Pumps for Heat and Mass Transfer Processes

2021 ◽  
Vol 27 (3) ◽  
pp. 428-441
Author(s):  
D. V. Nikitin ◽  
Yu. V. Rodionov ◽  
M. A. S. Makhmud ◽  
A. I. Skomorokhova ◽  
A. N. Pakhomov ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Vacuum Pump ◽  
Specific Power ◽  
Two Stage ◽  
Second Stage ◽  
Mass Transfer Processes ◽  
Impulse Drying ◽  
Liquid Ring ◽  
Account Heat

The paper examines the calculation of a liquid ring vacuum pump, using the example of the drying process of various materials. It was found that for two-stage convective vacuum-impulse drying it is economically efficient to use a two-stage liquid ring vacuum pump with the ability to turn off the second stage. A method for calculating the specific power of one-stage and two-stage liquid ring vacuum pumps, taking into account heat and mass transfer and thermal processes that occur during operation is proposed.

Thermal Characteristics of Conventional and Flat Miniature Axially Grooved Heat Pipes

1995 ◽  
Vol 117 (4) ◽  
pp. 1048-1054 ◽  
Author(s):  
D. Khrustalev ◽  
A. Faghri
Keyword(s):  
Thermal Characteristics ◽  
Heat Pipes ◽  
Heat Fluxes ◽  
Vertical Position ◽  
Maximum Heat ◽  
Evaporation And Condensation ◽  
Maximum Heat Transfer ◽  
Mass Transfer Processes ◽  
Grooved Surface ◽  
Heat Transfer Capacity

A detailed mathematical model of low-temperature axially grooved heat pipes (AGHP) is developed in which the fluid circulation is considered along with the heat and mass transfer processes during evaporation and condensation. The results obtained are compared to existing experimental data. Both capillary and boiling limitations are found to be important for the flat miniature copper-water heat pipe, which is capable of withstanding heat fluxes on the order of 40 W/cm2 applied to the evaporator wall in the vertical position. The influence of the geometry of the grooved surface on the maximum heat transfer capacity of the miniature AGHP is demonstrated.

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