ON VARIABLE-PROPERTY, BLOWING, AND TRANSIENT EFFECTS IN CONVECTIVE DROPLET EVAPORATION WITH INTERNAL CIRCULATION

1986 ◽  
Author(s):  
R. Haywood ◽  
Metin Renksizbulut
Keyword(s):  
Droplet Evaporation ◽  
Transient Effects ◽  
Internal Circulation ◽  
Variable Property

scholarly journals Subcritical and Supercritical Droplet Evaporation within a Zero Gravity Environment; On the Discrepancies between Theoretical and Experimental Results

2009 ◽  
Vol 1 (3) ◽  
pp. 317-338 ◽  
Author(s):  
Hongtao Zhang ◽  
Vasudevan Raghavan ◽  
George Gogos
Keyword(s):  
High Pressure ◽  
Ambient Pressure ◽  
Local Maximum ◽  
Droplet Evaporation ◽  
Experimental Results ◽  
Spherically Symmetric ◽  
Transient Effects ◽  
Ambient Temperatures ◽  
Wide Range ◽  
Thermo Physical Properties

A comprehensive axisymmetric numerical model has been developed to study high pressure droplet evaporation. In this model, high pressure transient effects, variable thermo-physical properties and inert species solubility in the liquid-phase are considered. First, the axisymmetric model has been utilized to explain the discrepancy between theoretical and experimental results on microgravity droplet evaporation that has been reported in the literature [J.R. Yang and S.C. Wong, Ref. 35]. In addition, this effort led to a thorough validation of the model against the most extensive microgravity experimental data available in the literature on droplet evaporation. Second, the validated model has been utilized to investigate spherically symmetric droplet evaporation for a wide range of ambient pressures and temperatures. The predictions show that the average droplet evaporation constant decreases with ambient pressure at sub-critical ambient temperatures, becomes insensitive to pressure at ambient temperatures around the critical temperature of the fuel and presents a local maximum while increasing with the ambient pressure at super-critical ambient temperatures.

scholarly journals Deviations from classical droplet evaporation theory

2021 ◽  
Vol 477 (2251) ◽  
pp. 20210078
Author(s):  
Joshua Finneran ◽  
Colin P. Garner ◽  
François Nadal
Keyword(s):  
Droplet Evaporation ◽  
Transient Effects ◽  
Predictive Tool ◽  
Transient Regimes ◽  
Wide Range ◽  
Classical Models ◽  
Cold Vapour ◽  
Input Domain ◽  
Steady Temperature Field ◽  
Transient Models

In this article, we show that significant deviations from the classical quasi-steady models of droplet evaporation can arise solely due to transient effects in the gas phase. The problem of fully transient evaporation of a single droplet in an infinite atmosphere is solved in a generalized, dimensionless framework with explicitly stated assumptions. The differences between the classical quasi-steady and fully transient models are quantified for a wide range of the 10-dimensional input domain and a robust predictive tool to rapidly quantify this difference is reported. In extreme cases, the classical quasi-steady model can overpredict the droplet lifetime by 80%. This overprediction increases when the energy required to bring the droplet into equilibrium with its environment becomes small compared with the energy required to cool the space around the droplet and therefore establish the quasi-steady temperature field. In the general case, it is shown that two transient regimes emerge when a droplet is suddenly immersed into an atmosphere. Initially, the droplet vaporizes faster than classical models predict since the surrounding gas takes time to cool and to saturate with vapour. Towards the end of its life, the droplet vaporizes slower than expected since the region of cold vapour established in the early stages of evaporation remains and insulates the droplet.

Spray Computations in a Centerbody Combustor

1989 ◽  
Vol 111 (4) ◽  
pp. 710-718 ◽  
Author(s):  
M. S. Raju ◽  
W. A. Sirignano
Keyword(s):  
Liquid Phase ◽  
Flow Field ◽  
Gas Phase ◽  
Linear Interpolation ◽  
Flame Stabilization ◽  
Integration Scheme ◽  
Transient Effects ◽  
Internal Circulation ◽  
Runge Kutta Method ◽  
Vaporization Process

A hybrid Eulerian–Lagrangian method is employed to model the reactive flow field of a centerbody combustor. The unsteady two-dimensional gas-phase equations are represented in Eulerian coordinates and liquid-phase equations are formulated in Lagrangian coordinates. The gas-phase equations based on the conservation of mass, momentum, and energy are supplemented by turbulence and combustion models. The vaporization model takes into account the transient effects associated with the droplet heating and liquid-phase internal circulation. The integration scheme is based on the TEACH algorithm for gas-phase equations, the Runge-Kutta method for liquid-phase equations, and linear interpolation between the two coordinate systems. The calculations show that the droplet penetration and recirculation characteristics are strongly influenced by the gas- and liquid-phase interaction in such a way that most of the vaporization process is confined to the wake region of the centerbody, thereby improving the flame stabilization properties of the flow field.

A Theoretical Study of Saline Droplet Evaporation in Solar-Thermal Driven Full Separation Multi Effect Distillation (FS-MED) System

2017 ◽  
Author(s):  
Yan Wei ◽  
Penghua Guo ◽  
Ben Xu ◽  
Thomas Rodriguez ◽  
Luis Escobar ◽  
...  
Keyword(s):  
Life Cycle ◽  
Water Droplet ◽  
Droplet Evaporation ◽  
Solar Thermal ◽  
Inorganic Salts ◽  
Detailed Calculation ◽  
Internal Circulation ◽  
Evaporation Model ◽  
Definition Of ◽  
Full Separation

The significant changes of population, environment and climate have led to the increased need for freshwater. However, the shortage of naturally available freshwater is becoming more frequent than ever. Desalination, removal of salt and other minerals from seawater, brackish water, and wastewater, is a promising solution to provide the increasing need of freshwater. Multi stage flashing (MSF) and multi effect distillation (MED) can be classified as conventional thermal-driven desalination technologies. Nevertheless, the disposal of high concentrated brine is a big environmental concern. Despite the tremendous improvements in conventional desalination technology, the desalination process is very energy consuming. Due to high expenses of the conventional energy resources, renewable energy sources can provide alternatives. Considering the fact that Concentrated Solar Power (CSP) has been significantly developed during the past two decades, inorganic salts are the perfect candidates as Heat Transfer Fluid (HTF) for high temperature applications in solar thermal energy storage, fully separating water and salts in the desalination process arises naturally, since the leftover salts can be collected instead of disposing them to the environment. A full separation multi effect distillation (FSMED) system was proposed by other researchers, where the air fed to the full separation tank (FST) is preheated by a heat source, and the highly concentrated brine from the last effect is sprayed in the FST, so that the brine droplets can be completely evaporated by leaving behind inorganic salts. Obviously, the full separation process of salts and water involves multiphase heat and mass transfer. However, a key question is the characterization of the lifetime of brine droplets inside the FST during its entire evaporation process, and the effects from the internal circulation to droplet evaporation. If the droplet has strong internal circulation, the definition of two stages of evaporation becomes inaccurate, it has to be corrected based on the detailed calculation of time scale at each stage. In the current study, a 1D quasi-steady evaporation model was developed to characterize the effects from internal circulation to the life cycle of droplets in the FST, compared with the results using the dynamic evaporation model. To simplify the analysis, water droplet with impurity particles was considered, and a case study was also provided to compare the life cycle of water droplets without internal circulation. Finally, a correction to the definition of two-stage of water droplet evaporation was provided. It is expected that the computation results will be beneficial for thermal driven desalination community.

HIGH-SPEED TRANSIENT EFFECTS IN CHALCOGENIDE GLASSES

1981 ◽  
Vol 42 (C4) ◽  
pp. C4-579-C4-582
Author(s):  
T. Shiraishi ◽  
D. Adler
Keyword(s):  
Chalcogenide Glasses ◽  
High Speed ◽  
Transient Effects
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