scholarly journals A New Finite-Conductivity Droplet Evaporation Model Including Liquid Turbulence Effect

2006 ◽  
Vol 129 (8) ◽  
pp. 1082-1086 ◽  
Author(s):  
M. S. Balasubramanyam ◽  
C. P. Chen ◽  
H. P. Trinh
Keyword(s):  
Film Theory ◽  
Droplet Evaporation ◽  
Finite Conductivity ◽  
Effective Thermal Diffusivity ◽  
New Approach ◽  
Atomization Spray ◽  
Turbulence Effects ◽  
Turbulence Effect ◽  
Evaporating Spray ◽  
Two Temperature

A new approach to account for finite thermal conductivity and turbulence effects within atomizing droplets of an evaporating spray is presented in this paper. The model is an extension of the T-blob and T-TAB atomization/spray model of Trinh and Chen [Atomization and Sprays, 16(6), pp. 907–932]. This finite conductivity model is based on the two-temperature film theory in which the turbulence characteristics of the droplet are used to estimate the effective thermal diffusivity for the liquid-side film thickness. Both one-way and two-way coupled calculations were performed to investigate the performance of this model against the published experimental data.

A Turbulence Model of Bi-Component Fuel Droplet for Atomizing Sprays

2011 ◽  
Author(s):  
Omid Samimi Abianeh ◽  
C. P. Chen
Keyword(s):  
Thermal Conductivity ◽  
Film Theory ◽  
Fuel Vapor ◽  
Finite Conductivity ◽  
Fuel Droplets ◽  
Turbulence Effects ◽  
Turbulence Effect ◽  
Injector Flows ◽  
High Reynolds ◽  
Droplet Liquid

A new approach to account for simultaneously finite thermal conductivity, finite mass diffusivity and turbulence effects within atomizing liquid sprays is presented in this paper. The main contribution of this paper is to incorporate the liquid turbulence effect in modeling the multi-component droplet liquid jet evaporation. For this study, we consider a binary mixture of heptane and decane liquid fuel injected into a hot gas environment. The finite conductivity model is based on a newly developed two-temperature two-layer film theory of Chen et al. [1], where the turbulence characteristics of the droplet are used to estimate the effective thermal conductivity. Fuel droplets inherit turbulence from high Reynolds number issuing liquid injector flows. The present paper extends the formulation of Chen et al. [1] to estimate effective mass transfer diffusivity within the drop. In this model four regions are considered, interior and the surface of the droplet, the liquid gas interface and the surrounding gas phase. An approximate solution to the quasi-steady energy equation was used to derive an explicit expression for the heat flux from the surrounding gas to the droplet–gas interface, with inter-diffusion of fuel vapor and the surrounding gas taken into account. The thermo-transport properties including their dependence on temperature are considered. Validation studies were carried out by comparison with the experimental results.

Advanced Model of Bi-Component Fuel Droplet Heating and Evaporating With Liquid Turbulence Effects at High Pressure

2011 ◽  
Author(s):  
Omid Samimi Abianeh ◽  
C. P. Chen
Keyword(s):  
Thermal Conductivity ◽  
High Pressure ◽  
High Pressures ◽  
Film Theory ◽  
Ideal Gas ◽  
Fuel Vapor ◽  
Finite Conductivity ◽  
Fuel Droplet ◽  
Liquid Behavior ◽  
Turbulence Effects

A new approach to account for finite thermal conductivity, finite mass diffusivity and turbulence effects within atomizing liquid sprays at high pressure condition is presented in this paper. The finite conductivity model is based on a newly developed two-layer film theory, where the turbulence characteristics of the droplet are used to estimate the effective thermal conductivity [1]. The present paper extends the formulation to model the multi-component mass diffusivities within the droplet phase at high pressures but less than components critical pressures. An approximate solution to the quasi-steady energy equation was used to derive an explicit expression for the heat flux from the surrounding gas to the droplet–gas interface, with inter-diffusion of fuel vapor and the surrounding gas taken into account. The Peng-Robinson equation of state (EOS) is used for extension of the model to the high pressures. The latent heat of vaporization and fuel enthalpies are also corrected for high pressure. The model includes the non-ideal gas and liquid behavior, and variable thermo-transport properties including their dependence on pressure and temperature. For this study a mixture of decane and hexadecane fuel droplet was considered. Predictions of the high-pressure single droplet model are in good agreement with the available data in literature.

A New Approach for Reliable Estimation of Hydraulic Fracture Properties Using Elliptical Flow Data in Tight Gas Wells

2009 ◽  
Vol 12 (02) ◽  
pp. 254-262 ◽  
Author(s):  
Yueming Cheng ◽  
W. John Lee ◽  
Duane A. McVay
Keyword(s):  
Hydraulic Fracture ◽  
Finite Conductivity ◽  
Tight Gas ◽  
Well Test ◽  
Pressure Data ◽  
Gas Wells ◽  
New Approach ◽  
Fracture Properties ◽  
Elliptical Flow ◽  
Half Length

Summary Gas wells in low-permeability formations usually require hydraulic fracturing to be commercially viable. Pressure transient analysis in hydraulically fractured tight gas wells is commonly based on analysis of three flow regimes: bilinear, linear, and pseudoradial. Without the presence of pseudoradial flow, neither reservoir permeability nor fracture half-length can be independently estimated. In practice, as pseudoradial flow is often absent, the resulting estimation is uncertain and unreliable. On the other hand, elliptical flow, which exists between linear flow and pseudoradial flow, is of long duration (typically months to years). We can acquire much rate and pressure data during this flow regime, but no practical well test analysis technique is currently available to interpret these data. This paper presents a new approach to reliably estimate reservoir and hydraulic fracture properties from analysis of pressure data obtained during the elliptical flow period. The method is applicable to estimate fracture half-length, formation permeability, and skin factor independently for both infinite- and finite-conductivity fractures. It is iterative and features rapid convergence. The method can estimate formation permeability when pseudoradial flow does not exist. Coupled with stable deconvolution technology, which converts variable production-rate and pressure measurements into an equivalent constant-rate pressure drawdown test, this method can provide fracture-property estimates from readily available, noisy production data. We present synthetic and field examples to illustrate the procedures and demonstrate the validity and applicability of the proposed approach.

scholarly journals New Approach, Taking into Account Elastic and Inelastic Processes, for Transport Properties of a two Temperature Plasma

1985 ◽  
Vol 40 (9) ◽  
pp. 885-891 ◽  
Author(s):  
C. Bonnefoi ◽  
J. Aubreton ◽  
J.-M. Mexmain
Keyword(s):  
Thermal Conductivity ◽  
Electron Temperature ◽  
Plasma Electron ◽  
Temperature Plasma ◽  
Heavy Particles ◽  
New Approach ◽  
Definition Of ◽  
Thermal Conductivity Λ ◽  
Two Temperature ◽  
Inelastic Processes

Abstract We have developed a modified Chapman-Enskog method for a two-temperature partially ionized plasma: electron temperature (Te) and heavy particles temperature (Th). We introduce a new definition of the diffusion forces and then calculate the reactive thermal conductivity λR.

An Investigation on Turbulence Assessment Methods for the Offshore Helideck Availability Study

2015 ◽  
Author(s):  
Sung-In Park ◽  
Min-Ho Kim ◽  
Seungmin Kwon ◽  
Hye-Ryoun Chi ◽  
Jae-Bong Lee ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Offshore Platforms ◽  
Airflow Velocity ◽  
3 Dimensional ◽  
Effect Assessment ◽  
Turbulence Effects ◽  
Turbulence Effect ◽  
Computational Fluid Dynamics Cfd ◽  
The Mean ◽  
Availability Assessment

The aim of this study is to investigate methods of assessing the turbulence effect for the helideck availability study. Due to the limited space on offshore platforms, a helideck is normally positioned on cramped areas and this makes turbulence flows around the helideck. CAP 437, the representative standard for the offshore helideck design suggests various criteria for the helideck availability assessment and recommends a Standard Deviation of Vertical airflow Velocity (SDVV) value to be used for the turbulence effect assessment. Although there is a specific value of SDVV recommended in CAP 437, different interpretations are possible in the calculation of the value resulting in totally different assessment outcomes even under the same analysis condition. In this study, two different approaches are investigated and their results are compared. One approach is based on the spatial variation of the mean vertical velocity while the other utilizes the Turbulence Kinetic Energy (TKE) value from the Computational Fluid Dynamics (CFD) simulation. With a CFD tool, Kamelon FireEX (KFX), a couple of 3-dimensional simulations is performed and turbulence flows around an offshore semi-rig are obtained. SDVV values are calculated using both approaches and compared each other as well as with criteria recommended in CAP 437. It is hoped that the result of this study is helpful to engineers for understanding evaluation methods of turbulence effects in the helideck availability assessment.

scholarly journals Numerical Simulation of Liquid Jet Atomization Including Turbulence Effects

2007 ◽  
Vol 129 (4) ◽  
pp. 920-928 ◽  
Author(s):  
Huu P. Trinh ◽  
C. P. Chen ◽  
M. S. Balasubramanyam
Keyword(s):  
Current Model ◽  
Droplet Breakup ◽  
Spray Angle ◽  
Liquid Jet ◽  
Primary Breakup ◽  
Turbulence Effects ◽  
Turbulence Effect ◽  
Blob Model ◽  
Secondary Breakup ◽  
Liquid Jet Atomization

This paper describes numerical implementation and validation of a newly developed hybrid model, T-blob/T-TAB, into an existing computational fluid dynamics (CFD) program for primary and secondary breakup simulation of liquid jet atomization. This model extends two widely used models, the Kelvin-Helmholtz (KH) instability of Reitz (the “blob” model) (1987, Atomization Spray Technol., 3, pp. 309–337) and the Taylor-Analogy-Breakup (TAB) secondary droplet breakup of O’Rourke and Amsden (1987, SAE Technical Paper No. 872089) to include liquid turbulence effects. In the primary breakup model, the level of the turbulence effect on the liquid breakup depends on the characteristic scales and flow conditions at the liquid nozzle exit. Transition to the secondary breakup was modeled based on energy balance, and an additional turbulence force acted on parent drops was modeled and integrated into the TAB governing equation. Several assessment studies are presented, and the results indicate that the existing KH and TAB models tend to underpredict the product drop size and spray angle, whereas the current model provides superior results when compared to the measured data.

A Film-Theory-Based Model for a Multicomponent Droplet Evaporation at Both Low- and High-Pressure Environments

2005 ◽  
Vol 128 (3) ◽  
pp. 290-294 ◽  
Author(s):  
Guangfa Yao
Keyword(s):  
Mass Transfer ◽  
High Pressure ◽  
Heat And Mass Transfer ◽  
Film Theory ◽  
Droplet Evaporation ◽  
Published Data ◽  
Real Gas ◽  
New Model ◽  
The Real ◽  
Transfer Equations

Modeling of a multicomponent droplet evaporation is investigated based on the film theory in both low- and high-pressure environments. Unlike the classical film theory, effects of blowing due to evaporation on gas-side heat and mass transfer are included through the film thicknesses. The corresponding gas-side heat and mass transfer equations are derived in terms of film thicknesses. In a high-pressure situation, the real gas behavior is considered. Based on the derived equations, a new model for multicomponent droplet evaporation is formulated and validated against the published data.

scholarly journals Spectral tomographic analysis of Bremsstrahlung X-rays generated in a laser-produced plasma

2016 ◽  
Vol 34 (4) ◽  
pp. 645-654 ◽  
Author(s):  
Y.J. Rhee ◽  
S.M. Nam ◽  
J. Peebles ◽  
H. Sawada ◽  
M. Wei ◽  
...  
Keyword(s):  
Experimental Data ◽  
Variational Principle ◽  
Energy Distribution ◽  
Tomographic Reconstruction ◽  
Spectral Characteristics ◽  
X Rays ◽  
Temperature Model ◽  
New Approach ◽  
Tomographic Analysis ◽  
Two Temperature

AbstractA new approach is proposed to analyze Bremsstrahlung X-rays that are emitted from laser-produced plasmas (LPP) and are measured by a stack type spectrometer. This new method is based on a spectral tomographic reconstruction concept with the variational principle for optimization, without referring to the electron energy distribution of a plasma. This approach is applied to the analysis of some experimental data obtained at a few major laser facilities to demonstrate the applicability of the method. Slope temperatures of X-rays from LPP are determined with a two-temperature model, showing different spectral characteristics of X-rays depending on laser properties used in the experiments.

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