Heat and Mass Transports in Porous Wicks Driven by a Gas-Phase Diffusion Flame

2005 ◽  
Author(s):  
Mandhapati P. Raju ◽  
James S. T’ien
Keyword(s):  
Gas Phase ◽  
Diffusion Flame ◽  
Capillary Rise ◽  
Phase Region ◽  
Standoff Distance ◽  
Dimensional System ◽  
Liquid Region ◽  
Two Phase ◽  
One Dimensional ◽  
Porous Wick

A one dimensional stagnation point diffusion flame stabilized next to a porous wick is studied using a numerical model. The bottom end of the one-dimensional wick is dipped inside a liquid fuel (ethanol) reservoir. The liquid is drawn towards the surface of the wick through capillary action against gravity. The model combines heat and mass transfer equations in the porous media with phase change and gas-phase combustion equations to investigate steady-state flow structure in the porous wick and flame characteristics in the gas phase. In one-dimensional system, the only steady solution in the porous wick that is stable is found to be in the funicular regime. There are two regions in the wick: a vapor-liquid two-phase region near the surface exposed to the flame and a purely liquid region deep inside the wick. The physics behind the two-phase flow driven by capillarity and evaporation has been studied in detail. The coupling between the flame and the porous transport involves three different length scales: flame standoff distance, wick height above the reservoir and capillary rise. Attempt is made to study the effect of the non-dimensional numbers that contains these scales. In the limit of fast chemical kinetics (large Damkohler number), the computed results depend only on two non-dimensional ratios: the ratio of wick height to capillary rise and the ratio of wick height to flame standoff distance. Thus, a simplified similitude has been identified.

scholarly journals Modification of the Redlich-Kwong-Aungier Equation of State to Determine the Degree of Dryness in the CO2 Two-phase Region

2021 ◽  
Vol 24 (4) ◽  
pp. 17-27
Author(s):  
Hanna S. Vorobieva ◽  
Keyword(s):  
Experimental Data ◽  
Equation Of State ◽  
Gas Phase ◽  
Saturated Vapor ◽  
Phase Region ◽  
Working Fluid ◽  
Two Phase ◽  
Real Gas ◽  
Liquid Phases ◽  
Good Agreement

The degree of dryness is the most important parameter that determines the state of a real gas and the thermodynamic properties of the working fluid in a two-phase region. This article presents a modified Redlich-Kwong-Aungier equation of state to determine the degree of dryness in the two-phase region of a real gas. Selected as the working fluid under study was CO2. The results were validated using the Span-Wanger equation presented in the mini-REFPROP program, the equation being closest to the experimental data in the CO2 two-phase region. For the proposed method, the initial data are temperature and density, critical properties of the working fluid, its eccentricity coefficient, and molar mass. In the process of its solution, determined are the pressure, which for a two-phase region becomes the pressure of saturated vapor, the volumes of the gas and liquid phases of a two-phase region, the densities of the gas and liquid phases, and the degree of dryness. The saturated vapor pressure was found using the Lee-Kesler and Pitzer method, the results being in good agreement with the experimental data. The volume of the gas phase of a two-phase region is determined by the modified Redlich-Kwong-Aungier equation of state. The paper proposes a correlation equation for the scale correction used in the Redlich-Kwongda-Aungier equation of state for the gas phase of a two-phase region. The volume of the liquid phase was found by the Yamada-Gann method. The volumes of both phases were validated against the basic data, and are in good agreement. The results obtained for the degree of dryness also showed good agreement with the basic values, which ensures the applicability of the proposed method in the entire two-phase region, limited by the temperature range from 220 to 300 K. The results also open up the possibility to develop the method in the triple point region (216.59K-220 K) and in the near-critical region (300 K-304.13 K), as well as to determine, with greater accuracy, the basic CO2 thermodynamic parameters in the two-phase region, such as enthalpy, entropy, viscosity, compressibility coefficient, specific heat capacity and thermal conductivity coefficient for the gas and liquid phases. Due to the simplicity of the form of the equation of state and a small number of empirical coefficients, the obtained technique can be used for practical problems of computational fluid dynamics without spending a lot of computation time.

Surface Melting, Spallation, and Stresses Induced in Metals by Pulsed Electron Beam Heating

1971 ◽  
Vol 38 (2) ◽  
pp. 363-370 ◽  
Author(s):  
L. W. Woodruff ◽  
W. H. Giedt ◽  
J. L. Hesse
Keyword(s):  
Electron Beam ◽  
Equation Of State ◽  
Target Surface ◽  
Surface Melting ◽  
Phase Region ◽  
Internal Stresses ◽  
Two Phase ◽  
One Dimensional ◽  
Pulsed Electron Beam ◽  
Specific Objective

The present study was undertaken to investigate the applicability of one-dimensional computer programs for predicting the response of materials exposed to rapid surface heating produced by a pulsed electron beam. A specific objective was to determine modifications necessary to account for surface melting and spall. Measured values of mass loss, impulse, and internal stresses in lead and gold were satisfactorily predicted using a one-dimensional finite-difference program which simultaneously solved the conservation equations and a hydrodynamic equation of state. Required program modifications included: (a) specifying spall to occur to the depth below the target surface at which the energy deposited was sufficient to initiate melting, and (b) revising the equation of state for the material in the two-phase region.

NUMERICAL AND EXPERIMENTAL INVESTIGATION OF THE FLOW CHARACTERISTICS OF R134a FLOWING THROUGH ADIABATIC HELICAL CAPILLARY TUBES

2012 ◽  
Vol 20 (04) ◽  
pp. 1250019 ◽  
Author(s):  
SUKKARIN CHINGULPITAK ◽  
JATUPORN KAEW-ON ◽  
SOMCHAI WONGWISES
Keyword(s):  
Experimental Data ◽  
Capillary Tube ◽  
Flow Characteristics ◽  
Phase Region ◽  
Liquid Region ◽  
Alternative Refrigerants ◽  
Capillary Tubes ◽  
Local Pressure ◽  
Two Phase ◽  
Comparison Results

This paper presents numerical and experimental results of the flow characteristics of R134a flowing through adiabatic helical capillary tubes. The local pressure distribution along the length of the capillary tubes is measured at inlet pressures ranging from 10 to 14 bar, mass flow rates from 8 to 20 kg h-1, and degrees of subcooling from 0.5°C to 15°C. The theoretical model is based on conservation of mass, energy and the momentum of the fluids in the capillary tube. The model is divided into three regions: subcooled liquid region, metastable liquid region and equilibrium two-phase region and can be applied for various tube geometries, new alternative refrigerants and critical or noncritical flow conditions. The model is validated by comparing results from the present experimental data with that of the available literature. Based on the comparison results, the model used in the present study provides reasonable agreement with the experimental data.

Steady-State Network Thermofluid Models of Loop Heat Pipes

2007 ◽  
Author(s):  
Nima Atabaki ◽  
Nirmalakanth Jesuthasan ◽  
B. Rabi Baliga
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Steady State ◽  
Phase Region ◽  
Vapor Transport ◽  
Two Phase ◽  
Liquid Transport ◽  
One Dimensional ◽  
Flow And Heat Transfer ◽  
Transport Line

A loop heat pipe (LHP) with one evaporator, a vapor-transport line, a single condenser, a liquid-transport line, and a compensation chamber is considered. The evaporator is an internally grooved circular pipe, with an annular wick installed on its inner surface. The wick is made of sintered powder metal. The condenser is a horizontal tube that is fitted with excellent thermal contact inside a metallic sleeve that is immersed in a constant-temperature bath maintained at a fixed sink temperature. Two different network thermofluid models of this LHP operating under steady-state conditions are presented. In the first (basic) model, quasi one-dimensional mathematical models of the fluid flow and heat transfer in each of the elements of the LHP are used; the pressure drop in the two-phase region of the condenser is ignored; and a relatively simple correlation is used to model the heat transfer in the two-phase region of the condenser. In the second (segmented) model, quasi one-dimensional control volumes or cells are used for the simulation of fluid flow and heat transfer in the vapor-transport line, the condenser, and the liquid-transport line, in order to better account for the variation of fluid properties and the quality (in two-phase regions); and the pressure drops in the two-phase regions are accounted for. The working fluid considered in this investigation is ammonia, but the proposed models can be used with any suitable fluid. Results pertaining to the LHP performance for a range of operating conditions are presented. Some of these results are compared to corresponding results of an earlier experimental investigation in the literature: good agreement is obtained with both models.

Two-Phase, Two-Component Critical Flow in a Venturi

1972 ◽  
Vol 94 (1) ◽  
pp. 147-151 ◽  
Author(s):  
R. V. Smith
Keyword(s):  
Gas Phase ◽  
Gas Flow ◽  
Critical Flow ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Two Phase ◽  
One Dimensional ◽  
Flow Equations ◽  
Heat Transfer Coefficients ◽  
Wide Range

This paper reports the results of an analytical and experimental investigation whose object was to test the hypothesis that the flow of the gas phase controls critical and near critical two-phase flow for cases where the gas flow is essentially in separate streams. The results substantiate the hypothesis. The analytical results also indicate that one dimensional flow equations with reasonably accurate estimates for the droplet size and for the drag and heat transfer coefficients will adequately describe critical and near critical flow over a wide range of flow conditions.

Solution Properties and Phase Behavior of Ammonium Hexylene Octyl Succinate in Water and Water-Oil System

1970 ◽  
Vol 3 (1) ◽  
Author(s):  
Md. Hamidul Kabir ◽  
Ravshan Makhkamov ◽  
Shaila Kabir
Keyword(s):  
Critical Micelle Concentration ◽  
Phase Behavior ◽  
Liquid Crystalline ◽  
Carbon Number ◽  
Phase Region ◽  
Solution Properties ◽  
Middle Phase ◽  
Two Phase ◽  
Lamellar Liquid Crystal ◽  
Drug Ingredient

The solution properties and phase behavior of ammonium hexylene octyl succinate (HOS) was investigated in water and water-oil system. The critical micelle concentration (CMC) of HOS is lower than that of anionic surfactants having same carbon number in the lipophilic part. The phase diagrams of a water/ HOS system and water/ HOS/ C10EO8/ dodecane system were also constructed. Above critical micelle concentration, the surfactant forms a normal micellar solution (Wm) at a low surfactant concentration whereas a lamellar liquid crystalline phase (La) dominates over a wide region through the formation of a two-phase region (La+W) in the binary system. The lamellar phase is arranged in the form of a biocompatible vesicle which is very significant for the drug delivery system. The surfactant tends to be hydrophilic when it is mixed with C10EO8 and a middle-phase microemulsion (D) is appeared in the water-surfactant-dodecane system where both the water and oil soluble drug ingredient can be incorporated in the form of a dispersion. Hence, mixing can tune the hydrophile-lipophile properties of the surfactant. Key words: Ammonium hexylene octyl succinate, mixed surfactant, lamellar liquid crystal, middle-phase microemulsion. Dhaka Univ. J. Pharm. Sci. Vol.3(1-2) 2004 The full text is of this article is available at the Dhaka Univ. J. Pharm. Sci. website

A ONE-DIMENSIONAL TWO-PHASE FLOW MODEL AND EXPERIMENTAL VALIDATION FOR A FLASHING VISCOUS LIQUID IN A SPLASH PLATE NOZZLE

2015 ◽  
Vol 25 (9) ◽  
pp. 795-817 ◽  
Author(s):  
Mika P. Jarvinen ◽  
A. E. P. Kankkunen ◽  
R. Virtanen ◽  
P. H. Miikkulainen ◽  
V. P. Heikkila
Keyword(s):  
Viscous Liquid ◽  
Experimental Validation ◽  
Flow Model ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
One Dimensional
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