scholarly journals Overview of a Theory for Planning Similar Experiments with Different Fluids at Supercritical Pressure

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3695
Author(s):  
Andrea Pucciarelli ◽  
Sara Kassem ◽  
Walter Ambrosini
Keyword(s):  
Heat Transfer ◽  
Similarity Theory ◽  
Fluid Dynamic ◽  
Supercritical Pressure ◽  
Dimensionless Numbers ◽  
Body Of Knowledge ◽  
Definition Of ◽  
Complex Phenomena ◽  
Semi Empirical

The recent advancements achieved in the development of a fluid-to-fluid similarity theory for heat transfer with fluids at supercritical pressures are summarised. The prime mover for the development of the theory was the interest in the development of Supercritical Water nuclear Reactors (SCWRs) in the frame of research being developed worldwide; however, the theory is general and can be applied to any system involving fluids at a supercritical pressure. The steps involved in the development of the rationale at the basis of the theory are discussed and presented in a synthetic form, highlighting the relevance of the results achieved so far and separately published elsewhere, with the aim to provide a complete overview of the potential involved in the application of the theory. The adopted rationale, completely different from the ones in the previous literature on the subject, was based on a specific definition of similarity, aiming to achieve, as much as possible, similar distributions of enthalpies and fluid densities in a duct containing fluids at a supercritical pressure. This provides sufficient assurance that the complex phenomena governing heat transfer in the addressed conditions, which heavily depend on the changes in fluid density and in other thermophysical properties along and across the flow duct, are represented in sufficient similarity. The developed rationale can be used for planning possible counterpart experiments, with the aid of supporting computational fluid-dynamic (CFD) calculations, and it also clarifies the role of relevant dimensionless numbers in setting up semi-empirical correlations for heat transfer in these difficult conditions, experiencing normal, enhanced and deteriorated regimes. This paper is intended as a contribution to a common reflection on the results achieved so far in view of the assessment of a sufficient body of knowledge and understanding to base successful predictive capabilities for heat transfer with fluids at supercritical pressures.

An Examination of Women's Perspectives on Power

1992 ◽  
Vol 16 (4) ◽  
pp. 415-428 ◽  
Author(s):  
Cynthia L. Miller ◽  
A. Gaye Cummins
Keyword(s):  
Women’S Experiences ◽  
Body Of Knowledge ◽  
Women's Experiences ◽  
Growing Body ◽  
Personal Authority ◽  
Women’S Perceptions ◽  
Definition Of ◽  
Men's Experience ◽  
The Way

Historically, theoretical and popular conceptions about power have not included or addressed women's experiences. This study adds to the growing body of knowledge about women by examining women's perceptions of and relationship to power. One hundred twenty-five women, ranging in age from 21 to 63, were asked to define and explore power through a variety of structured and open-ended questions. The results showed that women's definition of power differed significantly from their perception of society's definition of power, as well as from the way power has traditionally been conceptualized. More theoretical and empirical attention should be given to understanding the role of personal authority in both women's and men's experience of power.

Statecraft as a Ruling, Caring, and Weaving dunamis

2021 ◽  
pp. 195-216
Author(s):  
Melissa Lane
Keyword(s):  
Body Of Knowledge ◽  
Explicit Reference ◽  
Political Expertise ◽  
Definition Of

Chapter 10 focusses on Statesman 303d4-305e7 and considers the Visitor’s seemingly three definitions of statecraft in the dialogue: 305c10-d5, 305e2-6, and 311b7-c7. By focusing on the role of the dunamis of given forms of expertise, and the metaphorical method of smelting metals at work in this section of the dialogue, it argues that a definition of statecraft (hē politikē) as ruling, caring, and weaving is reached in 305e2-6 and then fleshed out in 311b7-c7 by the explication of the ergon (task) which it is the role of that dunamis to accomplish. This is broadly consonant with a passage in Republic 5 identifying any given dunamis in terms of that over which it is set and what it accomplishes (apergazetai), a schema filled out in the Statesman by explicit reference to the ergon of a dunamis (305c4-5). Political expertise is not a passive body of knowledge but rather actively and precisely organized toward the realization of its distinctive task.

Investigation and Modeling of the In-Tube Heat Transfer of Fluids at Supercritical Pressure During Heating

2017 ◽  
Author(s):  
Chen-Ru Zhao ◽  
Zhen Zhang ◽  
Han-Liang Bo ◽  
Pei-Xue Jiang
Keyword(s):  
Heat Transfer ◽  
Numerical Modelling ◽  
Convection Heat Transfer ◽  
Turbulence Models ◽  
Vertical Tube ◽  
Supercritical Pressure ◽  
Flow And Heat Transfer ◽  
Pressure Water ◽  
Predicted Values ◽  
Semi Empirical

Investigations and numerical modelling are performed on the heat transfer to CO2 at supercritical pressure under buoyancy affected conditions during heating in a vertical tube with inner diameter of 2 mm. Numerical modelling are carried out using several low Reynolds number (LRN) k-ε models, including the model due to Launder and Sharma (LS), Abe, Kondoh and Nagano (AKN), Myong and Kasagi (MK) models. The numerical results are compared with the corresponding experimental data and the predicted values using the semi-empirical correlation for convection heat transfer of supercritical fluids without deterioration. The abilities of various LRN models to predict the heat transfer to fluids at supercritical pressures under normal and buoyancy affected heat transfer conditions are evaluated. Detailed information related to the flow and turbulence is presented to get better understanding of the mechanism of the heat transfer deterioration due to buoyancy, as well as the different behavior of various LRN turbulence models in responding to the buoyancy effect, which gives clues in future model improvement and development to predict the buoyancy affected heat transfer more precisely and in a broader range of conditions as they come to be used to simulate the flow and heat transfer in various applications such as in the supercritical pressure water-cooled reactor (SCWR) and the supercritical pressure steam generator in the high temperature gas cooled reactor (HTR).

Similarity theory and dimensionless numbers in heat transfer

2009 ◽  
Vol 30 (3) ◽  
pp. 439-445 ◽  
Author(s):  
E Marín ◽  
A Calderón ◽  
O Delgado-Vasallo
Keyword(s):  
Heat Transfer ◽  
Similarity Theory ◽  
Dimensionless Numbers

Uncertainty of the Diffusion Measurements on Scaffolds for Cell Growth

2011 ◽  
Vol 312-315 ◽  
pp. 770-775 ◽  
Author(s):  
Guido Sassi ◽  
Marco Bernocco ◽  
Mariapaola Sassi
Keyword(s):  
Dynamic Properties ◽  
Fluid Dynamic ◽  
Solid Particles ◽  
Liquid Volume ◽  
Model Parameters ◽  
Diffusivity Measurement ◽  
Fitting Procedures ◽  
Definition Of

The regenerative medicine uses gel and porous solid matrices as scaffolds for the growth of the stem cells in 3D structures. The structural and fluid dynamic properties of the matrices have been recognized to highly affect the behaviour and functions of the cells. The procedures of production and the clinical use of the matrices need a reliable and reproducible characterization of their properties, this means that the concepts of metrology must be applied to the measurement and definition of all the relevant properties. This paper deals with the calculation of uncertainty for diffusivity measurement in solids and the role of uncertainty in designing the measurement. Diffusion of a solute in spherical solid particles dispersed in a limited liquid volume where considered as measurement method for a Ca-alginate polymer. The model sensitivity to the concentration measurements, the model parameters and the fitting procedures have been discussed.

Progress in Developing an Improved Empirical Heat Transfer Equation for Use in Connection With Advanced Nuclear Reactors Cooled by Water at Supercritical Pressure

2009 ◽  
Author(s):  
J. Derek Jackson
Keyword(s):  
Heat Transfer ◽  
Nuclear Reactors ◽  
Supercritical Pressure ◽  
Thermal Design ◽  
Mean Flow ◽  
Flow Acceleration ◽  
Design Procedures ◽  
Structure Changes ◽  
Physically Based ◽  
Semi Empirical

Consideration of advanced power plant such as nuclear reactors cooled by water at pressures above the critical value has stimulated a renewed interest in heat transfer to supercritical pressure fluids. Severe deterioration in the effectiveness of heat transfer can be encountered as a result of the extreme dependence on temperature of the physical properties of such fluids, particularly near the pseudocritical temperature where their molecular structure changes from being liquid-like to gaseous. This deterioration arises mainly as a result of the non-uniformity of density, which can lead to significant influences of bulk flow acceleration and fluid buoyancy. A good physical understanding has been arrived at of the mechanisms by means of which such influences can modify the mean flow and turbulence fields and thereby the advection and turbulent diffusion of heat and effectiveness of heat transfer. However, this progress in understanding the physics has so far not resulted in such effects being reliably accounted for in the empirical equations which are available for thermal design. With a view to addressing this matter, the author has recently attempted to update and improve an existing physically-based semi-empirical model of variable property heat transfer. The aim has been to combine it with a soundly-based empirical forced convection equation to extend the applicability and reliability of currently available thermal design procedures. In the present paper, progress in validating this approach and optimising the performance of the extended equation is reported.

An Semi-Empirical Model of Turbulent Convective Heat Transfer to Fluids at Supercritical Pressure

2008 ◽  
Author(s):  
J. Derek Jackson
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Critical Pressure ◽  
Supercritical Pressure ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Governing Equations ◽  
Semi Empirical

Recently, there has been a renewed interest in heat transfer to fluids at supercritical pressure because of the consideration now being given to the Supercritical Pressure Water-cooled Reactor (SPWR). This will supply high temperature ‘steam’ to turbines at pressures well above the critical value. The particular feature of fluids at pressures just above the critical pressure which makes them of special interest is that as they change from being liquid-like to gaseous the transition occurs in a continuous manner over a narrow band of temperature without the discontinuous behaviour encountered when phase occurs in fluids at sub-critical pressure. However, when heat takes place within fluids at supercritical pressure, extreme non-uniformities of physical and transport properties can be present. The governing equations for flow and convective heat transfer have to be written in a form which takes account of the temperature dependence of the properties. They are complicated, highly non-linear and strongly inter-dependent. The proportionality between heat flux and temperature difference found in constant property forced convection no longer exists. Also, the effectiveness of heat transfer can be very sensitive to imposed heat flux. Particular problems arise due to the non-uniformity of density by virtue of the fluid being caused to accelerate where the bulk density is falling or as a consequence of the flow field and turbulence being modified by the influence of buoyancy. Severe impairment on heat transfer can be encountered due to such effects. The requirements for achieving similarity and the approach to the correlation of data on heat transfer to fluids at supercritical pressure are matters that need to be carefully considered and soundly based. This necessitates representing the general form of the governing equations and the boundary conditions in non-dimensional form to identify the parameters that are involved. In this paper, an extended model of turbulent heat transfer to fluids at supercritical pressure is presented which utilises a semi-empirical multiplier to account for the combined effects of flow acceleration and buoyancy.

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