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Melting of pure metal in presence of turbulent natural convection with Rayleigh number ranging from 106 to 109 has been studied numerically. The governing equations are…
Melting of pure metal in presence of turbulent natural convection with Rayleigh number ranging from 106 to 109 has been studied numerically. The governing equations are formulated in terms of stream function—vorticity—temperature and the moving distorted solid/liquid interface is tracked using body‐fitted coordinates. The turbulent flow is taken into account using an algebraic eddy‐viscosity model with Prandtl's mixing length. Results indicate that turbulent natural convection plays a more significant role than laminar flow in the process of melting. Heat transfer and melting rates are significantly increased and a correlation for the average Nusselt number at the heated wall in the quasi‐steady melting regime is proposed.
A numerical study is reported of natural convection melting of ice within a vertical cylinder. A stream function‐vorticity‐temperature formulation is employed in…
A numerical study is reported of natural convection melting of ice within a vertical cylinder. A stream function‐vorticity‐temperature formulation is employed in conjunction with body‐fitted coordinates for tracking the irregular shape of the timewise varying solid‐liquid interface. A parabolic density profile versus temperature is assumed for water. Numerical experiments are carried out for a temperature of the cylinder wall ranging from 4°C to 10°C. Results show that natural convection heat transfer involving density anomaly leads to complex flow patterns and strongly affects the time evolution of the phase front. The maximum Nusselt number at the heated cylinder wall is obtained for Tw = 4°C while the minimum is observed for Tw = 8°C.
A numerical study has been conducted for natural convection heattransfer for air around two vertically separated horizontal heated cylindersplaced inside an isothermal…
A numerical study has been conducted for natural convection heat transfer for air around two vertically separated horizontal heated cylinders placed inside an isothermal rectangular enclosure having finite wall conductances. The interaction between convection in the fluid filled cavity and conduction in the walls surrounding the cavity is investigated. Results have been obtained for Rayleigh numbers (Ra) between 103 and 106, dimensionless wall thickness (W) between 0.5 and 1.375 and dimensionless wall‐fluid thermal conductivity ratio (α) between 0.01 and 5.0. The results indicate that wall heat conduction reduces the average temperature differences across the cavity, partially stabilizes the flow, and decreases natural convection heat transfer. The overall heat transfer coefficient for both cylinders is correlated with CRan for different W and α.
A numerical study is conducted for natural convection dominated melting inside discretely heated rectangular enclosures. This study finds applications in the design and…
A numerical study is conducted for natural convection dominated melting inside discretely heated rectangular enclosures. This study finds applications in the design and operation of thermal energy storage units and the cooling of electric equipment. Results show the benefits of discrete heating over uniform heating for optimizing the melting process. For enclosures of high aspect ratios (A ∼> 4), configurations leading to well controlled heat source temperatures and long melting times are obtained. For cavities of low aspect ratios (A ∼< 4), it is found that the source span η is the most influential parameter. For η ∼ < 0.45, the melting times are shorter and the heat source temperatures remain equal and moderate during the entire melting process. A map for determining the cavity size and the source distribution that optimizes the melting process is presented.
The efficient distribution of bank notes is a first-order responsibility of central banks. The authors study the distribution patterns of bank notes with an administrative…
The efficient distribution of bank notes is a first-order responsibility of central banks. The authors study the distribution patterns of bank notes with an administrative dataset from the Bank of Canada’s Currency Inventory Management Strategy. The single note inspection procedure generates a sample of 900 million bank notes in which the authors can trace the length of the stay of a bank note in the market. The authors define the duration of the bank note circulation cycle as beginning on the date the bank note is first shipped by the Bank of Canada to a financial institution and ending when it is returned to the Bank of Canada. In addition, the authors provide information regarding where the bank note is shipped and later received, as well as the physical fitness of the bank note upon return to the Bank of Canada’s distribution centers. K–prototype clustering classifies bank notes into types. A hazard model estimates the duration of bank note circulation cycles based on their clusters and characteristics. An adaptive elastic net provides an algorithm for dimension reduction. It is found that while the distribution of the duration is affected by fitness measures, their effects are negligible when compared with the influence exerted by the clusters related to bank note denominations.
This article discusses prospects of strengthening new increasingly global economic activities and environmental governance by focusing on the institutional relationship…
This article discusses prospects of strengthening new increasingly global economic activities and environmental governance by focusing on the institutional relationship between information society policy issues and environmental policy issues. These two sets of issues have some common denominators insofar as they are both comprehensive and go beyond traditional sector policy rationalities, as illustrated by the notions of “sustainable development” and “ecological modernization” in the case of environmental issues, and neither can avoid the problem of governance subjects such as social legitimacy and institutional dynamics between the main actors. The article also identifies a more functional relationship between these issues and discusses challenges common to both as well as asking whether there is institutional potential and capacity to find “synergy” by integrating environmental policy elements into moves towards information society and vice versa. The case study of Finland reveals that information society strategy lacks environmental policy objectives and discusses the factors behind this failure. The lack of integration of different policy areas is an issue of organizational power with policy actors showing no real interest in radically changing prevailing bureaucratic institutions and socioeconomic structures. Beyond organizational factors the policy problems seem to be based on the inconsistency of different policy rationalities with information society reasoning being justified by economic‐technical rationality whereas environmental policies are justified by natural scientific rationality, which policy makers do not consider to be in their interests. The article concludes with the assertion that the principles of ecological modernization could potentially unite environmental policies and positive environmental aspects of information society policies.
Dans la décennie qui précéda la guerre, la documentation avait fait en France de tels progrès qu'on avait vu se transformer les méthodes traditionnelles des dépôts de conservation. Cette situation de la documentation française n'avait pas été sans susciter une vive émulation à l'étranger, comme en témoignent les travaux des congrès de Paris en 1937 et d'Oxford en 1938 pour ne parler que de ceux‐là. A la veille de la guerre, la France possédait une fédération, l'Union Française des Organismes de Documentation, fondée en 1932, et un organe de direction, le Comité Français de la Documentation, qui fonctionna dès 1938, et qui fut reconnu officiellement par arrêté du Ministre de l’Éducation Nationale en date du 24 juillet 1939. Ce Comité avait adhéré à la Fédération Internationale de Documentation de La Haye en 1938.