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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 26 (1991), S. 301-305 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Die Wärmeübertragung in einem gewendelten Dampferzeugerrohr ist sehr verschieden von der in einem geraden Rohr. So ist zum Beispiel der kritische Wärmestrom in gewendelten Rohren geringer als im geraden Rohr für unterkühltes Sieden, aber beträchtlich höher bei höheren Dampfgehalten. In dieser Arbeit wurden Methoden entwickelt, um das Einsetzen des Blasensiedens und der Nettodampferzeugung sowie die Bedingung für den kritischen Wärmestrom in gekrümmten Kanälen vorauszuberechnen. Diese Methoden beruhen auf der Annahme, daß diese Vorgänge durch die örtlichen hydro- und thermodynamischen Bedingungen bestimmt werden, die sich aus Rechenverfahren der Fluiddynamik ermitteln lassen. Mit den verfügbaren experimentellen Daten herrschte gute Übereinstimmung.
    Notes: Abstract The heat transfer characteristics of a coiled steam generating tube are very different from those of a straight tube. For example, the critical heat flux (CHF) in coiled tubes is less than that in straight tubes for subcooled boiling and significantly higher at higher qualities. In this paper, predictive methods are developed for the determination of the point of onset of nucleate boiling, the point of net vapour generation and the critical heat flux condition in curved ducts. The methods are based on the assumption that these phenomena are governed by the local hydro- and thermodynamic conditions which can be predicted using computational fluid dynamics techniques. Good agreement has been obtained with available experimental data.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 10 (1990), S. 569-589 
    ISSN: 0271-2091
    Keywords: Numerical simulation ; Centrifugal force ; Finite difference method ; Laminar flow Heat transfer ; Coils Bends ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The advent of standard algorithms for the numerical solution of partial differential equations has given researchers a new tool for fluid flow calculations. In this paper, single-phase flow in curved ducts is numerically simulated by imposing a spatially varying centrifugal force on a fluid flowing in a straight tube. The resulting set of partial differential equations is solved using the HARWELL-FLOW3D computer program. Comparison with other numerical and experimental results shows that this simplified formulation gives accurate results. The model neglects certain geometric terms of the order d/D, the duct-to-coil diameter ratio. The effect of these terms is investigated by considering the flow in a 90° bend for large d/D. It is shown that while there may be significant error in the prediction of the local variables for large d/D, the circumference-averaged quantities are well predicted.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 14 (1992), S. 253-266 
    ISSN: 0271-2091
    Keywords: Bifurcation ; Laminar flow ; Curved ducts ; Numerical accuracy ; Finite difference methods ; Secondary flows ; Asymmetry ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The bifurcation phenomenon whereby multiple-vortex secondary flow occurs in place of the normal two-vortex flow in laminar flow in curved ducts has previously been studied numerically by several researchers. However, the various results have been conflicting on many points. The present paper describes a set of numerical experiments conducted to study the effect of numerical accuracy on the solution. The results show that the transition from two- to four-vortex structure depends strongly on the differencing scheme and to a lesser extent on the grid size. The study also shows that as the Reynolds number of the flow increases, a two-vortex structure is re-established via a path which involves strongly asymmetric secondary flow patterns. These results are in agreement, at least qualitatively, with recent experimental theoretical and numerical results.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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