15 Fakultätsübergreifend / Sonstige Einrichtung
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/16
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Item Open Access Fluid flow and heat transfer in an axially rotating pipe subjected to external convection(1992) Weigand, Bernhard; Beer, HansThe effects of external insulation and tube rotation on the heat transfer to a fluid flowing inside a tube are examined by analysis. The turbulent flow is assumed to be hydrodynamically fully developed. Heat transfer was found to be strongly suppressed by tube rotation. It is shown that the significance of external insulation on the Nusselt number increases with growing rotation rate of the pipe.Item Open Access Wärmeübertragung in einem axial rotierenden, durchströmten Rohr im Bereich des thermischen Einlaufs. T. 2, Einfluß der Rotation auf eine laminare Strömung(1989) Weigand, Bernhard; Beer, HansDer Einfluß der Rotation auf das Temperaturprofil und die Wärmeübergangszahl einer laminaren Rohrströmung im Bereich des thermischen Einlaufs wird theoretisch untersucht. Es wird angenommen, daß das Geschwindigkeitsprofil voll ausgebildet ist. Die Rotation hat einen destabilisierenden Einfluß auf die Laminarströmung, die umschlägt und turbulent wird. Aufgrund der Anfachung der Turbulenz durch die Rotation verbessert sich die Wärmeübertragung mit steigender Rotations-Reynoldszahl und die thermische Einlauflänge nimmt beträchtlich ab.Item Open Access Heat transfer and solidification of a laminar liquid flow in a cooled parallel plate channel: the stationary case(1991) Weigand, Bernhard; Beer, HansA simple numerical model is presented to predict the steady-state ice layers on the cooled walls inside a parallel plate channel for arbitrary entrance velocity profiles. The effect of two different entrance velocity distributions (a parabolic velocity distribution and a slug flow) on the shape of the ice-layers are examined. The quality of an approximative solution given in literature was checked by comparing with the numerical results. For the case of a fully developed parabolic velocity distribution at the entrance of the cooled channel the results are compared with experimental findings of Kikuchi. A generally good agreement was found.Item Open Access Solidification of flowing liquid in an asymmetric cooled parallel-plate channel(1992) Weigand, Bernhard; Beer, HansAn experimental study has been performed to investigate the ice-formation phenomena of water flow between two horizontal parallel plates, with the lower wall kept at a temperature below the freezing temperature of the liquid. A detailed and comprehensive investigation of the morphology of the ice-structure is given.Item Open Access A theoretical and experimental investigation of smooth- and wavy ice layers in laminar and turbulent flow inside an asymmetrically cooled parallel-plate channel(1993) Weigand, Bernhard; Beer, HansThe present paper shows the adaption of the numerical model originally developed by Weigand and Beer [14] for calculating steady-state ice layers inside an asymmetrically cooled parallel-plate channel. The investigation shows the characteristics in ice formation behaviour due to asymmetrically cooled walls. Further, a simple analytical model is presented for calculating smooth ice layers in turbulent flow. The study is supported by own measurements of the freezing fronts inside an asymmetrically cooled channel. A comparison between theoretical calculations and measurements shows generally good agreement.Item Open Access Freezing in turbulent flow inside tubes and channels(1993) Weigand, Bernhard; Beer, HansA simple and quite flexible numerical model is presented to predict the steady state ice-layer formation inside a cooled two dimensional channel or a tube containing a turbulent flow. The effects of arbitrary entrance velocity distributions upon the shape of the ice-layers are examined. The presented numerical scheme is verified by comparing the predicted ice-layers with measurements and generally good agreement was found.Item Open Access Wärmeübertragung in einem axial rotierenden, durchströmten Rohr im Bereich des thermischen Einlaufs. T. 1, Einfluß der Rotation auf eine turbulente Strömung(1989) Weigand, Bernhard; Beer, HansDer Einfluß der Rotation auf das Temperaturprofil und die Wärmeübergangszahl einer turbulenten Rohrströmung im Bereich des thermischen Einlaufs wird theoretisch untersucht und mit Meßwerten verglichen. Es wird angenommen, daß das Geschwindigkeitsprofil voll ausgebildet ist. Die Rotation hat aufgrund der radial ansteigenden Zentrifugalkräfte einen ausgeprägten Einfluß auf die Unterdrückung der turbulenten Bewegung. Dadurch verschlechtert sich die Wärmeübertragung mit steigender Rotations-Reynoldszahl und die thermische Einlauflänge nimmt beträchtlich zu.Item Open Access A perturbation analysis of transient freezing of a laminar liquid flow in a cooled two-dimensional channel(1993) Weigand, Bernhard; Höhn, Werner; Beer, Hanshe paper shows the applicability of a regular perturbation method for predicting the transient development of the ice layer thickness inside a cooled planar channel subjected to laminar flow. Applying the perturbation expansion to the conservation equations, closed-form solutions for the velocity and temperature distributions in the fluid for an arbitrarily shaped channel could be derived under the assumption that the axial variation in solid layer thickness is small. The distributions obtained for the steady-state ice layer thickness and the velocity were checked by numerical calculations and generally good agreement was found.Item Unknown Ice-formation phenomena for water flow inside a cooled parallel plate channel : an experimental and theoretical investigation of wavy ice layers(1993) Weigand, Bernhard; Beer, HansA numerical model is developed for predicting steady-state ice formation inside a cooled two-dimensional channel. The study takes into account the strong interactions existing between the turbulent flow, the shape of the ice and the heat transfer at the ice-water interface which lead to the formation of wavy ice layers with one wave. The presented analysis is found to be able to predict realistic variations of the ice layer thickness for a wide range of Reynolds numbers and cooling parameters. The numerical results were verified by comparing the predicted ice layers with measurements and generally good agreement was found.Item Open Access On the universality of the velocity profiles of a turbulent liquid flow in an axially rotating pipe(1994) Weigand, Bernhard; Beer, HansIf a fluid enters an axially rotating pipe, it receives a tangential component of velocity from the moving wall, and the flow pattern change according to the rotational speed. A flow relaminarization is set up by an increase in the rotational speed of the pipe. It will be shown that the tangential- and the axial velocity distribution adopt a quite universal shape in the case of fully developed flow for a fixed value of a new defined rotation parameter. By taking into account the universal character of the velocity profiles, a formula is derived for describing the velocity distribution in an axially rotating pipe. The resulting velocity profiles are compared with measurements of Reich [10] and generally good agreement is found.