15 Fakultätsübergreifend / Sonstige Einrichtung
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/16
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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 A numerical and experimental study of wavy ice-structure in an asymmetrically cooled parallel-plate channel(1992) Weigand, Bernhard; Beer, HansIce formation of flowing water in a pipe or a channel, whose wall is kept at a uniform temperature below the freezing temperature of the water, is a basic engineering problem. It Introduces many practical problems, such as pressure drop, diminution of flow rate and sometime, breakage of the pipe as a result of flow blockage by ice. The phenomenon of freezing of flowing water involves interactions between the turbulent flow, the shape of the ice layer and the heat transfer at the ice-water interface. Under certain conditions these interactions result in an instabilily of the ice layer. This instability is caused by the strong laminarization of the turbulent flow due to converging ice layers in the entrance region of the cooled channel and results in a wavy ice structure. Wavy ice layers with one wave, occuring in a parallel.plate channel subjected to symmetrically oooled walls were investigated experimentally by Seld et al. and by Weigand and Beer. More recently Weigand and Beer were able to predict numerically the shape of wavy ice layers with one wave occuring in a symmetrically cooled channel. Wavy ice layers in a parallel-plate channel with one wave in the case of asymmetrically cooled walls were investigated experimentally by Tago et al. and by Weigand and Beer. No numerical calculation of asymmetric wavy freezing fronts was done in the past. Therefore, the subject of this paper is the presentation of a numerical model for calculating steady state ice layers with one wave in the entrance region of an asymmetric cooled channel. The method is based on a work performed by Weigand and Beer. The given numerical study is supported by a detailed experimental investigation.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 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 Open Access 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.