Abstract
Usually design recommendations for evaporators are based on experiments. However, the value of the added mass coefficients of objects in vorticity flows is the same as those in inviscid flow. This gives the possibility to apply analytical modelling to the hydrodynamics of bubbles in evaporator tubes, and to draw conclusions with regard to tube design.
It is shown that a swirl should be created in vertical tubes with up-flow, since hydrodynamic lift forces drive bubbles, once detached from the wall, back towards the wall. So-called rifled tubes create this swirl, and the geometry of rifled tubes is therefore
studied in some detail. A combination of CFD modelling and analytical modelling is applied, the latter using a Lagrangian approach. The full added mass tensor for bot.It growing, truncated spheres on a plane wall and for deforming, detached spheres in
the vicinity of such a wall is presented as a function of the governing geometrical parameter. Explicit expressions for the hydrodynamic forces are given, in particular for the contributions to the inertia lift force normal to the wall. This force hampers bubble
migration. Design recommendations for rifled tubes are given.
Original language | English |
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Title of host publication | CMFF'06 : conference on modelling fluid flow : proceedings of the 13th international conference on fluid flow , September 6-9 2006, Budapest, Hungary, Vol.1 |
Editors | T. Lajos |
Place of Publication | Budapest |
Publisher | Budapest University of Technology and Economics |
Pages | 424-431 |
ISBN (Print) | 963-06-0361-6 |
Publication status | Published - 2006 |