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Session: Volumetric expanders III
Session starts: Tuesday 08 October, 11:20
Presentation starts: 12:00
Room: Van Beuningen Zaal

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Mirko Morini (MechLav - University of Ferrara)
Claudio Pavan (MechLav - University of Ferrara)
Michele Pinelli (ENDIF - University of Ferrara)
Eva Romito (ENDIF - University of Ferrara)
Alessio Suman (ENDIF - University of Ferrara)

Abstract:
The scroll fluid machine has gained popularity since the 1970s as a compressor in air conditioning and refrigeration applications. Its main advantages are the small number of moving parts and its reduced noise and vibrations. Recently, this technology has gained renewed interest due to its potential adaptability to be used as an expander in micro ORC systems. The ever increasing request for higher efficiency in machine operation (e.g. eco-design) has led to the need for designers to thoroughly investigate the kinematic and thermodynamic behavior of these machines by means of geometric, thermodynamic and, very recently, CFD methods. The relationship between the scroll spiral profiles, and, therefore, scroll pockets evolution, and the machine overall performances both in terms of energy and mechanics is the first step towards understanding scroll machine working behavior. In [1], a method for the design of spiral profiles for performance enhancing of the whole refrigeration plant is presented. In [2], particular attention is paid to the stress to which the scroll profiles are subjected as a function of the geometry of the pockets in order to minimize the thickness of the spiral by saving the mechanical integrity of the scroll. Scroll machine performance evaluation as a function of spiral geometry can be performed by means of thermodynamic models by taking into consideration volumetric loss due to leakage flows [3,4,5]. The use of CFD methods for the evaluation of scroll machine performance is not widespread in literature. In [6] an analysis oriented to the evaluation of the pressure distribution in the pockets and in the leakages through the flank gap is presented. In this paper, geometric, thermodynamic and CFD methods for the modeling of scroll machines are presented. The comparison between two geometric models for the design of the scroll spiral profiles is presented. The two methods are then compared by evaluating overall performances by means of a simplified thermodynamic model. Finally, a CFD transient Dynamic Mesh (DM) strategy is implemented and a sensitivity analysis in terms of grid, boundary conditions and time step performed.