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Poster De Conférence Année : 2013

Dimensional Analysis of Milk Concentrate Spraying

Résumé

The world trade in dairy powders has consistently been increasing for the last fifteen years . Therefore, there is an obvious need in the dairy industry to develop tools to optimise powder production and control powder structure and functionalities. For this purpose, it is necessary to better understand the wet agglomeration mechanisms leading to powder structuration in various processes such as spray -drying, with an emphasis on the role of process parameters (operating conditions, physicochemical properties of the inlet food matter, and process design) in the final properties of dried agglomerates . Liquid atomisation, which directly influences the wett ing/nucleation stage of wet agglomeration, has been identified as a crucial step in spray -drying operations: the size of final agglomerates was indeed shown to be highly correlated to the size of sprayed droplets . That is why we intended in this work to focus on the role of process conditions in liquid atomisation. We carried out 148 laser diffraction measurements of the mean size of droplets produced with a bi-fluid nozzle in various process conditions (liquid and air flow -rates) at two different dist ances from the nozzle. Ternary mixtures of water -ethanol - glycerol, along with skim milk concentrates (dried extract ranging from 30 to 40 % (w/w)) were employed to investigate the influence of physicochemical characteristics of the sprayed liquid (surface tension, viscosity, density). Our experimental results were consistent with the pioneer work of Mandato et al. Regarding the predominant influence of operating conditions over liquid hysicochemical properties. In addition, we showed that droplet size increased with the distance to nozzle, indicating that droplet coalescence owing to inertial effects occurs quickly after liquid atomisation at the nozzle outlet. Finally, in order to model accurately the link between process conditions and droplet size, we extended the dimensional analysis approach first proposed by Mandato et al. by introducing key dimensionless numbers (air-to -liquid ratio and aerodynamic Weber number) in the process relationship. This enabled to discuss the relative influence of operating conditions and liquid physicochemical properties on the size of sprayed droplets, as a function of the distance to the nozzle
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Dates et versions

hal-01454378 , version 1 (02-02-2017)

Identifiants

  • HAL Id : hal-01454378 , version 1
  • PRODINRA : 209579

Citer

Jérémy Petit, Serge Mejean, Laurence Galet, Philippe Accart, Pierre Schuck, et al.. Dimensional Analysis of Milk Concentrate Spraying. 6. th International Granulation Workshop, Jun 2013, Sheffield, United Kingdom. , 2013. ⟨hal-01454378⟩
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