Flow through Packed and Fluidized Beds
Chemical engineering operations commonly involve the use of packed and fluidized beds. These are devices in which a large surface area for contact between a liquid and a gas (absorption, distillation) or a solid and a gas or liquid (adsorption, catalysis) is obtained for achieving rapid mass and heat transfer, and particularly in the case of fluidized beds, catalytic chemical reactions. You will find a good deal of information about flow through packed and fluidized beds in the book by McCabe, Smith, and Harriott (1) and Perry’s Handbook (2). Here, only a brief summary is given. First, let us consider flow through a packed bed.
Assessing the Feasibility of Optical Probe in Phase Holdup Measurements and Flow Regime Identification
Abstract Despite the hydrodynamics of trickle beds experiencing pilot size, on the contrary, the possibility of measuring hydrodynamic parameters locally and for large scale and finding an indicator to pinpoint the flow regime from trickling to pulsing remains obscure, to assess the feasibility of getting such information the reactor bed was randomly packed with equal-sized spherical beads of 3 mm diameter. Gas and liquid holdup measurements and flow regime identification were achieved at various flow conditions from trickling to the pulsing regime by an optical probe method using time series processing method. This method is shown to be simple and efficient provides quantitative information about the gas and liquid holdup variation in different flow regime. The various experimental results were compared to available literature models and correlations for confrontation and recommendations. The trickle-to-pulse flow transition boundary shifted towards higher gas and liquid superficial velocities, aligning with the findings on a variation of holdup along the axial direction confirmed to broaden the trickle flow domain. [Correction added after online publication June 26, 2015: To unify the adjective everywhere in this manuscript, optic fiber probe was changed to optical probe.]
Language Socialisation and Language Shift in the 1b Generation: A Study of Moroccan Adolescents in Italy
Abstract This paper reports on a longitudinal ethnographic study of the language socialisation of a group of Moroccan adolescents who migrated to Italy in the late 1990s. The approach is based on the notion of language socialisation, which sees the process of acquiring a language as linked to that of becoming a member of a culture. The participants live in small towns in a semi-rural area in Northern Italy and were closely observed during their initial contact with Italian Ethnographic observations continued in the following years, and were conducted both in the homes and in school programmes. Five years later, in-depth interviews were carried out on a range of issues dealing with ethnolinguistic identity, and language knowledge and use in a variety of domains and intercultural relationships. Written materials were also collected on personal experiences and attitudes towards Italy and Morocco. These data, taken together, show how socialisation into the new culture is producing a very rapid shift in language use and associated attitudes towards the different languages in the repertoire, i.e. Italian, Moroccan and Standard Arabic, and other European languages. Patterns of language use, linguistic ideologies and ethnolinguistic identity of this multilingual community are discussed in relation to educational policies.