An experimental investigation of the swirling flow in a tall-form counter current spray dryer

This work studies the air flow in a large swirl counter-current dryer using sonic anemometry. Air velocity and turbulence fields are reported at isothermal conditions and in the absence of particles. In a tall-form unit the structure of the flow is largely influenced by the design of the exit. A contraction originates a central jet and suppresses the formation of recirculation zones despite the vortex acquires a high swirl intensity Ω (i.e. 1<Ω<2). Access to a full scale tower has permitted to: (a) identify asymmetries owed to the design of inlet and exhaust ducts, (b) present the first detailed turbulence data in production units, characterized by a highly anisotropic field and the axial decay of the turbulence kinetic energy, (c) study the flow stability, identifying the precession of the vortex core and oscillations at a constant Strouhal number and (d) study the impact that a rough wall has in the strength of the swirl. This work presents the first clear evidence of significant friction in spray dryers. The swirl intensity Ω decays exponentially in the dryer at a rate between 0.08 and 0.09, much higher than expected in pipe flow and independent of Re in the range 105-2.2{dot operator}105. Production dryers have a large characteristic wall roughness due the presence of deposits, which explains the stronger friction and the discrepancies found in the past between data at full scale or clean laboratory or pilot scale units. It is essential to address this phenomenon in current numerical models, which are validated on laboratory or pilot scale facilities and ignore the role of deposits, thus causing an overprediction of the tangential velocity above 30-40%

Socioeconomic Differences in Alcohol-Specific Parenting Practices and Adolescents’ Drinking Patterns

Item does not contain fulltextThe aim of this study was to investigate to what extent alcohol-specific parenting practices relate to adolescents’ alcohol use, binge drinking, and alcohol-related problems, and whether these associations are moderated by socioeconomic status (SES), i.e. parents’ education level and family income. The present data were collected within the framework of a representative study on alcohol use among Dutch students. The present findings are based on data from respondents who had been drinking in the past year (81.5%), and of whom one of the parents had filled out a short questionnaire including SES characteristics (52%). The sample consisted of 1,344 adolescents. Adolescents were approached in a school setting; parents received a short questionnaire at the home address. The results show that applying strict rules about alcohol use and having qualitative good conversations about drinking alcohol seem to prevent adolescents from heavy drinking patterns, whereas parental alcohol use seems to promote adolescents’ drinking. A positive association was found between frequency of alcohol communication and availability of alcohol at home on the one hand and adolescents’ drinking on the other. Some moderating effects of SES were found