Air Flow, Temperature and Humidity Patterns in a Co-Current Spray Dryer: Modelling and Measurements

Kieviet, FG Frank; Kerkhof, Pjam Piet

doi:10.1080/07373939708917325

Cited by 38 publications

(20 citation statements)

References 1 publication

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“…Huang et al [18] carried out a computational study on the air flow velocity, temperature and humidity at different axial positions in the spray chamber. Their model was in good agreement with the experimental results of Kieviet and Kerkhof [19] and Kieviet, [20] although the number of comparable measurement points was low because of the considerable difficulties in performing experiments. Droplet-droplet interactions during spray drying were investigated by Mezhericher et al [21] applying transient calculations.…”

Section: Introductionsupporting

confidence: 79%

Numerical investigation of droplet-droplet collisions in a water and milk spray with coupled heat and mass transfer

et al. 2019

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Large scale simulation models can aid in improving the design of spray dryers. In this work an Eulerian-Lagrangian model with coupled gas phase and droplet heat and mass transfer balances is used to study airflow dynamics, temperature and humidity profiles at different positions in the spray. The turbulent gas flow is solved using large eddy simulation (LES). A turbulent dispersion model accounts for the stochastic subgrid fluid velocity fluctuations along the droplet trajectory. The dispersed phase is treated with Lagrangian transport of droplets, and collisions between droplets which are detected with a stochastic Direct Simulation Monte Carlo (DSMC) method. The outcome of a binary collision is described by collision boundary models for water and milk concentrates. The drying of droplets is modeled by the reaction engineering approach (REA). The effect of the inlet air conditions and of droplet viscosity on the temperature and humidity distributions are analyzed. Most of the heat and mass transfer occurs in the first 10-20 cm from the nozzle where the slip velocities and temperature and humidity driving forces are higher. The droplets size increases, both in the axial and radial direction, because of the dominance of coalescence over separation in the droplet spray studied here. Because the spray domain considered in this work is relatively small, the droplet residence time is small, and consequently the amount of evaporation is still low. The droplet size distributions of milk concentrates are affected by the predominance of coalescence over separation events. The coalescence dominated regime increases when the droplet viscosity is higher.

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Section: Introductionsupporting

confidence: 79%

Numerical investigation of droplet-droplet collisions in a water and milk spray with coupled heat and mass transfer

et al. 2019

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“…However for counter-current spray towers, these two-dimensional representations cannot accommodate the swirling gas flows and hence cannot reproduce realistic droplets/particles trajectories. A number of researchers including Crowe (1983), Livesley et al (1992), Oakley and Bahu (1993), Langrish and Zbicinski (1994), Zbicinski (1995), Kieviet (1997), Kieviet and Kerkhof (1997), Southwell et al (1999), Straatsma et al (1999), Zbicinski and Zietara (2004), and Mezhericher et al (2008Mezhericher et al ( , 2010 have carried out simulations of spray drying of various materials, such as milk, maltodextrin, detergent, using this approach.…”

Section: Introductionmentioning

confidence: 99%

Zonal modelling of a counter-current spray drying tower

Ali

Mahmud

Heggs

et al. 2020

Chemical Engineering Research and Design

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A generic multi-zonal modelling methodology for spray drying towers is proposed to provide relatively quick (seconds) simulations on desktop computers for decision making on changing process parameters for automatic process control. A multi-zonal model comprises combinations of all or some of six differing zones: plug-flow, semi-plug-flow and well-mixed zones in either co-or counter-current flow. This approach is demonstrated by predicting the dried powder characteristics of a detergent powder from a pilot-scale counter-current spray drying tower. The types, sizes and locations of the different zones are obtained by a detailed analysis of predictions from a previous 3-dimensional Computational Fluid Dynamics (CFD) simulation of gas and particle flow dynamics and drying kinetics within the tower. The multi-zonal model consists of seven zonesfive in counter-current and two in co-current flow. The trends of the predicted gas temperature profiles are close to those from the CFD results. The particle exit temperature, moisture content and residence times over the full particle size distribution (PSD) range are very close to the CFD values unlike the previous simulated results from our plug-flow model. The outcome clearly demonstrates that the prerequisite to have a sound conceptual model of spray drying towers, such as the multi-zonal model developed here, is a detailed knowledge of the gas and particle flow fields within the tower.

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“…To model product quality in spray drying Kieviet et al [8] used air temperature and humidity histories combining air property measurements and particle track. Air flow pattern was measured with a hotwire probe placed in different locations.…”

Section: Introductionmentioning

confidence: 99%

Evolution of particle properties during spray drying in relation with stickiness and agglomeration control

et al. 2011

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Air Flow, Temperature and Humidity Patterns in a Co-Current Spray Dryer: Modelling and Measurements

Cited by 38 publications

References 1 publication

Numerical investigation of droplet-droplet collisions in a water and milk spray with coupled heat and mass transfer

Numerical investigation of droplet-droplet collisions in a water and milk spray with coupled heat and mass transfer

Zonal modelling of a counter-current spray drying tower

Evolution of particle properties during spray drying in relation with stickiness and agglomeration control

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