Mapping the Shrinkage Behavior of Skim Milk Droplets During Convective Drying

Chew, Jia Han; Woo, Meng Wai; Chen, Xiao; Selomulya, Cordelia

doi:10.1080/07373937.2014.985791

Cited by 10 publications

(4 citation statements)

References 18 publications

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“…The perfect shrinkage result was already expected, as it was a consideration of the developed model (Equation 17), which is a coherent consideration for the first drying stage. However, the dimensionless Peclet number can be used to indicate the tendency of crust formation in a droplet and therefore can express the degree of deviation from the perfect shrinkage (Chew et al 2015). Thus, the compaction of solids needs to be analyzed to obtain a more accurate transition criterion from the free water evaporation stage to the crust formation stage.…”

Section: Resultsmentioning

confidence: 99%

“…Different morphologies depend on how shrinkage occurred, which is influenced by material properties, drying rate and initial diameter. If drying is rapid, solids tend to accumulate in the outer layer of the droplet, where the particle exhibits less shrinkage as the crust formed is practically solid (Chew et al 2015). In the classic experimental tests carried out by Nešić & Vodnik (1991), the suspended droplets were practically spherical and the authors estimated the error of treating them as spheres as less than 1%.…”

Section: Introductionmentioning

confidence: 99%

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Simulation of a single spherical droplet drying considering shrinking and temperature profiles: first drying stage

Chaves

Birchal

Junior

2023

An. Acad. Bras. Ciênc.

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A model including simultaneous droplet heating and water evaporation is proposed to simulate temperature, shrinking and mass profiles of a spherical droplet subjected to convective drying, being valid for the first drying stage. Experimental data on drying skim milk and colloidal silica obtained in the literature were used for validation, but there is no restriction in the model that prevents it from being suitable for other materials. There were not significant differences observed concerning to the droplet components (dissolved or insoluble materials). The initial heating time of the particle upon reaching the constant temperature is relatively short (Δt ≈ 7s) for both simulated materials and water evaporation during the first drying stage occurs mostly at the wet bulb temperature of the air. Discrepancy between simulated and experimental values did not exceed 9% for skim milk and 7% for colloidal silica in this first stage, indicating good applicability of the model. Considering the applicability of the model in a more generic way, Whitaker correlation evaluated at the film temperature showed better results. Finally, the small discrepancy found is discussed and some improvements are proposed.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Simulation of a single spherical droplet drying considering shrinking and temperature profiles: first drying stage

Chaves

Birchal

Junior

2023

An. Acad. Bras. Ciênc.

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“…Based on the observation results and the CDC, many models and theories have been proposed to describe the generation process of dry powder from a single droplet. [12][13][14][15][16] Focusing on the behavior of the solid phase during the drying process, the development of the shell formation theory 17) and the introduction of a solid diffusion coefficient 18) have been reported. Although many drying models/theories for a single droplet have been proposed, they are insufficient for understanding the droplet drying process inside a spray dryer.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study on Spray Drying Process: Effect of Nonuniform Temperature Field and Interaction between Droplets on Evaporation Rates of Individual Droplets

Okada

Ohsaki

Nakamura

et al. 2021

CHEMICAL & PHARMACEUTICAL BULLETIN

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Spray drying process is widely used to produce particulate materials in the pharmaceutical industries, such as porous materials for direct compression, solid dispersion for improvement of drug dissolution properties, micro encapsulation to stabilize active compounds, taste masking, preparation of dry powder for inhalation. However, as many factors affect the physical properties of dried particles and the spray drying processes have complex behaviors in which heat and mass transfer occur simultaneously, the detailed mechanisms of dry particle generation have yet to be sufficiently elucidated. In this study, computational fluid dynamics was used to simulate water droplet evaporation in a spray dryer, and the evaporation kinetics of "individual droplets" in the droplet aggregate (group) were analyzed. The numerical simulation revealed that each droplet had different evaporation rates owing to the following two reasons. First, the driving force of evaporation, ΔT, changed every moment as the droplets traveled through different temperature fields in the drying tower. Second, it was calculated the driving force for droplet evaporation differed from the ideal system because the evaporation of other droplets changed the fluid characteristics around the droplets. The obtained results are important findings that lead to the understanding the spray drying process to design and manufacture the pharmaceutical products.

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“…The REA model equations are presented in section 3.2. The model constants for the drying kinetics of skim milk droplets with 40% TS content (as used in this work) are obtained from the literature [200,201].…”

Section: Droplets/particle Domainmentioning

confidence: 99%

Towards a multizone vortex dryer for dairy sprays

Rahman

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Conventional co-current spray dryers are widely used in the dairy industry to produce milk powder. These dryers are known for their high capital costs and low thermal efficiencies and are responsible for almost 27-55% of the total energy consumption of the dairy industries. In comparison to co-current dryers, countercurrent dryers have higher thermal efficiencies but they are not employed in the food industry due to the risks of product degradation.The conventional spray dryers used in the food industry suffer from multitude of disadvantages. They operate at relatively low air temperatures to avoid product degradation, which results in small drying rates [13]. Furthermore, the terminal velocities of the particles result in small gas-solid slip velocities, restricting the heat and mass transfer. The advent of multi-stage spray dryers (two or three stages) with integrated fluidized beds has improved the energy efficiency of the process by 13% [13][14][15][16][17]. Nevertheless, the drying systems are still far from beingThe evolution of a vortex chamber technology is a Radial Multizone Dryer (RMD) [44][45][46][47], shown in Figure 1.1-b. In this configuration, hot air enters axially into the central zone while the vortex is created via relatively cold airflow entering the RMD via the tangential channels; see Figure 1.1a. The process intensification is developed as an outcome of both: multizone drying operations with high and low temperature air feeding zones, and high-G acceleration. Consequently, the drying occurs in two steps: (i) the majority of drying takes Chapter 6 summarizes the conclusions drawn in the previous chapters and provides recommendations for future research.Experimental investigations of the atomization and counter-current spray drying process 9 Chapter 2 EXPERIMENTAL INVESTIGATIONS OF THE ATOMIZATION AND COUNTER-CURRENT SPRAY DRYING PROCESSThis chapter presents an experimental analysis of a counter flow spray drying process using water and skim milk as a feed. The study is performed by examining the droplet size distribution of sprays and the temperature profiles in the dryer. The influence of air inlet temperature, air mass flow rate, feed flow rate, and droplet size on air temperatures in the dryer is evaluated. The evaporation and deposition zones are found to be highly dependent on droplet sizes. The obtained results show that it is possible to achieve efficient contact between hot air and spray in a small volume using a counter-current mechanism.

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Mapping the Shrinkage Behavior of Skim Milk Droplets During Convective Drying

Cited by 10 publications

References 18 publications

Simulation of a single spherical droplet drying considering shrinking and temperature profiles: first drying stage

Simulation of a single spherical droplet drying considering shrinking and temperature profiles: first drying stage

Numerical Study on Spray Drying Process: Effect of Nonuniform Temperature Field and Interaction between Droplets on Evaporation Rates of Individual Droplets

Towards a multizone vortex dryer for dairy sprays

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