A dimensional analysis approach for modelling the size of droplets formed by bi-fluid atomisation

Abstract

a b s t r a c tThis paper presents a dimensional analysis (DA) § approach of the atomisation process using a bi-fluid nozzle, allowing to predict droplet sizes of model solutions and skimmed milk concentrates in large ranges of operating conditions. Experimental results confirmed the atomisation mechanism described in the literature, by underlining that the spraying operation is controlled by the coupling of liquid physicochemical properties (viscosity, surface tension, density) and operating conditions (air pressure and liquid flow rate). It was also highlighted that droplet coalescence occurs from a certain distance to the nozzle, counteracting the atomisation mechanism and leading to a reincrease in the droplet size when moving away from the nozzle. Consequently, the modelling of droplet size by DA was improved by adapting the model coefficients of the dimensionless process relationship to the involved mechanisms: either atomisation only close to the nozzle outlet or atomisation followed by droplet coalescence at longer distance to the nozzle.

Impact of Spray-Drying Process Parameters on Dairy Powder Surface Composition and Properties

“…Concurrently, the higher the spraying pressure, the smaller the droplets, the higher the drying rate, and again, the closer the surface and the bulk compositions. [12,147] These observations are in agreement with literature data obtained with laboratory-scale spray-dryers, where more lactose and less protein (in comparison with the bulk composition) were observed at the surface of skim milk powder spray-dried at elevated temperatures. [23,24] Besides, the surface fat content of the investigated powders (around 5% -7%), determined by XPS analysis, was significantly inferior to literature values.…”

“…[11] However, the production still cannot ensure the quality of the final products because of the lack of information concerning the impact of process parameters on powder functionalities. [12] Many food features can now be attributed to the lack of homogeneity between the powder surface and the core or the particle bulk composition. [4,8] Consequently, the current study aims at understanding the impact of the main drying parameters on some dairy powder properties.…”

Lactobacillus rhamnosus GG encapsulation by spray-drying: Milk proteins clotting control to produce innovative matrices

“…Petit et al, (2015) showed that the formation of droplets by shear effect during spraying 291 in bi-fluid nozzles was essentially controlled by air pressure and liquid viscosity. Thus, the outlet 292 air temperature in the feed solution was not expected to influence the increase factor measured 293 during spraying only, and the same increase factor was considered for the calculations related to 294 spray-drying experiments.…”

Experimental Investigation of Spray Characteristics of Pre-Filming Air-Blast Atomizers II – Influence of Liquid Properties

“…The coefficients of the proposed dimensionless process model are determined separately by a power law using the Origin 2018 software. A least-square fit has been employed to correlate the determined model with the measurement results which was used also by previous researchers (Glathe, Wozniak, & Richter, 2001;Petit et al, 2015). Identified coefficients on the basis of the experimental results were listed in Table 4.…”