Flow regime assessment in falling film evaporators using residence time distribution functions

Abstract

A falling film evaporator (FFE) is an industrial device to concentrate solutions. The aim of this study wasto identify the flow regime, and characterize and model the residence time distribution (RTD) functions ofa FFE. Experimental runs were carried out with skim milk at three different feed mass flow rates. Flowwas characterized using experimental Reynolds number ( Ref ). The RTD function in the FFE was measuredin four sections of the vacuum evaporator equipment. These RTD functions were modeled by a combina-tion of perfectly mixed reactor tanks in series. In this study, when the flow regime changed from wavy-laminar to laminar, the mean residence time increased. The flow was analyzed as a main and a minorretarded flow, where two layers of product flowed through the evaporation tubes. The future of this workconsists of extending the RTD approach to other products and operating conditions in the evaporatordevice

Simulation of Water Evaporation on Ultimonitored Thermomix®: Potential Approach for Studies on Milk Evaporation

“…In dulce de leche industrial production, the presence of the exhauster is mandatory, primarily becau se it increases the evaporation rate, consistent with the present results. Simulations of the evaporation process should investigate the exhaust system or pressure reduction (vacuum evaporation), as demonstrated by Silva et al (2015), Silveira et al (2013), Rovedo et al (1991), Martinez et al (1990), andPauletti et al (1990). Silveira et al (2015) compared the efficacy of a pilot scale single stage evaporator in the evaporation of water and skim milk.…”

“…Sweetened condensed milk, dulce de leche, evaporated milk, and dairy powder products are the main dairy products obtained by evapora tion (SILVEIRA et al, 2013;SILVA et al, 2015;SILVEIRA et al, 2015;SCHUCK et al, 2016).…”

“…Many studies have concerned flow pro perties of concentrates, and heat transfer and industrial performance during evapo ration of food, but relatively few studies address evaporation of dairy products at labor atory scale (KIM et al, 1983;DODEJA et al, 1990;TEJINDER, 2000;RIBEIRO;ANDRADE, 2003;SILVEIRA et al, 2013;SOROUR et al, 2013;SILVEIRA et al, 2015).…”

Evolution of soluble solid content and evaporation rate curves during the manufacture of dulce de leche (dl)

“…Evaporation of dairy liquids is an important step in the dairy industry. Sweetened condensed milk, dulce de leche (DL), and evaporated milk are the main dairy products obtained by evaporation, as well as dairy powder products (Schuck et al, 2016;Silveira et al, 2015;Silva et al, 2015;Silveira et al, 2013). The concentration operation strongly modifies the product's physicochemical conditions, negatively impacting the concentrate as well as the process (Tanguy et al, 2016).…”

Interfacial shear stress, heat transfer and bubble appearance in falling film evaporation

“…The fluid product falls downward along the inside of tubes (or outside, depending on the application: milk, black liquor) [1][2][3] driven by the force of gravity, ensuring the wettability of the entire heated surface. The heat for the evaporative process is provided by film condensation of saturated steam on the opposite side of the tube.…”