Residence-time distribution of air flow in a spray drying chamber.

Abstract

Residence-time distribution in a spray dryer is very useful for the analysis of drying of atomized droplets. Also, for better understanding of spray dryer performance, it is most desirable to obtain the air flow

Effect of processing parameters on spray drying of full-fat soymilk

“…Many models assume the droplets travel at the same velocitv* as the drying media. This assumption is reasonable based on studies such as those reported by Usui et al (1985), Sano (1989), andZhelev (1989). These authors have found that the Peclet number, the ratio of bulk mass transfer to difEusion mass transfer of the air, remains constant for a particular dryer regardless of the characteristic air velocity.…”

“…Zhelev (1989) found that the mixing inside the central core flow approached full mixing. Usui et al (1985) studied the residence time of air without droplets inside the drying chamber and obtained comparable experimental and simulation results when modeling the flow as a series combination of piston flow and perfect mixing.…”

“…Researchers such as Bailey et al (1970) assumed laminar air flow. Usui et al (1985), however, reported that the air flow is turbulent. Crowe (1980) states that the Reynolds number (Re) based on the relative gas-droplet velocity is less than 1000, thus compressibility and rarefaction effects can be neglected.…”

“…More recent efforts at dynamic modeling of spray dryers include the work of Usui et al (1985), Zaror and Perez-Correa (1991), Govaerts et al (1994), Perez-Correa and Farias (1995),…”

Factors Influencing Flow Pattrens, Temperature Fields and Consequent Drying Rates in Spray Drying

“…Residence times of air flowing in a spray-drying chamber, with and without liquid spray, have been measured by Keey and Pham (1977), Pinilla, et al (1984), and Usui, et al (1985b). Such results have often been reported and interpreted in terms of overall Peclet numbers.…”