Heat Transfer Coefficients to Liquids with Food Particles in Axially Rotating Cans

Abstract

Heat transfer rates were measured for steam-heated, rotating cans containing potato spheres in water. Can rotational speed (9.3-101 rpm), sphere size (22.2-35.0 mm), and potato volume fraction (0.107-0.506) were varied in 14 triplicated experiments. Overall heat transfer coefficients were correlated within 225% with physical properties and operating variables by an equation derived by dimensional analysis. Film coefficients (h,) for heat transfer from the water to potatoes in the can were determmed by thermocouple measurement of potato surface temperatures; values were found to be finite and nearly invariant, averaging h, = 160 * 30 W/m*K. The lack of variation of hp suggested that for the experimental conditions tested, there was little relative motion between liquid and particles.

Thermal Processing of Liquid Foods with or without Particulates

“…He was unable to explain the reason behind this negligible effect. Deniston et al (1987) determined the heat transfer rates to steam-heated, axially rotating cans containing potato spheres in water. They attributed the insensitivity of h fp to can rotational speed (9.3-29.1-101 rpm) to three experimental conditions resulting in small changes in relative particle-fluid velocity: (1) closeness of density of potato particle (1,063 kg/m 3 ) to that of water, so that particle settling due to gravity was minimal; (2) since the particle was located at the can center, centrifugal force acting on it was small; and (3) stiffness of the thermocouple wire hindered the particle motion.…”

“…They attributed this to the decreased relative particle-to-fluid velocity due to the drag exerted on the fluid by the particles. Deniston et al (1987) reported a slight increase in h fp with increasing particle volume fraction, which was lowered for higher particle contents. They attributed this to the tight packing in the can (higher particle volume fraction), which restricted the particle free movement.…”

“…Extensive research has been done in the retort method Clifcorn et al 1950;Conley et al 1951;Deniston et al 1987;Hassan 1984;Lenz and Lund 1978;Naveh and Kopelman 1980;Peralta Rodriguez and Merson 1983;Quast and Siozawa 1974;Rao and Anantheswaran 1988) to study heat transfer in liquid foods (with or without particulates) because development of a mathematical model to optimize these thermal processes requires the knowledge of heat transfer coefficients (Clark 1978). In the retort method, the main focus has been to determine the effect of various parameters on heat transfer coefficients.…”

An Empirical Methodology for Evaluating the Fluid to Particle Heat Transfer Coefficient in Bi-axially Rotating Cans Using Liquid Temperature Data

“…For the proper design and successful optimization of the rotational retort process, a felicitous methodology to predict particle lethality during processing is extremely helpful. Several studies have been conducted on the evaluation of heat transfer to canned liquid particulate mixtures in end-over-end rotation (Lekwauwa and Hayakawa 1986;Sablani and Ramaswamy 1995, 1996, 1997, 1998, 1999Krishnamurthy et al 2000;Meng and Ramaswamy 2005); however, there are very few studies available to determine U and h fp in axial mode of rotation (Lenz and Lund 1978;Hassan 1984;Deniston et al 1987;Fernandez et al 1988;Stoforos andMerson 1990, 1991). Furthermore, there are several limitations associated with the axial mode methods applied to predict lethality during heating for the real food particle system with finite internal and surface resistance to heat transfer (0.1<N Bi <40).…”

“…Similar to the traditional thermal processing, it is also necessary for the particles and fluid to receive the predetermined minimum heat treatment in the form of minimum process lethality (F o ) during agitation processing. In order to predict the heat penetration data and to fully understand and mathematically describe the mechanism of heat transfer in liquid particle systems, it is necessary to have data on the associated heat transfer coefficients (Deniston et al 1987;Hassan 1984;Merson and Stoforos 1990). For the proper design and successful optimization of the rotational retort process, a felicitous methodology to predict particle lethality during processing is extremely helpful.…”