Abstract
Starting with the retort processing of canned food products, horizontal axial and End-over-End (EoE) rotation have been the innovative approaches for mechanical agitation for temperature uniformity. Shaking process of reciprocal agitation has been recently introduced, and the objective of all these processes is to reduce processing time to enable energy savings and improved quality. Rather effective EoE rotation has been demonstrated in computational - experimental studies, and reciprocal agitation process was reported to impose forces up to 3-4 g to enhance the convection mixing. While liquid foods (with Newtonian fluid properties) face a significant process improvement with increased EoE rotation reciprocal agitation rates, effects of these process are limited for non-Newtonians. An increase in the rotational rate was even demonstrated to reverse the mixing effect converting the heat transfer to conduction. Considering the possible advantages of the individual process, the objective of this study was to demonstrate a combined effect of simultaneous EoE and reciprocal agitation (RA-EoE) on heat transfer – temperature uniformity enhancement and determine optimal rotation and oscillation rates. For this purpose, this study was computationally carried out in 2-dimensional (2-D) geometry where a rectangular cross-section consisted of a Newtonian (water) liquid with 10% head space (air). The use of a 2-D case was preferred to avoid computational expenses of 3-D simulations. To predict temperature changes and velocity evolution inside the system, a multi-phase model was developed using a finite volume method, based on discretization of governing equations for liquid and gas phases in a non-inertial reference frame of moving mesh, up to 80 rpm rotation and reciprocal agitation rates were used, and the results demonstrated a possible improvement in the temperature increase and uniformity combining the two agitation methods.
