Drying of Almonds II: Multiple Particles

Abstract

Computational modeling is an efficient and effective tool for modeling of drying process for food products. Developing validated computational models for drying processes is essential to build energy efficient drying units, producing uniform quality of dried products. This work presents drying behavior of almonds with a specific focus on understanding interaction among multiple almonds. Eight (2x2x2) particles, and twenty-seven (3x3x3) particles arranged in the shape of a cuboid were used to conduct drying experiments in a Mettler Toledeo Moisture Analyzer unit. Experiments were conducted to measure the moisture loss data with respect to drying time using Almond kernels. Experimental data was used to understanding drying kinetics as well as variation in moisture content with respect to their positions in a cuboid. Computational fluid dynamics (CFD) based simulations were carried out for the flow, heat transfer and drying of particles in the unit. Actual geometry of individual particles were considered in simulations, to predict the variation in velocity, heat and mass transfer coefficients for all the particles. Simulations predicted moisture loss data that matches well with the experimentally measured values. Average moisture for each layer was also compared for various intermediate drying times. Simulation results captured the overall drying process for multiple particles system adequately.The results are compared with the results obtained with drying of a single almond. The approach, models and presented results will be useful for designing large scale drying units for almonds.

CFD modelling of almond drying in a tray dryer

“…It is therefore essential to develop fully coupled model equations for flow, temperature, moisture variation and solids temperature representing processes occurring in a tray dryer which need to be solved simultaneously. Based on our earlier work for single and multiple particles (Chilka and Ranade [9,10] ), it showed that temperature equilibrium within the almond particle was achieved quickly. The Biot number for heat transfer and mass transfer for almonds is 0.17 and 2.1, respectively.…”

“…The higher the Lewis number, the faster the mass transfer as compared to heat transfer will be. is the correction factor applied to the heat transfer coefficient h p , with the value obtained from the single and multiple particle study (Chilka and Ranade). D is the effective diffusivity estimated using Equation , and k is the almond thermal conductivity.…”

“…To capture the corresponding varying drying characteristics, estimation of temperature dependent variables is essential. Experiments and modelling of a single almond kernel, as described in Chilka and Ranade, [9,10] was used to estimate the effective diffusivity at different temperatures. Using the drying data at different temperatures, effective diffusivity as a function of temperature expressed using the Arrhenius law was obtained.…”

“…Transport properties that are crucial for drying characteristics are heat and mass transfer coefficients. The experiments and modelling of multiple particles by Chilka and Ranade [10] were used to determine the average heat transfer coefficient values for an almond kernel, which were extended for modelling of bulk drying characteristics.…”

“…Almonds are the food product considered in this study. In our earlier work (Chilka and Ranade [9,10] ), a detailed analysis for drying of single and multiple almond particles was carried out. Drying behaviour of a single almond particle, eight, and twentyseven almond particles arranged in 2 Â 2 Â 2 and 3 Â 3 Â 3 configurations were studied.…”