Insights in convective drying of fruit by coupled modeling of fruit drying, deformation, quality evolution and convective exchange with the airflow

Abstract

Coupled modeling of fruit drying, deformation and quality evolution of a half-circular apple fruit slice is combined with modeling of the convective heat and mass exchange with the airflow. The aim was to gain more insight in the fruit drying kinetics, more particular in heterogeneities and couplings in moisture content and shrinkage as well as quality loss within the fruit during drying. Further aims were to investigate the impact of several modeling assumptions and to analyze the effect of the peel on the drying behavior. Large differences in internal moisture distribution and deformation were observed within the fruit slice. They were caused by the complex airflow field around the slice, which induced a spatial variation in convective heat/mass transfer coefficients (CTCs) over the fruit surface. The differences with imposing a single, constant CTC across the fruit surface (non-conjugate approach) indicated the need for including spatially-resolved CTCs (conjugate approach). The impact of including deformation in the model was also quantified. Not accounting for explicit airflow modeling or deformation affected the fruit temperature, and thereby also the fruit quality decay. The presence of a peel affected the drying process and the deformation, resulting in an asymmetrical collapse towards the center of the fruit slice. Coupling the modeled hygrothermal history of the fruit during drying, to fruit quality modeling opens new opportunities for optimizing drying processes. Thereby, the process can be optimized not only in terms of drying time or energy consumption, but also to achieve the best product quality.

3D simulation of transport phenomena of onion drying with moving boundary in a vacuum oven

“…The concept of shrinkage velocity was well described in the literature (Joardder, Kumar, & Karim, ). In this study, the deformation of onion was considered as an isotropic hyperelastic material in line with similar studies of fruits and vegetables in the literature (Defraeye & Radu, ). Food does not have isotropic deformation.…”

Physics-Based Digital Twin Identifies Trade-Offs Between Drying Time, Fruit Quality, and Energy Use for Solar Drying

“…Such model output lacks a spatial and temporal resolution of the governing variables, i.e., moisture content and temperature, and only capture gradients in the lateral direction of the product. There are advanced mechanistic models available that are based on the fundamental physical processes that occur during drying, including heat and mass transport and structural deformation (Datta et al, 2012;Gulati et al, 2016;Defraeye and Radu, 2018). Recently, a multiscale model was presented, where fruit drying was modeled from the cellular scale up to the entire product by upscaling method (Prawiranto et al, 2020).…”

Numerical Investigation of the Deformable Porous Media Treated by the Intermittent Microwave

“…Namely, when the material deformation is small, the total deformation is the summation of the mechanical deformation (e.g., elastic deformation [30,31], elastoplastic deformation [32,33], viscoelastic deformation [34][35][36][37]) and the deformation due to the moisture and temperature changes [11,[38][39][40]. While for a large deformation, the total deformation is multiplicative, split into the mechanical deformation (e.g., hyperelastic deformation [41][42][43]) and the moisture loss-induced deformation.…”

“…From the previous studies, Young's modulus is used as a constant [31,[34][35][36]44] or a function of moisture content [30,32,33,42,43,45]. In most of the theoretical models, the materials are assumed to be solely rubber-like and undergo an ideal shrinkage during the processes [32,33,36,41,43,45]. However, the Poisson's ratio, a more realistic description, is considered as a variable, varying with moisture and temperature [46][47][48].…”