ARS | Publication request: Spatial variation of drying rates within a multi-tray cabinet dryer (abstract)

Submitted to: National Meeting of Institute of Food Technologists/Food Expo
Publication Type: Abstract Only
Publication Acceptance Date: February 9, 2012
Publication Date: June 28, 2012
Citation: Milczarek, R.R., Vallot, L., Tom, M.Y., Mchugh, T.H. 2012. Spatial variation of drying rates within a multi-tray cabinet dryer (abstract). National Meeting of Institute of Food Technologists/Food Expo. (00).

Technical Abstract: For dried fruit and vegetable products, uniform product quality is desirable. This can be achieved through uniform drying conditions, including temperature, humidity, and air velocity. Modeling the airflow over a single layer of product on a single tray is relatively straightforward, and mathematical models of drying behavior often assume this configuration. However, cabinet dryers often contain many trays of material, creating turbulent conditions and nonuniformity of airflow throughout the dryer. Thus, the objective of this work was to characterize the degree of nonuniformity of drying rates within different areas of a cabinet dryer. In a full factorial designed experiment, damp sponges were placed at 81 locations (9 locations on each of 9 trays) in a benchtop cabinet food dehydrator. The sponges were dried using a constant inlet temperature and fan speed. Drying trials were performed in triplicate, and the average drying rate at each location (expressed as the coefficient of the exponential fit of moisture loss over time) was calculated. One replication of the drying experiment was repeated using diced apricot as a model fruit material. For the sponge drying experiment, 25 statistically different (p < 0.05) drying rates were identified throughout the cabinet; these spanned a range of 4 orders of magnitude. Samples closest to the fan had the fastest drying rates, and some left/right asymmetry was observed. Compared to the sponges, the apricot samples exhibited slower moisture loss, but the spatial variation in drying rate was similar between the two materials. This study demonstrates that, in a typical cabinet dryer, spatial inhomogeneity in drying rate can be quite large. The results of this work will guide the multiphysics modeling of airflow through different food dryer designs in order to optimize fan placement, tray configuration, and timing of tray rearrangement during drying.