Effective Moisture Diffusivity, Activation Energy and Energy Consumption in Thin-layer Drying of Jujube (Zizyphus jujube Mill)

Authors
A. Motevali
A. Abbaszadeh
S. Minaei
M. H. Khoshtaghaza
B. Ghobadian
Department of Agricultural Machinery Engineering, College of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran.
Abstract
Jujube (Zizyphus jujube Mill), a valuable medicinal plant, is consumed either as fresh fruit or dried product in Iran. Drying jujube guarantees a longer shelf time while preserving its quality to be used in medical and pharmaceutical industries. In this research paper, the influence of several drying conditions on the effective moisture diffusivity, activation energy, energy consumption and required specific energy in the drying of jujube is presented. Temperature levels of 50, 60 and 70 ºC and hot air velocities of 0.5, 1 and 1.5 (m s-1) were used as the treatments. Effective moisture diffusivity of jujube fruit during the drying process was in the range of 1.1532-5.1895×10-10 (m2 s-1) for the first period and 0.4036–2.3064×10-10 (m2 s-1) for the second period. Also, the values of energy of activation in both periods were determined to be between 34.97 and 74.20 (kJ mol-1). The energy consumption and the required specific energy for drying were in the range of 79.1- 92.46 (kW h) and 203.59 – 900.08 (kW h kg-1), respectively. Results show that energy consumption diminished when temperature increased at each air velocity, while it increased with increasing hot air velocity.

Keywords

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Journal of Agricultural Science and Technology
Volume 14, Issue 3
May and June 2012
Pages 523-532