Moisture transformation and transport during the drying process for Radix Paeoniae Alba slices

• DOI: 10.1016/j.applthermaleng.2016.08.123
• Publication Date: 2016-08-24T16:03:49Z
• Authors: Ran Li; Chuanping Liu; Chenwei Zhang; Jianbiao Shen; Li Wang; Chao Jia
• Keywords: 04 agricultural and veterinary sciences; 0405 other agricultural sciences; 6. Clean water

Abstract The moisture-binding type and change in moisture content of Radix Paeoniae Alba (RPA) slices were determined during their drying process. Water in RPA slices exists in two types: bound water (BW) and free water (FW). During the drying process, FW diffuses from inside the sample to outside it; simultaneously, it is mutually transformed with BW. The drying rate (R) exhibits a nonlinear relationship with the moisture content (M) of RPA slices, and the slope of R (dR/dM) changes non-monotonically with M. When the diffusion law of FW as well as the mutual transformation between FW and BW are considered, the drying process of the slices can be divided into three stages: FW drying, mix-drying, and BW-drying periods. Mutual transformation between FW and BW is simplified as a reversible conversion process, and a drying model is established for RPA slices based on Fick’s second law.