Analysis and modeling of heat and mass transfer and adsorption isotherms of the aqueous extracts vacuum contact drying. (April 2023)

• Record Type: Journal Article
• Authors: Xu, Peng; Zhang, Zhentao; Peng, Xueyuan; Yang, Junling; Yuan, Tiejian; Yang, Zhaoyang; Jia, Xiaohan; Li, Xiaoqiong
• Is Part Of: Applied thermal engineering. Volume 224(2023)
• Publication Date: 2023-04
• Subjects: Aqueous extracts -- Vacuum drying -- Sharp interface formulation -- Mathematical models -- Adsorption isotherms; Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2023.120141
• Languages: English
• ISSNs: 1359-4311

Abstract

Highlight: The viscosity and viscosity models of aqueous extracts (AE) was provided. The heat transfer coefficient is 6–9 W/ (m 2 ·K) when superheat is between 50 and 75 ℃. Initial moisture of AE increases by 10 %, vacuum drying time increases by 4 min. The specific heat capacity and the thermal conductivity of AE are given. Page and Peleg are the best models for AE vacuum drying and adsorption isotherms. Abstract: Vacuum contact drying is the most merit drying technology to ensure the quality and throughput of traditional Chinese medicine aqueous extracts. To study the heat and mass transfer of colloidal semi-solid porous media during vacuum contact drying, the sharp interface formulation was established to simulate the thin layer (4 mm) Lonicera japonica Thunb. aqueous extracts vacuum drying at high-temperature (110 and 120 ℃) and low-pressure (10, 15 and 20 kPa). And mathematical models were used to investigated drying kinetics and adsorption isotherms. Results show that the sharp interface model can predict final temperature and moisture ratio with the error is less than 20 %. The models of viscosity variation, specific heat capacity, heat capacity, effective thermal conductivity and heat transfer coefficient of boiling under different conditions were investigated to provide reference for subsequent research. When the vacuum drying superheat is between 50 ℃ and 75 ℃, the boiling heat transfer coefficient is among 6 to 9 W/ (m 2 ·K). The Page is the most suitable semi-empirical model to describe the water migration law of the aqueous extracts. The adsorption isotherms of the extract powder were investigated by experiment and the Peleg is the most suitable model.