Heat and mass transfer in coffee fruits drying
Heat and mass transfer in coffee fruits drying
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DOI：
10.1016/j.jfoodeng.2004.09.008
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发表时间：
2005-09
影响因子：
5.5
通讯作者：
M. A. Sfredo;J. Finzer;J. R. Limaverde
中科院分区：
文献类型：
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作者：
M. A. Sfredo;J. Finzer;J. R. Limaverde
本文介绍了咖啡果在振动盘和固定床干燥器中的分批干燥。振动的振幅和频率分别为：Ax=0.211×10− 3和Ay=0.945×10− 3 m; 60 Hz。该设备包括一个垂直的干燥隧道，其中引入了两个装有咖啡樱桃的铝托盘。初始水分含量为约66%（ppm），最终水分含量为约11%。通过测量咖啡果托盘的重量来监测干燥。这些数据使干燥动力学和传热传质系数，以及有效的水分扩散率的测定。在所有的计算中，考虑了咖啡果在干燥过程中的收缩。振动的作用是提高干燥速率和有效水分扩散率，从而提高传热传质系数。在45°C的温度下，振动系统中的干燥时间比没有振动的系统中的干燥时间小约11%。温度为45°C时，有效水分扩散率在0.1×10− 10和1×10− 10 m2/s之间;温度为60°C时，有效水分扩散率在0.3×10− 10和3×10− 10 m2/s之间。
This work presents batch drying of coffee cherries on vibrated trays and in a fixed bed drier. The amplitude and the frequency of vibration were: Ax=0.211×10−3and Ay=0.945×10−3m; 60Hz. The equipment consists of a vertical drying tunnel, in which two aluminum trays with coffee cherries were introduced. The initial moisture content was approximately 66% (wb) and the final moisture content was about 11%. The monitoring of the drying was effected by measuring the weight of the tray of coffee cherries. This data enabled the determination of the drying kinetics and of the heat and mass transfer coefficients, and the effective moisture diffusivity. In all the calculations, the shrinkage of the coffee cherries during the drying was considered. The vibration acted to increase the drying rate and the effective moisture diffusivity and consequently the heat and mass transfer coefficients. The drying time, in the vibrated system at a temperature of 45°C was approximately 11% smaller than in the system without vibration. The effective moisture diffusivity was between 0.1×10−10and 1×10−10m2/s for a temperature of 45°C and between 0.3×10−10and 3×10−10m2/s for a temperature of 60°C.