核桃热泵干燥特性及数学模型研究

STUDIES ON THE HEAT PUMP DRYING CHARACTERISTICS AND MATHEMATICAL MODEL OF WALNUTS

以热泵恒温干燥箱研究38、45、50、55℃干燥温度、2 m/s风速条件下及1、2、3、4 m/s风速、45℃干燥温度条件下核桃热泵干燥特性曲线和干燥速率曲线的相关规律,通过origin软件对实验数据进行拟合得到核桃热泵干燥数学模型。结果表明:干燥温度对核桃干燥速率影响较大,55℃下的最大干燥速率是50、45、38℃时的1.08、1.24、1.49倍,在一定温度范围内,干燥温度越高,干燥时间越短;风速在干燥初期对核桃干燥速率影响较大,后期影响较小,风速增大到一定程度后,再增大风速对干燥速率几乎无影响,风速为2 m/s时的干燥时间比1 m/s时的缩短约23.8%,风速为3 m/s时的干燥时间比2 m/s时缩短约18.7%,风速为4 m/s时的干燥时间比3 m/s时缩短约15.3%;Page模型能较好地模拟核桃热泵干燥的整个过程,预测值与实际值基本吻合。

In order to explore the regularity of the heat pump drying characteristics curves and drying rate curves of walnuts, a heat pump constant temperature drying oven was used. The drying experiments were carried out at the temperature of 38 ℃ ,45 ℃ ,50 ℃ and 55 ℃ at a constant air velocity,and at the air velocity of 1 m/s,2 m/s,3 m/s and 4 m/s at a constant temperature. Then the experimental data was used to fit by software （Origin） and got the drying mathematical model. The results indicated that drying temperature has a greater influence on the drying rate of walnut, maximum drying rate under the condition of 55 ℃ was 1.08 times of 50 ℃, 1.24 times of 45 ℃, 1.49 times of 38 ℃, to a certain temperature range, the higher the drying temperature, the shorter the drying time. Air velocity has a greater influence at the beginning of the drying, adding air velocity has little effect on the than the air velocity of lm/s, m/s, the air velocity of 4 m/s but a less influence latterly. When the air velocity increases to a certain degree, drying rate, the air velocity of 2 m/s shortened the drying time by about 23.8% the air velocity of 3 m/s shortened the drying time by about 18.7% than the air velocity of 2 shortened the drying time by about 15.3% than the air velocity of 3 m/s. Page model could simulate the heat pump drying of walnuts well and the measured value basically agreed well with calculated value.