冷冻速率对蚕豆热物性变化规律影响的实验研究

研究了不同冷冻速率下蚕豆热物性的变化规律。利用Hot Disk得到蚕豆在-30～30℃下的热导率变化曲线;通过DSC和低温冷冻实验台,冷冻速率在5～80℃/min条件下将蚕豆切片进行冷冻实验,得到了不同冷冻条件下冻结点、结晶点及比热容的变化规律。测试结果表明:蚕豆热导率随着温度的降低先减小再增大;冻结点随着降温速率的增大而增大;蚕豆的结晶点在降温速率小于20℃/min时出现浮动,但总体上,结晶点随着降温速率的增大而降低。在不同降温速率下,比热容随温度的变化规律基本相同,但在冷冻相变过程中发生剧烈变化。通过对冷冻过程中蚕豆热物性的实验研究,为冷冻干燥种子的传热传质分析提供了实验数据的支撑。

Experimental study on the effect of freezing rate on thermal properties of viciafaba

The changes of thermo-physical properties of broad bean under different freezing rates were studied. The curve of thermal conductivity of broad bean at-30 to 30℃ was obtained by Hot Disk.Through the DSC and low-temperature freezing test-bench, the broad bean slices were frozen at the freezing rate of 10~80 °C/min, and the changes of crystallization point, freezing point and specific heat capacity under different freezing conditions were obtained. The results show that the thermal conductivity of broad bean decreases first and then increases with the decrease of temperature.The crystallizat pointion of broad bean appear floating,when the cooling rate is less than 20°C/min.However, in general, the crystallization point decreases with the increase of cooling rate. The freezing point increases with the increase of cooling rate.The variation law of specific heat capacity with temperature is basically the same under different cooling rates, but changes dramatically during the freezing phase transition.The experimental study of the thermal properties of broad bean during the freezing process can provide the experimental data for the heat and mass transfer analysis of the freeze-dried seeds.