基于多维非稳态导热乘积法的粮粒热物性测定

Measurement of grain physical properties based on multi-dimensional unsteady thermal conduction product method

采用恒温箱结合黄铜短圆柱试样盒形成恒温边界,保证在被测试样中形成多维度热流。运用非稳态导热乘积法结合参数估计法对粮食颗粒导热系数、比热容等进行反演计算。同时考虑在恒温箱上开孔影响恒温箱效果,以及增加试验操作难度,系统采用ZigBee无线数据采集模块实现信号采集与传输。通过对玉米颗粒及稻谷的热物性参数灵敏度分析,发现比热容灵敏度系数较低,针对此,测算系统首先估算出热导率和热扩散率,再对比热容估计结果进行修正。建立试验测试装置,对包括皖稻121在内的4种粮食进行热物性测算,结果与相关文献吻合,同时利用皖稻121的热物性测算结果,理论计算和数值仿真监测点温升随时间变化情况,结果表明,理论计算温升变化趋势与实测温升较为一致,进一步验证了参数估计值的准确性与可靠性。

Formed constant temperature boundary with constant tern perature bath and combined with the brass short cylindrical sample box, the formation of multi-dimensional heat flow is guaranteed in the test sample. The unsteady thermal conductivity multiplication method and parameter estimation method were used to calculate the thermal conductivity and specific heat capacity of grain. At the same time, considering the effect of opening holes on the thermostat, and increasing the difficulty of experimental operation, the ZigBee wireless data acquisition module is used for signal acquisition and transmission. By analyzing the thermophysical parameter sensitivityanalysis of corn and paddy, the sensitivity coefficient of specific heat capacity is found to be low. In view of this, the calculation system first estimated the thermal diffusivity, and then compared the results of heat capacity estimation. An experimental test device was set up to calculate the thermal properties of four kinds of food including ＂Wandao 121＂. The results were consistent with the relevant litera- ture. At the same time, the thermal properties of ＂Wandao 121＂, the theoretical calculation and the numerical simulation were used to monitor the temperature rise over time. The results show that the theoretical trend of temperature rise is consistent with the measured temperature rise, further verifying the value of the parameter esti- mation accuracy and reliability.