热式质量流量传感器混合对流传热模型

Heat Transfer Model of Mixed Convection for Thermal Mass Flow Sensor

考虑自然对流的影响,改进King定律,深入研究热式气体质量流量传感器的混合对流传热模型.针对恒流式热式气体质量流量传感器原理样机,分析不同流速下自然对流与强迫对流的关系.从自然对流的角度进行分析,指出King定律模型中指数n与对流强度比Gr/Re^2之间的变化规律.在天津大学常压气体流量标准实验装置上进行实验研究,实验管道管径为200,mm,流速范围为0.03~23.05,m/s.结合实验数据,建立指数n的数学模型,改进King定律模型,在低流速范围(0.03~1.00,m/s)内,与原King定律模型比较,质量流量测量精度有较大提高,平均误差从69.27%,减小到1.15%,.

Considering the impact of free convection,the King’s law was refined and a modified heat transfer model of mixed convection for thermal gas mass flow sensor was further studied.According to the prototype of thermal gas mass flow sensor with constant current,the relationship between free convection and forced convection over a wide velocity range was discussed.In the light of the influence of free convection,the relationship between the exponent n of King’s model and the convection intensity ratio 2 Gr/Re was observed.The calibration was carried out on the standard device of gas flow under normal pressure in Tianjin University.The experimental pipe diameter was 200,mm and the flow rate was 0.03-23.05,m/s.Based on the experimental data,the mathematical model of exponent n was established and the King’s model was improved.In the range of low flow rate(0.03-1.00,m/s),the accuracy of mass flow measurement was greatly improved compared with the results of the original King’s model.The mean error of 69.27%,was reduced to 1.15%,.