电磁流量计在制冷系统中的应用及不确定度评定

Application of electromagnetic flowmeter in refrigeration system and the uncertainty assessment

电磁流量计在制冷系统中被广泛用作流量的监控仪表。为了保障流量计在机组运行中监测到的数据准确可靠,根据JJG 1033-2007《电磁流量计检定规程》,通过构建数学模型,对用水流量标准装置校准电磁流量计的测量结果的进行不确定度评定,并从各影响量引入的不确定度分量进行了详尽分析,得出测量重复性、标准装置、温度和膨胀系数等因素引入的标准不确定度分别为0.014%、0.055%、0.001 2%、0.000 23%。由不确定度传播率,最终得出合成标准不确定度为0.06%。试验数据表明电磁流量计测量重复性和标准装置引入的不确定度分量在最终评定结果中占比达到99.9%,而温度、压力、膨胀系数等其他因素引入的不确定分量占比仅为0.1%。因而在实际应用中可以忽略由温度、压力、膨胀系数等其他因素对流量测量的影响。

The electromagnetic flowmeter is widely used as a flow monitoring instrument in the refrigeration system.In order to ensure the accuracy and reliability of the data monitored in the unit operation,according to JJG 1033—2007,By constructing a mathematical model,the uncertainty of the measurement results of the electromagnetic flowmeter is assessed,and the uncertainty components of the influence of the measurement repeatability,standard device,temperature and expansion coefficient are 0.014%,0.055%,0.0012%,0.00023%,respectively.From the uncertainty propagation formula,the resultant standard uncertainty is 0.06%.The test data show that the measurement reproducibility and the standard device accounted for 99.9%of the final evaluation results,while the uncertainty component introduced by the change of temperature,pressure and expansion coefficient was only 0.1%.Therefore,the influence of temperature,pressure,expansion coefficient and other factors on the flow measurement can be ignored in practical application.