Simple flow meter and viscometer of high accuracy for gases
Simple flow meter and viscometer of high accuracy for gases
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DOI：
10.1088/0026-1394/42/1/002
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发表时间：
2005-02-01
期刊：
影响因子：
2.4
通讯作者：
Berg, RF
中科院分区：
文献类型：
--
作者：
Berg, RF
本文提出了一个气体层流通过圆形截面长毛细管的模型和测量方法。使用已知尺寸的石英毛细管线圈的模型产生已知粘度的气体的流量，不确定度为0.04%。或者，将模型和毛细管与流速的独立测量相结合，产生具有类似不确定性的气体粘度。该模型修正了哈根-普瓦勒耶方程，用于（1）偏离理想气体行为，（2）毛细管壁处的滑移，（3）毛细管入口处的动能变化，（4）气体沿着毛细管长度的膨胀，（5）粘性加热和（6）长毛细管盘绕时发生的离心效应。变成一个小体积。的修正表示在熟悉的无量纲parameters.Measurements室温附近使用氦气，氮气，氩气，丙烷和六氟化硫表明，该模型描述了在雷诺数为1000大的各种性质的气体的流速。将流速与毛细管长度和半径的独立测量相结合，得到了25 ℃下五种气体的新的绝对粘度值，不确定度为0.04%。通过将氦粘度的结果与最近使用量子力学和统计力学的计算结果进行比较，独立地验证了这个小的不确定性。目前的结果允许一个构建一个流量计或粘度计的类似精度没有测量的毛细管半径，只有一个标称测量的毛细管长度。
A model and supporting measurements are presented for the laminar flow of gases through a long capillary with a circular cross section. Using the model with a coil of quartz capillary of known dimensions yields the flow rates of a gas of known viscosity with an uncertainty of 0.04%. Alternatively, combining the model and capillary with an independent measurement of flow rate yields the gas viscosity with similar uncertainty. The model corrects the Hagen-Poiseuille equation for (1) departures from ideal gas behaviour, (2) slip at the capillary walls, (3) kinetic energy changes at the capillary entrance, (4) gas expansion along the length of the capillary, (5) viscous heating and (6) centrifugal effects that occur when a long capillary is coiled to fit. into a small volume. The corrections are expressed in terms of familiar dimensionless parameters.Measurements near room temperature using helium, nitrogen, argon, propane and sulfur hexafluoride demonstrated that the model describes the flow rates of gases with widely varying properties at Reynolds numbers as large as 1000. Combining the flow rates with independent measurements of the capillary length and radius yielded new absolute viscosity values for the five gases at 25 degrees C with an uncertainty of 0.04%. This small uncertainty was verified independently by comparing the result for the viscosity of helium to recent calculations using quantum mechanics and statistical mechanics. The present results allow one to construct a flow meter or viscometer of similar accuracy with no measurement of the capillary radius and only a nominal measurement of the capillary length.