封闭管道中流量的测量.使用流量计或皮托静压管测量圆管中涡流或不对称流动条件下流量用速度面积法

[中文适用范围]： 本国际标准规定了通过电流计或皮托静压管测量圆形管道中旋流或不对称流动条件下的流量的速度面积方法。 它规定了所需的测量、要采取的预防措施、要应用的校正，并描述了在非对称或旋流中进行测量时引入的额外不确定性。 然而，仅考虑具有可忽略的径向分量的流动。 此外，如果在测量横截面上的任何一点，局部速度与管道轴线的角度大于 40°，或者指数不对称度 Y（在附录 F 中定义）大于 0.15。 本国际标准仅涉及 ISO 3354 和 ISO 3966 中定义的测量局部速度的仪器。 如果使用皮托静压管，则本国际标准仅适用于与局部速度相对应的马赫数不超过 0.25 的流动。 [外文原描述]： ISO 7194:2008 specifies velocity-area methods for measuring flow in swirling or asymmetric flow conditions in circular ducts by means of current-meters of Pitot static tubes. ISO 7194:2008 specifies the measurements required, the precautions to be taken, the corrections to apply, and describes the additional uncertainties which are introduced when a measurement in asymmetric or swirling flow has to be made. Only flows with a negligible radial component are considered, however. Furthermore, it is not possible to make a measurement in accordance with ISO 7194:2008 if, at any point in the measuring cross-section, the local velocity makes an angle of greater than 40° with the axis of the duct, or where the index of asymmetry Y (defined within ISO 7194:2008) is greater than 0,15. ISO 7194:2008 deals only with instruments for measuring local velocity as defined in ISO 3354 and ISO 3966. If Pitot static tubes are used, ISO 7194:2008 applies only to flows where the Mach number corresponding to local velocities does not exceed 0,25.