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Analysis of influence of pipeline internal surface roughness on flow rate measured by means of standard pressure differential devices

The paper presents the analysis of scientific and technical sources on the influence of constructive features of pressure differential flowmeters on flow rate measurement error. According to the research results, the significant surface roughness of pipe sections downstream of the orifice plate does not significantly affect the flow measurement result. The influence of the pipe roughness upstream of the orifice plate depends on geometric characteristics of roughness, the pipe diameter, the relative area of the orifice plate throat, and the Reynolds number. The change in the uncertainty of the orifice discharge coefficient under conditions of inhomogeneous measuring pipe roughness in the pipe section with a length of 10D upstream of the orifice plate is analyzed. The authors have determined that even a pipe section length of 1.5D with high roughness might be enough to change the flowmeter readings by more than 1% at a large orifice diameter ratio.