抄録
Measurement uncertainty of a vortex shedding flowmeter, which has increasing popularity in many fields of industries, is influenced by the geometry of pipe works and pipe fittings upsteream of the flowmeters. However, in spite of practical importance, no international nor domestic standard specifies the installation conditions of the flowmeter because of a lack of systematic experimental data.
National Research Laboratory of Metroloy in Japan has carried out the intensive measurements of the effect of installation conditions on the flowmeter to make contribution to the flowmetering standards in cooperation with six manufactures of the flowmeter. A test line of 150mm in diameter for a water flowmeter was used for the experiment at a Reynolds number range about 2×105 to 7×105. The effects of six kinds of piping configurations were examined at various straight pipe lengths upstream of the flowmeter for all four kinds of liquid vortex flowmeters commercially available in Japan.
Basic performance of the vortex flowmeter was revealed in comparison with a turbine meter in the experiment to evaluate repeatability of measurements. Uncertainty of measured date in the experiments was estimated about 0.1%. It was found that each magnitude of the installation effect strongly depends on the design of the flowmeter. The experimental results are presented in details and are summarized as a recommendation of the required minimum upstream straight pipe lengths to reduce the effect less than 0.5% for all the flowmeters concerning each pipe configuration and fitting.
