Air Speed Measurement Standards Using Wind Tunnels

Abstract

Accurate air speed measurement is essential to understand flow phenomena and practical engineering problems, such as wind turbines, air ventilation systems, air filter testers, and fan testers, etc. Standard wind tunnels can provide good testing environments for calibrating and testing industrial anemometers, which are widely used for measuring air speeds in applications to various on-site air speed measurements. Air speed standards can be established by adopting a wind tunnel. In this case, some knowledges are required, regarding measurement accuracy and uncertainty assessment. To certify an industrial anemometer, a calibration certificate is issued by an accredited laboratory, which is recognized by an accreditation organization in a country, according to the ISO/IEC 17025 guide (ISO, 2005). The national metrology institutes in every country advise the accreditation organization in recognizing the accredited laboratory by providing technical supports with the national measurement standards. Traceability is established from the national standards to the industrial standards, by transferring national measurement standards from the national metrology institutes to the accredited laboratories. If an industrial anemometer is exported to a foreign country, an international calibration certification must be issued to provide the measurement accuracy requested by a customer in the foreign country. Mutual recognition arrangement realizes the international certification procedures by harmonizing the calibration and measurement capability (CMC) of industrial countries. International key comparisons are performed to fulfill the purpose of the mutual recognition arrangement. The international key comparisons are managed by the CIPM. In case of air speed metrology, three international key comparisons have been conducted by either world-wide or regional levels, up to date. In this book chapter, a brief explanation, regarding the air speed metrology, is introduced. At first, some basics of statistical methods to calibrate an industrial anemometer are explained. After that, an air speed metrology is briefly introduced by considering the traceability chain from the national measurement standards to the industrial or working standards, based on the literature. Finally, some information, regarding the mutual recognition arrangement and the international key comparisons, will be mentioned. From this approach, it is expected that some basic knowledge of the air speed metrology can be useful in understanding how to measure the industrial anemometers with good measurement accuracy and uncertainty.