Yoshiya Terao

Development of a new diverter system for liquid flow calibration facilities

Abstract The diverter system is a key component in achieving a high-accuracy liquid flow rate standard using a static gravimetric system with a flying start and stop method. A new system with double diverting wings has been developed in order to reduce the diverter timing error that dominates the uncertainty in the calibration of flowmeters. The basic concept of the new system is that each wing should move in the same direction at the beginning and end of measurement. The diverter timing error has been estimated using a small prototype in a water flow circuit in order to make a comparison between the performance of the new system and those of conventional systems with a single diverting wing. The results show that the jet flow condition has little effect on the timing error estimated by the double-wing method, although the error with the single-wing system is dependent on the liquid flow rate. Therefore, the triggering of the timing system can be easily adjusted over a wide range of flow rate by using the new diverter system. Furthermore, this system is adopted for a new calibration facility for hydrocarbon flow measurements at NMIJ.

Friction factor and mean velocity profile for pipe flow at high Reynolds numbers

The friction factor for a fully developed pipe flow is examined at high Reynolds numbers up to ReD = 1.8 × 107 with high accuracy using the high Reynolds number actual flow facility “Hi-Reff” at AIST, NMIJ. The precise measurement of the friction factor is achieved by the highly accurate measurement of the flow rate, and the measurement uncertainty is estimated to be approximately 0.9% with a coverage factor of k = 2. The result examined here is obviously different from the Prandtl equation and the experimental results from the superpipe at Princeton University. The deviation of the present result from the Prandtl equation in the lower Reynolds number region is approximately 2.5% and −3% at the higher Reynolds number. For ReD 2.0 × 105, and it increases with the Reynolds number and reaches −6% at ReD = 1.0 × 107. The Karman constant estimated by the measured fric...

Final report on the CIPM air speed key comparison (CCM.FF-K3)

CCM.FF-K3, a key comparison (KC) for air speed, has been performed among four national metrology institutes (NMIs). These were NMi–Netherlands and PTB–Germany, representing EUROMET, NIST–USA representing SIM, and NMIJ–Japan representing APMP. NMIJ served as the Pilot Laboratory. An ultrasonic anemometer had been chosen as a transfer standard and was circulated among the participants over the period from April 2005 to December 2005. Each participant reported calibration results at 2 m/s and 20 m/s with corresponding uncertainty budgets. At 20 m/s, the weighted mean was accepted as the KCRV, while at 2 m/s, a median from key comparison results was estimated as the KCRV. The final report presents the degree of equivalence between NMIs and the KCRV as well as the degree of equivalence between NMIs. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Final report on the APMP air speed key comparison (APMP.M.FF-K3)

Key comparison APMP.M.FF-K3 has been undertaken by the APMP Technical Committee for Fluid Flow, and was piloted by the National Metrology Institute of Japan (NMIJ, AIST). The objective was to demonstrate the degrees of equivalence of the air speed standards, held at the participating laboratories, relative to the CCM.FF-K3 key comparison reference value and to provide supporting evidence for the Calibration and Measurement Capabilities (CMCs) claimed by the participating laboratories in the Asia-Pacific region. A selected transfer standard was circulated among the six participants in eleven months starting February 2009. The repeated calibration results at NMIJ demonstrated sufficient reproducibility of the transfer standard. At 2 m/s and 20 m/s, a linkage to the global key comparison (CCM.FF-K3) was established by applying corrections to the participant results based on the results from the linking laboratories, thus making it possible to extend the relevant graphs of equivalence. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Further Investigation of Discharge Coefficient for PTC 6 Flow Nozzle in High Reynolds Number

The discharge coefficients of the throat tap flow nozzle based on ASME PTC 6 are measured in wide Reynolds number range from Red=5.8×104 to Red=1.4×107. The nominal discharge coefficient (the discharge coefficient without tap) is determined from the discharge coefficients measured for different tap diameters. The tap effects are correctly obtained by subtracting the nominal discharge coefficient from the discharge coefficient measured. Finally, by combing the nominal discharge coefficient and the tap effect determined in three flow regions, that is, laminar, transitional and turbulent flow region, the new equations of the discharge coefficient are proposed in three flow regions.Copyright

Experimental Results of Flow Nozzle Based on PTC 6 for High Reynolds Number

Discharge coefficients for three flow nozzles based on ASME PTC 6 are measured under many flow conditions at AIST, NMIJ and PTB. The uncertainty of the measurements is from 0.04% to 0.1% and the Reynolds number range is from 1.3×105 to 1.4×107. The discharge coefficients obtained by these experiments is not exactly consistent to one given by PTC 6 for all examined Reynolds number range. The discharge coefficient is influenced by the size of tap diameter even if at the lower Reynolds number region. Experimental results for the tap of 5 mm and 6 mm diameter do not satisfy the requirements based on the validation procedures and the criteria given by PTC 6. The limit of the size of tap diameter determined in PTC 6 is inconsistent with the validation check procedures of the calibration result. An enhanced methodology including the term of the tap diameter is recommended. Otherwise, it is recommended that the calibration test should be performed at as high Reynolds number as possible and the size of tap diameter is desirable to be as small as possible to obtain the discharge coefficient with high accuracy.Copyright

Uncertainty Examination of New Water Flow Calibration Facility for Nuclear Power Application

A new test facility has been constructed at National Metrology Institute of Japan (NMIJ) for calibration of feed water flowmeters at nuclear power stations for Reynolds numbers of up to 16 million. This very large Reynolds number is achieved at a flow rate of 3.33 m3 /s (12,000 m3 /h) and water temperature of 70 degrees C in a 600 mm pipe. This new facility has four sets of pumps and reference flowmeters installed in parallel upstream of the test section. These flowmeters are calibrated at 0.83 m3 /s (3,000 m3 /h) one by one without dismounting from the loop by using a 50 t weighing tank; this tank has been used as the primary standard for the existing flow facility. Then the flow rate can be increased up to 3.33 m3 /s (12,000 m3 /h) with all of the pumps and flowmeters working at the same time. This paper describes the concept of the new facility, the fundamental uncertainty estimation, and the examination of its measurement capability.Copyright

Further experiments for mean velocity profile of pipe flow at high Reynolds number

This paper reports further experimental results obtained in high Reynolds number actual flow facility in Japan. The experiments were performed in a pipe flow with water, and the friction Reynolds number was varied up to Reτ = 5.3 × 104. This high Reynolds number was achieved by using water as the working fluid and adopting a large-diameter pipe (387 mm) while controlling the flow rate and temperature with high accuracy and precision. The streamwise velocity was measured by laser Doppler velocimetry close to the wall, and the mean velocity profile, called log-law profile U+ = (1/κ) ln(y+) + B, is especially focused. After careful verification of the mean velocity profiles in terms of the flow rate accuracy and an evaluation of the consistency of the present results with those from previously measurements in a smaller pipe (100 mm), it was found that the value of κ asymptotically approaches a constant value of κ = 0.384.This paper reports further experimental results obtained in high Reynolds number actual flow facility in Japan. The experiments were performed in a pipe flow with water, and the friction Reynolds number was varied up to Reτ = 5.3 × 104. This high Reynolds number was achieved by using water as the working fluid and adopting a large-diameter pipe (387 mm) while controlling the flow rate and temperature with high accuracy and precision. The streamwise velocity was measured by laser Doppler velocimetry close to the wall, and the mean velocity profile, called log-law profile U+ = (1/κ) ln(y+) + B, is especially focused. After careful verification of the mean velocity profiles in terms of the flow rate accuracy and an evaluation of the consistency of the present results with those from previously measurements in a smaller pipe (100 mm), it was found that the value of κ asymptotically approaches a constant value of κ = 0.384.

High Reynolds Number Experimental Facilities for Turbulent Pipe Flow at NMIJ

In this paper, we report on high Reynolds number and highly accurate experimental facilities for turbulent pipe flow established by the National Metrology Institute of Japan (NMIJ). One of the facilities, called the High Reynolds number actual flow facility (Hi-Reff), is capable of handling a maximum bulk Reynolds number of \({Re}_\mathrm{D} = 2.0 \times 10^7\). The most remarkable feature of this facility is its highly accurate flow rate measurements. The expanded uncertainty of the volumetric flow rate is estimated as 0.040–0.10%. Such a low flow rate measurement uncertainty contributes to extremely accurate estimations of inner-scale variables such as friction velocity. This paper presents the details and advantages provided by this NMIJ facility in relation to turbulent pipe experiments.

Development of High Accurate Flow Nozzle for Feedwater Flowrate Measurement in Nuclear Power Plant

The high accurate throat tap flow nozzle with four different diameter taps is developed and its discharge coefficients are measured in the Reynolds number range from 1.5×106 to 1.4×107 using the high Reynolds calibration facility of AIST,NMIJ. The discharge coefficient of a throat tap nozzle extrapolated according to ASME PTC 6 are confirmed to deviate 0.37% at Red=1.4×107 from the experimental results. The high accurate flow nozzle developed can reduce this extrapolation error of the discharge coefficient to high Reynolds numbers by using the equations of discharge coefficients, which is determined as a function of Reynolds number and tap diameter based on the experimental results of four different diameter taps. The error of extrapolated discharge coefficient using the derived equations is estimated to be less than 0.1% at Red=1.4×107. The present results show that the throat tap flow nozzle developed is expected to work as a high accurate flowmeter even under the extrapolation of the discharge coefficient toward high Reynolds numbers.Copyright