Browsing by Author "Papadopoulos, Christos E."
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Item Open Access Flow measurement and monitoring using orifice plates(1996-03) Papadopoulos, Christos E.; Yeung, HoiThe orifice meter is still commonly used for natural gas measurement despite its many limitations. Considerable efforts in recent years have resulted in improved knowledge of factors such as installation effects and the value of discharge coefficient but a serious problem still remains with the measurement of differential pressure since, when line static pressures are as high as 200 bar, differential pressures of 500mbar have to be measured. Furthermore, the flow is never absolutely steady and the performance of the pressure transducers under such conditions is not yet fully understood. This thesis demonstrates the need to apply modern signal processing and analysis techniques to enhance the performance of process instrumentation systems. The use of two static pressure transducers of resonance type upstream and downstream the orifice meter, with a high frequency response, can offer the ability, by using spectral analysis and spectrum estimation methods, to extract additional information regarding the meter’s performance as well as diagnostic information about the whole process plant. It also demonstrates a method to check and, at the same time, to safeguard the flow information obtained from an orifice meter with the use of a third pressure transducer upstream of a Mitsubishi flow conditioner. Furthemore, information about the performance of the package orifice - conditioner using the discharge coefficient (Cd) and the amplitude spectrum from the three pressure transducers can be obtained.Item Open Access Uncertainty analysis in the management of gas metering systems(2000-09) Papadopoulos, Christos E.; Yeung, HoiIn the natural gas market, open access along with gas brokering and marketing has resulted in multiple gas contracts through one physical measuring point Accurate metering of natural gas has become more important than ever as deregulation subjects pipeline companies to competition. A more competitive market is driving the need for real-time accurate electronic flow measurement. Modern electronic natural gas metering systems (ENGMS) introduced additional, though necessary, complexity in the estimation and verification of the reported results. Additionally, it becomes more and more important to be able to verify these results. The application of Monte Carlo simulation as a combined energy flow measurement uncertainty estimation method seems to offer specific advantages over the more complex, traditional uncertainty estimation methods while at the same time fully conforms with the method of the ISO/GUM, (the authoritative document for uncertainty evaluation). Since, Monte Carlo simulation relies on randomness, it seems to capture more naturally and to have a more direct connection with the underlying physics of measurement uncertainty. Typical comparisons of estimated uncertainties using the Monte Carlo method and the conventional method (RSS) have been carried out. In general Monte Carlo gave slightly higher estimated uncertainties. This is due to the fact that the simplified conventional methods inevitably neglect correlations between the variables. A methodology for gas management decision making based on Monte Carlo uncertainty estimation is proposed. According to this, uncertainty analysis could be incorporated in any management decision making process regarding metering systems and importantly through all stages, from selection and design of a metering system up to real operation. In addition to the Monte Carlo simulation, work regarding possible improvements to orifice flow measurement quality is considered.