However, it is difficult for a single method mentioned above to cover all the flow patterns of the twophase flow to. Basics of capacitive sensing and applications davidwang abstract capacitive sensing is becoming a popular technology to replace optical detection methods and mechanical designs for applications like proximitygesture detection, material analysis, and liquid level sensing. Electrical capacitance tomography twophase oilgas pipe. Electrical capacitance tomography ect is a novel technology that can deal with the complexity of two phase gasoil flow measurement by explicitly deriving the component distributions on two adjacent planes along a pipeline.
A capacitance sensor configuration has been designed to characterize horizontal two. Pdf different configurations of capacitance sensor for gasoil two. Research of gassolid twophase flow capacitance cross. Electrical capacitance tomography technique is a new technique for multiphase flow measurement. One of the most common observations in twophase flow is the complete separation between the two phases at moderately low velocities, where such a. The thickness of the dielectric layer separating the two. A capacitive sensor system for the analysis of twophase. Using a composite material analysis and an effective permittivity ratio, predictive relations for capacitance as a function of liquid film thickness. Conclusions 15 quickfield was used to optimize and calibrate a capacitance void fraction sensor. Development of a twophase flow coupled capacitance. Capacitive array sensor for twophase liquid characterization. Through this coupling, the model parameters such as the connectivity, the time constant, temporal oil saturation, etc.
Continuous and precise measurement required for a two phase flow sensor is obtained using the pc connected via rs232 interface. Gas volumetric flow rate is estimated by crosscorrel. By measuring the height at various locations in the channel, the mass flow rate can be calculated. Capacitive measurement technique for void fraction.
The most common type is the liquidgas twophase flow which is found many. These issues are discussed, and the design of a 12. A capacitive sensor has the benefit of being fast and noninvasive. Pipeline transportation of natural gas in the presence of a liquid phase or mixture of crude oil and water are examples of twophase flow. To overcome this limitation, we develop a twophase flow coupled crm model that couples the pressure equation fluid continuity equation and the saturation equation oil mass balance. Horizontal twophase flow characterization for small diameter tubes with a capacitance sensor. Phaseshift detection for capacitance sensor measuring. A capacitance measurement system is developed for the measurement of gasliquid twophase flow in glass micropipes with inner diameters of 3. Capacitance sensors are frequently applied for void fraction measurements in two phase flow. Twophase flow rate measurement using a capacitive sensor and a. Multielectrode capacitance sensors for the visualization of transient twophase flows multielectrode capacitance sensors for the visualization of transient twophase flows reinecke, n mewes, d. In laboratory experiments, highspeed images were recorded for human classification of liquid. As a typical flow regime in a micropipe twophase flow system, slug flow is chosen for this investigation.
Highresolution gasoil twophase flow visualization with. Understanding these two phase parameters is essential to evaluating the stability threshold of tube bundle configurations. Many current sensors are dependent on the flow regime of the multiphase stream. Pdf horizontal twophase flow characterization for small. If the targetground capacitance is considerably larger than the probetarget capacitance 100 times, the total change in resistance to the current flow is negligible and. If modelled accurately, the approximation model can be used to calibrate the capacitance sensor to acquire the actual holdup for twophase stratified flow. Two phase flow modelling is strongly dependent on flow patterns. A concave parallel plate capacitance sensor has been developed to measure the two phase flow void fraction for the purpose of objectively identifying flow regimes. This concept of design had been implemented and verified in both software and hardware. The threeplate sensor can be used for either spacingvariation or areavariation sensors. The concept involves vaporliquid twophase flow through narrow, parallel channels which results in a laminar, stratified flow with a slope at the liquidvapor interface. By using montecarlo method, the gassolid twophase flow model is established. Finite element simulations were made for optimizing the design.
University of dayton research institute dayton united states personal authors. Development of a capacitance based void fraction sensor. To optimize these devices, the prediction of twophase flow heat transfer of evaporating refrigerants has to be improved. A concave parallel plate capacitance sensor has been developed to measure the twophase flow void fraction for the purpose of objectively identifying flow regimes. In daily life, airconditioning devices are all around us. Pi capacitive position sensor electronics incorporate a proprietary design providing superior linearity, low sensitivity to cable capacitance, low background noise and low drift. Microcontroller based capacitance meter for a two phase. Capacitance sensors for voidfraction measurements and. An online adaptive estimation method for water holdup.
For the typical flow conditions used in this study, the void fractions of the bubbly flow, slug flow, and churn flow were 7. A capacitance sensor is formed by two electrodes of various shapes, usually a fragment of a cylinder. Development of a fastresponse capacitive sensor for two and threephase annularduct flow marlon mauricio hernandez cely supervisor. Technical report,01 jan 2015,30 apr 2017 corporate author. The integrated linearization system ils compensates for influences caused by errors, such as nonparallelism of the plates. Instead of suppressing nonlinear response, the sensor was optimized in such a way that a sinelike function was displayed on top of the linear function. Two phase or multiphase flows are presented in many process industries such as in our target application, the oil and gas industry. Twophase flows experiments in plug, slug, and churn twophase flows show that the probe output signals are consistent with the corresponding flow patterns for plug flow, slug flow, and churn flow. With broad application prospects, the purpose of this technique is to identify each phases composition of twophasemultiphase flow system in a closed pipe. Using this model, different sensor concepts could be tested and the. Understanding these twophase parameters is essential to evaluating the stability threshold of tube bundle configurations. Electronic circuit diagram a wave generation circuit, b current generation.
The numerical results agree well with experimental data of airdistilled water towphase flow. Pdf an electrostatic shielding was implemented on capacitance sensor in order to mitigateeliminate external interference. C capacitance in picofarads k dielectric constant of material a area of plates in square inches d distance between the plates. In this thesis, a novel design of a twophase characterization sensor that measures multiphase flow component fractions is described. Each single pcb is fabricated thought standard fabrication process. Twophase, void fraction, capacitance sensor, flow pattern identification. The design methodology of capacitance sensors for voidfraction measurement in adiabatic twophase flow systems is presented in this paper. Different configurations of capacitance sensor for gasoil two phase flow measurement.
Evaluating the two phase flow parameters across tube bundles is crucial to the analysis of vibration excitation mechanisms. A static two phase pipe flow model made of perspex was used to characterise the sensor. Following the sensor verification test using light diesel oil and air, a cryogenic experiment using liquid nitrogen was conducted. This study examines the velocities of twophase liquidvapor flows with the use of high speed visualization. Capacitive sensor phasing and ungrounded targets lion. A capacitance sensor for twophase void fraction measurement and. These parameters include the temporal and local variation of void fraction and phase redistribution. Study of sensor of electrical capacitance tomography ect. A concave electrode design with active guarding was chosen.
Another important issue on capacitance sensors response influence is the guard electrode. This sensor applies the difference between the relative permittivity. With a twoplate sensor, the sensor capacitance is the measured variable. A sinusoidal function approach article pdf available in sensors 167. The design methodology and operation of the capacitance based void fraction sensor is discussed.
A sensor has been developed with a number of requirements with regard to speed and accuracy in mind. Simple and fast serial analysis using quickfield along with matlab. Intel 8051 microcontroller based capacitance meter has been developed based on the time lag involved in charging and discharging the capacitor. Pdf different configurations of capacitance sensor for. The capacitance relationship is illustrated with the following equation. The value of the capacitance is shown using a led interface. Void fracti study of void fraction measurement in a two phase flow by using differential pressure and electrical capacitance tomography. A capacitive sensor system for the analysis of twophase flows of oil and conductive water a capacitive sensor system for the analysis of twophase flows of oil and conductive water demori, marco.
A new capacitance type void fraction sensor was designed, produced, and tested. Exploring capabilities of electrical capacitance tomography sensor and velocity analysis of twophase r4a flow through a sudden expansion descriptive note. For the purpose of objective flow pattern identification, a capacitance sensor was developed for horizontal twophase flow in small diameter tubes. Capacitive sensors are suitable for many applications and its success is. One of its most promising applications is the visualization of gasoil flows. A capacitance sensor has been developed for measuring timeaveraged void fractions in twophase pipe flow. The exhaust gas composition was assessed by a sickmaihak s. Capacitance sensor for void fraction measurement in twophase flow.
A capacitance sensor is formed by two electrodes of various shapes, usually a fragment of a cylinder, mounted at the outside of the wall of a dielectric pipeline through which a twophase medium flows. Capacitive measuring system for twophase flow monitoring 2 fig. In this work, electrical capacitance tomography ect and neural networks were used to automatically identify twophase flow patterns for refrigerant r4a flowing in a horizontal tube. Twophase flow denotes the simultaneous flow of two distinct and immiscible substances and it can be commonly encountered in a wide spectrum of industrial applications, for instance in the transport of oil and gas in pipelines or in the chemical processing industry, where twophase flows occur in reactors, bubble columns and plant components. A capacitance sensor for twophase liquid film thickness. The rules of 12electrode sensor parameters such as capacitance, capacitance change, and change rate of capacitance and sensitivity map the basis of airwater two phase flow permittivity. Design of helical capacitance sensor for holdup measurement in two phase stratified flow. In flow channels where high speed visualization cannot be used, there are other noninvasive techniques for analyzing flow the flow, such as electrical capacitance tomography ect. This is implemented by measuring the capacitance of the medium inside the acrylic pipeline at two different positions. Measurement of gasliquid twophase flow in micropipes by. Void fraction measurement a va a capacitance measurement b optical characterization 2. Sensors free fulltext a new capacitance sensor for. Horizontal twophase flow occurs widely in the petroleum, nuclear, and chemical industries. Pdf capacitance sensor for void fraction measurement in.
Evaluating the twophase flow parameters across tube bundles is crucial to the analysis of vibration excitation mechanisms. Optical techniques laser doppler single phase flows two phase flows 1. The paper takes gassolid twophase flow crosscorrelation measurement system as the research object, adopts the method of computer simulation to research the measuring mechanism of crosscorrelation velocity. A new method comsol was used to analysis the electrical capacitance tomography of reconstruction image and simulation research. However, they require more study before implementation. This experimental study uses electrical capacitance tomography ect technique for measuring the void fraction in two phase bubble flow regime. Pdf design of helical capacitance sensor for holdup. Twophase flow modelling is strongly dependent on flow patterns.
Experimental studies based on airwater and oilwater twophase stratified flows are carried out to validate the sinusoidal model. Then, a horizontal oilwater two phase flow experiment is carried out to measure the response of the double helix capacitance sensor, in which a novel method is proposed to calibrate the liquid. Electrical capacitance probe characterization in vertical. Flow pattern mapping of horizontal evaporating refrigerant. Article simulation analysis of capacitance method in two. We introduce a gasliquid twophase flow meter which combines a capacitive sensor and a venturi tube. A static twophase pipe flow model made of perspex was used to characterise the sensor.
Preliminary results obtained with a 12electrode system are displayed. Compared with the static numerical simulation, this realtime dynamic 3d simulation method can research on a designed capacitance sensor combining the dynamic characteristics of the twophase flows for. Tomographic imaging of twophase flow using capacitance. Improving the current twophase flow models should therfore focus on incorporating more flow phenomena into the models. Schematic representation of the measurement system. The effect of design parameters on the capacitance output has been theoretically and experimentally investigated for two types of sensor configurations. The aim of this paper was to develop a capacitance based sensor capable of measuring void fraction in a continuous twophase flow field. For the purpose of objective flow pattern identification, a capacitance sensor was developed for horizontal two phase flow in small diameter tubes. Local void fractions and bubble velocity in vertical air.
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