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  • 1.
    Baidar, Binaya
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Nicolle, Jonathan
    Institut de recherche d’Hydro-Québec, Varennes, QC, Canada.
    Gandhi, Bhupendra K.
    Department of Mechanical and Industrial Engineering, Indian Institute of Technology Roorkee, India.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sensitivity of the Winter-Kennedy method to different guide vane openings on an axial machine2019In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 68, article id 101585Article in journal (Refereed)
    Abstract [en]

    This work studies the effects of guide vane openings (GVOs) on the Winter-Kennedy (WK) flow measurement method using CFD. The dependence of the WK coefficient with GVOs and its physical mechanism are presented. Although the WK method is reported to be sensitive to different factors including GVO, it is still unclear to which extent the GVO can be changed without modifying the WK coefficient significantly and the mechanism leading to such modification, if any. A numerical model of a Kaplan model turbine with a semi-spiral casing is developed and used to such purpose. Previously conducted experiments on the model turbine are used to validate the numerical results. The magnitude and behavior of the secondary flow are investigated together with the WK coefficients. The GVO is found to have an impact on the WK method, and the impact increases with the GVOs as the flow structure change. A suitable location to minimize the impact of the GVO is suggested. Furthermore, the theoretical WK constant with a suitable location and configuration are also presented; this can be useful in the absence of the measured WK coefficient.

  • 2.
    Berrebi, Jonathan
    et al.
    Luleå tekniska universitet.
    Martinsson, Pär-Erik
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Willatzen, M.
    University of Southern Denmark.
    Delsing, Jerker
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Ultrasonic flow metering errors due to pulsating flow2004In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 15, no 3, p. 179-185Article in journal (Refereed)
    Abstract [en]

    Transit-time ultrasonic flow meters present some advantages over other flow meters for district heating industries. They are both accurate and non-intrusive. It is well-known that ultrasonic flow meters are sensitive to installation effects. Installation effects could be static or dynamic. Among the possible dynamic installation effects is pulsating flow. The influence of pulsating flow on the prediction and the zero-crossing operations is investigated. Expressions are found for the prediction error and the zero-crossing error. The relative errors due to the prediction and the zero-crossing are plotted. The prediction error can reach dramatic values while the zero-crossing operation is hardly influenced by flow pulsations.

  • 3.
    Berrebi, Jonathan
    et al.
    Luleå tekniska universitet.
    van Deventer, Jan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Delsing, Jerker
    Reducing the flow measurement error caused by pulsations in flows2004In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, no 5-6, p. 311-315Article in journal (Refereed)
    Abstract [en]

    Different types of errors are generated by pulsations in flows. Among these errors is the sampling error due to a unadapted time-averaging of the flow rate. An improved model for pulsations in flows including harmonics is derived. The localization of the harmonics is performed by a detector. The period of the pulsations is estimated. It is then possible to reduce the sampling error by performing a correct averaging. The reduction of the sampling error is confirmed by simulations.

  • 4. Carlander, Carl
    et al.
    Delsing, Jerker
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Installation effects on an ultrasonic flow meter with implications for self diagnostics2000In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 11, no 2, p. 109-122Article in journal (Refereed)
    Abstract [en]

    A small ultrasonic flow meter for water was exposed to five different test configurations, a reference experiment, a single elbow, a double elbow out of plane, a reduction in pipe diameter and a pulsating flow experiment. All tests were performed in a flow calibration facility ranging over Reynolds number from 25 to 110 000. The experiments with the four installation effects were compared with a reference experiment. The error and the change in standard deviation compared to the reference experiment were calculated. The standard deviation serve as a measure of the noise level of the flow meter. The results show that all disturbances generated errors in the flow measurement. The maximum errors were mainly in the range of 2–4% of flow rate, but at very low flow rates the pulsating flow caused larger errors. In most of the flow range there were no or smaller errors. All installation effects also generated an increase in the noise level. The different pipe configurations increased the standard deviation up to more than 100%. The pulsating flow induced even higher enlargements in the noise level. The errors and the increase in the standard deviation are present in about the same flow ranges. The results demonstrate not only that the installation effects tested introduce errors in the flow measurements but also that these effects can be detected from the noise level in the data. The noise level was determined from the standard deviation. This could be interpreted as that the disturbances amplify the turbulence intensity. Thus the standard deviation can be used as a measure of the turbulence. The presence of a disturbance could be recognised by comparing the magnitude of the noise level in the present data with a reference level valid for the measured flow rate. A procedure like this could possibly be performed by the meter itself in operation.

  • 5.
    Carlson, Johan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ing, Ros Kiri
    Laboratoire Ondes et Acoustique, Paris.
    Ultrasonic speckle correlation imaging of 2D particle velocity profiles in multiphase flows2003In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 14, no 4-5, p. 193-200Article in journal (Refereed)
    Abstract [en]

    Two-dimensional ultrasonic speckle correlation velocimetry (USV) is a new technique that allows imaging of moving scattering media, at a high frame-rate. In this paper we apply the technique to determine two-dimensional particle velocity profiles of multiphase flows. Experiments are realized with suspensions of Sonazoid (medical contrast agent) and Magnetite (Fe3O4) in water. All measurements are performed in a vertical pipe with the flow moving downwards. The two-dimensional particle velocity profiles are then compared with a reference liquid volume flow velocity. As expected from theory, the heavier Magnetite particles have slightly higher velocity than the liquid, whereas the contrast agent simply follows the liquid motion. The proposed technique can be used in combination with other techniques to measure the mass flow of the solid phase, in solid/liquid multiphase flow. This is generally more interesting than measuring the bulk mass or volume flow.

  • 6.
    Delsing, Jerker
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Flow measurement facilities2006In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 17, no 3, p. 139-Article in journal (Other academic)
  • 7.
    Delsing, Jerker
    Department of Heat and Power Engineering, Lund Institute of Technology.
    The zero-flow performance of a sing-around ultrasonic flowmeter1991In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 2, no 4, p. 205-208Article in journal (Refereed)
    Abstract [en]

    Zero-flow performance was tested on a new sing-around flowmeter. Design considerations were made to correct for the influences of speed of sound and use was made of reciprocity. The meter was tested from 1 000 to 20 000 sing-around loops, the loop period being approximately 64 μs. To investigate averaging phenomena, 1-100 primary velocity values were averaged to form one value. The temperature range tested was 2-45°C, with measurements at 5°C intervals. The measurements show a zero-flow stability of better than ±0.6 mms-1 (± 1lh-1 for 25 mm diameter pipe) over the entire temperature range. The standard deviation at each temperature tested was less than 0.45 mm s-1. This implies that flow velocities as low as 6 cm s-1 (100 lh-1, 25 mm diameter pipe) could be measured with an accuracy of better than ±1%. The tests were made with water, but equivalent results are expected for other liquids as well as gases.

  • 8.
    Delsing, Jerker
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Nilsson, Ulf R.C.
    Luleå tekniska universitet.
    In situ detection of inaccurate gas flow meters using a fingerprint technique1998In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 9, no 3, p. 143-152Article in journal (Refereed)
    Abstract [en]

    This work describes an in situ method for the testing of mechanical flow meters. The method was developed on diaphragm gas meters, but can be applied to most mechanically-based flow meters. The proposed fingerprint method analyses the behaviour of the meter during a work cycle. The result from the analysis is a ''fingerprint'' of the meter, in which mechanical errors in the meter can be detected. This is explained by the mechanical connection between the sensing mechanism and the mechanical output from the meter. An error analysis of a diaphragm meter was carried out to deduce the type of errors that are likely to occur in such meters. The most severe malfunctions are leakage, internal friction and liquid in the meter. These errors can either lead to measuring errors or can cause the meter to cease functioning. The fingerprint method has been tested on meters with simulated errors and on used meters taken from the gas grid in Lund. The fingerprint method can correctly diagnose errors such as leakage, increased friction and liquid in the meter.

  • 9.
    Dunca, Georgiana
    et al.
    POLITEHNICA University of Bucharest.
    Bucur, Diana Maria
    POLITEHNICA University of Bucharest.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Popa, Radu
    POLITEHNICA University of Bucharest.
    Discharge evaluation from pressure measurements by a genetic algorithm based method2015In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 46, p. 49-55Article in journal (Refereed)
    Abstract [en]

    This paper presents an alternative to the Gibson method, for discharge estimation of a turbine inside a hydropower plant. The method proposes a genetic algorithm which includes an integration procedure for the water hammer equations using the method of characteristics. The decision variables are represented by the steady-state regime discharge before the valve closure and the pipe friction factor. The recordings of pressure/differential pressure in measuring sections are used.

  • 10. Håkansson, Evert
    et al.
    Delsing, Jerker
    Effects of flow disturbances on an ultrasonic gas flowmeter1992In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 3, no 4, p. 227-233Article in journal (Refereed)
    Abstract [en]

    A series of tests are carried out to assess the effects of flow disturbance on a small dimension ultrasonic gas flowmeter. Flow disturbances generated by cone couplings, and single and double elbows are investigated. Measurements with a 100 D straight pipe upstream with a smooth connection to the meter body are used as a reference. Our measurements show that the symmetrical disturbance produced by a cone coupling at a 12 D distance from the transducer path does not impair the performance of the flowmeter. An asymmetrical disturbance, such as a single or a double elbow at the same distance, seems generally to give an underestimation of the flow velocity, resulting in reading errors of -1% or worse. Measurements with straight pipes of 10 D, 20 D, 40 D and 80 D between the disturbance and the flowmeter have also been made showing that 10 D can cause an overestimation of flow velocity. Increasing the length of the straight pipe generally decreases the error. More than 80 D straight pipe between the disturbance and the flowmeter is required to give a result within ±1% of reference conditions. The angle between the elbow plane and the transducer plane is changed from 0 to 315° in 45° steps. The meter error is plotted as a function of inlet angle, showing a clear relationship between these values.

  • 11. Håkansson, Evert
    et al.
    Delsing, Jerker
    Effects of pulsating flow on an ultrasonic gas flow meter1994In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 5, no 2, p. 93-101Article in journal (Refereed)
    Abstract [en]

    A series of tests was carried out to assess the effects of pulsating flow on a small-dimension ultrasonic gas flowmeter. Three different parameters were investigated: pulsation amplitude, pulsation frequency and mean flow velocity. The measurements were carried out in air using a 100D straight pipe upstream of the ultrasonic gas flowmeter. The performance of the flowmeter was tested at mean flow rates from 1.2 to 9.6 m s-1, using four different pulsation frequencies (2, 5, 10 and 20 Hz) with pulsation amplitudes from 0 to ≈70% r.m.s. Our measurements reveal three major phenomena affecting the ultrasonic flowmeter performance. (1) Sampling phenomena, i.e. aliasing: it is shown that a mismatch between the setting of the sampling parameters in the flowmeter and the frequency of the pulsations can result in large positive and negative errors due to aliasing. (2) Errors due to changes of the flow profile caused by an imaginary high Reynolds number due to the pulsating flow: it is shown that these errors are proportional to the pulsation amplitude and inversely proportional to the pulsation frequency. Further, the error caused by a change in the flow profile generally appears in the laminar and transition areas. (3) Non-linearities when averaging very high or low flow velocities, respectively: very large pulsation amplitudes result in instantaneous flow velocities, sometimes exceeding both the maximum and the minimum limits of the calibrated range of the meter. For the ultrasonic meter tested, this results in large negative errors due to non-linearities on the extremes of the error curve of the meter.

  • 12. Jonsson, Pontus
    et al.
    Ramdal, J.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Development of the Gibson method – unsteady friction2012In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 23, no 1, p. 19-25Article in journal (Refereed)
    Abstract [en]

    The Gibson method is commonly used for discharge measurements at hydropower plants to estimate turbine efficiency. This paper presents a detailed numerical study of this method in order to estimate the physical quantities of importance in the method. Additionally, a modification of the Gibson method is proposed that adds temporal acceleration to the calculation procedure. The modification is numerically and experimentally validated for Reynolds numbers ranging from ≈0.6×106 to 1.7×106. Using both simulations and experimental data, it is shown that the modified method, the unsteady Gibson method, can reduce the flow estimation error by as much as 0.4% compared to the standard Gibson method. Depending on the conditions, the unsteady Gibson method corrects, or partly corrects, both under- and overestimations of the flow rate that are calculated when using the standard Gibson method.

  • 13. Martinson, Emil
    et al.
    Delsing, Jerker
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Electric spark discharge as an ultrasonic generator in flow measurement situations2010In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 21, no 3, p. 394-401Article in journal (Refereed)
    Abstract [en]

    In this paper, a different way to create acoustic signals for ultrasonic gas flow measurements is investigated. The aim is to develop an ultrasonic flow meter system that is capable of operation in extreme environments. These environments might consist of extremely high temperatures, moisture, contaminating particles, low gas pressure and large geometries. Traditional ultrasonic transducers are sensitive to these conditions: their performance suffers, or they may even stop functioning if exposed to such environments. The development of new transducer technology is therefore crucial to allow ultrasonic flow measurements in harsh environments. In this paper, the gap discharge emitter is evaluated as a candidate to be used in these applications. Its capabilities as a sound source are investigated, and its impact on flow meter performance is estimated. It can be concluded that, despite the uncertainties it introduces to a flow meter system, it stands out as a strong candidate to be used as an acoustic emitter in a gas flow meter system for extreme environments.

  • 14.
    Nilsson, Ulf R. C.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    New method for finding inaccurate gas flow meters using billing data: finding faulty meters using billing data1998In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 9, no 4, p. 237-242Article in journal (Refereed)
    Abstract [en]

    A method that uses billing readings to find inaccurate meters is presented. This method uses these readings to form an individual load index (LI), which is primarily affected by the climate rather than the customer's individual behaviour. Meters used in installations where the gas is used in industrial processes are therefore excluded since the consumption is not affected by the climate. The individual LI is compared with an average LI, and meters that differ from the average LI are examined. The method was tested on the gas distribution network in the city of Lund, which consists of approximately 1500 meters. Based on the results obtained so far, the LI method will be a useful aid in tracking down faulty meters. However, laboratory tests of a large number of meters selected by the LI method are still needed. Extrapolation of the results indicates that at least 1% of the installed meters have substantial errors

  • 15.
    Saemi, Simindokht
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Raisee, Mehrdad
    Center of Excellence in Design and Optimization of Energy Systems (CEDOES), School of Mechanical Engineering, College of Engineering, University of Tehran.
    Nourbakhsh, Ahmad
    Center of Excellence in Design and Optimization of Energy Systems (CEDOES), School of Mechanical Engineering, College of Engineering, University of Tehran.
    Numerical Investigation of the Pressure-Time Method2017In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 55, p. 44-58Article in journal (Refereed)
    Abstract [en]

    The pressure-time method is a discharge measurement technique commonly used to estimate the flow rate in hydro-power plants to assess the turbine hydraulic efficiency. In this paper two-dimensional Reynolds-averaged Navier-Stokes equations with the low-Reynolds k-ω SST turbulence model are used to model and evaluate the pressure-time method. The flow rate decrease is modeled by valve closure and use of the dynamic mesh technique. The results are compared with experimental data showing the close trend. Moreover, the affecting parameters in the pressure-time method including compressibility, calculation of the losses and finding the upper time limit of integration of the pressure-time diagram are studied in detail. Furthermore, the flow characteristics with both compressible and incompressible assumptions are investigated. The obtained results demonstrated the compressibility effect even before the complete valve closure. The physics of the flow, in the closed conduit in the pressure-time method, before the complete valve closure is studied based on the time variation of the wall shear stress and the γγ parameter. The γγ parameter represents the difference between the turbulence structure in a transient accelerating or decelerating flow and the one in the quasi-steady condition. It is demonstrated that for the pressure-time method, some part of the flow decrease excursion can be characterized as quasi-steady and the rest is unsteady. The dominance of inertia and turbulence dynamics is investigated to evaluate the wall shear stress in the part of the excursion with the unsteady assumption. It is found that the inertia has a dominant effect during the excursion. The flow rate is calculated by evaluating all the terms of losses, e.g., wall shear stress, normal stresses, Reynolds stresses and density variation. Based on the relative magnitude of each term the results indicate that the wall shear stress is a good approximation of the losses for the flow rate calculation and the other terms can be neglected. Due to the primary role of losses in the flow rate calculation other methods in losses calculation are also considered for comparison (e.g., quasi-steady friction or steady-state friction factor). The available methods to find the upper time limit of the flow rate approximation integral still have significant errors. The flow rate reduction is calculated at each time step before complete valve closure using CFD methods.

  • 16.
    Saemi, Simindokht
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics. School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
    Sundström, Joel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Raisee, Mehrdad
    Hydraulic Machinery Research Institute, School of Mechanical Engineering, College of Engineering, University of Tehran, Iran.
    Evaluation of transient effects in the pressure-time method2019In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 68, article id 101581Article in journal (Refereed)
    Abstract [en]

    The pressure-time is a method for measuring the flow rate in closed conduits and is typically used in hydropower applications. The scope of the present paper is to examine the flow physics in the pressure-time method using experimental measurements and two-dimensional numerical simulations. The Unsteady Reynolds-averaged Navier–Stokes (URANS) equations and the low-Re k-ω SST turbulence model are employed for the simulations. The contributions of inertia, pressure gradient, viscous and turbulent shear stresses are investigated in the flow during a pressure-time measurement. It is shown that away from the wall and at the first times, the turbulent shear stress balances with the pressure gradient. By increasing the time, the inertia effect becomes dominant and balances with the pressure gradient and turbulent shear stress. Close to the wall, both viscous and turbulent shear stresses are the dominant terms which are decreasing by increasing the time. It is also shown that the prediction of the friction losses can be improved by modeling the dependence of the friction factor on the dimensionless parameter instead of the Reynolds number.

  • 17.
    Stener, Jan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Carlson, Johan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Sand, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Pålsson, Bertil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Monitoring Mineral Slurry Flow using Pulse-Echo Ultrasound2016In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 50, p. 135-146Article in journal (Refereed)
    Abstract [en]

    Ultrasound based flow measurement methods have a large potential for the mining industry and its processing plants. Ultrasound travel through dense suspensions and is not affected by the magnetic fields sometimes present in this type of equipment.A cross-correlation based method is used for localized particle velocity measurements in one and two dimensions. Simultaneously, using the same data, information about local particle concentration is extracted from the power spectral density of the backscattered signal. Experiments are carried out both in simplified geometry and in full scale equipment in an iron ore pilot benefication plant.In the simple geometry it is possible to assess the precision of the methods by comparing the measurements to theory and numerical simulations. The results from the pilot plant experiments show that these methods can be applied to real world processes

  • 18.
    Sundström, Joel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Department of Energy and Process Engineering, Norwegian University of Science and Technology.
    Transient wall shear stress measurements and estimates at high Reynolds numbers2017In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 58, p. 112-119Article in journal (Refereed)
    Abstract [en]

    Transient wall shear stress measurements using hot-film anemometry have been performed in a large-scale laboratory setup at high Reynolds numbers. Starting from Reynolds numbers 1.7×1061.7×106 and 0.7×1060.7×106, the flow was brought to a complete rest by closing a knife gate thus replicating a pressure-time (also know as Gibson) flow rate measurement in a hydropower plant. Ensemble-averaged mean wall shear stresses obtained from 22 repeated runs have been compared with estimates obtained using the pressure-time method. The objective of the work has been to assess the accuracy of the frictional formulation entering the pressure-time integral. It is shown that both the standard method, a quasi-steady approach as well as the recently introduced unsteady method all reproduce the measured wall shear stresses quantitatively during most of the transient. The last phase, following the complete closure of the gate, which is characterized by a slow decay towards zero shear stress at the wall is, however, not captured by the available methods. In general, the unsteady formulation produces the smallest flow rate estimation error, which in turn, implies the best modeling of the frictional losses.

  • 19.
    Sundström, Joel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Saemi, Simindokht
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics. School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
    Raisee, M.
    Hydraulic Machinery Research Institute, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Improved frictional modeling for the pressure-time method2019In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 69, article id 101604Article in journal (Refereed)
    Abstract [en]

    The pressure-time method is classified as a primary method for measuring discharge in hydraulic machinery. The uncertainty in the discharge determined using the pressure-time method is typically around ±1.5 %; however, despite dating back almost one hundred years in time, there still exists potential to reduce this uncertainty. In this paper, an improvement of the pressure-time method is suggested by implementing a novel formulation to model the frictional losses arising in the evaluation procedure. By analyzing previously obtained data from CFD, laboratory and full-scale pressure-time measurements it is shown that the new friction model improves the accuracy of the flow rate calculation by approximately 0.1–0.2% points, compared to currently utilized friction models. Despite being a small absolute improvement, the new friction model presents an important development of the pressure-time method because the relative improvement is significant.

  • 20.
    Svensson, Bernt
    et al.
    Luleå tekniska universitet.
    Delsing, Jerker
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Application of ultrasonic clamp-on flow meters for in situ tests of billing meters in district heating systems1998In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 9, no 1, p. 33-41Article in journal (Refereed)
    Abstract [en]

    Three methods of using ultrasonic flow meters for the purpose of testing small- and medium-sized billing flow meters in district heating subscriber stations in situ were investigated. Four subscriber stations, six billing flow meters, and three ultrasonic clamp-on meters were part of the investigation. The obtained results show that clamp-on meters have measurement accuracy problems on the ordinary steel piping in the subscriber stations. When using well defined pipes mounted in series with the billing flow meters the results are clearly better; provided that the flow rates exceed a Reynolds number of approximately 10 000. In this flow region, billing flow meter deviations >±5% can be detected. A flow rate below this Reynolds number renders the method less reliable. The useful flow range is extended when using calibration data from the clamp-on meter to correct the measured data, making it possible to determine deviations >±10% in flow rates below a Reynolds number of 10 000. The investigation also showed that not all clamp-on meters are suited for this type of in situ test.

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