Among the flow measurement technologies, the Ultrasonic Cross-Correlation Flowmeter (UCCF) has received much attention due to its high accuracy, performance independency from sound speed and no pressure drop. In industrial plants, due to space constraints and equipment special arrangement, the Flowmeter is not always located at the ideal position. Under these conditions, the calibration factor plays an important role in increasing the accuracy of the flow measurement. The calibration factor is the function of the flow Reynolds number, the straight pipe length at the upstream of the Flowmeter and the roughness of the pipe. In present study, with the aid of CFD simulation and using Reynolds Stress Model (RSM), the air flow inside the pipe was simulated in range of Reynolds number from 3. 16×104 to 3. 16×105. Then, with the aid of UCCF analytical model, the effect of the mentioned parameters including flow Reynolds number, the straight pipe length at the upstream of the Flowmeter and the roughness of the pipe, on the performance of the UCCF were investigated. The simulation results show that the changes in shape and curvature of velocity profile inside the pipe has an important role in analyzing and interpretation of the changes in calibration factor. As the flow Reynolds number increases, the velocity profile at the pipe section becomes flatter, so the calibration factor increases. The results also demonstrate that as the flow moves inside the pipe (prior to fully developed length), the curvature of the velocity profile increases firstly and then decreases. In contrast, the calibration factor decreases firstly and then increases. It was also concluded that by changing the pipe material from carbon steel to cast iron and increasing the pipe roughness, the velocity profile becomes more rounded, so the calibration factor decreases.

In the present study, CFD simulation of Transit-time Ultrasonic Flowmeter with the PZT-5J piezoelectric sensor was modeled for light, heavy, and medium crude oil by the wave equation in the acoustic wave propagation path and finite element solving method in the unsteady state and it was implemented, using COMSOL Multiphysics 5. 3 software. Different samples of light, heavy, and medium crude oil at different temperatures were modeled and simulated under constant pressure, using CFD tools. the maximum received voltage and speed of sound in samples were calculated by the proposed model. To evaluate the accuracy of the proposed model, the simulation results were compared with the empirical data obtained from the experimental work of the researchers. The average values of the maximum voltage of received signals for an Ultrasonic Flowmeter containing light, heavy, and medium light crude oil samples are 0. 9491, 1. 0115, and 0. 943 v, respectively. The difference between the simulation results and the experimental data for the speed of sound in the light, heavy, and medium crude oil samples was at most about 0. 2336%, 0. 4339%, and 0. 1378%, respectively. Therefore, the high costs of designing and optimizing the transit-time Ultrasonic Flowmeter for crude oil can be reduced, using the proposed model.

Ultrasonic transducers play a significant role in generating and receiving the acoustic waves in Ultrasonic Flowmeters. Depending on the required accuracy, the Ultrasonic transducers can be installed either in one pair or more in an Ultrasonic Flowmeter. The main part of an Ultrasonic transducer is its piezoceramic element. In this work, four piezoceramic elements with different diameter to thickness ratio were fabricated and one of them with center frequency of 200 kHz was selected for the numerical simulations. The piezoceramic element and its gaseous propagation environment were simulated numerically using the finite element method. Similar to the experiments, air was considered as the propagation medium and PZT-5H was used as the piezoceramic element. The results showed that the numerical simulation is in good agreement with the experimental data which indicates that numerical simulation could be an efficient alternative way to reduce trial and errors. It leads to good results if reasonable assumptions are used.

In this work, the effect of flow rate change, temperature, and fluid type are considered on meter factor in turbine meter with the aid of Computational Fluid Dynamics (CFD) simulation. Continuity and momentum equations along with the proper boundary conditions are numerically solved in a steady finite volume frame. SIMPLE algorithm is used for coupling the velocity and pressure field. For the simulation of turbulent flow, the RNG k-e, and for discretizing the advection scheme the second order upwind are used. The drag and lift force on turbine impellers, and the meter factor utilizing angular momentum balances are gained. The results show that the accuracy increases with temperature enhancement and is almost constant with augmenting flow rate. Moreover, the shift from heavy oil to light oil causes the measurement accuracy to increase.

One of the most common of measuring mass fluid flow rate through the pipes are orifice Flowmeter. Orifice Flowmeters work based on the fluid pressure difference before and after of the orifice which could be measured acual mass flow rate. The orifice pressure drop and the discharge coefficient are related on geometrical shape of orifice, the ratio of orifice diameter to the pipe diameter and Reynolds number of fluid flow. In this study, the performance and accuracy of an orifice flow meter for measuring the mass flow rate of cooling water in a sample thermal power plant is examined. In order to determine the water pressure drop on both sides of the discharge orifice, the orifice Flowmeter with connections taken into account and fluid flow inside it is simulated. Due to the turbulent flow of water, the standard k-e turbulence model is used. The performance orifice curve has been obtained numerically and it compares with the actual performance curve orifice obtained from experimental data. This comparision shows a good match. Also the orifice discharge coefficient obtained by numerical and experimental methods and compared with values given by valid standards that indicates good agreement. The numerical analysis has determined that maximum flow velocity occurs about one orifice diameter downstream of the orifice location and in this point, velocity of flow is more than four times the average velocity of flow in the pipe entrance.

Ultrasonic transit time Flowmeters, despite their popularity suffer from the poor accuracy at low values of flow rates and small pipe diameters, where time delays in the range of nanoseconds are to be detected. To overcome this problem, a novel technique is presented in this paper. We have named it "Time Expansion Method, TEM" in which the information carried by phase angles of high frequencies are transferred to low frequencies phase angles, causing the width of the relevant time gate to be expanded. As a result, at a specified flow rate and/or pipe diameter, the system resolution and accuracy is increased. In other words, at a given resolution and accuracy, the lower flow rates inside the narrower pipes can be measured. The theory of the method is developed and its most important parameters are formulated. To practicaly study the method a prototype Flowmeter was designed and successfully tested. By applying the innovative "Time Expansion Method" the flow rate information at a frequency of 2500 Khz (the working frequency of Ultrasonic piezoelectric transducers) was transferred to the much lower frequency of 200Hz, expanding the related transit time 12500 times, resulting an identical improvement Flowmeter sensitivity. Consequently a Flowmeter with much less sophisticatied structure and expense can measure an original transit time difference of about 25 picoseconds which matches flow rate sensitivity of about 0.2mm/s or 5.5 lit/ h in a 4" (100-mm) pipe.

The present study is a numerical model for prediction of turbine Flowmeter performance, using the equation of motion based on torque balance theory. In this model, numerical simulations were carried out for a 2-inch diameter G65 and PN/ANSI 150 gas turbine Flowmeter which was made by Vemmtec Company, in steady state, using Multiple Reference Frame (MRF) model and Standard k-ε turbulence model using Fluent software. In order to model torque balance equation and calculate angular velocity of rotor, a UDF (User Defined Function) code was created and was added to the software. To evaluate the model’ s accuracy, simulation results were compared with experimental data which was obtained from manufacturer of the meter. The difference between the simulation results and experimental data was 0. 16%, approximately, which indicates the validity of the proposed model in simulating of turbine gas Flowmeter performance. The results obtained from the simulation depicted that the velocity distribution asymmetry was more than 0. 4Qmax at the downstream of the meter, and because this phenomenon had no negative effect on flow measurement, the suitable length for the flow development for the downstream of meter was done using simulation at least 10 times the diameter of the pipe was proposed. Therefore, using the proposed model, the capital cost of design and optimization of turbine Flowmeters can be reduced.