This paper reviews the latest development and emerging technologies on the application of process tomography to multiphase flow measurement in industrial and biomedical fields. In the industrial applications, electrical resistance tomography and electrical capacitance tomography are popularly applied in multiphase flow measurement dependent on the electrical properties of the objects. In particular, applications to circulating fluidized bed, trickle-bed reactor and temperature measurement are discussed. In the biomedical applications, in most cases, measurement is conducted in a static condition. Two latest applications in flowing condition are reviewed, which are thrombus detection in blood flow and cell sensing with a microfluidic device. Finally, the challenges to process tomography for multiphase flow measurement on industrial and biomedical applications are addressed.

Application of Process Tomography to Multiphase Flow Measurement in Industrial and Biomedical Fields: A Review

A dual-modality electrical tomography sensor for measurement of gas–oil–water stratified flows

A portable electrical impedance tomography (EIT) system has been developed with Red Pitaya STEMlab for biomedical applications. The Red Pitaya STEMlab is a portable device to realize voltage generation and data acquisition for the EIT system. The EIT system includes a modified howland circuit as a voltage-controlled current source, a high-speed analogy multiplexer module, an 8-electrode array, and a personal computer. The generalized vector sampled pattern matching algorithm and the Tikhonov regularization algorithm are used to reconstruct the image generated by the EIT system. The reconstructed images by using Red Pitaya STEMlab are compared with a commercial impedance analyzer IM3570 within the frequencies of $f = 100$ KHz. The results show that the maximum difference of the image correlation between Red Pitaya STEMlab and IM3570 is 5.36%. Finally, the EIT system is used to image the conductivity of eggs during heating process. These results verified that the developed portable EIT system with Red Pitaya STEMlab could measure the biological tissue in a high accuracy at low cost.

Development of a Portable Electrical Impedance Tomography System for Biomedical Applications

Multi-phase flow meters are of huge importance to the offshore oil and gas industry. Unreliable measurements can lead to many disadvantages and even wrong decision-making. It is especially important for mature reservoirs as the gas volume fraction and water cut is increasing during the lifetime of a well. Hence, it is essential to accurately monitor the multi-phase flow of oil, water and gas inside the transportation pipelines. The objective of this review paper is to present the current trends and technologies within multi-phase flow measurements and to introduce the most promising methods based on parameters such as accuracy, footprint, safety, maintenance and calibration. Typical meters, such as tomography, gamma densitometry and virtual flow meters are described and compared based on their performance with respect to multi-phase flow measurements. Both experimental prototypes and commercial solutions are presented and evaluated. For a non-intrusive, non-invasive and inexpensive meter solution, this review paper predicts a progress for virtual flow meters in the near future. The application of multi-phase flows meters are expected to further expand in the future as fields are maturing, thus, efficient utilization of existing fields are in focus, to decide if a field is still financially profitable.

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Multi-Phase Flow Metering in Offshore Oil and Gas Transportation Pipelines: Trends and Perspectives.

Because of the ?soft-field? nature, all electrical tomography sensors suffer from electric field distortion, i.e. the fringe effect. In electrical resistance tomography (ERT) sensors, small pin electrodes are commonly used. It is well known that the pin electrodes result in severe electric field distortion or the fringe effect, and the sensing region of such an ERT sensor spreads out of the pin electrode plane to a large volume. This is also true for electrical capacitance tomography (ECT) sensors, even though it is less severe because of larger electrodes and grounded end guards used. However, when the length of electrodes in an ECT sensor without guards is reduced to almost the same dimension as those in an ERT sensor, the fringe effect is equally obvious. To investigate the fringe effect of ERT and ECT sensors with and without guards, simulations were carried out with different length of electrodes and the results are compared with the corresponding 2D simulation. It is concluded that ECT and ERT sensors with longer electrodes have less fringe effect. Because grounded end guards are effective in reducing the fringe effect of ECT sensors, we propose to apply grounded guards in ERT sensors and integrate ECT and ERT sensors together. Simulation results reveal that ERT sensors with grounded guards have less fringe effect. While commonly current excitation is used with ERT sensors, we propose voltage excitation instead to apply the grounded guards. The feasibility of this approach has been verified by experiment. Finally, a common structure for reducing the fringe effect is proposed for ECT and ERT sensors for the first time to simplify the sensor structure and reduce the mutual interference in ECT/ERT dual-modality measurements.

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Fringe effect of electrical capacitance and resistance tomography sensors

Evaluation of fringe effect of electrical resistance tomography sensor

Electrical Capacitance Tomography (ECT) has been developed for many years and made great progresses. Successful applications of ECT depend on the accuracy and speed of image reconstruction. In this paper, we propose a new image reconstruction method based on deep neural network. The proposed neural network mainly consists of three parts, i.e. a forward problem network, an inverse problem network and a permittivity prediction network. Compared to previous reconstruction algorithms, the benefit of our method is that it can not only reconstruct the object shape, but also predict its permittivity value with the preset resolution which is desired in many multiphase flow applications. In experiment, 10000 frames of simulation data and additional measured capacitance data were used. The results show that the proposed method can reconstruct images more accurately than typical iterative methods with real permittivity values of objects predicted correctly, and reduce the computational cost to about 2.24 seconds per frame for an image resolution of 200*200.

Jiangtao Sun

Papers

A dual-modality electrical tomography sensor for measurement of gas–oil–water stratified flows

Fringe effect of electrical capacitance and resistance tomography sensors

Evaluation of fringe effect of electrical resistance tomography sensor

Permittivity Reconstruction in Electrical Capacitance Tomography Based on Visual Representation of Deep Neural Network

3D imaging based on fringe effect of an electrical capacitance tomography sensor