Drift Flux model is widely used in literature to predict void fraction in two-phase gas-liquid flow. Drift flux model has been used for all flow regimes. The distribution parameter implemented in the model is very crucial for the accuracy of the model. A new distribution parameter was developed in this paper as a function of two dimensionless parameters and flow regime (slug or plug). The new model showed a superior predicted void fraction accuracy over all available models in literature. In this paper, the influence of the flow regimes was implemented in the formulation of the drift flux model distribution parameter for the first time in literature. The drift velocity was found to be negligible in the horizontal configuration. The proposed model was validated using unbiased data from literature from different sources and for a wide range of liquid viscosity from water up to high viscosity oil (600 cP) and pipe diameter from 19 mm up to 152 mm. The mean relative absolute error of the proposed model using all data bank is around 16% while the least error model available in literature is around 19%. Moreover, the most recent models of Rassame and Hibiki (2018) and Kong et al. (2018b) give 33% and 50%, respectively.

A method based on Electrical Capacitance Tomography (ECT) and an improved Least Squares Support Vector Machine (LS-SVM) is proposed for void fraction measurement of oil-gas two-phase flow. In the modeling stage, to solve the two problems in LS-SVM, pruning skills are employed to make LS-SVM sparse and robust; then the Real-Coded Genetic Algorithm is introduced to solve the difficult problem of parameters selection in LS-SVM then. In the measurement process, the flow pattern of oil-gas two-phase flow is identified by using fast back-projection image reconstruction and a fuzzy pattern recognition technique and the void fraction is computed using the void fraction model corresponding to the identified flow pattern. Experimental results demonstrate that both the improvement of LS-SVM and the parameter optimization are effective. The results also show that the real-time performance of the proposed void fraction measurement method is good, and the measurement precision can satisfy the application requirement.

Two-phase flow happens widely in the industrial plants and certain equipment. This paper attempts to study the characteristics of two-phase flow in a vertical piping system. This was achieved by comparing the void fraction, in the working fluid, by employing Constant Electric Current Method (CECM) with the actual observation using high-speed camera. The experiment requires a complete set of two-phase flow system information and was conducted based on various flow conditions. In order to carry out this experiment, the two-phase flow loop was constructed using a specific experimental apparatus and components. The flow channels were constructed using three pipes with three different inner diameters of 21. 0 mm, 47. 0 mm and 95. 0 mm. The flow direction was vertical upward co-current flow with liquid superficial velocity range of 0. 025 m/s to 3. 0 m/s and gas superficial velocity range of 0. 025 m/s to 3. 0 m/s, depending on the size of the pipe. The flow pattern investigation focuses on experimental work, which was based on systematic observation and measurements using a high-speed camera and some measuring apparatus. The void fraction measurement using the CECM sensor was integrated into two-phase flow system with constant electric current running in the pipe and data acquisition system controlled virtually via LabVIEW software. Both result of the flow pattern and void fraction graph were then compared to determine the type of flow pattern from the void fraction graph. Information from the previous studies and experiments were collected and the assumption of any theoretical simplifications were used as a reference. According to the result, the flow pattern in pipe can be easily determined using CECM.

Air can have an adverse effect on the performance of an aero-engine lubrication system. A numerical analysis was conducted to explore the influence of inlet void fraction and pipe layout on the characteristics of oil-gas two-phase flow in a 90° elbow. The pipes were arranged horizontally and vertically with inlet void fractions of 0.05-0.15. The laws governing flow velocity, void fraction, and pressure along the pipe were determined separately. The results revealed the formation of large-scale vortices with high gas volume fractions inside both types of elbows, which exacerbate oil-gas separation and cause additional head loss. The maximum pressure drop was observed at approximately one pipe diameter downstream of the elbow outlet, which initially increases with the inlet void fraction and then gradually stabilizes. Asymmetric secondary flow vortices in the horizontal elbow were found to enhance oil-gas separation and accelerate lubricating oil to greater extent than in a vertical elbow under the same conditions. Consequently, the maximum pressure drop caused by flowing through the horizontal elbow is higher than that in the vertical elbow.

Polyolefins have been widely used in the electrical insulation and cable industry in recent years. One of the main usages of these materials is dielectric insulation in coaxial cables. Low attenuation and high signal transmission speed are among the desired features in coaxial cables. The role of polyethylene foam on signal transmission speed in the coaxial cables is the main focus of this study. In the present study, the velocity factor of coaxial samples with different dielectric structures is investigated in both theoretical and experimental approaches. In theoretical formulation, only the void fraction of foam is taken into consideration and other foam properties such as cell density, cell size, and foam structure are neglected. This is the reason for the difference observed between theoretical and experimental results. In theoretical results, a linear increase in the velocity factor is witnessed with the increase of the void fraction while in experimental results there are some exceptions. The foaming degree of the samples was reached 63% causing a 37. 7% decrease in theoretical relative permittivity and consequently a 26. 8% increase in theoretical velocity factor. On the other hand, up to 36% increase is observed in the experimentally measured velocity factor of foamed dielectric samples compared to the samples with solid polyethylene dielectric.

Filters are widely used for dewatering in the mining industry. In general, different parameters affect vacuum filtration, such as solid percentage, vacuum level, particle size distribution, filter cloth, and chemical additives. These parameters can influence filtration properties such as cake moisture, throughput, and filter cloth lifetime. Moisture and throughput usually are used to determine the quality of filtration. In this study, new variables were used to express the filtration and characteristics of filter cake at a microscopic scale. The quality of the filter cake can be precociously analyzed using the void fraction and density of the filter cake. The present study aimed to propose some new variables to properly analyze the filtration process, improve the filtration rate, and decrease the cake moisture of Gol-E Gohar iron ore concentrate. In this regard, a series of filtration experiments were implemented using laboratory-scale bottom top-feed vacuum filters. The results showed that an increase in the solid percentage decreased the void fraction from 0.45 to 0.40 and increased cake density from 0.30 to 0.33 gr.cm-3, respectively. Increasing the particle size increased the void fraction from 0.415 to 0.43. Furthermore, the type of structural or capillary moisture of the filter cake could be determined using a void fraction.

Simulation and analysis of two phase flow that crosses over tube bundles is crucial in safety analysis and design of kettle reboilers and steam generators. The geometry complexity of the tube bundle flow field increases the difficulty of the conventional numerical analysis. One of the methods to reduce the numerical calculations cost is to use the porous media theory instead of the complete tube bundle modeling. Drag and tube bundle resistance force equations have been used in the porous media analysis. Based on available experimental results, two tube bundle arrangements have been considered. Due to existence of symmetric geometry and uniform energy source over the tube bundle, the two dimensional symmetric models have been used as well. It was observed that the predicted pressure drop in this research has acceptable adaptation with the experimental results. Meanwhile, by considering different outlet boundary conditions, calculated void fraction is compared to the experimental results and showed better accuracy than similar CFD research. It was observed that the enhancement of the tube bundle thermal power increases the void fraction in the heating area of the reboiler.

Introduction: Breast cancer is among the main reasons for most cancer-associated loss of life in women worldwide. The use of autologous lipotransfer has become increasingly popular for breast reconstruction. With the emerging data on the efficacy of stromal vascular fraction (SVF) in oncological safety and survival rates, although many studies have focused on improving the preservation of fat graft volume with this material, questions regarding safety and efficacy still remain. The present study aimed to determine the advantages and disadvantages of SVF in fat grafting, especially in its preservation. Materials and Methods: Our search was conducted on published research between 2000 and 2022 using several international databases, including Scopus, PubMed, Web of Science, and Google Scholar. We also reviewed additional evidence from relevant published articles. Results: Although the SVF is easier to isolate than adipose-derived mesenchymal stem cells (ADSCs), it contains a heterogeneous mix of cells. The SVF may act through angiogenesis promotion by endothelial/progenitor cells and immunomodulation by ADSCs. The SVF-enhanced fat grafts improve volume retention in animal models. Although limited clinical data supports improved breast augmentation with SVF without increased cancer recurrence, optimal SVF isolation and cell ratios require further research. Conclusion: Based on the obtained findings, although SVF shows promise to improve fat grafting outcomes in breast reconstruction, more clinical studies on oncologic safety and technical considerations are warranted.