Papers by Keyword: Two-Phase

Abstract: The current research paper presents an investigation into the behavior of two-phase flow of liquid-vapour R134a within vertical circular channels with a 1 mm diameter, utilizing the Volume of Fluid (VOF) method. The main objective of these simulations was to create a numerical flow regime map to delineate the boundaries of different flow patterns for liquid-gas R134a. The injection of vapor was performed through an annular (concentric) nozzle configuration. To optimize computational efficiency, a two-dimensional axisymmetric assumption was made. The results of this study led to the identification of four fundamental flow patterns: bubbly flow/confined bubble flow, slug flow, churn flow, and annular flow. The accuracy of these findings was confirmed by comparing them with experimental flow visualization results, demonstrating a strong agreement. This study highlights the effectiveness of Computational Fluid Dynamics in establishing a reliable two-phase flow pattern map.

Abstract: Indonesia is a country prone to hydrological disasters, with high potentials to mud flows in some areas. The mud flows need to be channeled to the appropriate place, and the piping system is one of the best alternatives. Through this research, the analysis of flow characteristics and changes in the density concentration in two-phase (liquid-solid) fluid systems is presented. One-inch diameter transparent PVC pipe was used as the test pipe. The pressure drop, experimental friction factor, and Reynolds number on the experimental variables show an interesting relation between the variables. At 10% ratio of liquid-solid discharge, the flow discharge ranges from 0.00000800 m³/s to 0.00001817 m³/s, while at 100% ratio, the discharge reaches 0.00002133 m³/s. The ratios of liquid-solid discharge ratio of 10% to 100% have influences on increasing pressure reduction (∆P). At increasing density from 1000 to 1010 (at mixture ratios of 10% to 20%), the pressure drop (∆P) also tends to increase. At 10%, the f value ranges from 0.0005004 to 0.0011364, where the experimental friction factor tends to be lower than the theoretical friction factor.

Abstract: Two-phase flow has been used in so many industrial processes, such as boilers, reactors, heat exchangers, geothermal and others. Some parameters which need to be studied include flow patterns, void fractions, and pressure changes. Research on void fractions aims to determine the composition of the gas and liquid phases that will affect the nature and value of the flow property. The purpose of this study is to find out the characteristics of the void fraction of various patterns that occurs and to determine the characteristics of the velocity, length, and frequency of bubbly and plug. Data acquisition was used to convert the data from analog to digital so that it can be recorded, stored, processed, and analyzed. High-speed camera Nikon type J4 was used to record the flow. The condition of the study was adiabatic with variation of superficial gas velocity (J_G), superficial fluid velocity (J_L), and also working fluid. To determine the void fraction by using the digital image processing method. The results of the study found that the flow patterns which occurred in this study were bubbly, plug, annular, slug-annular and churn flows. It also showed that the void fraction value is determined by the superficial velocity of the liquid and air. The higher the superficial velocity of the air, the lower the void fraction value.

Abstract: The present paper offers an analysis of heat transfer and fluid flow in two phase thermosyphon loop with minichannels. A one-dimensional model of two-phase flow and heat transfer in a closed thermosyphon loop with minichannels was examined. The created general model is based on mass, momentum, and energy balances in the evaporators, rising tube, condensers and the falling tube. The separate two-phase flow model is used in calculations. The numerical results obtained for the selected heater and cooler using the general model of thermosyphon loop indicate that the mass flux increases with increasing length of the heated section and decreases with increasing length of the cooled section of the loop. It was found that the heat transfer coefficient for flow boiling and flow condensation in the steady state increases with increasing heat flux in the heater and cooler with minichannels, respectively. The design and configuration of heaters and coolers has a considerable impact on the efficiency of thermosyphon loop. These factors make it possible to optimize the computer processor cooling.

Abstract: The paper concerns with the numerical modeling of wet steam flow through a blade cascade in transonic regime with non-equilibrium condensation in 2D. Real thermodynamics of vapor phase is implemented in the way which mostly avoid iterations in order to calculate thermodynamic properties. This equation of state is represented by the function for non-dimensional entropy with independent variables scaled density and scaled internal energy. Other equations of state are used for comparison, namely special gas equation which comes from IAPWS-95 formulation and simple pseudo perfect gas relation. We applied simple homogeneous non-equilibrium approach to model two-phase flow. Laminar compressible Navier-Stokes system of equations is used for the mixture properties. Liquid phase is described by the standard method of moments of droplet number distribution function. We consider obtained numerical results to be in good agreement with the measured data. We note the fact that robust and accurate closure of supplementary liquid system (nucleation rate and droplet growth model) is still not available and most often ad-hoc corrections are proposed by the authors. Results show differences among used equations of state as well. This is apparent mainly in the vicinity of condensation shock region on the suction side.

Abstract: In this paper, the FEM software ABAQUS is used to analysis the pile-soil load share ratios, load share value of pile side friction and tip resistance for three bases, including natural raft foundation, conventional piled raft foundation and two-phase varying stiffness piled raft foundation. Furthermore, the deformation and settlement of deformation-coordinating device are studied as well. Based on the research of the working characteristic of piles and soil, it highlights the good working mechanism of two-phase varying stiffness piled raft foundation. The analysis results show that two-phase varying stiffness piled raft foundation, with obvious two phase stress characteristics, has a working principle between natural raft foundation and conventional piled raft foundation, fully making use of the bearing capacity of foundation soil, effectively improving the joint bearing capacity of piles and soil.

Abstract: The characteristics and the utilization situation of fruit and vegetable wastes (FVW) were analyzed, and a detailed research conducted on FVW treatment process techniques of single-phase and two-phase anaerobic digestion were summarized. Then the advantages and disadvantages between these two processing techniques are reviewed, respectively. Furthermore, future trends in research and development of FVW treatment process technology have also been briefly discussed, which would provide some new ideas for processing FVW.

Abstract: A numerical study using computational fluid dynamics (CFD) under air/water two-phase flow condition without thermal transmission is carried out utilizing the commercial CFD code CFX. A detailed geometry of 5×5 rod bundles with two grid spacers in the Pressurized Water Reactor (PWR) is set up for analyzing. The Multiple Size Group (MUSIG) model based on the population balance equation is employed to describe the characteristic of flow field in which the dispersed phase has a large variation in size, and the breakup and coalescence interaction among different sizes of the bubbles. The effects of the size fraction at inlet, the size group quantities, the breakup and coalescence coefficients, the momentum transfer model, and so on, are studied. The results demonstrate that various parameters and two-phase model have different impacts on the analysis results. The detailed CFD modeling methodology for two-phase flow conditions in PWR fuel assemblies is developed according to the above-mentioned investigations. The flow field patterns and air/water phase distributions in the computational results shows that the two-phase modeling methodology in the present work is reasonable.

Abstract: The future of the energy sector in the coming years is expected to be significantly affected by unconventional gas resources. Flow through porous media has many applications in the chemical, petroleum, gas, and pulp and paper industries, as well as in soil remediation and material characterization. In petroleum and natural gas production, flow through porous media has significance in the production of gas and/or oil. There are many characteristics of tight reservoir rock resulting in high and complex water saturation such as tiny pore throat, poor sorting, high displacement pressure, and so on. The one hand, the gas seepage is affected by the slippage effect, resulting in the abnormal gas relative permeability. On the other hand, the residual water of the tight core is controlled by displacement pressure. This study is directly related to gas reservoir engineering and is specifically focused to obtain fundamental information for two phase flow through low permeability porous media (Tight Sand Gas).

Abstract: This paper presents a simple two-phase flow model for liquid-cut gas wells, which considers phase slippage and can be applied to various flow patterns. The model is developed from 312 measured pressure losses of gas wells in China, covering a wide range of flow patterns: annular flow, churn flow, and slug flow. Unlike most available methods, this new model introduces a derivation factor, ψ, to modify the void fraction, which not only considers the phase slippage but also unifies the slip model with the homogenous model. Parameter, ψ, is obtained from test data using the regression analyses method. It is a function of gas velocity number, liquid velocity number and liquid viscosity number. Frictional factor is estimated using the simple homogeneous modeling approach. The evaluation results using 145 published data indicate that the new model performed better than the other models.