Two-phase Mixture Research Articles

Experimental Results for a Novel Flash Evaporation and Phase Separation System for Desalination of Sea Water

Abstract A novel system combining dynamic flash evaporation and vapor separation for desalination has been investigated in this work. The feed water passes through injection tubes which are connected to injector passages installed tangentially onto a separator tube. Flashing in the injection tubes is initiated from pressure drop due to friction and acceleration resulting in a two-phase mixture. Centrifugal force from tangential injection separates the two-phase mixture. In this compact system, vapor production and phase separation occur on the order of several milliseconds. Tap water and seawater were used as inlet feed water for the system. Thermal conversion efficiency to analyze the vapor production efficacy and phase separation efficiency to evaluate the purity of the condensate were investigated to evaluate the system. Thermal conversion and phase separation efficiencies up to 98% were obtained with the single stage system. Further improvement in purity of condensate was achieved with a two-stage system. In the two-stage system, the vapor captured along with some entrained droplets from the first stage was directed to a second set of injector passages connected in series to the first stage retrieval tube. With a two-stage system and seawater with salt concentration by mass of 2.5%, collected condensate with salt concentrations lower than 0.02% by mass was achieved, which is comparable to that of potable water. Thus, the novel dynamic flash evaporation and vapor separation system have been demonstrated to be very effective in producing potable water.

A unified numerical model for two-phase porous, mush and suspension flow dynamics in magmatic systems

SUMMARYMagmatic systems in the Earth’s mantle and crust contain multiple phases including solid crystals, liquid melt and low viscosity fluids. Depending on depth, tectonic setting and chemical composition, magmatic systems can range from partially molten rock at low melt fraction to magma mushes at intermediate melt fraction to magmatic suspensions at high melt fraction. However, the theories underpinning most process-based models of magmatic systems describe magma as a single-phase fluid, or as a two-phase mixture either in the porous flow regime at low melt fractions or in the suspension flow regime at high melt fractions. Connections between the two-phase end-member theories are poorly established and hinder investigations into the dynamics of mush flows at intermediate phase fractions, leaving a significant gap in bridging trans-crustal magma processing from source to surface. To address this knowledge gap and unify two-phase magma flow models, we develop a 2-D system-scale numerical model of the fluid mechanics of an n-phase system at all phase proportions, based on a recent theoretical model for multiphase flows in igneous systems. We apply the model to two-phase, solid-liquid mixtures by calibrating transport coefficients to theory and experiments on mixtures with olivine-rich rock and basaltic melt using a Bayesian parameter estimation approach. We verify the model using the method of manufactured solutions and test the scalability for high resolution modelling. We then demonstrate 1-D and 2-D numerical experiments across the porous, mush and suspension flow regimes. The experiments replicate known phenomena from end-member regimes, including rank-ordered porosity wave trains in 1-D and porosity wave breakup in 2-D in the porous flow regime, as well as particle concentration waves in 1-D and mixture convection in 2-D in the suspension flow regime. By extending self-consistently into the mush regime, the numerical experiments show that the weakening solid matrix facilitates liquid localization into liquid-rich shear bands with their orientation controlled by the solid stress distribution. Although the present model can already be used to investigate three-phase mixtures using conceptually derived transport coefficients, more rigorous calibration to experiments and end-member theories is needed to ensure accurate timescales and mechanics. With a self-consistent way to examine multiphase mixtures at any phase proportion, this new model transcends theoretical limitations of existing multiphase numerical models to enable new investigations into two-phase or higher magma mush dynamics.

Optimization design and analysis of a novel total flow and Kalina cycle coupled system driven on low-medium temperature geothermal source with two-phase mixture

A novel total flow and Kalina cycle coupled system has been proposed to utilize the geothermal energy with a certain dryness. To confirm the feasibility and advantages of the proposed system, Particle Swarm Optimization is introduced to optimization design the operating conditions of the system. At design conditions, maximum net output power which is as the single-subjective optimized goal reaches 781.88 kW and the corresponding thermal efficiency and exergy efficiency achieves 12.96 % and 48.54 %, respectively. Meanwhile, thermodynamic properties in each state point of the system are calculated and compared with those of the basic Kalina cycle by selecting the evaporating pressure and the concentration of basic ammonia water as variables. The maximum net output power of the novel system is 111.92 kW more than that of the basic Kalina cycle, while the thermal and exergy efficiencies are also 1.07 % and 6.95 % higher at their respective design condition. In terms of exergy destruction, the evaporator and the condenser occupy the most parts of the system total exergy destruction. Comprehensively analyzing the system performance from the aspects of thermodynamic first and second laws, the proposed novel system has an excellent performance and a great potential to apply in the industrial field.

Numerical investigation on forced convection enhancement within an oil cooler through the simultaneous use of porous media and nanofluid

Traditional strategies for improving heat transmission in industrial systems include nanofluids and porous inserts. In these kinds of systems, increasing the rate of thermal transmission can also be accomplished by utilizing porous materials that have a higher thermal conductance. Al2O3, CuO, and ZnO in engine oil (20w50) nanofluid are studied numerically in three dimensions to see how they affect forced convection in a porous media oil cooler. Within the oil cooler, the porous medium was placed. A two-phase mixture model was used in conjunction with the Darcy–Brinkman–Forchheimer equation indicating the drag forces to simulate nanofluid flow in porous media. In addition, utilizing temperature laboratory data, a more specific thermophysical feature of the fluid was identified and characterized. ANSYS-FLUENT, a commercial computational fluid dynamics (CFD) software, is used to partition the governing equations using the finite volume method. In addition, the thermal boundary parameters of the oil cooler walls were made to be temporally constant and spatially uniform. The effects of varying volume fractions (ranging from 0% to 5%), Darcy number (ranging from 10−2 to 102), overall Nusselt number, pressure reduction, and the performance evaluation criteria (PEC) were analyzed and compared for a variety of distinct nanoparticles. The increased Darcy number (10−2 to 102) had a significant effect on the enhanced heat transfer coefficient, according to the data. In light of the findings, it can be deduced that the high-volume percentage of the nanoparticles will improve thermal transmission and, more significantly, the PEC factor. Furthermore, the given variables were compared, leading to the creation of diagrams for different variables.

Predicting pressure-drop for pseudo-homogeneous slurry flows using the mixture model at high solids concentrations

The main contribution of this paper is applying computational fluid dynamics (CFD) using the two-phase mixture model with algebraic slip, and turbulent dispersion to the slurry flow experiment of Kaushal et al. (2012). The results obtained were compared to the experimental results and numerical results reported by the same authors who used the mixture model as well as a more advanced Eulerian granular flow model. The authors reported that the mixture model predicted the pressure drops with very high errors, especially for the highest solids loading simulated with errors as high as 400% compared to their experimental data. They conclude that the mixture model cannot be used to predict the pressure drop of the slurry flow investigated at higher concentrations (30-50% solid fraction). In contrast to this, the pressure-drop predictions of the two-phase mixture model with algebraic slip and turbulent dispersion used in this study were in good agreement with the measured values. This calls the conclusion of Kaushal et al. (2012). to question, because they did not present any justification for 3-4 times higher pressure drop observed in their study using the mixture model in combination with the fact that no anomalies in particle concentration profiles were observed by them for the mixture model. A comparison between the two mixture models reveals that although they differ in some details, the basic structure of the models is the same. We conclude that the mixture model with algebraic slip, turbulent dispersion, and a suspension viscosity model can be used for pressure drop predictions for the slurry flow investigated even for high solids fraction. We also demonstrate that the laterally averaged solids concentration profiles are not predicted very accurately by the mixture model as well as the more complex granular model. The concentration profiles predicted by the mixture model is easily understood in contrast to the profiles predicted by the granular flow model. From an engineering viewpoint, preference should be given to a simpler model, as was used in this study which can predict pressure drop with similar accuracy compared to a more complex approach with a larger number of uncertainty parameters. Further research is necessary to correctly predict the solids concentration profile for slurry flow in pipelines.

Effect of sediment particles on the velocity profile of sediment–water mixtures in open-channel flow

The presence of sediment particles in open-channel flow has an important effect on turbulence; thus, an empirical, turbulent eddy viscosity formula was established for application in the limit for low concentrations. The current study establishes a theoretical relation for the mixture viscosity based on the two-phase mixture model. The percentage contribution of the three mechanisms of mixture viscosity, namely, fluid turbulence (FT), particle turbulence (PT), and inter-particle collisions (IPCs), was calculated under different conditions. The study results indicate that the contribution of FT is dominant, whereas those of PT and IPCs are not significant when the particle inertia (PI) is small, suggesting that the movement of sediment-laden flows is mainly controlled by the fluid properties. The effects of PT and IPCs increase with increases in sediment concentration and PI. Specifically, the effect of collisions among particles generally becomes dominant near the bed surface. A good agreement between the calculated velocity profile of the mixture and available experimental data for large particle sizes and high concentrations proves that the proposed relation for mixture viscosity is more reasonable than the previous empirical relation owing to the consideration of the effects of PT and IPCs, and, thus, can be applied to both dilute and dense suspensions.

A Study on Accounting for Drift Velocities on Liquid Jets Injected in Cross Flow

The efficiency and combustion performance of propulsion systems, like internal combustion (IC) engines and gas turbines, is known to be related to the performance of the fuel and air mixing process. Operating conditions and fuels are rapidly changing, therefore new CFD models which accurately accounts for all physical aspects, still maintaining a simple framework, are extremely important. In this work we consider the drift velocity contribution, which often is overlooked or neglected, defined as the velocity of the dispersed phase relative to the mixture volumetric mean velocity in a single fluid formulation, a key variable in two-phase mixture model. Water test cases are here considered for the study. The present work investigates the structure and the droplet velocity field of a plain liquid jet injected into a high-pressure air crossflow. Because of the large scale separation between the small features of the interface and the overall jet we use the diffuse-interface treatment in a single-fluid Eulerian framework. A Σ- Y family model is implemented in the OpenFOAM framework which includes liquid diffusion due to drift-flux velocities and a new formulation of the spray atomization. The main objective is to explore the droplet velocity distribution and the jet structure with and without considering the drift flux correction and compare the related results with the experimental data.

Experimental and Prenemilary Numerical Evaluation of Pressure Drops under the Conditions of the Stratified Gas-Liquid Flow in a Horizontal Pipe Filled with Metal Foam

The paper reports the results of experimental tests and numerical simulations related to the pressure drop during two-phase air-water mixture flow through a pipe containing metal foam packing. Aluminium foam with 40 PPI open cells was used in the tests. A horizontal pipe with an internal diameter of 10 mm was used, and the foam only occupied a section of the pipe length equal to 240 mm. In the section of the pipe upwards of the foam, stratified flow pattern was generated, i.e., the most characteristic type for the gas-liquid flow. The results of the experimental research were compared with the values derived on the basis of the empirical method, which was developed for several different metal foams and two-phase systems. The values derived from measurements and calculations were subsequently applied to validate one numerical simulation method that is known to be particularly applicable for two-phase gas-liquid flow through metal foams. As a final result, the phenomena resulting from the presence of foam in the stratified flow through a gas-liquid system, the deficiencies of the methods applied in calculating pressure drops and modeling their values in accordance with the adopted numerical procedure were indicated. All research and modelling were carried out with the purpose of testing the potential of metal foam use in pipes dedicated to heat exchanger design, particularly ones intended to improve energy efficiency.

Heat transfer and entropy generation of water/TiO2 nanofluid flow in a wavy channel using two-phase mixture approach

Heat transfer and entropy generation of water/TiO2 nanofluid flow in a wavy channel using two-phase mixture approach

Entropy generation analysis of a dual-height plate-fin heat sink with Nanofluid coolant applying two-phase mixture model

In this work, the two-phase mixture model is applied to solve the velocity field, the pressure field and obtain the entropy generation rates in a dual-height plate-fin heatsink. The governing equations were solved using the second-order upwind discretization scheme as well as SIMPLE scheme used in coupling the pressure and velocity fields. The Re, nanoparticle concentration (ψ), secondary fin height (hsf), and fin spacing (dsf) were considered within the ranges of 500-2000, 0%-1%, 5 mm-17.5 mm, and 0.25 mm-0.5 mm, respectively. The results demonstrated that S˙th almost decrease by 30% as hsf increases from 5 mm to 17.5 mm. The increase in hsf escalates S˙fr by 308% and 238% at Re numbers of 500 and 2000, respectively. In addition, the escalation of Re from 500 to 2000 increases S˙fr by 2125% and 1748% for hsf 5 mm and 17.5 mm, respectively. The fin spacing analysis revealed that the lowest S˙th and highest S˙fr belong to dsf=0.5 mm. The lower the dsf the higher the backward flow and mixing flow at the heatsink outlet, thereby delay in flow passage and intensification of S˙th and S˙fr.

Effect of Zr on growth kinetics, microstructure and microtexture of Nb3Sn by bronze technique

We have experimentally studied a systematic quantitative effect of Zr on the factors influencing the critical current density of Nb3Sn, such as growth kinetics, microstructure and microtexture using a diffusion couple method. The Nb3Sn phase develops in the interdiffusion zone of the Cu(Sn)/Nb diffusion couple. For the Zr-alloyed diffusion couples, a two-phase mixture of Zr-containing Nb3Sn and sub-micron β-(Nb,Zr) solid solution second-phase develops. The growth kinetics of Zr-containing Nb3Sn is higher than the Zr-free Nb3Sn phase. Enhancement of growth kinetics is attributed to an increase in the diffusion flux of the Sn atoms along the grain boundaries of Nb3Sn owing to grain refinement. The Zr-free Nb3Sn phase has a weak crystallographic texture. On the other hand, the Zr-containing Nb3Sn phase develops not only with a strong crystallographic texture, but also has similar texture component as that of the adjacent Nb-rich parent phase.

Reviving the rock-salt phases in Ni-rich layered cathodes by mechano-electrochemistry in all-solid-state batteries

The rock-salt phase (RSP) formed on the surface of Ni-rich layered cathodes in liquid-electrolyte lithium-ion batteries is conceived to be electrochemically "dead". Here we show massive RSP forms in the interior of LiNixMnyCo(1−x-y)O2 (NMC) crystals in sulfide based all solid state batteries (ASSBs), but the RSP remains electrochemically active even after long cycles. The RSP and the layered structure constitute a two-phase mixture, a material architecture that is distinctly different from the RSP in liquid electrolytes. The tensioned layered phase affords an effective percolation channel into which lithium is squeezed out of the RSPs by compressive stress, rendering the RSPs electrochemically active. Consequently, the ASSBs with predominant RSP in the NMC cathode deliver remarkable long cycle life of 4000 cycles at high areal capacity of 4.3 mAh/cm2. Our study unveils distinct mechano-electrochemistry of RSPs in ASSBs that can be harnessed to enable high energy density and durable ASSBs.

DEVELOPMENT OF OPTIMUM TECHNOLOGY REGIMES FOR PROCESSING TITANOMAGNETITE CONCENTRATES IN THE JEP UNIT

For separation of titanium oxides into slag phase the electric arc furnaces are used in the existing technological schemes. A cheaper waste-free technology for processing titanium concentrate based on a continuous metallurgical jet-emulsion process (JEP) and unit was proposed. The following technological features of the new continuous metallurgical process JEP were considered: creation of a large reaction surface with subsequent organization of the forced movement of the formed gas suspension under pressure; implementation of the principle of gas-dynamic locking of the output channel in an oscillator reactor developed on the basis of this idea; creation of a non-equilibrium stationary oscillatory mode at a given pressure level; bottom supply of a two-phase working mixture prepared in an oscillator reactor to a vertical column reactor. The possibility of implementing a waste-free technology for processing titanomagnetite concentrates was substantiated, that simultaneously ensures the production of commercial titanium slag with smelting of the naturally alloyed metal. It was shown that the technology of almost complete separation of the iron-containing and titanium-containing components from titanium-magnetite concentrate is possible to implement in the JEP type unit in order to obtain the titanium slag with Ti2O5 content 46 % or more. The optimal consumption of materials was determined for complete reduction of iron and conversion of the titanium oxides into slag without formation of carbides.

Level swell analysis of stagnant water pool in filtered containment venting systems

A filtered containment venting system (FCVS) prevents over pressurization of containment vessel and releasing of radioactive materials during the severe accidents in nuclear power plants. During the venting process, it has been reported that the two-phase mixture level in a wet FCVS tends to swell and fluctuate. The behaviors depend on inlet/boundary conditions and physical properties of the injected gas, which vary as the accident progresses. Proper controlling and monitoring of the FCVS pool water level is crucial because it affects filtration performance including scrubbing process and thermal-hydraulic stability. In order to investigate this phenomenon, the current study proposes a set of nitrogen and steam injection experiments using a vertical pipe with a diameter of 105 mm to evaluate the effects of flow conditions and physical properties of gases. Drift flux analysis was carried out to predict the two-phase mixture water level and its fluctuations. The experimental two-phase mixture level was consistent with the values predicted by the drift flux model for nitrogen and steam injection, and the model's capability was confirmed for the system pressure ranging from atmospheric to 0.20 MPa and initial water level ranging from 0.6 to 2.6 m for both small and large diameter pipe configurations. The fluctuation amplitudes in the current experiment were smaller than those observed in experiments conducted on small-diameter pipes. The mean two-phase mixture water level increased upon pressurization of the scrubbing pool. However, it was found that the effect of pressurization on the two-phase mixture level fluctuation amplitude was negligibly small.

Sensitivity analysis of a three-dimensional simulation of turbidity currents in a sloping flume

Sensitivity analysis is necessary in numerical models to establish the optimal model configuration and simulate turbidity currents accurately. The sensitivity of turbidity currents simulated by a three-dimensional numerical model named the semi-implicit cross-scale hydroscience integrated system model (SCHISM) was assessed using domain discretization, the turbulence closure model, and the transport scheme. The results show that a higher horizontal resolution with an appropriate aspect ratio, localized sigma coordinates with shaved cells (LSC2) grid with sufficient layers, a two-phase mixture turbulence closure model, and transport schemes with critical depth ratio lower than 1 could improve the model performance on the turbidity currents. The study can provide helpful guidance to establish accurate turbidity current simulations in complex water environments.

3D printable low density B2+BCC refractory element based complex concentrated alloy with high compressive strength and plasticity

While complex concentrated alloys (CCAs), involving large fraction of refractory elements, are promising candidates for structural applications, their relatively high densities, processing challenges, and low plasticity, has retarded their development. Here, we report a 3D printable low-density precipitation strengthened CCA, Al10Nb15Ta5Ti30Zr40. The chemical homogeneity in the alloy deposited using laser bed powder fusion process is substantially better as compared to as-cast ingot. This homogeneity is attributed to the enhanced solubility at the high temperatures experienced during laser melting, small melt pool dimensions, and the high cooling rates. The as-built CCA exhibited an excellent balance of room temperature mechanical properties, a compressive yield stress ∼1400 MPa, peak stress ∼1700 MPa, and plastic strain exceeding 45%. These properties can be attributed to its unique as-processed microstructure consisting of refined grains incorporating a high density of sub-grain boundaries, containing a nanoscale two-phase mixture of an ordered B2 and disordered BCC solid solution phases.

A comparative numerical analysis and environment assessment to examine hydrothermal behavior of two serpentine heatsink with water/silver Nano fluid applying two-phase mixture model

In the present study, the hydrothermal characteristics of two different a) serpentine (Conf. A), and b) double serpentine (Conf. B) heatsinks with water/silver Nano Fluid (NF) were studied. To this end, the Finite volume method was performed, and the governing equations were discretized based on the second upwind approach and solved numerically applying the Semi-Implicit Method for Pressure Linked Equations (SIMPLE) scheme. The results demonstrated that the thermal resistance (R) of Conf. A is lower than that of Conf. B at low Re numbers, and these two configurations have an identical R as Re increases to 2000. Also, the convective heat transfer in Conf. A is slightly higher than that in Conf. B and for Re=2000 both configurations have a same h value. Moreover, the increasing of nanoparticle concentration from 0% to 1% increases h by 12.55% and decreases the pressure drop (ΔP) by 4.25%. In addition, the CPU mean temperature of Conf. A is 0.8% and 0.1% lower than that of Conf. B for Res of 500 and 2000, respectively. On the other hand, ΔP in Conf. A is 74% higher than that in Conf. B. Besides, Conf. B exhibits a better temperature uniformity as compared to other configuration. The parameter of figure of merit was obtained as 1.47 to 1.52 at Res of 500 and 2000, respectively, which showed that Conf. B provides a higher hydrothermal performance over the other configuration.The environmental impact of the designed heat sink is equal to 0.5388.

Machine Learning-Based Approach for Modeling the Nanofluid Flow in a Solar Thermal Panel in the Presence of Phase Change Materials

Considering the importance of environmental protection and renewable energy resources, particularly solar energy, the present study investigates the temperature control of a solar panel using a nanofluid (NFD) flow with eco-friendly nanoparticles (NPs) and a phase change material (PCM). The PCM was used under the solar panel, and the NFD flowed through pipes within the PCM. A number of straight fins (three fins) were exploited on the pipes, and the output flow temperature, heat transfer (HTR) coefficient, and melted PCM volume fraction were measured for different pipe diameters (D_Pipe) from 4 mm to 8 mm at various time points (from 0 to 100 min). Additionally, with the use of artificial intelligence and machine learning, the best conditions for obtaining the lowest panel temperature and the highest output NFD temperature at the lowest pressure drop have been determined. While the porosity approach was used to model the PCM melt front, a two-phase mixture was used to simulate NFD flow. It was discovered that the solar panel temperature and output temperature both increased considerably between t = 0 and t = 10 min before beginning to rise at varying rates, depending on the D_Pipe. The HTR coefficient increased over time, showing similar behavior to the panel temperature. The entire PCM melted within a short time for D_Pipes of 4 and 6 mm, while a large fraction of the PCM remained un-melted for a long time for a D_Pipe of 8 mm. An increase in D_Pipe, particularly from 4 to 6 mm, reduced the maximum and average panel temperatures, leading to a lower output flow temperature. Furthermore, the increased D_Pipe reduced the HTR coefficient, with the PCM remaining un-melted for a longer time under the panel.

Entropy analysis and parametric optimization on the Nano fluid flow and heat transfer of a pin-fin heatsink with the splitter using the two-phase mixture model

The nanofluid (NF) flow rate and concentration (φ) in a pin-fin heat sink with the splitter (WS) were numerically investigated and the optimum Re and φ values were determined by applying a parametric optimization analysis on the thermal and frictional entropy generation rates (S˙th and S˙fr). To this end, the discretization of the governing equation was done by the second-order upwind scheme, the finite volume method. The results were compared with those obtained for the pin-fin heatsink without the splitter (WOS). Based on the findings, the intensification of Re and φ reduces S˙th by almost 43-45% and 10-13%, respectively, for both WS and WOS heatsinks. An insignificant difference between S˙th of two configurations was obtained (0.37-2.93%). Although S˙fr diminishes by 12% as φ intensifies from 0 to 1%, the escalation of Re from 500 to 2000 intensifies S˙fr by 2312% and 4618% in WS and WOS heatsinks, respectively. In addition, S˙fr of WS heatsink is nearly 43-48% lower than that WOS heatsink due to using splitters. The absence of the splitter in the WOS heatsink leads to a delay in flow separation from the pin-fin bodies and deteriorates the heat dissipation, thereby increasing the CPU temperature and S˙fr intensification.

Numerical simulation of detonation re-initiation in a 90° bifurcated channel filled with n-heptane/air mixture

This paper aims to study the detonation re-initiation through multiple reflections when the detonation enters the horizontal channel holding liquid fuel from the vertical branch. Based on the Eulerian-Lagrangian method, the detonation diffraction, reflection and re-initiation of gas phase (C7H16/Air) and two-phase (n-heptane/Air) are compared, and the effects of droplet diameters on re-initiation and the interaction between shock wave and droplets are analyzed. The results show that compared with the detonation propagating in pure gaseous mixture, detonation is easier to be decoupled in two-phase mixtures during the diffraction stage due to the droplet fragmentation and evaporation process, and lots of unburned fuels are left behind the detonation wave. As the droplet diameter increases, the detonation wave propagates slower and the cell size increases. The number of transverse waves formed after the first reflection gradually decreases, and the transverse detonation in mixture with larger droplets is decoupled during the downstream propagation. The shock wave interacts with the droplet, leading to the occurrence of droplet breakup. At this stage, the total mass of the droplets remains basically unchanged. After that, the droplet evaporation process occurs, and the droplet mass decreases rapidly.