Flash Evaporation Research Articles

Selective removal of Fe(Ⅲ) from HNO3 leach liquor of saprolitic laterite ore: Precipitation efficiency, hydrolysis mechanism, and removal strategy

HNO3 leach liquor of saprolitic laterite ore contains Fe3+, Al3+, Sc3+, Ni2+, Co2+, Mg2+, etc. Efficient removal of Fe3+ while reducing the loss of valuable metals is the key to solution purification. In this paper, a detailed study was carried out on the removal of Fe3+ by hydrolysis precipitation. First, thermodynamic calculations were conducted to analyze the precipitation pH changes and possible hydrolysis products at different temperatures. Subsequently, the experimental results show that more than 99 % Fe can be removed via low-temperature hydrolysis at 25–80 ℃ and pH = 3.0–3.5, but over 40 % Al and 30 % Sc also precipitate together, causing valuable metals losses. Differently, under high-temperature conditions (180 ℃, pH = 1.0, 0.5 h), 99.49 % of Fe can be selectively removed as Fe2O3 product, while other valuable metals hardly precipitate. It was found that the low-temperature Fe removal residue exhibits irregular agglomeration and uneven particle size, and contains 9.48 % NO3– and 25.86 % Fe. The high-temperature Fe removal residue presents a nanoscale spherical shape with uniform particle size and only contains 0.087 % NO3–, and the Fe content is up to 69.07 %. Finally, the Fe3+ hydrolysis mechanism was analyzed and an efficient Fe removal process from the HNO3 system including pH adjustment of leach liquor, selective Fe removal at high temperature, flash evaporation to recover free HNO3, and solid–liquid separation to obtain Fe2O3 products was proposed.

In Vitro Exploration of Dark Cytotoxicity of Anthocyanin-Curcumin Combination, A Herbal Photosensitizer.

Photodynamic therapy can be used to treat a variety of lesions noninvasively, including oral cancer. High-power laser therapy has also been used to treat oral squamous cell carcinomas. The two main components of photodynamic treatment are the photosensitizer and the light source. Herbal formulations of photosensitizers are used to mask the disadvantages of other photosensitizers. A methanol-diluted 25 grams of Punica granatum was used to create an anthocyanin extract using the flash evaporation method. Dimethyl sulfoxide (DMSO) was used as the first dilution agent for curcumin; later further dilution was done with distilled water. Following that, MCF-7 cells (a cancer cell line) were cultured with the produced samples, and the mono-tetrazolium salt (MTT) assay was used to determine the vitality of the cells. Cell reduction was significantly evident in all three groups, but the most significant cell death was found in the anthocyanin-curcumin group, at 29%. The combination of anthocyanin-curcumin has one of the photophysical properties (dark cytotoxicity)and hence can aid as a photosensitizer.

Performance Evaluation of Single Stage Flash Evaporation Desalination Unit Integrated with a Parabolic Trough Solar Collector for Basrah City Climate, Iraq

Solar energy is the most suitable among all renewable energy options for competing with fossil fuels in desalination due to its ability to utilize both heat and power for the process. In this study, the Parabolic Trough Solar Collector (PTSC) for powering a Single Stage Flash (SSF) desalination unit was proposed for Basrah city climate, Iraq. The desalination system comprises two directly coupled sub-systems: the PTSC and the SSF desalination unit. The preheated feed brine water coming from condenser was used as a Heat Transfer Fluid (HTF) for PTSC, which gets heated to a desired temperature referred to as the Top Brine Temperature (TBT). The numerical simulations were performed via EBSILON professional 16.02 (2022) software. The effects of TBT, mass flowrate of feed brine water to get the desired TBT, solar collector area, and vacuum pressure inside flash chamber on the performance of the desalination system was studied. A major finding of the current study can be summarized as follows: The collector efficiency is enhanced eventually as TBT increases. The maximum values of distillate water in June are around 5.5, 4.56, 3.69, 2.75 and 1.85 kg/h for 12.408, 10.434, 8.3472, 6.26, and 4.1736 m² collector area respectively, when TBT 107 °C and vacuum pressure 40 kPa. For 1.598 m² collector area, the total distillate in the 1st of June amounted to 7.9 kg, with an average production rate of around 0.7 kg/h. The solar SSF system's productivity per solar collector unit area at 20 kPa, 15 kPa, and 10 kPa vacuum pressures was 4.7 kg/day/m², 5.3 kg/day/m², and 6.25 kg/day/m², respectively. The average Performance Ratio (PR) values are determined to be 0.694, 0.577, and 0.491 for 10 kPa, 15 kPa, and 20 kPa, respectively. These results are very acceptable when compared with an existing literature.

Exploring the reinforcement and conductivity mechanism of K2FeO4‐modified multiwalled carbon nanotubes in carbon black/natural rubber composites

AbstractThis study employs potassium ferrate (K2FeO4) for the oxidation treatment of multi‐walled carbon nanotubes (MWNTs) under neutral and acidic conditions. A wet flash evaporation process is utilized to prepare natural rubber/MWNTs/carbon black composites, enhancing the performance of rubber composites. The increased oxidation level of MWNTs enhances their hydrophilicity, increases the quantity of oxygen‐containing hydroxyl groups on the surface, promotes dispersion within the natural rubber matrix, and ultimately improves the performance of the rubber products. The effective dispersion of MWNTs reduces electron transport resistance, forming a favorable electron transport channel in natural rubber. Experimental results indicate that K2FeO4 achieves the highest oxidation degree and optimal performance in an acidic environment. Compared to untreated MWNTs rubber composites, the oxidized MWNTs rubber composites exhibit a 34.9% reduction in the Payne effect, a 15.7% decrease in wear, a 12.7% reduction in rolling resistance, and a two‐order‐of‐magnitude increase in conductivity. This study provides a novel approach for preparing water‐dispersible MWNTs and high‐performance rubber composites, holding potential applications in premium rubber products and conductive rubber fields.Highlights The wet flash refining process improved the dispersion of MWNTs. K2FeO4 oxidation of MWNTs was enhanced under acidic conditions. Oxidized MWNTs combined with CB to form a CB‐MWNTs‐CB filler network. Oxidized MWNTs and CB increased the “ball‐chain” arrangement in NR.

Experimental Investigation of the Performance of a Novel Adiabatic Swirl-Flow Separation Apparatus in Air–Water Two-Phase Flow

Abstract Experiments were performed for determining the efficacy of a swirl-flow apparatus for phase separation of a premixed two-phase air–water mixture. In the experiments gas and liquid flow rates were parametrically varied. The goal of this study was to determine the ideal operating conditions for phase separation of an adiabatic mixture and to serve as a benchmark for future desalination experiments involving separation of vapor-saline water two-phase mixture generated by flash evaporation. The novel swirl-flow apparatus enables the formation of a stable air core (lighter fluid) in the middle of the separator tube due to centrifugal force induced by strategically injecting the two-phase mixture tangentially into the tubular test section. Separated air is removed by tapping into the air core using a retrieval tube that is mounted in the center of the test section. Conditions under which maximum phase-separation efficiency is obtained in the swirl-flow apparatus were identified and a correlation for the phase-separation efficiency is proposed for the range of experimental conditions explored in this study.

Deposition of CsFAPbI3 thin films by single source flash evaporation

Formamidinium-cesium lead iodide (CsFAPbI3) is a promising perovskite material for photovoltaic applications with a suitable bandgap of 1.45 eV and excellent optoelectronic properties. In this work, CsFAPbI3 perovskite thin films were deposited by single-source flash evaporation on glass substrates using presynthesized crystalline powders as the source material in which the source challenges of simultaneously controlling the evaporation of organic and inorganic sources are avoided. The structural properties of the powders were evaluated by X-ray diffraction, thermal properties by TGA analysis and optical properties by UV-Vis absorption. We find that the formation of mixed phases is inevitable in flash evaporation of thin films. This undesirable phase could reduce the optical bandgap and the thermal stability which can affect the performance of the thin films. To obtain the cubic phase, a post-annealing process should be employed. We carried out structural, morphological, and optical characterizations to determine the phase purity in the films. These preliminary results suggest that flash evaporation deposition parameters can be optimized to understand the formamidinium evaporation and condensation dynamics for improve the properties of CsFAPbI3 perovskite thin films.

Synchronous Regulation Strategy of Pyrrolidinium Thiocyanate Enables Efficient Perovskite Solar Cells and Self-Powered Photodetectors.

Developing inventive approaches tocontrol crystallization and suppress trap defects in perovskite films is crucial for achieving efficient perovskite photovoltaics. Here, a synchronous regulation strategy is developed that involves the infusion of a zwitterionic ionic liquid additive, pyrrolidinium thiocyanate (PySCN), into the perovskite precursor to optimize the subsequent crystallization and defects. PySCN modification not only orchestrates the crystallization process but also deftly addresses trap defects in perovskite films. Within this, SCN- compensates for positively charged defects, while Py+ plays the role of passivating negatively charged defects. Based on the vacuum flash evaporation without anti-solvent, the air-processed perovskite solar cells (PSCs) with PySCN modification can achieve an extraordinary champion efficiency of 22.46% (0.1 cm2) and 21.15% (1.0 cm2) with exceptional stability surpassing 1200 h. Further, the self-powered photodetector goes above and beyond, showcasing an ultra-low dark current of 2.13 × 10-10 A·cm-2, a specific detection rate of 6.12×1013Jones, and an expansive linear dynamic range reaching an astonishing 122.49dB. PySCN modification not only signifies high efficiency but also ushers in a new era for crystallization regulation, promising a transformative impact on the optoelectronic performance of perovskite-based devices.

Heterointerface Energetics Regulation Strategy Enabled Efficient Perovskite Solar Cells

AbstractIn the domain of perovskite photovoltaics, the heterointerfaces are subject to substantial trap‐assisted non‐radiative recombination, predominantly attributed to the energy offset, interface defects, and the roughness of the contact. This phenomenon at the heterointerfaces, where carrier non‐radiative recombination and energy dissipation occur due to defects and suboptimal energy level alignment, can be principally held accountable for the Voc losses. Herein, a heterointerface energetics regulation (HER) strategy is proposed by introducing potassium trifluoroacetate (KTFA) in the perovskite precursor solution to eliminate the trap defects and optimize surface potential and Fermi level. It is first demonstrated that non‐doping K+ but precipitating at the upper and buried perovskite will improve energy‐level alignment for charge extraction dynamics. In addition, the TFA− exhibits strong electrostatic force with undercoordinated Pb2+ in the buried contact of perovskite and Sn4+ in the SnO2 electron transporting layer. Based on the vacuum flash evaporation green treatment without anti‐solvent, the Rb0.02(Cs0.05FA0.95)0.98PbI0.91Br0.03Cl0.06 and Cs0.05FA0.95PbI3 based device can achieve maximum efficiency of 23.36% and 24.48%, respectively. Further, the modified devices exhibit 92% initial efficiency output after 1200 h of aging. HER strategy for addressing interface defects and bandgap alignment are poised to advance both the performance and stability of perovskite solar cells.

Experimental study on bubbles behaviors in pure water flash evaporation process

Experimental observations were conducted on the phenomenon of flash evaporation. The bubbles appear and grow due to the liquid becomes superheated by a sudden decrease in pressure. During experiments the pure water is flashed at an initial temperature range of 55–90 ℃, an initial liquid film height range of 10–60 mm, and a superheat range of 2–22 K. The spatial and temporal distribution of the bubbles are analyzed during the flashing. And the distribution of bubbles under different superheat and the photo of the behaviors of bubbles were studied. The flashing evaporation can be divided into three stages according to the rate of the bubbles number change and the NEF(non-equilibrium fraction) can express the rate of bubble number at different stages. The number of bubbles is affected by the difference of enthalpy under the same volume of the liquid.

A Mathematical Model for the Operational Evaluation of the Dynamics of Heat and Mass Exchange in Flash Evaporators

A Mathematical Model for the Operational Evaluation of the Dynamics of Heat and Mass Exchange in Flash Evaporators

Advancements in Zinc Oxide (ZnO) thin films for photonic and optoelectronic applications: A focus on doping and annealing processes

This study focuses on the potential of Zinc oxide (ZnO) as a versatile material for photonic and optoelectronic applications, owing to its direct wide bandgap (Eg ≈ 3.175 eV) and significant excitonic energy. ZnO, both in pure and doped forms, exhibits promise in various domains, including solar cells, photoelectrochemical cells, thin film transistors, gas sensors, and nanogenerators. The manuscript delves into the methodologies for producing ZnO:B films, including reactive evaporation, evaporation from two sources, and flash evaporation, each addressing the challenges of achieving the desired film composition and structure. The investigation reveals that the optimized ZnO:B films possess crystalline phases with hexagonal lattice structures, demonstrating significant enhancements in electrical conductivity upon specific annealing treatments. The research underscores the impact of doping and microstructure modifications on the optoelectronic properties of ZnO films, contributing to advancements in semiconductor-based thin films and powders.

Computer simulation of a solar multi-effect distillation multi-stage flash effluent purification system

Abstract This study integrates multi-effect distillation (MED), multi-stage flash (MSF) evaporation, and solar interface evaporation technologies to enhance water purification processes. We evaluate the material and performance of interface evaporators, with a particular focus on managing the energy balance in solar water evaporation. The research further develops thermal regulation in photothermal materials to maximize light absorption, minimize heat loss, and speed up steam conversion. We employ a novel approach using corn starch and ionic liquid-modified silica hydrogels, noted for their hydrophilicity and broad-spectrum light absorption. The goal is to assess these hydrogels for photothermal conversion efficiency and salt resistance, examining their evaporation performance across various media—pure water, highly saline water, and oily wastewater—and their effectiveness in purifying industrial sewage. Monomer [VEIm]Br and cross-linking agent polymerization occurred to prepare the obtained SiO 2 – PILs.Ag / PPy / SiO 2 – PILs surface of polypyrrole and Ag particles presenting a three-dimensional porous structure is able to enhance the light absorption performance, between 200-2500 nm range of light absorption rate as high as 90%. Experiments proved the introduction of ionic liquid grafted silica on the introduction of the mechanism to improve the thermal insulation and salt resistance for the actual wastewater purification to provide a strategy.

Experimental study of energy conversion on pure water static flashing evaporation considering the gravity

Energy conversion of pure water during the static flash evaporation is analysed with water static pressure taken into consideration.The experiment is conducted by varying the initial temperature and height of water in the range of 50 ℃ to 80 ℃ and 3 mm to 60 mm, respectively. The enthalpy difference is the main driving force of the flashing and the superheat can represents the enthalpy difference at the macro level which can be calculated by measuring the temperature of the water. The results indicates that the the gravity has a great effect on the energy conversion during the flashing. According to the evolution of the NEF, the flashing can be divided into rapid evaporation stage(RES) and gradual evaporation stage(GES) and the heat and mass transfer obviously show differences at the two stages. The NEFtp and τtp are introduced as evaluation index to express the completeness of the flashing during the RES and the duration of RES. The initial height of water can increase NEFtp and τtp and the superheat show different effect on the NEFtp. The gravity restrains the growth of the bubbles and extend the the duration of RES. The initial height and superheat positively increase the evaporated mass and mass flow rate during the flashing. It is clear that the gravity can not be ignore when the flashing is studied.

Hybridized power-hydrogen generation using various configurations of Brayton-organic flash Rankine cycles fed by a sustainable fuel: Exergy and exergoeconomic analyses with ANN prediction

This paper investigates different configurations of organic Rankine flash cycles combined with a Brayton cycle by performing thermodynamic, exergy, and exergoeconomic analyses. The thermal energy of the cycle is produced through burning gaseous methane generated via gasification of biomass. A systematic analysis of these configurations is conducted to enhance the exergy efficiency of the cycles. Additionally, the reutilization of the thermal energy that would otherwise be wasted in the Brayton cycle contributes to a notable enhancement in the overall thermal efficiency of the combined cycle. A range of working fluids, namely m-Xylene, o-Xylene, p-Xylene, toluene, and ethylbenzene are analyzed for the organic Rankine cycle. Predictions using an artificial neural network (radial base function) are also carried out. The results indicate that the p-Xylene increases exergy efficiency more than other working fluids. Further, the improved organic Rankine cycle mitigates exergy destruction by 10 %. Although applying double flash evaporators improves the exergy efficiency by 3 %, it increases the unit cost of power generated by more than 10 %. The application of a data-driven model to predict various configurations of combined organic Rankin cycle with a Brayton cycle fed by biomass has rarely been investigated.

Surface Controlled Silicon Nanoparticles Production and Their Effects on High Capacity and High Cyclability of All-Solid-State Lithium-Ion Batteries

Si nanoparticle is expected as anode for high density Lithium-ion batteries as as it facilitates high capacity and high cyclability simultaneously owing to its structural robustness to suppress fracture during cycled (de)lithiation reactions. Direct TEM observation has revealed that the particle size of 150 nm is the threshold for facture and the particles smaller than 150 nm are anticipated to contribute to the structural stability during cycles. However, the surface of silicon nanoparticle is oxidized spontaneously and the specific surface area increases significantly with decreasing the particle size. Accordingly, the specific oxygen content of the Si active material becomes inevitably high for smaller nanoparticles. High oxygen content in Si anode decreases the initial efficiency and capacityas a result of irreversible silicate formation. Therefore, smaller nanoparticle with a limited amount of oxidation would be ideal and necessary to attain high capacity and high cyclability. However, there is few report on the approach to suppress oxidation of smaller silicon nanoparticles and discuss the effect of size and oxygen content separately. Also, no general understanding of the effect of the particle size and oxygen for the case of all-solid-state batteries (ASSBs). In this work, we have produced Si nanoparticles with differently controlled size and oxygen content by plasma flash evaporation (PFE) from low-cost powder feedstock, and the effect of characteristic oxide surface structure on the battery performance of ASSBs with Argyrodite electrolyte has been identified.We have successfully produced the nanoparticles as small as 20 nm and reduced the oxygen content x in SiOx representation from the standard amount of 0.24 to 0.049. As a result, the initial discharged capacity can be improved by 110% while attaining similar cyclabilities. When we compare the nanoparticles with different sizes ranging from 20 nm to 165 nm and having small oxygen content x < 0.05, although the initial discharged capacities are almost the same for these particles, only the particle with 165 nm shows rapid capacity decay in 10 cycles, whereas the 20 nm and 84 nm particles tend to maintain the capacity similarly. This confirms that the particles smaller than 100 nm are effective to maintain high capacity also in ASSBs under a low 0.1 C-rate condition. Furthermore, XPS analysis revealed that the surface of the particles with less oxidation is composed of suboxide Si-O bond oxide preferentially and the amount of Si-O4 bond is less than the conventional particles covered by the oxide shell, with which the Si-O bond ratio is described by the conventional random bond model. No apparent dependence of the capacity with the amount of Si-O4 bond. However, the surface oxide shell thickness estimated by the Si-O bond amount and the total oxygen content has shown a clear linear correlation with the charged capacity, irrespective of the particle size. This suggests that the surface oxide thickness affects significantly the amount of the lithiation reaction and is ideally as thin as possible to attain high capacity, especially for the case of ASSBs.

Experimental study of the depressurization phenomena of supercritical carbon dioxide system

Depressurization accidents pose a significant safety concern for supercritical carbon dioxide (S–CO2) nuclear and power systems. However, due to the limited availability of system-level experiments, clear understandings of the phenomena associated with S–CO2 depressurization accidents are lacking. To address this gap, this paper conducted a series of experiments on a S–CO2 system to investigate the characteristics of depressurization accidents. Several key phenomena, including flash evaporation, transcritical transient heat transfer, fluid-thermo-structure coupling effect, and the fluid field changes in containment vessel, were identified and analyzed. Furthermore, the impact of break size and location, containment vessel, and initial system conditions on depressurization accidents was investigated. The acquired results provide crucial groundwork for establishing a Phenomenon Identification Ranking Table (PIRT) tailored to depressurization accidents in S–CO2 nuclear and power systems. This will significantly enhance the design and safety analysis of these systems.

A proposed method of solar-driven spray flash evaporation assisted by MPCM applied to solution regeneration with experimental analysis

Solution regeneration belongs to a separation and purification technology for multi-component liquid systems, which is involved in many fields such as liquid desiccant air-conditioning, desalination, and sewage treatment. Solar-driven evaporation technology has enormous energy-saving potential in solution regeneration, but it has the disadvantages of instability and slow regeneration rate. In this work, the method of solar-driven spray flash evaporation assisted by microencapsulated phase change material (MPCM) is proposed for solution regeneration. The spray flash evaporation experimental platform working with NaCl-MPCM suspension is constructed, and the spray characteristics and heat and mass transfer characteristics of NaCl-MPCM suspension are examined under different operating parameters. The results show that the addition of MPCM to the solution can significantly improve its equivalent specific heat capacity, which mitigates dispersed and discontinuous defects of solar energy. Furthermore, it can effectively reduce the severe temperature drop of the solution during the flash evaporation process, which ensures a high driving potential difference between the solution and flash evaporation environment. It is worth mentioning that under the same operating conditions, the regeneration amount per unit mass flow rate of the NaCl-MPCM suspension (wMPCM = 10 wt%) is 24.8 g/kg, which is about 19 % higher than that of the NaCl solution. Additionally, the flash performance of the NaCl-MPCM suspension can be further improved by reducing the initial fluid velocity at the nozzle or the flash evaporation pressure. This study aims to provide guidance for the efficient utilization of solar-driven flash evaporation assisted by MPCM.

Combined pinch and exergy analysis for post-combustion carbon capture NGCC integrated with absorption heat transformer and flash evaporator

Natural gas combined cycle power plant (NGCC) with post-combustion carbon capture (PCC) is a transitional technology for achieving net-zero emissions, but PCC significantly decreased its energy efficiency. In the work, absorption heat transformer and flash evaporator (AHT-FE-aided system) was used to mitigate the energy penalty of NGCC caused by PCC. Subsequently, heat exchange networks (HENs) were constructed for the system, followed by a combined pinch and exergy analysis (CPEA). The results showed that the improved HEN of the NGCC with AHT-FE-aided PCC (proposed system) resulted in 13.4 % less exergy destruction than the NGCC with PCC (reference system). To fully understand the exergy destruction and environmental impact of this system, an exergy distribution analysis and a technical evaluation were conducted. The net energy and exergy efficiency of the proposed system (48.11 %/46.04 %) were 1.73 % and 1.65 % higher than the reference system (46.38 %/44.39 %) respectively. The energy penalty of PCC in the proposed system (8.76 %) was lower than the reference system (11.89 %). In addition, the proposed system decreased fuel consumption by 5.90 g NG/kWh. This study confirms that the AHT-FE-aided system reduces the energy penalty of NGCC caused by PCC, and that CPEA is an effective tool to guide improvements in this area.

An Ejector and Flashbox-Integrated Approach to Flue Gas Waste Heat Recovery: A Novel Systematic Study

In this study, a comprehensive examination was conducted to explore the technology involved in the recovery of waste heat from flue gas emitted by a 1000 MW unit. Traditional methods are constrained in their ability to harness waste heat from flue gas solely for the purpose of generating medium-temperature water. The system being examined not only recovers waste heat but also utilizes it to generate steam, thereby greatly improving resource efficiency. The process entails utilizing the flue gas to heat water to a certain temperature, followed by subjecting it to flash evaporation. This process leads to the generation of low-pressure waste heat steam. Within the steam ejector, the waste heat steam combines with high-pressure motive steam extracted from the source, resulting in the formation of medium-pressure steam. Within the steam ejector, the waste heat steam blends with high-pressure motive steam drawn from the source, forming medium-pressure steam that eventually feeds into the A8 steam extraction pipe (low-pressure turbine pumping pipe). The present study examines the fluctuation patterns in motive steam flow, suction coefficient, waste heat steam volume, and outlet temperature of the flue water heat exchanger when different motive steam sources are used. Additionally, the research calculates the reduction in CO2 emissions, the coal consumption for power supply, and the cost savings in fuel for the retrofitted system. The findings indicate that maximizing energy utilization can be achieved by operating the retrofitted unit at the lowest feasible waste heat steam pressure. The implementation of the new system has resulted in a substantial decrease in coal consumption for power supply. When employing main steam as the extraction steam source, the consumption of coal for power generation decreases in proportion to the decrease in waste heat steam pressure while maintaining a constant unit load. When the waste heat steam pressure reaches 0.0312 MPa, the recorded coal consumption for power generation varies between 289.43 g/kWh at 100% turbine heat acceptance (THA) and 326.94 g/kWh at 30%THA. When comparing this performance with the initial thermal power plant (TPP) unit, it demonstrates reductions of 2.26 g/kWh and 1.52 g/kWh, respectively. After implementing modifications to this 1000 MW unit, it is projected that the annual CO2 emissions can be effectively reduced by 6333.97 tons, resulting in significant cost savings of approximately USD 0.23 million in fuel expenses. This system exhibits considerable potential in terms of emission reduction and provides valuable insights for thermal power plants aiming to decrease unit energy consumption.

Numerical Simulation Method for Flash Evaporation with Circulating Water Based on a Modified Lee Model

Flash evaporation processes are widely adopted in the desalination, food processing, waste heat recovery and other industries for heat extraction or product separation. In this paper, a pressure-driven phase transition model is developed by improving the Lee model and combined with the VOF (Volume of Fluid) method to numerically simulate the flash evaporation process. In this modified Lee phase transition model, the driving force for the rates of the local phase transition is calculated using the local temperature and static pressure magnitude. Numerical simulations are carried out in a water-circulating flash chamber and compared with the experimental results to obtain the values of the time relaxation parameters. And the non-equilibrium fraction of the outlet water can be effectively obtained under different conditions of flow rate, inlet temperature and initial liquid level height. The time relaxation factor takes values from 0.195 to 0.43 (Pout,v = 19.9 kPa) and from 0.31 to 0.92 (Pout,v = 31.2 kPa) with increasing superheat. In addition, the model can effectively represent the evolution of the unstable flow flash evaporation from the initial rapid boiling state to dynamic equilibrium.