Thermodynamic Model Calculations Research Articles

Electrified Solar Zero Liquid Discharge: Exploring the Potential of PV-ZLD in the US.

Current brine management strategies are based on the disposal of brine in nearby aquifers, representing a loss in potential water and mineral resources. Zero liquid discharge (ZLD) is a possible strategy to reduce brine rejection while increasing the resource recovery from desalination plants. However, ZLD substantially increases the energy consumption and carbon footprint of a desalination plant. The predominant strategy to reduce the energy consumption and carbon footprint of ZLD is through the use of a hybrid desalination technology that integrates renewable energy. Here, we built a computational thermodynamic model of the most mature electrified hybrid technology for ZLD powered by photovoltaic (PV). We examine the potential size and cost of ZLD plants in the US. This work explores the variables (geospatial and design) that most influence the levelized cost of water and the second law efficiency. There is a negative correlation between minimizing the LCOW and maximizing the second-law. And maximizing the second-law, the states that more brine produces, Texas is the location where the studied system achieves the lowest LCOW and high second-law efficiency, while California is the state where the studied system is less favorable. A multiobjective optimization study assesses the impact of considering a carbon tax in the cost of produced water and determines the best potential size for the studied plant.

Multi-fidelity simulation of aeroengine across wide operation range using auxiliary fully coupled method

Multi-fidelity simulations for the design point or equilibrium lines of aeroengines are implemented using fully coupled methods, simultaneously optimizing computational resources and speed. Fully coupled methods remove the requirement of characteristic maps by directly incorporating computational fluid dynamics models of subcomponents into the thermodynamic model of an aeroengine. However, poor convergence remains an urgent problem for fully coupled methods, particularly when performing multi-fidelity simulations in the near-boundary region. In response to this challenge, an auxiliary fully coupled method was developed in this study. This auxiliary method introduces a parametric priori knowledge and auxiliary coordinate transformations into the existing direct fully coupled method. An automated multi-fidelity simulation platform was established in-house and validated using the KJ66 turbojet engine. The simulation results of the equilibrium line were then compared with experimental data to validate the high accuracy and reliability of the multi-fidelity simulation. Moreover, two fundamental selection schemes for matching parameters (mass flow or static pressure, transferred between the computational fluid dynamics and thermodynamic models) were implemented and systematically compared. The results demonstrate that the adaptive selection of matching parameters extends the application of multi-fidelity simulations to a broader operation range. In addition, the auxiliary fully coupled method was applied to a multi-fidelity simulation of a wider operation range, such as an adjustable nozzle area and variable power extraction. It was also compared with the existing direct fully coupled method with respect to the stable convergence scope. For the mass-flow matching scheme, the maximum stable convergence scope of the direct method was extended from 105 % to 315 % by the auxiliary method. For the static-pressure matching scheme, the auxiliary method also broadened the maximum stable convergence scope of the direct method from 55 % to 190 %. The comparison reveals that the auxiliary fully coupled method exhibits a wider range of far-off-design conditions, including the near-boundary region.

Neutralization of Anthropogenic Acidic Particles by NH3 From Wildfire Over Tropical Peatland

AbstractAcidity is an essential characteristic of aerosol particles that influences chemical and physical properties. Aerosol particles in tropical Asia, such as Singapore, have been reported as highly acidic due to intense anthropogenic sulfur emissions. At the same time, the region has also been experiencing wildfire over tropical peatlands, which is recognized as an intense source of NH3. Here, we investigated the role of NH3 from wildfire on aerosol particles in Singapore by employing the aerosol mass spectrometric technique. The observation was conducted both during wildfire haze (2015 October and 2019 September–October) and non‐haze (2018 October and 2019 April) periods. The observation result demonstrated that inorganic ionic species in Singapore were neutralized by NH4+ during the haze periods. Namely, the degree of neutralization of aerosol particles (i.e., measured NH4+ concentration/predicted NH4+ concentration by assuming that NH4+ fully neutralized SO42−, NO3−, and Cl−) was lower than 0.77during the non‐haze periods. On the other hand, the corresponding values were higher than 0.93 during the haze periods. In addition, NO3− concentration during the daytime of the haze period in 2015 was higher than that in other observation periods. A thermodynamic model calculation suggested that the regime shifts from the “NH3 sensitive region” to the “NH3 and HNO3 sensitive region” or “HNO3 sensitive region” might have occurred during the haze period. In the future, continuous monitoring of both gas‐ and particle‐phase inorganic chemical species will need to be conducted to investigate the impact of wildfire haze on atmospheric chemical processes in more detail.

Calculation of a heat exchanger using heat pipes in the exhaust air heat recovery system

Objective. The purpose of the work is to develop practical recommendations for the design and manufacture of a heat exchanger using heat pipes, which could find widespread use in heating, ventilation and air conditioning systems at facilities for various purposes. Method. The research is based on methods of thermodynamic analysis, full-scale and computational modeling of processes and objects of refrigeration and cryogenic technology, air conditioning and life support systems. Result. The implementation of the practical recommendations studied in the work on the use and design of heat exchangers using heat pipes in ventilation, heating and air conditioning systems will provide significant savings in energy spent on heating and/or cooling the air supplied to the room served by the HVAC system. To reduce heat loss in a building, it is rational to maintain air balance and compensate for the exhaust air with an organized influx of outside air, to heat which the heat of the removed exhaust air is utilized. Conclusion. Compared to a heat exchanger based on a glycol recuperator, a regenerator using heat pipes is less energy-intensive, requires virtually no maintenance, and is also more energy efficient due to the absence of a pumping device that requires electricity in the design. At the same time, the ability to completely separate the supply and exhaust ventilation flows of the regenerator on heat pipes is preserved, which is extremely in demand in medical institutions, due to the need to comply with strict sanitary standards.

Phase diagrams of bismuth ferrite barium titanate thin films with misfit strains and their improved electrical properties

Phase diagrams of BiFeO3-BaTiO3 (BF–BT) thin films were constructed via thermodynamic model calculation, as well as their electrical properties. The calculated morphotropic phase boundary (MPB) of BF–BT thin films without strain is located near the composition of 0.663BF–0.337BT, which agrees well with the experimental results of reported BF–BT ceramics (between 0.66BF–0.34BT and 0.71BF–0.29BT). The permittivity, tunability and [Formula: see text]of BF–BT thin films on Si substrates are higher than those on SrTiO3(ST) plates, which are also in accordance with the measured data in the literature. Further calculation indicates that 0.7BF–0.3BT and 0.6BF–0.4BT thin films can achieve enormous piezoelectric coefficient [Formula: see text] ([Formula: see text]1200 and [Formula: see text]1000 pm/V, respectively) by selecting the substrates with the TEC respectively of 0.3 and 3.1 × 10[Formula: see text]/[Formula: see text]C, because of the phase transition from aa phase to rhombohedral phase. Such results help to clarify the phase diagrams of BF–BT thin films, implying that huge [Formula: see text]can be achieved by choosing the composition near MPB on the substrates with small TEC.

Investigation of leaching behaviors of carbonation-cured CSA cements using an electrically accelerated leaching test

The present study provides the investigation of leaching behaviors of carbonation-cured calcium sulfoaluminate (CSA) cements with varying initial sulfate contents using an electrically accelerated leaching test. The CSA cement samples were normally or carbonation-cured for 28 days before subjecting them to an electrically accelerated leaching condition for 14 days. The samples were characterized experimentally before and after accelerated leaching. In addition, the leaching behaviors of the CSA cement samples over a wide range of cumulative leached water were thermodynamically modeled to determine their likely performance in repository environments. The results indicate that the reaction of ye'elimite was significantly promoted by accelerated leaching, resulting in the formation of ettringite after leaching, regardless of the curing regime used. Calcium sulfates and C-(A)-S-H formed in the carbonation-cured samples were the first phases to decompose upon accelerated leaching, which is in good agreement with the thermodynamic modeling calculations. For the normally cured samples, the use of higher calcium sulfate in the mixture is preferred, considering the amount of leached ions, yet the opposite holds true for the carbonation-cured samples. In particular, the changes in the calculated volumes of the reaction products upon simulated leaching were smaller for the carbonation-cured samples than for the normally cured samples.

Processing of phosphorites with extraction of phosphorus, obtaining calcium carbide and ferroalloy

The article considers the results of studying the thermodynamic computer modeling of the interaction of phosphorite (Karatau basin, Kazakhstan) with carbon and coke performed using the HSC-10 software package and electric smelting of the phosphorite with coke and steel shavings in an arc furnace. The modeling allowed us to determine the equilibrium extraction degrees of phosphorus into gas (Р<sub>2</sub>, Р<sub>4</sub>), silicon into ferroalloy in the form of iron silicides (FeSi<sub>2</sub>, FeSi, Fe<sub>3</sub>Si, Fe<sub>5</sub>Si<sub>3</sub>, Si) and calcium into CaС<sub>2</sub>. At temperatures above 1500 °C, regardless of the amount of iron, the extraction degree of phosphorus into gas is more 99%. The resulting ferroalloy contains 21.2-23.8% of Si, 1.6-2.8% of Al; the calcium carbide has a capacity of 288-325 dm<sup>3</sup>/kg. The extraction degree of silicon into the alloy was 89.8%, calcium in CaC<sub>2</sub> – 72.5%, phosphorus into gas – 99.4%. The ferroalloy, formed at the electric smelting of the Chulaktau phosphorite together with coke and steel shavings and containing 24.9-29.8% of Si, is FS25 grade ferrosilicon, and the formed calcium carbide has a capacity of 278-290 dm<sup>3</sup>/kg and belongs to the third and second grades. The developed technology makes it possible to increase the degree of phosphorites’ comprehensive use two times (up to 87.5%).

Computationally Guided Synthesis of MXenes by Dry Selective Extraction.

MXenes are a rapidly growing family of 2Dtransition metal carbides and nitridesthatare promising for various applications, including energy storage and conversion, electronics, and healthcare. Hydrofluoric-acid-based etchants are typically used for large-scale and high-throughput synthesis of MXenes, which also leads to a mixture of surface terminations that impede MXene properties. Herein, a computational thermodynamic model with experimental validation is presented to explore the feasibility of fluorine-free synthesis of MXenes with uniform surface terminations by dry selective extraction (DSE) from precursor MAX phases using iodine vapors. A range of MXenesand respective precursor compositions are systematically screened using first-principles calculations to find candidates with high phase stability and low etching energy. A thermodynamic model based on the "CALculation of PHAse Diagrams" (CALPHAD) approach is further demonstrated, using Ti3 C2 I2 as an example, to assess the Gibbs free energy of the DSE reaction and the state of the byproducts as a function of temperature and pressure. Based on the assessment, the optimal synthesis temperature and vapor pressure are predicted and further verified by experiments. This work opens an avenue for scalable, fluorine-free dry synthesis of MXenes with compositions and surface chemistries that are not accessible using wet chemical etching.

A step toward precision gerontology: Lifespan effects of calorie and protein restriction are consistent with predicted impacts on entropy generation

Understanding aging is a key biological goal. Precision gerontology aims to predict how long individuals will live under different treatment scenarios. Calorie and protein restriction (CR and PR) extend lifespan in many species. Using data from C57BL/6 male mice under graded CR or PR, we introduce a computational thermodynamic model for entropy generation, which predicted the impact of the manipulations on lifespan. Daily entropy generation decreased significantly with increasing CR level, but not PR. Our predictions indicated the lifespan of CR mice should increase by 13 to 56% with 10 to 40% CR, relative to ad libitum-fed animals. This prediction was broadly consistent with the empirical observation of the lifespan impacts of CR in rodents. Modeling entropy fluxes may be a future strategy to identify antiaging interventions.

Chemically-patterned steels

A new type of microstructure design concept for high strength steels, consisting of a nanolaminate of martensite and austenite, was recently proposed using an approach termed ‘chemical patterning’. This approach generates a controlled chemical pattern in the austenite and then uses that pattern as the template for subsequent phase transformations during austenite decomposition. This approach allows access to new types of microstructures not previously utilised for alloy design.In this contribution, a computational thermodynamic and kinetic model to simulate the chemical patterning process is presented and it is shown to describe well the experimental variation in retained austenite fraction as a function of the temperature of the chemical patterning process. This model is sufficiently robust that it can be used for coupled alloy and process design and is used to design two new chemically-patterned alloys containing 30% and 50% retained austenite, respectively. The success of the model has been experimentally confirmed with two new chemically-patterned steels with higher austenite fraction, ∼30% for Fe-0.5C-6Mn-1.5Si (wt.%) and ∼50% for Fe-0.65C-6Mn-0.5Si-1Al (wt.%). Tensile, compressive and abrasive wear results are shown to demonstrate the interesting performance that can be obtained from these new types of microstructures.

A Computational Fluid Dynamics‐Thermodynamics Coupled Approach to Simulate Desulfurization in Ladle Furnace Based on Interface Equilibrium Assumption

This study proposes a coupled computational fluid dynamics and thermodynamics model based on the assumption of interface equilibrium at the steel–slag interface to simulate the desulfurization process in a ladle furnace. The species transport equation is solved to analyze the kinetic behavior and chemical content variation in the melt. The sulfur distribution ratio is calculated based on the slag sulfide capacity and oxygen activity. Subsequently, the solutions are coupled by introducing the species transfer and source terms generated by comparing the initial and predicted thermodynamic equilibrium states at the steel–slag interface cell. The model is validated by experimentally comparing the sulfur content. Furthermore, the model is applied under different kinetics and thermodynamics conditions. With an increase in the gas flow rate, the in‐phase effective diffusion coefficient increases, but the number of interface cells involved in the sulfur transfer process decreases. The complex relationship between the desulfurization process and the gas flow rate results from the mutual antagonism between these two factors. Moreover, the study findings demonstrate that a higher slag basicity enhances the calculated sulfur distribution ratio and final desulfurization ratio.

Leveraging Steric Moieties for Kinetic Control of DNA Strand Displacement Reactions.

DNA strand displacement networks are a critical part of dynamic DNA nanotechnology and are proven primitives for implementing chemical reaction networks. Precise kinetic control of these networks is important for their use in a range of applications. Among the better understood and widely leveraged kinetic properties of these networks are toehold sequence, length, composition, and location. While steric hindrance has been recognized as an important factor in such systems, a clear understanding of its impact and role is lacking. Here, a systematic investigation of steric hindrance within a DNA toehold-mediated strand displacement network was performed through tracking kinetic reactions of reporter complexes with incremental concatenation of steric moieties near the toehold. Two subsets of steric moieties were tested with systematic variation of structures and reaction conditions to isolate sterics from electrostatics. Thermodynamic and coarse-grained computational modeling was performed to gain further insight into the impacts of steric hindrance. Steric factors yielded up to 3 orders of magnitude decrease in the reaction rate constant. This pronounced effect demonstrates that steric moieties can be a powerful tool for kinetic control in strand displacement networks while also being more broadly informative of DNA structural assembly in both DNA-based therapeutic and diagnostic applications that possess elements of steric hindrance through DNA functionalization with an assortment of chemistries.

Investigation into the operation of an autothermal two-section subbituminous coal fluidized bed gasifier

Using a newly developed experimental setup, the features and advantages of an autothermal single-casing atmospheric subbituminous coal fluidized bed air-blown gasifier, combining a combustion and gasification section, and mixing the dispersed phase (inert material, char) and heat exchange between them through an annular transfer device, have been revealed. To increase the efficiency of the gasifier, an experimental-computational method was developed find the conditions for optimal operation, combining changing the annular flow’s geometry and regulating the primary air for gasification. A simple and reliable multizone thermodynamic calculation model makes it possible to predict the composition of char and syngas in the gasification section with acceptable accuracy. This method confirmed that a two-section fluidized bed gasifier can provide efficient gasification of solid fuels and is suitable for use in small-scale cogeneration plants. Syngas with a heating value of 3.6–4.5 MJ/m3 and CGE of 38.2%–42.3% was obtained in the experimental setup without optimizing the primary air flow rate. With optimization, the indicators increased to the heating value of syngas of 5.20–5.34 MJ/m3 and CGE of 42.5%–50.0%. With heat regeneration of 0.8, CGE increases to 70%.

A complementary VOCs recovery system based on cryogenic condensation and low-temperature adsorption

The control of volatile organic compounds (VOCs) emission has a significant influence on the environment and human health. Liquid nitrogen (LN2) condensation is a highly efficient method for VOCs recovery with a wide range of applications, but it is poor in the treatment of light hydrocarbons, especially methane and ethane, and has some shortcomings such as high emission concentration and large carbon emissions. In this paper, a novel cryogenic condensation system combined with low-temperature adsorption was proposed. The low-temperature exhaust gas treated by cryogenic condensation equipment is introduced into an adsorption bed, resulting in lower temperature and higher adsorption capacity of the adsorption bed, which not only effectively improves the recovery rate of VOCs, but also solves the spontaneous combustion problem caused by the adsorptive heat effect of traditional room-temperature adsorption method. A thermodynamic calculation model was established, and related experimental verifications were carried out. The results show that the economic value of the recovered VOCs condensate is 1.24 times of the cost of consumed LN2 and the carbon emission reduction is 1683 t per year, achieving an acceptable breakthrough time of 16,971 s at an adsorption temperature of 198.15 K exceeding that at 238.15 K by a factor of 16 when the cryogenic condensation temperature is 138.15 K with a 600 m3/h of waste gas. The effects of cryogenic condensation temperature, adsorption temperature, inlet gas concentration, flow rate, and the proportion of components on the system performance are analyzed in detail.

Performance of different UNIFAC parameter sets in describing experimental liquid–liquid equilibrium data of biodiesel systems

Several liquid phases with different compositions are generated throughout the biodiesel production chain. The complexity of the fatty compounds involved in the systems can impairs the process simulation and its thermodynamic comprehension. Fortunately, experimental data attained in this study revealed that the fatty classes can be simplified to pseudocomponents in the liquid–liquid equilibrium LLE since their compositions did not change between the liquid phases. Such approach provides a good description of the LLE behavior and benefits the computational simulation of the different steps involved in the biodiesel production and purification. Predictive models as the UNIFAC can used in simulations without the need of exhaustive experimental assays. The predictive capacity of four UNIFAC parameters sets found in the literature was evaluated assuming LLE data of dissimilar fatty systems composed of vegetable oils, partial acylglycerols, free fatty acid, ethyl esters, and ethanol. The UNIFAC-BESSA parameter set exhibited a satisfactory performance in estimating the LLE data with low deviations (1.55 – 4.56%), and can be thus used in computational simulations and thermodynamic modeling of biodiesel systems.

Field studies of a thermoelectric system for thermal action on the anterior segment of the human eyeball

Objective. The aim of the study is to develop the design of a thermoelectric system (TPS) for thermal action on the anterior segment of the human eyeball, as well as to conduct its field studies.Method. The study is based on the methods of thermodynamic analysis, natural and computational modeling of processes and life support facilities.Result. The design of TPP for thermal impact on the anterior segment of the human eyeball is presented. Its fullscale studies were carried out in accordance with the existing methods of thermophysical measurements. Curves of changes in the temperature of the surface of the gelatin model of the human eyeball over time during cooling and heating were obtained for the supply currents of the thermoelectric module (TEM) included in the TPP, equal to 2.5 A, 3 A, 3.5 A, A and 1 A, 1 .2 A, 1.4 A, as well as changes in the temperature of the object of influence over time when changing the cooling mode to heating and vice versa. To assess the possibilities of heat removal from the hot junctions of TEMs in the system, data were obtained on the change in their temperature over time during the cooling effect for various values of the module supply current.Conclusion. It has been established that standard modules produced by domestic firms can be used as TEMs in the system. The duration of entering the TPP mode is about 230 s. The refore, it seems appropriate to bring the TPP to the operating mode before the actual procedures are carried out. It has been established that the duration of TPP switching from cooling to heating mode and vice versa is 230 s, which requires further optimization of the design and operating modes of the device through the use of more advanced types of TEMs and the use of forced operation of thermal modules in the transient mode.

Modeling of regasification and recirculation processes during the transportation of liquefied natural gas

Objective. The purpose of the research is modeling and analysis of technological processes occurring at the transshipment terminal of liquefied natural gas.Method. The study is based on the methods of thermodynamic analysis, full-scale and computational modeling of processes and objects of refrigeration and cryogenic equipment in order to find optimal solutions in terms of efficiency, reliability and service life of low-temperature installations, machines and apparatus.Result. The article describes the operation algorithm of an LNG transshipment terminal and proposes a mathematical apparatus for modeling the technological processes occurring in it. Information about the causes of the formation of LNG vapors (Boil-off gas (BOG)) during its transportation and reloading is presented, methods for utilizing excess LNG vapors are considered.Conclusion. To maintain the cryogenic temperature of the unloading arms, an LNG recirculation line (recirculation pipelines) is provided.

Acetylcholine-based deep eutectic solvents for highly efficient SO2 absorption, selective separation from CO2 and their mechanism

The development of deep eutectic solvents (DESs)-based absorbents for selective uptake of SO2 from CO2 (SO2/CO2, g/g) is of interest to flue-gas desulfurization (FGD). In this work, a series of DESs are designed through acetylcholine chloride (ACC) as hydrogen bond acceptor (HBA) and ethylene glycol (EG), 1,3-propylene glycol (1, 3-PDO), glycerol (Gly), polyethylene glycol 200 (PEG200) and triethylene glycol (TG) as hydrogen bond donors (HBDs). All the DESs display good thermal stability under 150 °C and competitive capacities of SO2. ACC/PEG200 (1:1) is remarkable due to their absorption capacity of SO2 to 3.5 mol/mol (P = 1.0 bar, T = 303.2 K). All DESs show excellent selectivity separation of SO2 from CO2 more than 100, for example, up to 335 in ACC/TG (1:1). In this work, the relative mechanism reveals that DESs absorption of SO2 combining physisorption and chemisorption via a reaction equilibrium thermodynamic model and theoretical calculation. Furthermore, ACC/TG (1:1) maintains the reversible absorption capacity of SO2 after five absorption/desorption cycles. Considering high SO2 absorption capacity, desired selectivity, and excellent recyclability, DESs in this study are considered recyclable green absorbers, which can be potentially applied to SO2 capture towards CO2 mixture.

Dependence of tungsten crack behaviors on heat source parameters under transient heat flow

As a plasma facing material in TOKAMAK, tungsten may suffer plastic deformations, cracking, melting, even ablation induced by transient heat loads, such as Edge Localized Modes (ELMs). Focused on investigation of cracking behaviors of tungsten under transient heat flux and its dependence on pulse parameters, powder metallurgical pure tungsten samples have been tested with 1–100 pulses of intense pulse electron beams (IPEB) at 5 ms and 1 ms pulse duration. Three types of cracks were observed, including primary crack, secondary crack and blunt crack. The primary cracks can be assorted as branch, annular and network cracks according to their patterns. Branch cracks were formed in the irradiation area center, and annular cracks appeared surrounded the irradiation area. The width of annular cracks increases as the pulse number increasing. The initiation and evolution of annular cracks are mainly studies in this paper. Considering the ductile-to-brittle transition property, an ideal elasto-plastic mechanics model is adopted in the thermodynamic calculation model of tungsten under the IPEB irradiation. Irreversible plastic deformation plays an important role, which determined the tensile stress distribution during the temperature decreasing. The formation mechanism of annular crack and its dependence on the heat source parameters are discussed, based on the calculation results of temperature, stress distribution and evolution of tungsten under different pulse parameters with this model. It is found that the formation mechanism of annular crack depends on the high radial gradient of energy density E, and the radius of annular crack obviously depends on the energy density deposited per pulse and the heat source boundary gradient for large volume sample. The influence of pulse number on branch crack and annular crack is different. The widening of the annular crack with the increasing of pulse number is caused by the axial residual plastic strain after pulse irradiation.

Experimental investigation and thermodynamic modeling of Cu–Nb–Si system

AbstractThe phase equilibria of the Cu—Nb—Si system were investigated via a combination of key equilibrated alloys, thermodynamic modeling and first-principles calculations. Sixteen ternary alloys were prepared to determine the isothermal sections at 600 and 700 °C, by means of X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM−EDS). The three- and two-phase regions were determined. The existence of ternary compound τ1 (Cu4Nb5Si4) was confirmed. The solubilities of Cu in the NbSi2 and Nb5Si3 phases were measured. Based on the experimental equilibria data from the literature and the present work, a thermodynamic description of the Cu—Nb—Si system was carried out by using the calculation of phase diagrams (CALPHAD) method supported by first-principles calculations. The substitutional model and sublattice model were employed to describe the solution phases and intermediate phases, respectively. A set of self-consistent thermodynamic parameters of the Cu—Nb—Si system were conclusively obtained. Most of the reliable experimental data were reproduced by the present thermodynamic modeling.