Change In Mass Flow Rate Research Articles

Numerical Investigation of Bionic Axial Fan used in Split Air Conditioner

Abstract: Bionic axial fan is the main component in the outdoor unit split type room air-conditioner (AC) which impact the cooling and comfort. The present work aims to improve the aerodynamic performances of bionic axial fan by numerical technique. The detailed simulation has been carried out to investigate the aerodynamic performance of bionic axial fan with various design proposals for a detailed investigation and development of a prospective fan design prior to the manufacture and testing of costly prototypes. According to the biological fact that the serrations at the wing improve the acoustics as well the aerodynamic performances, various design modifications performed on the bionic axial fan blade. As the serrations at the trailing edge help to improve the aerodynamic performance, the fan blade design modified to investigate the change in mass flow rate. The flow field is simulated with the finite element Computational Fluid Dynamics (CFD) solver Altair-AcuSolve to analyse the influence of trailing edge serrations on the air flow rate of fan. The three-dimensional (3D) computational domain with SpalartAllmaras (SA) turbulence model is considered to predict the air flow rate. The present computation is carried out for the axial fan speed of 820 rpm. The flow rate is correlated with the test results to validate the CFD modeling approach. The result shows that the trailing edge serrations at the tip of the fan has predicted improvement in flow rate since it alter the length of separation bubble near the trailing edge which also helps to reduce the noise level.

Performance analysis of a novel gas-liquid separator with industrial application

This paper presents a novel gas-liquid separator characterized by its distinctive geometric design, capable of handling different volume fractions and mass flow rates. The separator's performance is comprehensively assessed across various gas volume fractions, bubble sizes, and mass flow rate fluctuations. The study reveals that variations in vapor volume fraction substantially affect both separation efficiency and pressure loss. An increase in vapor volume fraction from 0.1 to 0.5 leads to a 25% reduction in separation efficiency and a 3.3-fold decrease in pressure loss. In contrast, changes in mass flow rate exert a relatively minor influence on separation efficiency. Specifically, increasing the mass flow rate from 15 to 30 kg/s results in a mere 4% decrease in separation efficiency, whereas pressure loss increases by a factor of 3.2.Additionally, a reduction in bubble size from 1000 µm to 200 µm causes a 33% increase in pressure loss and a 14% decrease in separation efficiency. The incorporation of a meshpad in this design promotes the formation of a forced vortex, thereby enhancing the separation process.

Analysis of operation regulation on delay time in long-distance heating pipe systems for practical engineering

The distribution area of the district heating network (DHN) is extensive, and there are inherent time delays and thermal losses in the process of heat transfer through heating pipes. The delay in heat transfer within long-distance heating pipes may result in inadequate heat supply to end-users or excessive energy consumption at the heat source. Therefore, this paper presents a quasi-dynamic model for calculating the transmission delay time in the long-distance heating pipeline. And the model is validated through the measured values obtained from a heating pipeline. The influencing factors of delay time are further discussed, including operating parameters, pipe structure parameters and thermal insulator thickness. Additionally, the impact of pipe delay time in practical engineering is analyzed. In practical engineering, the transmission delay time varies when the pipe structural or operational parameters differ, even under the same outdoor temperature change. The change in inlet water temperature and mass flow rate can impact the change rate of outlet water temperature, thereby influencing the delay time. Furthermore, the delay time exhibited an increase with pipe length, diameter, and thermal insulator thickness; however, the effect of thermal insulator thickness on it was minimal. When the inlet water temperature rose or dropped by 5℃, the delay time grew by more 70 % per 1 km pipe length, about 40 % per 100 mm diameter and less 2 % per 100 mm thermal insulator thickness, respectively.

Road resuspension PM2.5 from two vehicles driving in parallel by CFD method: The characteristics and population exposure

Particulate matter (PM) from the road resuspension dust of vehicles driving can deteriorate urban air quality. The goal of our study was to develop a discrete phase model and sliding grid technology to simulate the distribution characteristics of resuspension PM2.5 from vehicle road dust, and to analyze PM2.5 exposure of drivers and pedestrians caused by resuspension dust. The results indicated that the maximum height of PM2.5 concentration at the XZ section at 1–10 s varied in a zigzag pattern, with the lowest at 3.37 m at 1 s and the highest at 5.85 m at 2 s. PM2.5 concentration diffusion presented a "two lungs within one bracket" shape at Z = −0.03 m section and PM2.5 was gradually diffused from the tire to the two sides of the vehicle at 1–10 s. PM2.5 concentration at y = 5.5 m line of X = −15 m section gradually decreased with ground height increasing. The average PM2.5 concentration at Z = 1.25 m section at 1–10 s was 1.86, 3.17, 6.85, 8.85, 12.78, 14.69, 16.64, 18.96, 21.50, and 22.98 μg/m3, respectively. The average PM2.5 concentration was directly proportional to the change in road dust mass flow rate. The range of PM2.5 concentration of points a (left driver), b (right driver), c1 (pedestrian standing still for 3 m on right side of right vehicle) and c2 (pedestrian walking at a speed of 1.5 m/s) were 0–49.8, 0–183.0, 0–16.5, and 0–59.8 μg/m3, and the time of the maximum PM2.5 concentration for a, b, c1, and c2 was 5, 6.5, 4.5 and 5 s, respectively. These results indicated that the driver of point b had the highest exposure concentration within 1–10 s, which was 5.8 times that of the driver of point a, 7.7, and 2.9 times that of pedestrians of points c1 and c2. These results can provide basic data for road dust emissions and population exposure risk management.

Dynamic Simulation of a Molten Salt-Steam Superheater for Load-Following Applications

Abstract The growing use of intermittent renewables in electrical grids increasingly motivates load-following operations as a crucial capability of dispatchable power plants. However, frequent load variations in steam generation equipment can cause premature heat exchanger failure. This paper simulates the dynamic behavior of a high pressure, U-tube/U-shell, salt-to-steam superheater typically found in tower-type concentrating solar power subcritical Rankine cycles. Results focus on responses during load-following and inlet temperature changes. The proposed model is a finite volume method, and thermodynamic and heat transfer properties of both fluids are allowed to vary spatially and temporally. Several flow ramping schemes are investigated, including proportionally equal ramps and proportionally dissimilar ramping, where one fluid reaches its mass flow setpoint faster than the other. Results indicate that salt outlet temperature overshoot can occur if ramp rates are of sufficiently high magnitude, and that U-bend metal temperature rate of change can be approximately 2.5× that observed at either outlet. If proportionally-matched ramping is not possible, ramping steam more slowly than the salt is preferred over the alternative, as cold side and U-bend temperature responses are better regulated. Additionally, mass flow rate and inlet temperature changes are shown to elicit unique responses in the tube bundle metal.

Investigation on mixing characteristics of rotating detonation combustor with convergent inlet

Mixing characteristics play an important role on the operational process of rotating detonation combustor (RDC). In this paper, a series of numerical calculations were conducted to analyze the influence of injection diameter, injection position, reactant mass flow rate, and equivalence ratio on mixing characteristics. Mixing performance parameters and total pressure loss in combustor dome and ignition zone were analyzed in detail. The findings indicated that all four injection conditions had significant influence on mixing characteristics, among which injection position was the most significant factor. When injection position was in convergent section, the mixing characteristics were better than those in ignition section. Reducing the fuel diameter gradually improved mixing characteristics, but also increased total pressure loss. The change of reactant mass flow rate had a minimal effect on mixing characteristics. As equivalence ratio decreased, mixing characteristics decreased and total pressure loss decreased. In addition, the comparative analysis also showed that penetration depth of hydrogen had an impact on flow field disturbance and distribution of return region, which led to the difference in mixing characteristics. When hydrogen was injected into the convergent structure section where air flow velocity did not reach sonic speed and was in acceleration phase, total pressure loss would be effectively reduced in combustor dome.

The effect of the laser beam intensity profile in laser-based directed energy deposition: A high-fidelity thermal-fluid modeling approach

Modeling the thermal and fluid flow fields in laser-based directed energy deposition (DED-LB) is crucial for understanding process behavior and ensuring part quality. However, existing models often fail to accurately predict these fields due to simplifying assumptions, particularly regarding powder particle-induced attenuation in laser power and energy density distribution, and the variable material properties and process parameters. The present work introduces a high-fidelity multi-phase thermal-fluid model driven by a combination of the discrete element method (DEM) and the finite volume method (FVM). Incorporating an enhanced attenuation model for laser energy enables a more precise approximation of powder particle-induced attenuation effects in the laser power and energy density distribution. The study focuses on the influence of laser beam intensity profiles during DED-LB of austenitic stainless steel (AISI 316 L), with model validation conducted through experimental measurements of deposited track dimensions for different beam shapes. The results of numerical simulations demonstrate the critical impact of powder-induced attenuation on the laser power and intensity profiles. Neglecting laser energy attenuation, a common assumption in numerical simulations of DED-LB, leads to overestimations of the absorbed energy of the laser beam, affecting thermal and fluid flow fields, and melt pool dimensions. The present study unravels the complex relationship between the attenuation coefficient (due to the powder stream) and powder stream characteristics, describing the variations of the attenuation coefficient with changes in the powder mass flow rate and powder stream incidence angle. The findings show the critical effects of laser beam shaping on melt pool behavior in DED-LB, with square beams inducing larger melt pool volumes and circular beams creating smaller but deeper melt pools. The proposed enhanced thermal-fluid modeling framework offers a robust approach for optimizing laser-based additive manufacturing across diverse materials and laser systems.

The steady behavior of the supercritical carbon dioxide natural circulation loop

The steady state behavior of thermodynamically supercritical natural circulation loops (NCLs) is investigated in this work. Experimental steady state results with carbon dioxide are presented for supercritical pressures in the range of 80–120 bar, and temperatures in the range of 20–65 °C. Distinct thermodynamic states are reached by traversing a set of isochors. An equation for the prediction of the steady state of NCLs at supercritical pressures is presented, and its performance is assessed using empirical data. Changes of mass flow rate as a result of independent changes of thermodynamic state, heating rate, driving height and viscous losses are shown to be accurately captured by the proposed equation. Furthermore, close agreement between the predicted and measured mass flow rate is found when the measured equipment losses are taken into account for the comparison. Subsequently, the findings are put forward in aid of the development of safe, novel supercritical natural circulation facilities.

Investigation on thermohydraulic characteristics of novel superheated steam supply system for low temperature nuclear heating reactor

In a new Chinese low temperature nuclear heating reactor (NHR) demonstration project, a novel superheated steam supply system was designed to meet new requests for the steam produced in the secondary circuit. Different from the previous version of NHR200-II, which used a vertical steam generator to produce saturated steam, this newly designed system features a preheater, a horizontal steam generator, and a superheater for generating superheated steam. Numerical simulation method was used to investigate the feasibility and thermal hydraulic characteristics of this novel superheated steam supply system. The simulation results verify the accuracy and reliability of the system design, showing that the three heat exchangers can operate in coordination under different power levels, and the superheated steam generated in the secondary circuit can meet the users’ requirements. The system also demonstrated a remarkable ability to recover from sudden disturbances within 13.64 % change of the secondary circuit mass flow rate or 2.39 % change of the secondary circuit temperature under full power condition. Besides, the system has a power adjustment ability of ±10 %, and the system can quickly return to the new steady state. RELAP5 simulation results can provide theoretical guidance for the subsequent experimental research of this novel superheated steam supply system.

Hybrid Heat Pipe Shutdown Rod as a Novel Concept of Passive Safety System for Microreactor

Ensuring the structural integrity of the monolithic core, which houses critical components such as heat pipes and fuel rods, is crucial for the safety of a microreactor. This research introduces a hybrid heat pipe shutdown rod as a novel passive safety system to address potential temperature rises in the monolithic core during accidents. It is designed to perform a dual function under accident conditions. It simultaneously absorbs neutrons and removes heat through structural modifications to the existing shutdown rod. Specifically, this system provides a heat transfer path within the monolithic core without increasing the size of the microreactor. By selecting cesium as the working fluid, we aimed to achieve rapid operation of the heat pipe to quickly reduce the temperature gradient in the monolithic core under accident conditions. The hybrid heat pipe was fabricated and evaluated and found to develop continuous flow even at temperatures around 205.1°C. However, its unique structure causes a pronounced converging–diverging effect, resulting in a temperature drop from about 70–170°C in the evaporator region, followed by a slight recovery to below 50°C in the condenser. This effect arises from changes in the cesium vapor mass flow rate due to phase changes and variations in the flow area between the evaporator and condenser. Despite these effects, the use of liquid cesium as the working fluid enables the hybrid heat pipe to operate under natural convection, avoiding startup problems that could cause flow blockage.

APPLICATION OF AN EXACT SOLUTION OF SPECIAL TYPE OF THERMOSOLUTAL CONVECTION EQUATIONS FOR THE INVESTIGATION OF EVAPORATIVE THREE-DIMENSIONAL FLOWS

The characteristics of gas-liquid flows with evaporation at the thermocapillary interface in an infinite rectangular duct, with a linearly distributed thermal load being applied on the upper and lower walls, are studied. The theoretical research of the three-dimensional convective flows is carried out within the framework of a two-sided model of evaporative convection based on the Navier-Stokes equations in the Oberbeck-Boussinesq approximation. A solution of a special type of governing stationary equations is used for describing the heat and mass transfer in a system of two immiscible fluids. We investigate the influence of the working (equilibrium) temperature of the system and intensity of the external thermal load on the structure of the velocity and temperature fields, as well as on changes in the evaporation mass flow rate and vapor content in the gas phase. The simulations are performed for the ethanol-air system. Based on the comparison of the calculated and experimental data, an effective way of nondimensionalization is proposed that allows one to consistently take into account the impact of the gas pumping velocity being a controlled parameter in experiments. It provides correct matching of the mathematical model to the experiment conditions, as well as a better qualitative and quantitative agreement between theoretical and measured values of evaporative mass flow rate. The results of the present study can aid in developing a theoretical basis for experimental research methods of evaporative convection and also in designing equipment for thermal coating or drying.

LNG 기화열을 이용한 수조 수온 냉각성능에 관한 실험적 연구

In this study, a heat transfer performance experiment was conducted by experimentally testing the vaporization process of liquefied natural gas (LNG) using a seawater vaporizer and the process of supplying cooled seawater to the aquaculture tank. By using liquid nitrogen instead of LNG, we experimentally analyzed changes in tank water temperature according to changes in liquid nitrogen supply mass flow rate, water supply mass flow rate, and injection angle of the aquaculture tank nozzle. When testing was conducted by fixing the water mass flow rate at 0.05 kg/s and changing the liquid nitrogen mass flow rate to 0.0058 kg/s, 0.0075 kg/s, and 0.0092 kg/s, the target temperature of 17°C was reached under the experimental condition of 0.0092 kg/s.
 When the water supply mass flow rate was set to 0.05 kg/s, 0.07 kg/s, 0.08 kg/s, and 0.10 kg/s at the constant mass flow rate of liquid nitrogen of 0.0092 kg/s, the target temperature of 17°C was reached under the experimental condition of 0.07 kg/s. When the angle of the water nozzle was adjusted to 0°, 30°, and 60°, the fastest way to reach the target temperature of 17°C was the 0° experimental condition in which water was injected tangentially to the water tank.

Experimental investigation of heat transfer and structure optimization for regenerative cooling channels using n-decane

Regenerative cooling technologies are considered one of the most effective and widely used active thermal protection methods for hypersonic aircraft scramjets. The heat transfer performance of hydrocarbon fuel and the geometric optimization of cooling channels are the key factors to be considered in designing regenerative cooling structures. Therefore, the present study experimentally and numerically investigated the heat transfer characteristics of n-decane in regenerative channels under asymmetric heating conditions and presented a new structure optimization method. The experiment was conducted at 3 MPa and 293 K with a mass flow rate of 0∼2.442 g/s per channel and a heat flux range of 0∼150 kW/m2. Experimental data show that the local Nusselt numbers exhibit a higher sensitivity to changes in mass flow rate compared to heat flux. Compared to symmetric heating, asymmetric heating mainly affects the heat conduction in the solid domain rather than the performance of convective heat transfer. The modified Dittus-Boelter correlation could predict the experimental data with a relative deviation of ±25 %. A rapid temperature prediction method based on heat flux distribution was proposed through heat transfer analysis, and it was utilized with a particle swarm optimization algorithm to conduct structure optimization.

Temperature stability of a Joule–Thomson microcooler operating with pure and mixed gases

Benefiting from the developments in micromachining technologies, Joule–Thomson (JT) cryogenic coolers have been miniaturized for cooling cold electronics based either on semiconductor, superconductor, or a combination of the two. The performance of these electronics is affected not only by temperature but also by temperature stability; however, many problems related to the temperature stability of JT microcoolers have not been solved. In this study, we investigate experimentally the performance of a JT microcooler operating with pure nitrogen gas, nitrogen/methane mixture, and nitrogen/ethylene mixture. The cool-down curves and the cooling powers of the microcooler operating with the three types of working fluids between 0.1 MPa and 6.0 MPa are presented. Based on the cooling power measurements, the effect of heat load on the temperature stability of the microcooler is discussed. The microcooler operating with nitrogen/ethylene mixture demonstrates the best temperature stability due to its characteristics of vapor–liquid–liquid equilibrium. Besides the properties of the working fluids, the degree of change in mass-flow rate of the microcooler also affects the temperature stability. This study is conducted to promote the widespread use of cryogenic electronics that are sensitive to the temperature fluctuation.

Pulsatile pressure enhanced rapid water transport through flexible graphene nano/Angstrom-size channels: a continuum modeling approach using the micro-structure of nanoconfined water

Several researchers observed a significant increase in water flow through graphene-based nanocapillaries. As graphene sheets are flexible (Wang and Shi 2015 Energy Environ. Sci. 8 790–823), we represent nanocapillaries with a deformable channel-wall model by using the small displacement structural-mechanics and perturbation theory presented by Gervais et al (2006 Lab Chip 6 500–7), and Christov et al (2018 J. Fluid Mech. 841 267–86), respectively. We assume the lubrication assumption in the shallow nanochannels, and using the microstructure of confined water along with slip at the capillary boundaries and disjoining pressure (Neek-Amal et al 2018 Appl. Phys. Lett. 113 083101), we derive the model for deformable nanochannels. Our derived model also facilitates the flow dynamics of Newtonian fluids under different conditions as its limiting cases, which have been previously reported in literature (Neek-Amal et al 2018 Appl. Phys. Lett. 113 083101; Gervais et al 2006 Lab Chip 6 500–7; Christov et al 2018 J. Fluid Mech. 841 267–86 ; White 1990 Fluid Mechanics; Keith Batchelor 1967 An Introduction to Fluid Dynamics ; Kirby 2010 Micro-and Nanoscale Fluid Mechanics: Transport in Microfluidic Devices). We compare the experimental observations by Radha et al (2016 Nature 538 222–5) and MD simulation results by Neek-Amal et al (2018 Appl. Phys. Lett. 113 083101) with our deformable-wall model. We find that for channel-height Å, the flow-rate prediction by the deformable-wall model is 5%–7% more compared to Neek-Amal et al (2018 Appl. Phys. Lett. 113 083101) well-fitted rigid-wall model. These predictions are within the errorbar of the experimental data as shown by Radha et al (2016 Nature 538 222–5), which indicates that the derived deformable-wall model could be more accurate to model Radha et al (2016 Nature 538 222–5) experiments as compared to the rigid-wall model. Using the model, we study the effect of the flexibility of graphene sheets on the flow rate. As the flexibility α increases (or corresponding thickness and elastic modulus E of the wall decreases), the flow rate also increases. We find that the flow rate scales as for ; for ; and for , respectively. We also find that, for a given thickness , the percentage change in flow rate in the smaller height of the channel is more than the larger height of the channels. As the channel height decreases for the given reservoir pressure and thickness, the increases with followed by after a height-threshold. Further, we investigate how the applied pulsating pressure influences the flow rate. We find that due to the oscillatory pressure field, there is no change in the averaged mass flow rate in the rigid-wall channel, whereas the flow rate increases in the flexible channels with the increasing magnitude of the oscillatory pressure field. Also, in flexible channels, depending on the magnitude of the pressure field, either of the steady or oscillatory or both kinds of pressure field, the averaged mass flow rate dependence varies from to as the pressure field increases. The flow rate in the rigid-wall channel scales as , whereas for the deformable-wall channel it scale as for , for , and for . We find that both the flexibility of the graphene sheet and the pulsating pressure fields to these flexible channels intensify the rapid flow rate through nano/Angstrom-size graphene capillaries.

Experimental investigation of hydrogen production performance of various salts with a chlor-alkali method

In this experimental study, the hydrogen production performance of aqueous solutions of NaCl, KCl, and CaCl2 salts via an electrochemical method through a chlor-alkali reactor is investigated. For this purpose, a laboratory-scale reactor consisting of anode and cathode compartments is built. The compartments of the reactor are separated by a cation exchange membrane which prevents the mixing of anolyte and catholyte solutions and also allows positive ions (Na+, K+, and Ca2+) and some water to pass through. Electrodes made of 316 stainless steel are used in the compartments of the reactor due to their economic efficiency. While the anode compartment of the reactor is fed with the aqueous solutions of NaCl, KCl, and CaCl2 salts one by one, the cathode compartment is fed with one of the diluted aqueous solutions of NaOH, KOH, and Ca(OH)2 bases depending on the type of salt used. Experiments are carried out at three different cell voltages (3, 4, and 5 V) and three different cell temperatures (30, 50, and 70 °C), and five different electrolyte flows (0.4, 0.6, 0.8, 1.0, and 1.2 g/s). Since the reactor dimensions are very small, experiments are also carried out with small changes in the electrolyte mass flow rate. It is observed that active chlorine gas causes serious contamination in the anode compartment and erosion on the electrode in this compartment. Therefore, the expected chlorine gas output from the anode compartment of the reactor is not observed. Luckily, a significant amount of hydrogen gas output is observed from the cathode compartment of the reactor. The minimum hydrogen production rate is 37.23 mL/h when the aqueous solution of CaCl2 is used with a mass flow rate of 0.4 g/s and cell voltage of 3 V at the cell temperature of 30 °C. The maximum hydrogen production rate is 437.72 mL/h when KCl salt solution is used with a mass flow rate of 1.2 g/s and cell voltage of 5 V at the cell temperature of 70 °C.

Transient Study (Annual) of the Heat Transfer of a Two-Channel Solar Air Collector

Abstract In this paper, a numerical heat transfer study of a solar air collector with two channels (SAC-2C) was carried out. Energy global balances in two dimension (2D) and unsteady state were considered, as well as bio-climatic conditions of Toluca city in Mexico (sub-humid temperate climate). Six mass flowrates (0.01, 0.05, 0.1, 0.2, 0.4, and 0.5 kg/s) were considered during the numerical simulation, for the coldest and the warmest day of each month during a complete year (2019). Among the results, it was found that thermal efficiency of the system increases up to 35% when the mass flowrate changes from 0.01 to 0.2 kg/s, meanwhile, maximum efficiency of 84% were obtained for a mass flowrate of 0.5 kg/s. Finally, based on a cost-benefit analysis, it was determined that the SAC-2C has a recovery time of the initial investment ($ 250 USD) of three and a half years. So that the SAC-2C has the capacity to produce 1, 654, 451 kW h/m2 of clean energy annually, which is equivalent to ceasing to produce 871, 895 kg CO2 per square meter of installation.

Thermo-economic assessment of sub-ambient temperature pumped-thermal electricity storage integrated with external heat sources

Thermally integrated pumped-thermal electricity storage (TI-PTES) offers the opportunity to store electricity as thermal exergy at a large scale, and existing studies are primarily focused on TI-PTES systems based on high-temperature thermal energy storage. This paper presents a thermo-economic analysis of a “cold TI-PTES” system which converts electricity into cold energy using a vapor compression refrigeration (VCR) unit and stores it at sub-ambient temperatures during the charging process, and generates electricity by using an organic Rankine cycle (ORC) working between the sub-ambient temperature and an external low-grade heat source during the discharging process. The effects of key parameters, i.e., mass flowrate and temperature of the storage medium, ORC evaporation temperature, component efficiencies, and pinch-point temperature differences, on the system performance are evaluated based on a whole-system thermo-economic model. The results reveal that the roundtrip efficiency and levelized cost of storage (LCOS) of the system increases while the electrical energy storage capacity decreases as the temperatures of the two cold storage tanks approach each other. When the temperature of the cold storage tank 1 rises from 1 °C to 8 °C while the cold storage tank 2 remains as 13 °C, there is an increase of 25% and 20% in the roundtrip efficiency and LCOS respectively while the energy storage capacity decreases by 69%. A roundtrip efficiency of 0.74 and LCOS of 0.32 $/kWh are achieved with a heat source temperature of 85 °C, using a mass flowrate and temperature of the cold storage medium of 50 kg/s and 1 °C. Furthermore, any change in cold storage medium mass flowrate changes both electrical energy storage capacity and power output by the same proportions. With a continuous high-flowrate external heat source, the LCOS can be as low as 0.17 $/kWh. By providing sufficient heat from an external heat source, the proposed system possesses a high potential for medium-to-large scale energy storage with a unique hybrid nature for electricity storage and thermal integration.

Influence of the Deposition Rate and Substrate Temperature on the Morphology of Thermally Evaporated Ionic Liquids

The wetting behavior of ionic liquids (ILs) on the mesoscopic scale considerably impacts a wide range of scientific fields and technologies. Particularly under vacuum conditions, these materials exhibit unique characteristics. This work explores the effect of the deposition rate and substrate temperature on the nucleation, droplet formation, and droplet spreading of ILs films obtained by thermal evaporation. Four ILs were studied, encompassing an alkylimidazolium cation (CnC1im) and either bis(trifluoromethylsulfonyl)imide (NTf2) or the triflate (OTf) as the anion. Each IL sample was simultaneously deposited on surfaces of indium tin oxide (ITO) and silver (Ag). The mass flow rate was reproducibly controlled using a Knudsen cell as an evaporation source, and the film morphology (micro- and nanodroplets) was evaluated by scanning electron microscopy (SEM). The wettability of the substrates by the ILs was notably affected by changes in mass flow rate and substrate temperature. Specifically, the results indicated that an increase in the deposition rate and/or substrate temperature intensified the droplet coalescence of [C2C1im][NTf2] and [C2C1im][OTf] on ITO surfaces. Conversely, a smaller impact was observed on the Ag surface due to the strong adhesion between the ILs and the metallic film. Furthermore, modifying the deposition parameters resulted in a noticeable differentiation in the droplet morphology obtained for [C8C1im][NTf2] and [C8C1im][OTf]. Nevertheless, droplets from long-chain ILs deposited on ITO surfaces showed intensified coalescence, regardless of the deposition rate or substrate temperature.

A prototype recuperated supercritical co2 cycle: Part-load and dynamic assessment

High efficiency, flexibility and competitive capital costs make supercritical CO2 (sCO2) systems a promising technology for renewable power generation in a low carbon energy scenario. Recently, innovative supercritical systems have been studied in the literature and proposed by DOE-NETL (STEP project) and by a few projects in the EU Horizon 2020 (H2020) program aiming to demonstrate supercritical CO2 Brayton power plants, promising superior techno-economic features than steam cycles particularly at high temperatures.The H2020 SOLARSCO2OL project, which started in 2020, is building the first European MW-scale sCO2 demonstration plant and has been specifically tailored for Concentrating Solar Power (CSP) applications. After a detailed explanation of the modelling approach for steady and unsteady cycle simulations, this paper presents the off-design and dynamic analysis of such plant layout, which is based on a simply recuperated sCO2 cycle. The entire system model has been developed in TRANSEO environment. The part-load analysis ranged from 50% of nominal up to a 105% peak load, discussing the impact on compressor and turbine operating conditions. Full operational envelop has been determined considering cycle main constraints, such as maximum turbine inlet temperature and minimum pressure at compressor inlet.The off-design performance analysis highlights the most relevant relationships among the main part-load regulating parameters, namely molten salt mass flow rate, CO2 mass flow rate, total CO2 mass in the loop, and shaft line speed. The results show specific features of different control approaches, discussing the pros and cons of each solution, considering also its upscale towards commercial applications. In particular, the analysis shows that at 51% of load an efficiency decrease of 20% is expected. Finally, the dynamic characterization of the closed loop shows the relatively fast responsiveness of the plant to compressor speed variations, causing quick changes in CO2 mass flow rate, together with longer time scale phenomena related to the plant heat exchangers. In this respect, sCO2 plants demonstrate to have the potential to provide primary reserve for the electrical grid, as far as thermal stresses on main plant components are kept under acceptable limits.