Steam Condensation Research Articles

Numerical investigation of thermal-flow processes in the ejector-condenser for selected geometrical parameters

The paper presents the results of analysis of thermal-flow processes in the ejector-condenser for selected geometrical param-eters using CFD (Computational Fluid Dynamics) methods. The ejector-condenser is the water-driven, two-phase ejector responsible for creating a sub-pressure allowing exhaust gases (steam and CO2 mixture) to be entrained, condensing steam, and then increasing the pressure above the atmospheric conditions. The axisymmetric numerical model was developed to take into account multiphase, turbulent flow with steam condensation in the presence of inert gas. The influence of the selected geometrical parameters, such as the motive nozzle's and mixing chamber's diameters on the ejector performance was investi-gated. CFD analysis results are presented in the form of developed scalar distributions as well as pressure, temperature and steam mass flow changes along the flow path. Performances for different geometry modes were calculated and compared using parameters such as compression ratio, expansion ratio, mass entertainment ratio and condensation efficiency. The max-imum achieved compression ratio for the analyzed geometrical variants is 1.113 for the assumed mass entertainment ratio of 0.0295. The condensation efficiency varies in a range of 49.6%–91.4% depending on motive fluid inlet conditions and geom-etry mode.

CFD Modeling of Film Condensation from a Steam-Air Mixture in Vertical Channels

Steam condensation in the presence of a noncondensable gas is of vital importance for passive cooling containment systems. The noncondensable gas causes a significant reduction in the condensation rate and heat transfer across the containment, which is important for postulated loss-of-coolant accidents in a nuclear reactor. In this work, computational fluid dynamics models of condensation and the adjacent single-phase steam-air mixture flow are developed for laminar and turbulent flow in vertical channels by two distinct wall condensation modeling approaches using the commercial code STAR-CCM+. The first is the fluid film model available in STAR-CCM+, which solves liquid layer governing equations with connections to the adjacent gas mixture flow. The second is a user-defined wall condensation model that neglects the fluid film and instead accounts for mass, momentum, and heat transfer via user-defined volumetric sink terms adjacent to the cold wall. The condensation models are assessed by first comparing the calculated results with the numerical solution of laminar flow, solved using a complete two-phase model that solves parabolic equations based on conservation of mass, momentum, energy, and species for each phase. Next, the results of a two-dimensional analysis are compared with COPAIN experiments and existing numerical solutions from three-dimensional analyses. The comparisons include new, detailed results that have not been reported in previous analyses of a COPAIN case. These new results include local field profiles of velocity, temperature, and air mass fraction, and local mass flux.

Теплоотдача при движении воды в трубе при температурах, близких к температурам кипения в переходном режиме

Currently, there is a problem of developing effective methods to calculate heat and mass transfer processes during steam condensation from a vapor-gas mixture in industrial devices. This is due to the need to create new reliable and highly efficient designs of heat exchangers for various purposes. The finite element method has been used in the ANSYS Fluent software package during the numerical simulation. An experimental plant is tested in the pipeline of an industrial enterprise at the production site of the Technopolis KHIMGRAD industrial park (Kazan-city). The applicability of the Lee model to solve problems of water flow in a pipeline with partial evaporation is proved. This model allows you to accurately account for the processes of evaporation and condensation, which is important for the design of cooling and air conditioning systems. The authors have designed a three-dimensional model of the flow area of the experimental module and a CFD model to calculate temperatures, phase velocities and their concentrations, considering the peculiarities of the ongoing processes of heat and mass transfer. A slight effect on the heat flow of a 180° rotation during the flow of a liquid medium in the range of the Reynolds numbers 1800–2600 is shown. The developed model is verified with the results obtained at the experimental plant. It is established that the model reproduces experimental data well. An analysis of studies of heat and mass transfer processes during the fluid flow in channels in the presence of phase transitions is carried out. The problems of calculating the parameters of heat transfer during the movement of a fluid in a transient mode are revealed, especially at values of the Reynolds number close to 2000. The experimental plant diagram is presented. It is found that in the range of Reynolds numbers of 2600–3600, the calculated temperature values differ from the temperature values obtained experimentally by less than 0,42 %. During the partial transition of water into steam in the range of Reynolds numbers of 1800–2600, the deviations were less than 6 %, which confirms the adequacy of numerical modeling of calculating the heat transfer process in a pipe. It is shown that considering the influence of temperature on surface tension, the coefficient of thermal conductivity of water and the coefficient of dynamic viscosity of water is important to obtain accurate results. The proposed approach can be used to optimize the operating parameters of condensers and evaporators, as well as to accurately calculate the heat transfer coefficient and determine the areas of vapor formation. It will improve the energy efficiency of industrial installations and reduce the cost of equipment operation.

The role of annealing and grain boundary controls on the mechanical properties of limestones and marbles

Chemical and mechanical processes are coupled in many geological and geochemical environments. Reactive processes anneal defects and restructure grain boundaries, modifying their elastic properties, levels of internal friction, wave propagation rates and fracture behaviors. The nature of these changes is, however, contingent on the initial state of the rock. In this study, impulse excitation was used to measure changes in mechanical properties as a function of dry and steam heating time at 300 °C for three carbonate rocks: Carrara marble, Carthage marble (Burlington Limestone), and Texas Cream limestone (Edwards limestone), with initial porosities of about 1 %, 3 %, and 27 %, respectively. Frequency-dependent phenomena along with mineral recrystallization were observed. This was coupled with small-angle X-ray and neutron scattering analysis to determine the relationship between changes in bulk mechanical and microstructural properties. An observed decrease in both the Young's and shear moduli in the experimental limestones as a function of heating time reflects and quantifies a reduction in the stiffness of the rock due to annealing. The internal friction of the samples first increases then decreases with reaction time, reflecting defect annealing, but this was balanced against grain boundary dissolution apparently driven by condensation of steam in the confined grain-boundary environment. This suggests an increase in the boiling point under confinement leading to dissolution, increased porosity and widening of the grain boundaries. In addition, comparison of small-angle X-ray and neutron scattering results suggests that it is inappropriate to assume that pores are empty for quantitative analysis of typical small-angle scattering samples.

Study on Thermal Chamber Expansion of VH-SAGD Process Using CO2-Inducing Effect for Heavy Oil Reservoirs

In heavy oil thermal recovery processes, higher pressure usually leads to low dryness and expansion difficulty for the injected steam in thermal recovery processes, which will result in lower oil recovery and more carbon emissions. This paper proposed a new CO2-inducing method to accelerate the steam chamber expansion, based on a core flooding experiment and numerical simulation. First, the CO2 showed significant viscosity reduction at high pressure in the PVT test. In the core flooding experiment, the CO2 provided strong flow conductivity in porous media for the thermal flooding, as the CO2 pre-injection restrained the steam condensation. Using the CO2-inducing method, CO2 pre-injection before steam built a fast flow channel in a relatively higher permeability layer and reduced the thermal injection pressure by about 1.0~2.4 MPa. As a result, the steam overlap around the injection wells became slower and the gravity drainage process was able to heat and displace the heavy oil above the channel. Furthermore, the CO2 gas trapped at the top reduced heat loss by about 12.4%. The field numerical simulation showed that this new method improved thermal recovery by 7.5% and reduced CO2 emissions by about 18 million kg/unit for the whole process. This method changes the conventional thermal expansion direction by CO2 inducing effect and fundamentally reduces heat loss, which provides significant advantages in low-carbon EOR.

COMBUSTION OF HYDROGEN IN OXYGEN-STEAM MIXTURE FOR INCREASING THE STEAM TEMPERATURE OF POWER PLANTS

In the work the problems that arise at combustion of hydrogen in oxygen-steam mixture for the purpose of combustion products (steam) mixing for heating steam, which is planned to be used in steam turbines of power plants were researched. The main problem is the formation of underburning H2 and, accordingly, the presence of O2, which have a negative effect on metals, and it will also prevent steam condensation in the condenser was determined. For solve this problem, calculations of the equilibrium concentrations of chemical reaction products in the combustion zone depending on the amount of ballast steam added to the oxidizer (oxygen) for the initial conditions: T0=528 K, p=0.1 MPa; T0=​​528 K, p=3.1 MPa; T0=​​584 K, p=10 MPa were made. The corresponding adiabatic temperatures were calculated. The dilution of the oxidant (oxygen) with steam significantly decreases the adiabatic temperature (Tb) and reduces the equilibrium concentrations of other substances in the combustion zone, but at the same time the laminar flame propagation velocity (SL) also significantly decreases was established. It is important when a certain concertation of ballast steam is achieved (the final percentage is determined by the design of the burner) there will be a sharp deterioration of combustion or even the formation of a flame will be impossible. The principal design of the hydrogen-oxygen-steam combustion chamber was proposed. The necessity of heating oxygen and hydrogen and the principle of determining the pressure under which it is advisable to supply oxygen and hydrogen to ensure the maximum intensification of mixing first of oxygen and steam, and then of the formed mixture and hydrogen, were substantiated. Bibl. 20, Fig. 5, Table 3.

Experimental Investigation of Large-Scale Vertically Coated Tubes for Enhanced Air–Steam Condensation Heat Transfer

Non-condensable gas plays a significant role in steam condensation, primarily by reducing heat transfer efficiency. Enhanced condensation heat transfer in the presence of non-condensable gas is crucial for improving thermal efficiency, reducing energy consumption, and lowering costs. However, experimental studies on applying coatings to enhance condensation heat transfer in large-scale vertical outer tubes with non-condensable gas are scarce. This study investigates the condensation heat transfer performance of vertical stainless steel- and brass-coated tubes compared to their bare counterparts at different air concentrations (0.4, 0.3, 0.15, and 0.08). All tubes have an outer diameter of 19 mm and an effective length of 1080 mm. Visualizations reveal that condensate flow rates as high as 0.5 m/s on bare tubes cause significant disturbances to the diffusion layer. At various air concentrations, the maximum condensation heat transfer coefficient of the coated stainless steel tube exhibited increases of 22.2%, 11.9%, 4.2%, and 19.6% compared with the uncoated stainless steel tube. Similarly, the maximum condensation heat transfer coefficient for the coated brass tube showed significant increases of 58.9%, 53.5%, 68.0%, and 70.7% compared with the uncoated brass tube. Notably, the enhancement effect on heat transfer performance is more pronounced when the same type of modified surface is applied to the brass tube compared with the stainless steel tube.

Nonlinear FOPID controller design for pressure regulation of steam condenser via improved metaheuristic algorithm

Shell and tube heat exchangers are pivotal for efficient heat transfer in various industrial processes. Effective control of these structures is essential for optimizing energy usage and ensuring industrial system reliability. In this regard, this study focuses on adopting a fractional-order proportional-integral-derivative (FOPID) controller for efficient control of shell and tube heat exchanger. The novelty of this work lies in the utilization of an enhanced version of cooperation search algorithm (CSA) for FOPID controller tuning, offering a novel approach to optimization. The enhanced optimizer (en-CSA) integrates a control randomization operator, linear transfer function, and adaptive p-best mutation integrated with original CSA. Through rigorous testing on CEC2020 benchmark functions, en-CSA demonstrates robust performance, surpassing other optimization algorithms. Specifically, en-CSA achieves an average convergence rate improvement of 23% and an enhancement in solution accuracy by 17% compared to standard CSAs. Subsequently, en-CSA is applied to optimize the FOPID controller for steam condenser pressure regulation, a crucial aspect of heat exchanger operation. Nonlinear comparative analysis with contemporary optimization algorithms confirms en-CSA’s superiority, achieving up to 11% faster settling time and up to 55% reduced overshooting. Additionally, en-CSA improves the steady-state error by 8% and enhances the overall stability margin by 12%.

Performances of the ITER Pressure Suppression System during unstable steam condensation regimes

Abstract The paper deals with the qualification of the main safety system of the nuclear fusion reactor ITER: the Vacuum Vessel Pressure Suppression System (VVPSS). This safety system manages the Loss of Coolant Accident (LOCA), that could occur in the Vacuum Vessel (VV), avoiding a significant increase of the internal pressure that could breach the primary confinement barrier. Steam condensation occurs at sub-atmospheric pressure. This condition is original respect the usual applications of steam direct condensation in nuclear fission reactors. An extensive experimental research program, funded by ITER Organization, on reduced scale experimental rigs (scale 1/22 and 1/10) have been carried out at the University of Pisa. Unstable condensation regimes occurred during some tests at about 500 g/s of steam mass flow rate (10 % of the maximum steam mass flow rate foreseen for the relevant accidental scenarios). In these conditions, high intensity vibrations of the whole experimental rig occurred. These events can be classified as ‘Chugging’ or Condensation Induced Water Hammer (CIWH). 
The performed tests have been analysed elaborating the images of the video-cameras located in the pool and comparing the steam jet shape with the acceleration values recorded by an accelerometer mounted on the sparger structure.
These elaborations permitted to evaluate the dynamic of bubble collapse, the volume of the developed external bubbles, the collapse frequency as function of thermal-hydraulic parameters. 
Moreover, the paper emphasizes the beneficial effects of non-condensable gases on the unstable condensation regimes. In fact, the non-condensable gas inhibits the occurrences of Water Hammer inside the sparger and eliminates the thermal stratification inside the water pool increasing the turbulence.

Experimental study on heat transfer characteristics of steam condensation in the presence of air and CO2 outside a vertical tube

Under severe accident conditions, in addition to steam and air, there are also other non-condensable gases inside the containment, such as CO2 produced by the molten corium concrete interaction (MCCI). Due to the significantly higher molecular weight and density of CO2 compared to steam and air, CO2 will have a significantly different impact on the steam condensation process compared to air. However, few scholars have paid attention to the impact of CO2 on the condensation process, and there is no empirical correlation applicable to this condition. Therefore, this article investigates the effect of different CO2 concentrations on the steam condensation heat transfer coefficient (CHTC) in the range of system pressure from 0.2 to 1.3 MPa and subcooling from 30 to 130 °C through experimental methods. Meanwhile, based on relevant experimental data, a new correlation suitable for calculating the steam CHTC in the presence of CO2 and air was fitted. The results indicate that under low steam concentration conditions, the addition of CO2 will reduce CHTC, while under high steam concentration conditions, CO2 will increase CHTC. The increase in system pressure will strengthen the condensation promotion effect of CO2 and weaken its inhibitory effect on condensation. In addition, by comparing experimental data under different component conditions, it was found that the new empirical correlation has high computational accuracy, and the calculation results of this correlation can contain more than 90 % of the data within a 15 % error range.

Numerical investigation of heat and mass transfer characteristics of steam condensation containing non-condensable gas in vertical corrugated tube

A numerical simulation of steam condensation containing non-condensable gas is conducted in this paper to analyze the heat and mass transfer characteristics in vertical corrugated tube. The species transport model, Euler liquid film model and diffusion-balance model with Dehbi factor to correct the diffusion effect are applied to simulate the mass and energy transfer processes. The effects of different corrugated tube structural parameters and inlet steam parameters on steam condensation rate, liquid film distribution and heat transfer are simulated. The results show that vortex and accumulated non-condensable gas in the corrugated region significantly influence condensation heat transfer, which are closely related to corrugation height (H=0–5 mm) and corrugation length (L=13, 16, 19, 22, and 25 mm) of the corrugations, as well as inlet velocity (Vin = 5, 7, 9, 11, 13, and 15 m·s−1) and inlet steam content (Ws = 0.6, 0.7, 0.8, 0.9, 0.99, and 1). The total heat transfer coefficient varies linearly with inlet velocity when inlet velocity increase from 5 m·s−1 to 15 m·s−1, which increase 89.6–108.1 %; total heat transfer coefficient increases almost exponentially when inlet steam content increase from 0.6 to 1, which increase 389–460 %; and the best corrugated tubes are those with corrugation height of 0.075 times diameter of tube and corrugation length of 0.325 times diameter of tube.

A Reliability Analysis of Steam Condenser Instrumentation Using Failure Mode and Effect Analysis (FMEA)

Abstract—PT PLN Nusantara Power UP Tenayan is a steam power plant (PLTU) with a capacity of 2 x 110 MW which is a buffer for the electricity system in the Central Sumatra section. In the production process of PT PLN Nusantara Power UP Tenayan it does not always go well,. So that it will have an impact on the production stages of the power plant. One of the production machines that often fails and disrupts the production stage is the steam condenser. This research uses the Failure Mode And Effect Analysis Method which aims to identify the type of failure, cause of failure, effect of failure, and determine the RPN value. The research phase begins with data collection from literature studies, interviews, field observations, data analysis, FMEA analysis, results and discussion, conclusions. Based on the results of the RPN calculation, each component of the steam condenser instrumentation does not exceed the RPN standard limit of less than 200, although the temperature indicator has the highest RPN value but is still categorized as reliable and not recommended for immediate maintenance action. The results of identifying the type of failure are that there are inaccurate indications, there are switches with sticky conditions, there are displays that are unclear or blurry, and there is a mismatch between the data displayed in the DCS and the data displayed in the local area. For recommended actions on the steam condenser instrumentation components, among others, carry out more incentive maintenance every 3 months, make improvements to the specifications of the switch according to the amount of pressure to be measured, move the sensor to a safer area and protected from water exposure, carry out a zero calibration process on the steam condenser instrumentation components every six months.

Analysis of cyclone separator solutions depending on spray ejector condenser conditions

The core design strategy for minimizing CO2 emissions in gas power plant entails combining a spray ejector condenser (SEC) and separator to accomplish steam condensation and CO2 purification. This innovative process involves direct-contact condensation of steam with CO2, facilitated by interaction with a subcooled water spray, along with a cyclone separator mechanism intended for generating pure CO2. The investigation of the SEC section, both experimentally and analytically, provides crucial insights into its operational dynamics. Given the susceptibility of cyclone efficiency to fluctuations in SEC conditions, this research endeavors to examine the impacts of CO2 volumetric flow rate and droplet break-up within the SEC on the separation efficacy of the cyclone separator. Additionally, the impact of cone size on the performance of the cyclone has been investigated. Here, a three-dimensional, transient, and turbulent cyclone separator is numerically simulated using Ansys Fluent 2021 R1. The Reynolds Stress Model is employed to simulate turbulent flow, while a mixture model is utilized to replicate swirl two-phase flow within the separators. The findings revealed that reductions in steam and CO2 flow rates were associated with a decrease in outlet temperature but an increase in SEC inlet temperature, leading to a rise in temperature difference and heat transfer rate. Furthermore, an augmentation in cyclone cone size (from 0.2 to 0.5 m) resulted in enhanced separation efficiency (from 77.30 % to 80.98 %) alongside an elevation in pressure drop (from 6.08 Pa to 10.91 Pa), suggesting a compromise between CO2 purification and energy consumption. Additionally, elevated CO2 flow rates induced a rise in pressure drop and separation efficiency, ultimately achieving maximum efficiency at a rate of 24 gs. Moreover, the exploration into droplet breakup manifesting in a boost in separation efficiency from 50.98 % to 100 % across droplet diameters ranging from 1 to 20 μm.

Thermodynamic study of water/solvent, bitumen/solvent, water/bitumen, and water/bitumen/solvent systems: From CPA EoS parametrization towards phase diagram construction

Various fluid phase equilibria happen in solvent-aided steam-assisted gravity drainage (SA-SAGD). An appropriate fluid model is a prerequisite for reservoir simulation, SA-SAGD operation analysis, and the design of various phase behavior experiments. Computational thermodynamics is a powerful tool for phase behavior studies in this application. We used the Cubic Plus Association Equation of State (CPA EoS) to predict equilibrium properties due to the presence of molecules with highly directional attractive forces. Calibration of the thermodynamic model is performed by parametrizing its unknown parameters versus two-phase equilibrium data. The model’s prediction capability of three-phase experimental data is evaluated, and it is used to construct the phase diagram of water/multicomponent solvent and water/multicomponent solvent/bitumen systems. For the water/multicomponent solvent system, the Txy diagram is obtained at 25 bar, and various phase equilibria regions are specified. These phase regions are presented on ternary diagrams for water/multicomponent solvent/bitumen systems at 25 bar and 475 K, 480 K, and 485 K. The steam/solvent coinjection analysis shows that at the same pressure, temperature, and steam/solvent composition, the multicomponent solvent/steam coinjection yields more aqueous phase compared to pure solvent/steam. This results in the transfer of more latent heat to bitumen, significantly contributing to its viscosity reduction. Analysis of the SA-SAGD operating conditions shows that a multicomponent solvent outperforms pure solvents in promoting steam condensation. The results aids in designing experiments, reducing the risk of failure of experiments, and saving time and resources in phase behavior studies.

Heat pump assisted sorption carbon capture with steam condenser heat recovery in a decarbonised coal-fired power plant

More than 50% energy input of coal-fired power plant is lost in the condensation of steam turbine in a temperature range of 30–35 ℃. Carbon capture technology has a negative influence on power generation efficiency of coal-fired power plant. Thus, it is essential to find an efficient method for waste heat recovery and increase the overall energy efficiency in coal-fired power plant with carbon capture. A novel integrated system including absorption heat pump and adsorption carbon capture based on coal-fired power plant is then presented. Waste heat from steam condenser is recovered by absorption heat pumps driven by steam extracted from low pressure steam turbine. The output hot medium from the absorption heat pumps is further heated to desorption temperature for the regeneration process of adsorbents by the extracted steam. The results show that heat penalty increases with the increase of the desorption temperature, and the heat recovery amount has an opposite trend. Compared with the conventional coal-fired power plant, thermal efficiency of the integrated system increases by 0.854%. The efficiency decrease of the compression work accounts for over a half of the total efficiency decrease due to the compression and the capture process. External heat recovery is applied in flue gas and the multi-compression process, and the thermal efficiency increase can be improved to 1.453% when compared with 0.725% of the system without external heat recovery. It proves that absorption heat pump could play a significant role in the energy saving of adsorption carbon capture system.

Condensation mechanism and pressure fluctuation of a steam centrifugal compressor based on a non-equilibrium condensation model

In this paper, the condensation mechanism and pressure fluctuation of a steam centrifugal compressor are deeply studied based on a non-equilibrium condensation model. The wet steam model is generated to predict the flow characteristics and the condensation of the steam centrifugal compressor. The effect of different inlet temperatures on the steam condensation characteristics is deeply explored. Numerical results show that the steam condensation phenomenon on the high span surface is increasingly obvious, and the mass fraction of liquid steam first increases and then decreases with the increase in temperature. The droplet particle diameter and the droplet number gradually increase with the increase in temperature. It is also found that the blade loading on the impeller blade also becomes more unstable with the increase in inlet temperature. The amplitude spectrum of pressure fluctuation on the both sides of impeller blade and diffuser blade is analyzed through the fast Fourier transform. The pressure fluctuation in the flow channel becomes severe first and then becomes stable with the increase in temperature, which is well consistent with the variation trend of liquid mass fraction. The quantitative relationship between condensation strength and operating temperature is established to explore the variation trend essence of surface-average wetness fraction of different span surfaces at different inlet temperatures, which further reveals the condensation sensitivity to temperature at different blade heights. It is further found that the condensation strength on the low span surface and the average wetness fraction of steam condensation in the flow field increasingly decrease with the increase in inlet temperature.

Preparation and thermal properties of biomimetic polymer-based flexible ultra-thin flat heat pipe

Inspired by the structure of the human spine, a flexible ultra-thin flat heat pipe featuring a biomimetic human spine design has been devised. This flat heat pipe, equipped with a biomimetic human spine structure, is capable of undergoing repeated bending at large angles. An experimental study was conducted to investigate the primary influencing factors. The results revealed that the optimal liquid filling ratio for the flexible ultra-thin flat heat pipe is 0.3. The dip angle is positively correlated with the heat transfer performance of the flexible ultra-thin flat heat pipe, and the bending angle is negatively correlated with the heat transfer performance of the flexible ultra-thin flat heat pipe. The maximum thermal conductivity of the flexible ultra-thin flat heat pipe can reach 1457.68 W/(m·K). The flexible ultra-thin flat heat pipe with liquid filling rate of 0.3 and bending angle of 0 degree has the fastest start-up speed. A visualized experimental platform was further designed to observe the internal flow of the working fluid within the flexible ultra-thin heat pipe in various bending states. The visual experimental results demonstrate that bending initiates the premature condensation of steam within the flexible section, and the condensed working medium subsequently generates resistance to the flow of subsequent steam, leading to an inability for the latter to be smoothly transported to the condensing section, thereby creating a vicious cycle.

CFD approach for determining the losses in two-phase flows through the last stage of condensing steam turbine

Analyzing and simulating wet steam flows within steam turbines holds significant importance, especially due to the presence of a liquid phase in the low-pressure stages of the turbine, resulting in consequential losses that demand careful consideration. Considering these conditions, this study employs advanced predictive CFD models to simulate the wet steam flow within the actual 3D geometry of the final stage in a 200 MW steam turbine, which is observed in the least research due to the complexity of modeling and analysis of three-dimensional flows. This advancement promises more precise and reliable results. Employing the ANSYS CFX software, this study engages in numerical simulations of steady-state compressible two-phase flow. Furthermore, the study offers practical equations to quantify the losses within the entire stage, which serves as a valuable metric for assessing loss levels and offers a benchmark for design improvements aimed at loss reduction. Based on the results, 10 % of losses occur along the stator and 1 % along the rotor, and a total of 11 % of losses occur along the entire stage. Finally, the efficiency of the stage is calculated to be 89 %. Steam condensation strengthens the shock waves, changes their location, diminishes Mach number and the flow velocity, and alters the flow angle. It reduces the efficiency of the turbine by 1.27 % and also reduces the work done by the turbine by 13.97 %. This emphasizes the significant influence of condensation on flow characteristics, emphasizing the necessity of conducting comprehensive investigations into this phenomenon.

Effective direct steam regeneration of bis-iminoguanidine solid sorbent used for carbon dioxide capture

A cost-effective, energy-efficient sorbent regeneration process for phase-changing guanidines used for CO2 capture was developed based on direct-steam stripping. This approach enhances the regeneration rate, simplifies the overall CO2 capture process, and reduces the energy cost compared to conventional conductive thermal regeneration. A direct-steam sorbent regeneration reactor was developed, demonstrating that aqueous bis(iminoguanidines) (BIG) sorbents, e.g., methylglyoxal-bis(iminoguanidine) (MGBIG) and glyoxal-bis(iminoguanidine) (GBIG), could be efficiently regenerated with up to ∼ 99 % CO2 recovery through direct-steam stripping. Using low-temperature steam at 100 °C, a 4.5 times faster regeneration rate for GBIG carbonate sorbent (e.g., 30 min for 10 g) was demonstrated compared to conductive-heating (e.g., 135 min for 10 g) at 130 °C. Additionally, fully regenerated MGBIG converts into an aqueous MGBIG solution when the steam condenses onto the sorbent surface. Condensed steam with the guanidine can be easily recycled as an aqueous solution into the gas–liquid contactor to achieve a continuous-flow CO2-capture process. Molecular dynamics simulation was employed to provide a better understanding of the process. Higher heat transfer rates from steam to guanidine carbonate, compared to air heating, were attributed to the vibration resonance of water molecules within MGBIG with that of vapor molecules and the effective transfer of kinetic energy from vapor to solid. Technoeconomic analysis demonstrated that direct-steam stripping significantly decreases the CO2 capture cost by 50 % compared to traditional conductive heating methods. Enhanced mass transfer facilitated by low-temperature steam and subsequent condensation effectively heats up the H2O-containing BIG-carbonate crystals, facilitating the desorption of CO2 from the solid crystals, thereby leading to fast, effective, and energy-efficient sorbent regeneration.

Thermoeconomic analysis of the IWERS system for steam heat recovery from bakery ovens

AbstractThe integrated waste energy recovery system (IWERS) recovers heat from bakery ovens in supermarkets and other commercial facilities to heat domestic hot water, resulting in energy savings. This article presents a thermoeconomic analysis of the system's operation in a supermarket over the course of 1 year. The study shows that exergy destruction in IWERS is directly proportional to ambient temperature. During the hottest months of the year, IWERS experiences a 4% decrease in exergy performance, while the exergy unit cost of the product increases by up to 4.2%. Additionally, the steam condenser is responsible for the highest relative exergy destruction, reaching almost 45%. Moreover, the addition of equipment upstream of the process increases the exergy cost of production due to the destruction of exergy in the equipment. These results provide valuable information with important implications for energy efficiency, economic savings, and sustainability. Improving system efficiency would generate substantial benefits in energy savings, economic savings, and environmental impact for all commercial and industrial establishments that use bakery ovens.