Steam Mass Flow Rate Research Articles

Research on fluid flow and heat transfer characteristics in a three-dimensional condenser

The condenser plays a crucial role in nuclear power plants, impacting equipment economics and safety through shell-side two-phase flow and heat transfer. However, existing research has oversimplified the tube bundles, lacking comprehensive information for optimal performance. In this research, a three-dimensional method incorporating mixture and multiphase flow condensation models was used to investigate flow behavior and heat transfer characteristics without simplifying the internal structure. Calculation details were enhanced by omitting the porous medium approach. The numerical model achieved reasonable accuracy when compared to theoretical calculations for a range of steam mass flow rates. Analysis of numerical results, including pressure, velocity, temperature, air mass fraction, and heat transfer coefficient, revealed that steam flow rate and air mass fraction were key factors influencing heat transfer. This research demonstrates the method’s capability to capture intricate calculation details, providing valuable insights for optimization design considerations in condenser performance.

Design and experimental study of solar-driven biomass gasification based on direct irradiation solar thermochemical reactor

Solar-driven biomass steam gasification is a promising technology to produce H2-rich syngas, meanwhile achieve flexible storage of renewable energy. However, the solar gasification application also faces numerous challenges, due to its involved complex chemical reaction characteristics and the inherent the multi-physics energy conversion processes. This work designs a novel direct irradiation solar gasification reactor, with the improved optical acceptance structure and reasonable test module, and the wheat straw particle is selected as experimental sample. Employing a 9 kWe high flux solar simulator, the maximum temperature of reaction bed in this prototype reactor reaches to 1260 °C, with the average solar flux of 1171.3 kW/m2. With adjustable radiation flux as experiment factor, under the highest total radiation of 3.35 kW, the molar fraction of H2 in the produced syngas is 47.1 % with the energy upgrade factor of 1.15, and the cellulose component completes decomposition. Increasing the mass flow rate of steam reduces the syngas output while raising the H2/CO ratio of the syngas. In addition, smaller biomass particle size facilitates the reaction, thereby improving the conversion efficiency of direct irradiation gasification. The investigation results provide a meaningful reference for the efficient utilization of abundant solar and biomass energy.

Thermodynamic Performance Characterization of a Small-Scale Organic Rankine Cycle with 5 kW Net Power Output

Abstract Indonesia’s current energy landscape predominantly depends on fossil fuels and non-renewable energy sources, thereby exacerbating the issue of global warming. On the other side, geothermal utilization in the country still needs to be expanded to reduce the dependency on fossil fuels, particularly through organic Rankine cycle (ORC) systems. As an example, Ulumbu Geothermal Power Plant in Flores Island currently uses a back pressure turbine, which releases expanded steam directly into the atmosphere at 98.7°C and 0.98 bar. This paper presents a thermodynamic analysis of a small-scale Organic Rankine Cycle with 5kW Net power output based on the waste heat data of the Ulumbu Geothermal Power Plant. The study includes selecting the working fluid based on Ozone Depletion Potential (ODP) and Global Warming Potential (GWP) values, thermal efficiency, refrigerant, and steam mass flow rate calculation. Among 20 refrigerants available in Indonesia, R245fa shows promise, offering a Rankine system efficiency of 10-11%, zero ODP, a GWP of 850, and the lowest refrigerant mass flow rate. These parameters inform useful initial parameters for designing a small-scale ORC system producing 5 kW of net power, promoting cleaner and sustainable energy solutions for communities.

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.

Evaluasi Kinerja Steam Jet Ejector Tingkat Pertama Terhadap Kevakuman Kondensor

The steam jet ejector is a device for extracting NCG from the condenser. NCG can increase the pressure in the condenser until a vacuum condition is not reached. The diffuser pressure on the steam jet ejector has a normal operational limit of below 1 atm, meaning that the ejector performance will be optimal if it is operated at the operational limit under vacuum conditions. The expected objectives are to determine the effect of the steam jet ejector on condenser vacuum, calculate the performance of the first level steam jet ejector through pressure analysis in the diffuser section, calculate the performance of the steam jet ejector in actual conditions compared to the design data conditions and analyze actions that can be taken to improve the performance of the tool. Based on the results of calculations and analysis, it was found that the increase in steam jet ejector pressure had an effect on the increase in condenser pressure from the design pressure of 0.10 bar to 0.107-0.123 bar under actual conditions. The decrease in steam jet ejector performance results in the condenser vacuum level decreasing, but the equipment performance is within normal operational limit conditions, namely below 1 atm. The decrease in steam jet ejector performance is influenced by the motive steam mass flow rate, NCG mass flow towards suction, entrainment ratio value, NCG pressure and motive steam pressure which exceeds the design data.

Numerical Investigation of a Two-Phase Ejector Operation Taking into Account Steam Condensation with the Presence of CO2

The application of a two-phase ejector allows for the mixing of liquid and gas and provides effective heat transfer between phases. The aim of the study is a numerical investigation of the performance of a water-driven, condensing two-phase ejector. The research was performed using CFD methods, which can provide an opportunity to analyze this complex phenomenon in 2D or 3D. The 2D axisymmetric model was developed using CFD software Siemens StarCCM+ 2022.1.1. The Reynolds-Averaged Navier–Stokes (RANS) approach with the Realisable k-ε turbulence model was applied. The multiphase flow was calculated using the mixture model. The boiling/condensation model, where the condensation rate is limited by thermal diffusion, was applied to take into account direct contact condensation. Based on the mass balance calculations and developed pressure and steam volume fraction distributions, the ejector performance was analyzed for various boundary conditions. The influence of the suction pressure (range between 0.812 and 0.90) and the steam mass flow rate (range between 10 g/s and 25 g/s) is presented to investigate the steam condensation phenomenon inside the ejector condenser. The provided mixture of inert gas (CO2) with steam (H2O) in the ejector condenser was investigated also. The weakening of the steam condensation process by adding CO2 gas was observed, but it is still possible to achieve effective condensation despite the presence of inert gas.

Influence of loading on the heat transfer rate and specific water consumption of detached loosed fresh palm fruits during vertical mini-batch sterilization

This study presents the effect of loading on the heat transfer rate and specific water consumption of detached loosed fresh palm fruits during sterilization. Sterilization is an integral process of palm oil extraction that consumes a lot of water. However, most industrial research in the past focused on fresh fruit bunch (FFB) sterilization dynamics. At the same time, the medium- and small-scale industries sterilize already detached loosed fresh palm fruits (LFPF) that have been removed from the spikelet as purchased from aggregators. Therefore, the process data generated from the sterilization of FFB might not be optimal for sterilizing LFPF. This study, therefore, investigates the transient response of variation in LFPF loading of the sterilization chamber to steam injection during steam sterilization of LFPF at 3 ± 0.5 bars using a vertical, single-peak LFPF sterilizer that combines the boiler and sterilizer in a single unit. The LFPF were loaded at mass intervals of 0.2 kg ranging from 0.2 kg to 2 kg. The vapour temperature dynamics, heat transfer rate, steam energy utilization efficiency and specific water consumption parameters were studied. The average vapour temperature varied from 100 °C to 130 °C for the LFPF mass range of 0.2 to 2 kg at steam injection temperature of 140 °C and pressure of 3 ± 0.5 bars. This temperature range matched the saturated vapour temperature of pure water at 1.0––2.8 bars absolute pressure but slightly lower than the saturated vapour temperature of 133.54 °C for pure steam at 3 bars. The percentage of steam energy utilization effectiveness is inversely related to the steam mass flow rate. While energy effectiveness increased with loading mass, the steam mass flow rate decreased with increased LFPF mass. The value of the heat transfer rate ranged between 1.7––55.4 W, while the specific heat transfer rate ranged between 8.5–––41.8 W/kg. The average specific water consumption ranged from 0.014 to 0.09 kg-water/kg-LFPF, with an average value of 0.031 kg-water/kg-LFPF. This value is lower than 0.112–––0.5 kg-water/kg-FFB, with an average value of 0.256 kg-water/kg-FFB for conventional FFB steam sterilization. This represents an 87.9 % reduction in water consumption in conventional FFB steam sterilization. An empirical model deduced for specific heat transfer rate and water consumption for steam sterilization of LFPF at 3 ± 0.5 bars and vapour temperature range of 100––130 °C showed a high coefficient of determination above 99 %.

Simulation of single-effect and triple-effect evaporator for fruit juice concentration using Aspen HYSYS

Abstract One of the most popular methods of fruit juice preservation is concentration since it offers a variety of advantages, like decreased volume, weight, packing, simpler transportation and handling, and a longer shelf life. The present paper studied the evaporation of fruit juice in single- and triple-effect evaporators using Aspen HYSYS software. The amount of juice was 3000 kg/h, and its concentration was raised from 10 to 50 °Brix. Four evaporator layouts were estimated and optimized: single-effect, modified single-effect, forward triple-effect, and triple-effect in parallel. It is a study of the effect of the temperature of saturated steam (120–300 °C) used to concentrate the juice and the pressure of the product (15–50 kPa) on the mass flow rate of steam required, economy, and overall heat transfer coefficient times area (UA) of the evaporator. The best operating conditions for each type of evaporation system were 15 kPa of the product’s pressure for all types of evaporators, 192, 240, 182, and 210 °C of the single-effect, modified single-effect, forward triple-effect, and parallel triple-effect, respectively. These operating conditions are equivalent to the steam required, economy, UA, and steam cost as follows: for each type, they were (3075, 338.4, 1224, and 1100 kg/h), (0.78, 7.1, 1.96, and 2.15), (40,182, 74,505, 539,987, 152,173 kJ/°C h), and (12.68 × 103, 12.76 × 103, 12.65 × 103, and 12.73 × 103 $/h), respectively.

Experimental investigation of generating superheated steam using a parabolic dish with a cylindrical cavity receiver: A case study

Abstract This study uses solar energy to convert steam from a saturated to a superheated state using a solar steam superheater system. This collector system comprised a parabolic dish with a cylindrical cavity. The parabolic dish is of 2 m diameter and 0.83 m focal distance, covered with a reflective surface made of 1,283 rectangular pieces of mirrors, each of 3.5 cm × 4 cm that were fixed in place with glue type (FnTai). The receiver is a stainless-steel cylindrical cavity having a diameter of 17 cm and a length of 25 cm. A helical copper coil with a diameter of 10 mm and a length of 6 m was inserted inside the cylindrical cavity. The experimental work utilized saturated steam produced separately from an auxiliary electric boiler system, which was made along with other system components. A 0.011 kg/s of saturated steam at a temperature of 112°C enters the copper coil and is heated by the solar radiation reflected by the parabolic dish onto the receiver. As a result, the temperature of the steam is increased to 169.5°C at the receiver outlet. It was found that the collector efficiency is 55.6%. In addition, the convection and radiation heat losses are 12.14 and 10.98%, respectively. Also, the heat losses of (spillage, reflection, and conduction) were estimated to be 21.18%. The mass flow rate and pressure of the saturated steam from the boiler and entering the receiver affected the superheated steam production process. The process of superheating the steam, coupled with the subsequent improvement in thermal performance, indicates an increased efficiency of the collector. This is achieved by boosting the generation of useful heat and mitigating heat losses.

A COMBINED DESALINATION AND REFRIGERATION SYSTEM BASED ON SOLAR EJECTOR TECHNOLOGY

A solar ejector technology-based system that combines refrigeration and desalination was investigated for the present study. The proposed model combined a conventional ejector refrigeration system with a desalination unit to examine its ability to achieve cooling as well as produce clean water. An analytical model of the ejector was developed using 1D compressible flow equations based on mass, momentum, and energy conservation. The output from the ejector was then fed to a 1D heat exchanger model to compute the clean water production. The analytical model was implemented using the Matlab platform. A 2D axisymmetric numerical simulation of the ejector system was also performed to comprehend the internal flow structures. It has been observed that the entrainment ratio, which is the ratio of the vapor refrigerant's mass flow rate to the motive steam's mass flow rate, falls as the stagnation temperature of the motive steam increases. It was noted that the coefficient of performance (COP) rises as the evaporator temperature rises, but it is seen to decline with the rise in generator temperature. The amount of desalinated water that can be produced with the system was also explored. It was observed that the production of desalinated water increased proportionally with the rise in generator temperature. At a generator temperature of 140°C, the system obtained clean water at a rate of about 2.9 g/s, which corresponds to a 24.5% mass flow rate of the input steam.

Dynamic characteristics and economic analysis of a coal-fired power plant integrated with molten salt thermal energy storage for improving peaking capacity

Improving the peaking capacity of coal-fired units is imperative to ensure the stability of the power grid, thus facilitating the grid integration and popularization of large-scale renewable energy. To address this issue, this paper introduces a new concept that combines molten salt energy storage with coal-fired power plants. The proposed design consists of extracting a portion of steam from the turbine side and adjusting the extracted steam mass flow rate by adjusting the valve opening to improve the dynamic characteristics of a coal-fired power plant in terms of both increasing the peaking depth and peaking speed. A coal-fired boiler with integrated thermal energy storage was dynamically modeled using Dymola and its accuracy was verified. The results show that the highest equivalent round-trip efficiency is achieved by extracting from the main steam and discharging into the feedwater during charging process and from reheater1 and discharging into the feedwater during discharging process; The peaking potential during charging and discharging is 12.83 % Pe and 6.86 % Pe respectively, with maximum peaking rates of 9.27 % Pe/min and 5.11 % Pe/min respectively, and the optimal peaking method is also proposed according to the different peaking situations. The total cost of equipment and materials to retrofit the conventional coal-fired units was 19,948,193 USD and the levelized cost of delivery was 151.29 USD/MWh.

Exergy analysis of a steam power station in a sulfuric acid plant

This study presents energy and exergy analyses of a Steam Power station of a sulfuric acid plant. A heat recovery system is implemented in the plant to recover waste heat from an exothermic chemical reaction of the sulfuric acid production process. This research aims to analyze system components to determine where energy losses are. A mathematical model was developed using the EES software to perform the calculations. Exergy analysis is computed for real ranges of the main operating parameters. It was found that the key sources of exergy destruction are the waste heat boiler 41 %, followed by the heaters 24.7 % then the steam turbine 18.6 %, and the condenser 13.8 % of the total exergy destruction. The 2nd law efficiency obtained for the waste heat boiler, the steam turbine, and the condenser is 80 %, 82 %, and 37.4 % respectively, while the overall plant exergy efficiency is 68.7 %. The effect of varying different parameters such as reference environmental temperature on main plant components is investigated. The effect of increasing steam inlet temperature, pressure, and mass flow rate on plant exergetic efficiency and exergy destruction is also presented. Results showed that lowering condenser vacuum pressure leads to a 7 % improvement in overall system exergetic efficiency.

4-E analysis and multiple objective optimizations of a novel solar-powered cogeneration energy system for the simultaneous production of electrical power and heating

Owing to its natural and rich advantages, exploration of solar energy technology has become increasingly popular in recent years to counter the growing crude oil prices. However, its universal adoption is still limited, not only due to environmental restrictions but also due to lower overall efficiency. Rankine cycle is optimised to conduct 4-E (Exergy, Energy, Economic and Ecological) analysis. Furthermore, three sets (R-113, R-11, and R-1233zd) of refrigerants are prioritised and ranked on the basis of 4-E analysis as outcomes. The contemporary study addressed all critical factors and explains the impact of solar irradiance, mass flow rate of molten salt and steam, turbine inlet pressure, and turbine inlet temperature which are eventually weighed and prioritised using combined multi-criteria decision making (MCDM) techniques. The energy efficiency, exergetic efficiency, power/ cost of electricity, and ecological emissions are taken as the indicators of the combined cycle, respectively. The energy efficiency of the hybrid system is improved to 75.07% after including cogeneration cycle, with an increment of 54.58%. In comparison to conventional thermal powerplant setups, the power/cost of electricity and ecological efficiency have been reduced by 68% and upgraded by 16%, correspondingly. Direct normal radiation is the most critical factor followed by turbine inlet temperature. Further, the result indicates that maximum exergy destruction that occurs in the central receiver declines to 39.92%, followed by heliostat and steam turbine which was 27% and 9.32% respectively. In conclusion, the hybrid cycle can furnish cheaper electricity, with lower carbon imprint in sustainable manner with better efficiency.

Study on reduction of pressure oscillation in low-velocity steam jet condensation

To mitigate the high-amplitude pressure oscillations generated during the steam low-speed jet condensation process and reduce the risk of dynamic load damage to the suppression pool and its adjacent facilities, this study designed a temperature-rising cylinder scheme based on the characteristics of low-speed steam jet condensation pressure oscillation and studied the mitigation effect of this scheme through experiments. The experimental results showed that this scheme could effectively reduce the time of low-velocity steam jet condensation in the high-amplitude pressure oscillation region. For instance, at a steam mass flow rate of 30 kg/m2s, the time was reduced from 6300 s to 700 s, which significantly improves the safety of the pool and nearby facilities. Moreover, the scheme does not affect the suppression ability of the pool and can ensure the long-term effective operation of the suppression system.

Enhancing conventional steam power plant performance through feed water heating repowering

ABSTRACT Repowering of old steam power plants is a viable solution to increase power and improve efficiency. This study investigates the feasibility of feed water heating repowering for the Neka steam power plant by considering the influences of steam mass flow rate on the condenser performance and the heat rate of the new cycle. Energy and exergy analyses were conducted using the first and second laws of thermodynamics and heat transfer relations in each scheme. The effect of increasing the steam mass flow rate on the performance of the condenser and the cycle was also investigated. The repowered cycle was simulated using Thermoflow software, and the results were validated with small errors. The results showed that replacing low and high-pressure heaters with new heat exchangers increased the power of the steam unit and the repowered cycle, energy, and exergy efficiencies by 15.7%, 49.3%, 5.93%, and 2.17%, respectively. Although the condenser pressure increased by 19 millibars, leading to a 0.63% increase in the heat rate, the total heat rate of the repowered cycle improved by 4.62%. Overall, the findings demonstrate that feed water heating repowering can be an effective strategy to increase the efficiency and power of conventional steam power plants.

Analysis of Combustion of a Steam Boiler with Chips and Bark as Fuel

PT. Medco is a business entity engaged in managing industrial plantation forests and one of the company’s branches is in South Papua—Merauke. This company manages wood to be processed into raw materials for paper and other purposes. Timber production activities that produce waste in very large volumes, these wastes still have a high calorific value which their utilization will produce fuels that can be used, one of which is as fuel for boilers for power generation. This study uses a qualitative method where research is conducted to obtain the necessary data to then be analyzed again by calculating combustion using the British Thermal Unit (BTU) analysis method. Preliminary data required for qualitative analysis include operational and technical steam boiler data. The fuel used in the combustion process is wood chips and bark obtained from production residue or what can be called waste. The results of the calculation of the combustion process in the 1 × 7 MW steam boiler (PLTU) PT. Medco shows Carbon (C) 34.47%, Hydrogen (H2) 4.22%, Sulfur (S) 0.06%, Oxygen (O2) 30.75%, Nitrogen (N2) 0.22%, Water (H2O) 27.80%, Ash 2.48% and a calorific value of Hight Heating Value (HHV) 9160.8 Btu/lb, Excess water 30% and fuel consumption of 16784 kg/h. The mass flow rate of steam is 35 tons or 66150 lb/h with a combustion gas temperature of 1490 °C and an adiabatic temperature formed in the furnace of 1075 °C. Primary air requirement is 43594.91 kg of air and the secondary air requirement is 18727.24 kg of air. The heat energy that is put into the steam boiler from the results of the combustion process is 98.24 × 106 BTU/h or 28.77204 MW, the heat that is utilized for the process of changing the fluid phase of the liquid in the water pipes along the boiler wall is only 83.038 × 106 BTU/h or 24.31975425 MW. So, it can be concluded that there is an energy loss of 15.2020 × 106 BTU/h or 4.452286 MW.

Fluidized bed chemical looping gasification of sewage sludge with bituminous coal to produce H2 rich syngas: An examination on fuel synergy and reaction conditions

Chemical looping gasification (CLG) is an efficient and economical solution to convert organic solid waste into hydrogen-rich syngas for fossil fuel substitution. In this work, chemical looping co-gasification (CLCG) of sewage sludge (SS) and bituminous coal (BC) with hematite as the oxygen carrier was examined in a fluidized bed. The SS-BC CLCG exhibited significant fuel synergy compared to the SS/BC CLG, enhancing the gasification efficiency and carbon conversion. The effects of several key operating variables including SS blending ratio, reaction temperature, and steam mass flow rate on CLCG performance were investigated and the optimum conditions were 20 wt% SS, 900 °C with a steam mass flow rate of 0.6 g/min. Moreover, a cyclic CLCG test was also performed to evaluate the stability of oxygen carrier reactivity and gasification performance at optimized operating conditions. After 13 cycles, the hematite still presented good or even improved performance with gasification efficiency of 80.94 %, syngas yield of 2.10 Nm3/kgfuel, and carbon conversion of 93.73 %. The improved porous structure and the ash catalyst effect were responsible for the promoted performance of the natural hematite oxygen carrier with increasing cycles. It is concluded that CLG is a promising technology to provide high-quality hydrogen-rich syngas from SS and BC mixtures.

Characterization and optimization of pore structure and water adsorption capacity in pinecone-derived activated carbon by steam activation

Activated carbon, due to its notable porosity and cost-effectiveness, emerges as a promising desiccant material. This research delves into the utilization of pinecones as a precursor for the production of activated carbon through steam activation. The resultant activated carbon samples presented a porous structure and exhibited a high water adsorption capacity, with the highest adsorption capacity reaching 0.35 kg/kg, placing it in competition with commercial silica gel. Various experimental parameters were systematically manipulated during the production process to optimize both the pore structure and water adsorption capacity of the activated carbon samples. Elevating the carbonization temperature from 700 °C to 900 °C proved effective in enhancing pore distribution and elevating water adsorption capacity. Furthermore, higher activation temperatures contributed to the formation of additional mesopores and macropores, possibly attributable to micropore enlargement through steam activation. Nevertheless, these elevated activation temperatures resulted in an undesired increment in mesopores concerning water adsorption. The extension of activation time led to increased micropore formation, albeit with concurrent disruption, culminating in heightened total pore volume and surface area. This extension shifted the water adsorption-desorption isotherm to higher relative pressure ranges, accompanied by a larger hysteresis loop. Moreover, an increased steam mass flow rate was found to enhance the pore structure and water adsorption capacity of the activated carbon. The activated carbons exhibited sigmoid-shaped isotherms, signifying their suitability for both open-cycle and closed-cycle adsorption systems.

Thermodynamic analysis and operation strategy optimization of coupled molten salt energy storage system for coal-fired power plant

The growing use of renewable energy requires greater flexibility than existing thermal power units. A steam-extraction system was developed to adjust the power output during a low-load period. The incorporation of molten-salt energy storage enables the decoupling of the boiler from the turbine, thus enabling the regulation of the output power during low-load operation. And the impact of key parameters on the performance of coal-fired units is analyzed to find the suitable operation parameters for the existing coal-fired power plant. The performance parameters of the system are optimized by a multi-objective grey wolf optimization algorithm, which conducts trade-off optimization between roundtrip efficiency and exergy efficiency to identify the Pareto Front for a certain range of extracted steam mass flow rates, hot-tank temperatures, and split ratios. The typical operating conditions of the combined system were analyzed, and a peak capacity of 64.1 MW and a power change factor of 17.33 % were achieved. The discharging process reduced the heat consumption of the unit, while the peak capacity and heat consumption of the combined system were used as objective functions to optimize the charging process. The peak capacity, power enhancement rate, and net profits of the system improved 1.12, 1.42, and 1.27 times after optimization. Heat consumption and efficiency were reduced by 2.61 % and 3.96 %. The molten-salt thermal storage system achieved a synergistic improvement in the operational flexibility and thermal efficiency of the thermal power system.

Effect of diameter and inclination of steam injection pipe on chugging dynamics in direct contact condensation

Low mass flux of steam and high degree of subcooling are the prominent factors for occurrence of unstable direct contact condensation, commonly known as chugging, when steam is injected into a subcooled water pool. Such an arrangement is typically used in the pressure suppression pool of the primary containment vessel in a boiling water reactor. With an attempt to identify the conditions of minimum pressure oscillations during the chugging regime, the present study investigates the effect of internal diameter (0.5–1 in.) and inclination (8.75˚) of steam injection pipe on steam bubble dynamics, pressure transients and heat transfer characteristics at different steam mass flow rates (5–25 kg/hr) and submergence depths of steam pipe (1–13 cm) within the water pool. The study reveals that the condensation cycle time decreases with a decrease in the internal diameter of the pipe. Furthermore, the frequencies of fluctuations in the interfacial area of the steam bubble and pressure transients in the steam pipe exhibit an increasing trend with an increase in steam mass flow rate and a decrease in internal diameter of the steam injection pipe. The chugging frequencies in the inclined and vertical orientation of steam injection pipe lie within the range of 0.5–3 Hz. The average heat transfer coefficient increases with an increase in the internal diameter of pipe and steam mass flow rate. The amplitude of pressure oscillations has decreased significantly whereas heat transfer coefficient has increased marginally upon changing the orientation of steam injection pipe from vertical to inclined. Therefore, smaller diameter and inclined orientation of steam injection pipe are favourable for mitigation of pressure oscillations in applications of direct contact condensation.