Conventional Steam Rankine Cycle Research Articles

Thermo-economic and environmental analyses of supercritical carbon dioxide Brayton cycle for high temperature gas-cooled reactor

The supercritical carbon dioxide (sCO2) Brayton cycle demonstrates special advantages for the high temperature gas-cooled reactor (HTGR) delivered into commercial operation recently in China, with its high efficiency, compactness, flexibility, and safety compared to the conventional steam Rankine cycle. However, the large temperature rise of 500 °C for the HTGR brings new challenges for the design of sCO2 cycle. Here, we present the first study on the thermodynamic, economic, and environmental performance of the HTGR-sCO2 system using the energy, exergy, economic, and environmental (4E) evaluation method. The cascaded sCO2 cycle made up of two independent sCO2 cycles is proposed, which are arranged in series on the cold side of reactor heat exchanger. We show that the cascaded sCO2 cycle can utilize the heat absorption from HTGR effectively by optimizing the cycle configurations of top and bottom sub-cycles. The improved cascaded sCO2 cycle minimizes the exergy loss, and increases the thermal efficiency to 43.2% when compared to the steam Rankine cycle of HTGR demonstration power plant and the single recompression cycle. By balancing the fixed-capital investment cost with the net power, the levelized cost of electricity can be reduced to 0.0283$/kWh. The life-cycle GHG emission intensity of HTGR-sCO2 systems is about 6.5gCO2,eq/kWh, which is much smaller than that of coal-fired power plants, suggesting a great potential for decarbonization of the HTGR-sCO2 system. Our study may find implications for the advancement of the sCO2 Brayton cycle in next-generation nuclear power plant.

Comprehensive analysis of a high temperature solar powered trigeneration system: An energy, exergy, and exergo-environmental (3E) assessment

In the present work, helium serves as the primary working fluid within the supercritical Brayton cycle, employed to generate power through a solar power tower system. The conventional Brayton cycle for recovering the wasted heat is combined with a cascaded vapor absorption-compression refrigeration system to increase the overall system’s performance. Additional benefits of this integrated system include the ability to supply enhanced heating and cooling for food storage applications at lower temperatures. A comprehensive analysis of the combined system was conducted based on exergy, energy, and exergo-environmental (3E) factors a using computational technique engineering equation solver. The combined system’s energy, exergy efficiency, and power output were determined to be 28.82%, 39.53%, and 14.865 kW, respectively. The coefficient of performances for cooling and heating were observed as 0.5391 and 1.539 respectively. Approximately 78.18% of the total exergy destruction within the entire plant can be attributed to the solar subsystem, which amounts to 22.763 kW. As direct normal irradiance rises, the environmental impact index decreases from 1.6504 to 0.6801, while the system’s environmental stability factor improves, increasing from 0.3773 to 0.5952. Moreover, the parametric assessment highlights the substantial influence of heliostat and receiver efficiencies, as well as the helium turbine’s inlet temperature, on the trigeneration system’s performance. In addition, compared to previously published research, the current proposed system outperforms supercritical CO2 cycle systems and the conventional steam Rankine cycle systems.

Thermodynamic Modelling, Technical and Operational Issues of Supercritical Carbon Dioxide Power Generation Cycles for Industrial Applications: A Literature Review

Future electricity production systems will be able to harness the power of supercritical carbon dioxide (S-CO<sub>2</sub>) as it moves through thermal cycles. It serves the same goal as sources of energy such as fossil fuels, nuclear power, solar power, and the recovery of waste heat (or surplus heat from industrial processes). When the heat source temperature is between 350°C and 800°C, CO<sub>2</sub> as a working fluid exhibits excellent thermal efficiency. Its novel technological benefits over conventional steam Rankine cycles, such as the use of small turbo gear and compact heat exchangers, have captured the attention of scientists. It has excellent operational flexibility and may induce significantly cheaper energy costs. Aligned with these goals, this paper presents a panoramic work, exploring the current state of the art of S-CO<sub>2</sub> power generation, with a particular emphasis on the technical and operational perplexities. After providing a comprehensive overview of the thermodynamic principles that underpin this study, the foundation is established for an engaging discourse on the continuous research and development of supercritical carbon dioxide (S-CO<sub>2</sub>) cycles in power generation. Upon delving into the thermodynamic facets of CO<sub>2</sub> that propel this investigation, the spotlight is cast upon dissecting the existing state of research and development of S-CO<sub>2</sub> cycles in power generation before transitioning into encapsulating the principal domains of application and noteworthy thermodynamic modelling inquiries of S-CO<sub>2</sub> cycles. The present advancements and hurdles within the primary application areas are succinctly summarized, while future research trends are identified.

Parametric and economic analysis of high-temperature cascade organic Rankine cycle with a biphenyl and diphenyl oxide mixture

High-temperature organic Rankine cycle (ORC) systems have the potential to improve the heat-to-power conversion efficiency and expand the temperature range for heat recovery, heat battery and solar power generation. Restricted by the critical temperature of the commonly used organic working fluids, the current ORC technology has a maximum working temperature of around 300 °C. This paper proposes a high-temperature cascade organic Rankine cycle (CORC) system using a biphenyl and diphenyl oxide (BDO) mixture as the top cycle fluid and conventional organic fluids for the bottom cycle. The BDO mixture has excellent heat stability over a wide operation condition from 12 °C to 400 °C in single-phase and binary-phase states. However, at present a detailed study on the ORC using the mixture is lacking. In this paper, a parametric analysis of the high-temperature CORC system is conducted. A mathematical model based on the equivalent hot side temperature is built to simulate the ORC efficiency. The thermodynamic and exergetic performances of the novel CORC system under different bottom ORC working fluids, mixing chamber temperatures, evaporation temperatures, and condensation temperatures are investigated. The results show the maximum thermal efficiency of the CORC system is 38.74 % and 40.26 % at top ORC evaporation temperatures of 360 °C and 400 °C. The largest exergy destruction takes place in the heat exchanger between the top and bottom ORCs. Besides, the heat regenerators have a significant impact on the thermodynamic performance and can elevate the CORC efficiency by about 4 %. The proposed system has a higher efficiency and a lower equipment cost than conventional steam Rankine cycle at 400 °C while eliminating the challenges of wet steam turbines.

Thermodynamic and techno-economic comparisons of the steam injected turbocompounding system with conventional steam Rankine cycle systems in recovering waste heat from the marine two-stroke engine

This paper aims at evaluating the merits and drawbacks of the steam injected turbocompounding (SIT) system proposed in the authors’ previous work. First, thermodynamic processes of the SIT systems and conventional steam Rankine cycle systems designed with single-pressure and dual-pressure configurations are introduced, followed by detailed techno-economic descriptions. Based on a 4.9 MW marine two-stroke engine, detailed thermodynamic and techno-economic comparisons among seven waste heat recovery systems are performed. It is concluded that both optimizing the evaporation pressure and adopting the dual-pressure steam generation configuration have almost no positive effect on the thermodynamic performance of the SIT system. The evaporation pressure also plays a less important role in determining the economic indexes of the SIT system. With the fuel-saving potential of 5.2% under the design condition and a depreciated payback period of 4.7 years, the SIT system is a good alternative to the conventional turbocompounding system and the steam Rankine cycle system. The dual-pressure SIT system is not recommended due to its long payback period. Since tankers are more likely to operate at part loads, the payback period of steam-based waste heat recovery systems increases by around 30% compared to that evaluated based on the container operational profile.

Assessment and working fluid comparison of steam Rankine cycle -Organic Rankine cycle combined system for severe cold territories

In this work, organic Rankine cycle (ORC) is employed to expand the available temperature region of the conventional steam Rankine cycle (SRC) in severe cold territories. The feasibility of the proposed steam Rankine cycle -Organic Rankine cycle combined system is investigated and verified. Working fluids are compared and screened, the matching scheme of different working fluids suitable for different working conditions and objects (thermodynamic or economic performance) are obtained. The results show that the net power increment (NPI) of the combined system increases with the decrease of the condenser outlet temperature (CT). The NPI of ORC system can be effectively improved by adding a regenerator. For wet working fluids, when the evaporating pressure of ORC system is close to the critical pressure of working fluid, there exists an optimal superheat degree with maximum NPI of the system. The combined system using ammonia and R600 as working fluid has the largest NPI values. When the CT of SRC is higher than 90 °C, the Rankine cycle using ammonia as working fluid has better performance. When the CT of SRC is less than 90 °C, the regenerative ORC system using R600 as working fluid has a better performance.

Numerical Investigation of a modified Kalina cycle system for high-temperature application and genetic algorithm based optimization of the multi-phase expander's inlet condition

As an alternative to the conventional steam Rankine Cycle, Kalina Cycle has witnessed a growing interest over the past years for high-temperature applications (A working fluid temperature of 500°C at the turbine inlet). However, the possibility of implementing an additional multi-phase expander on the weak ammonia-water solution loop of the Kalina cycle was hardly analyzed in the available literatures. In this research, two novel Kalina cycles (Kalina cycle-12A and Kalina cycle-12B) have been presented by integrating a multi-phase expander in addition to the turbine installed downstream of the Kalina evaporator. For Kalina cycle -12A, this additional multi-phase expander is positioned downstream of the Kalina separator and on the weak ammonia-water solution loop for Kalina Cycle-12B. A detailed mathematical model based on the thermodynamic laws has been developed to solve and optimize the Kalina Cycles. The influence of critical decision parameters, specifically the ammonia concentration on working fluid and evaporation pressure, were investigated. The optimization was performed based on the objective to maximize the net power output from the multi-phase expander under steady-state operating conditions. When the performance of the proposed Kalina cycles was compared with the conventional Kalina Cycle-12, both of them demonstrated superior performance, i.e., net power output and peak thermal efficiency increased by a maximum value of 3.23% for the proposed Kalina Cycle-12A cycle and 3.94% for the proposed Kalina Cycle-12B cycle. In terms of second law efficiency, Kalina Cycle-12A is 3.68 percent more efficient than Kalina Cycle-12, while Kalina Cycle-12B is 4.04 percent more efficient. Furthermore, 2nd law analysis also reveals, maximum destruction of exergy occurs at the condensers of the cycles.

High-temperature molten-salt thermal energy storage and advanced-Ultra-supercritical power cycles

The work explores the opportunities offered by higher temperature heat transfer/heat storage fluids, and higher temperature power cycles, in higher concentration solar thermal power plants. The goal is to design a renewable energy plant able to supply fully dispatchable electricity to the grid at a cost, inclusive of dispatchability, better than using wind and solar photovoltaic with external energy storage by batteries. By increasing the receiver/hot tank temperature from 565-575 to 730°C, the efficiency of the thermal cycle increases by 30% vs. current plants working with conventional steam Rankine cycles (thermal efficiency η∼52% vs. present η∼40%). The proposed design permits 24/7 electricity production at the rated power of the turbine practically all year-round. In the hypothesis of no cost penalty for the use of a novel heat transfer and heat storage fluid, and of the higher pressure and temperature of the power cycle, that is a reasonable long term goal of an industrialized and mass-produced solution, the Levelized Cost of electricity may be improved from the 7.29-7.97 ¢/kWh of a current technology 100 MW design of annual average capacity factor 93-95.5%, to the 6.18-6.68 ¢/kWh of a 126 MW design of annual average capacity factor 94.9-97.7% of the novel technology. The work demonstrates the benefits of internal thermal energy storage by molten salt in supplying energy to renewable energy only grid, and the opportunity to further evolve the basic design now employed towards higher temperatures.

Performance and size comparison of two-stage and three-stage axial turbines for a nitrogen gas Brayton cycle coupled with a sodium-cooled fast reactor

A nitrogen (N2) Brayton cycle is considered as an alternative to the conventional steam Rankine cycle to overcome essential risk during pressure boundary rupture accidents with sodium-water reaction in a steam-generator of a sodium-cooled fast reactor (SFR). The objectives of this study are to estimate the turbine performances after proposing three-dimensional (3-D) blade designs and to suggest an option of detailed turbine design for N2 Brayton cycle-SFR applications. A free-vortex design method was applied in the 3-D design. Three candidates, including two- and three-stage designs, were selected from the Smith charts. Aerodynamic losses were investigated and compared through computational fluid dynamics analyses for the cases selected above. According to the results, rotor blade with milder curvature increased proportions of secondary and tip leakage losses among the total aerodynamic loss. When comprehensively considering the turbomachinery size and cycle thermal efficiency, the size of the two-stage turbine could be reduced to under 55% of the three-stage turbine size, resulting in no significant decrement of the cycle efficiency.

Optimized operation of recompression sCO2 Brayton cycle based on adjustable recompression fraction under variable conditions

The use of supercritical carbon dioxide (sCO2) cycle has been proposed as a promising alternative to replace conventional steam Rankine cycle. This study entails the development of a power cycle model to assess the impact of fluctuations on the heat source and environmental conditions on a recompression sCO2 Brayton cycle during off-design operation. Two operational strategies are tested during off-design operation, including fixed recompression fraction and adjusted recompression fraction. It is found that a superior performance is obtained when the recompression fraction is adjusted according to heat addition and ambient temperature variations. The variations of the heat addition have a greater impact than ambient temperature on the cycle’s performance, showing up to 70% greater cycle efficiency when the heat addition ratio is reduced to 30%. In some conditions, the recompression cycle operates similarly to a regenerative cycle, hence no recompression fraction is required when the heat addition ratio is lower than 55%. The influence of the ambient temperature is more relevant when a dry cooler is used, and in this case, it is important to include a detailed cooler’s model in order to account for the variability of the thermophysical properties of the carbon dioxide close to its critical point.

Numerical and Experimental Thermal–Hydraulic Performance Analysis of a Supercritical CO2 Brayton Cycle PCHE Recuperator

The supercritical carbon dioxide (s-CO2) power cycles are mostly preferred due to their high thermal efficiency and power density in comparison with the conventional steam Rankine cycles. In this study, a printed circuit heat exchanger recuperator which is an important component in s-CO2 recuperative Brayton cycles is numerically and experimentally examined. Within this scope, thermal–hydraulic and structural analyses of a proposed PCHE have been carried out. The sub-heat exchanger model, which uses the output of a sub-heat exchanger as the input of the next one, is applied in the numerical thermal–hydraulic design by subdividing the printed circuit heat exchanger. From the results of this analysis, a heat exchanger is structurally designed and fabricated in compliance with ASME BPVC rules. The fabricated 25 kW printed circuit heat exchanger has reached to 1000 m2/m3 compactness value with 1 mm thickness of fin and 1.5 mm thickness of plate. The experiments were performed on a test bench working with supercritical carbon dioxide at high pressures. The results of the experimental and numerical analyses are in good agreement. The maximum difference between the heat loads and the effectiveness values is 4.9% and 5.4%, respectively. The difference between the overall heat transfer coefficients is 1.2%. It is shown that using the sub-heat exchanger model provides highly accurate printed circuit heat exchanger designs.

Energy-exergy efficiencies analyses of a waste-to-power generation system combined with an ammonia-water dilution Rankine cycle

This research investigates a waste-to-energy system combined with an ammonia dilution Rankine cycle. It uses cooling-energy recycling of dissolved natural-gas to reduce the working-fluid temperature. This project includes providing a solution for calculating the calorific value of waste by proposing a novel waste incineration power generation combined cycle. The energy-exergy analyses is utilized to study the effects of critical parameters on the efficiency and determines the points with higher efficiencies than the conventional steam Rankine cycle. Engineering Equation Solver (EES) software is used for delivering such accurate outlines. The ammonia dilution distillation temperature and the turbine's inlet and outlet pressures are considered vital parameters. The results revealed that mutually energy and exergy efficiencies rise as the ammonia solution's distillation temperature decreases. Besides, by increasing the inlet turbine pressure, the energy and exergy efficiencies increase. In addition, as the output pressure of the turbine increases, the combined cycle's energy efficiency decreases while the exergy efficiency increases.

Proposal and performance assessment of a combined system based on a supercritical carbon dioxide power cycle integrated with a double-effect absorption power cycle

The supercritical carbon dioxide Brayton cycle is a promising energy conversion approach to provide high efficiency for a wide range of applications, and it is considered to be more potent and appropriate alternative to the conventional steam Rankine cycle for the power generation. To take advantage of the attractive physical and transport properties near the critical point of the carbon dioxide, a large amount of heat is released to the heat sink before the carbon dioxide entering the compressor. In this study, a novel double-effect absorption power cycle is proposed to reuse the waste heat from the supercritical carbon dioxide power cycle for further improving the overall performance. Six decision variables are selected to perform the parametric analysis for determining the effect of these decision parameters on the performance of the proposed system, and the further parametric optimizations, exergy analysis and the comparative study are conducted for the proposed system and other carbon dioxide based system to reveal the superiority in overall performance for the proposed system. The results indicate that the major exergy destruction occurs in the heat source and the heat sink of the single supercritical carbon dioxide system. The exergy destruction in the heat sink can be effectively reduced by 16.23% by integrating the supercritical carbon dioxide system with absorption power cycle, and it can be further reduced by 3.87% by replacing absorption power cycle with the proposed double-effect absorption power cycle. In addition, compared with the single supercritical carbon dioxide system and the combined system integrating supercritical carbon dioxide power cycle with absorption power cycle, the exergy efficiency improvement of 10.94% and 3.00% and the reduction in the total product unit cost by 7.97% and 2.66% can be obtained by the proposed system, respectively.

Proposal and Thermodynamic Assessment of S-CO2 Brayton Cycle Layout for Improved Heat Recovery.

This article deals with the thermodynamic assessment of supercritical carbon dioxide (S-CO2) Brayton power cycles. The main advantage of S-CO2 cycles is the capability of achieving higher efficiencies at significantly lower temperatures in comparison to conventional steam Rankine cycles. In the past decade, variety of configurations and layouts of S-CO2 cycles have been investigated targeting efficiency improvement. In this paper, four different layouts have been studied (with and without reheat): Simple Brayton cycle, Recompression Brayton cycle, Recompression Brayton cycle with partial cooling and the proposed layout called Recompression Brayton cycle with partial cooling and improved heat recovery (RBC-PC-IHR). Energetic and exergetic performances of all configurations were analyzed. Simple configuration is the least efficient due to poor heat recovery mechanism. RBC-PC-IHR layout achieved the best thermal performance in both reheat and no reheat configurations ( = 59.7% with reheat and = 58.2 without reheat at 850 °C), which was due to better heat recovery in comparison to other layouts. The detailed component-wise exergy analysis shows that the turbines and compressors have minimal contribution towards exergy destruction in comparison to what is lost by heat exchangers and heat source.

Potential of Organic Rankine Cycles for Unmanned Underwater Vehicles

Steam Rankine cycles are typically employed as the power system for Unmanned Underwater Vehicles, but with the problem of low system efficiency. In this paper, Organic Rankine Cycles are proposed as an alternative, where the required output power is of the order of 10 kW. The working conditions and associated sizing constraints for power cycles operating at underwater environments are first detailed. The small-scale axial turbine is specifically designed for different operating conditions and incorporated into the system thermodynamic model. Using the established thermodynamic model for turbine and heat exchangers, various organic fluids are scrutinized to maximize system efficiency and to ensure the sizing constraint as encountered at underwater environment. Numerical results show the high-temperature dry fluid with trans-critical cycles can largely enhance system efficiency. The system efficiency of 25.32% and 23.01% is obtained using Cyclohexane and Toluene, respectively, while the sizing constraints are also satisfied. This corresponds to the increase of 6.57%–8.87% in terms of system efficiency compared to conventional steam Rankine cycles. Parameter studies are also performed to study the influence of pinch temperatures on system performance. The work provides the insight into the potential application of organic Rankine cycles for underwater vehicles.

Thermal performance and economic analysis of supercritical Carbon Dioxide cycles in combined cycle power plant

A closed-loop, indirect, supercritical Carbon Dioxide (sCO2) power cycle is attractive for fossil-fuel, solar thermal and nuclear applications owing to its ability to achieve higher efficiency, and compactness. Commercial Gas Turbines (GT’s) are optimised to yield maximum performance with a conventional steam Rankine cycle. In order to explore the full potential of a sCO2 cycle the whole plant performance needs to be considered. This study analyses the maximum performance and cost of electricity for five sCO2 cascaded cycles. The plant performance is improved when the GT pressure ratio is considered as a design variable to a GT to optimise the whole plant performance. Results also indicate that each sCO2 Brayton cycle considered, attained maximum plant efficiency at a different GT pressure ratio. The optimum GT pressure ratio to realise the maximum cost reduction in sCO2 cycle was higher than the equivalent steam Rankine cycle. Performance maps were developed for four high efficient cascaded sCO2 cycles to estimate the specific power and net efficiency as a function of GT turbine inlet temperature and pressure ratio. The result of multi-objective optimisation in the thermal and cost (c$/kWh) domains and the Pareto fronts of the different sCO2 cycles are presented and compared. A novel sCO2 cycle configuration is proposed that provides ideal-temperature glide at the bottoming cycle heat exchangers and the efficiency of this cycle, integrated with a commercial SGT5-4000F machine in lieu of a triple-pressure steam Rankine cycle, is higher by 1.4 percentage point.

Experimental investigation of thermal-hydraulic performance of discontinuous fin printed circuit heat exchangers for supercritical CO2 power cycles

The supercritical carbon dioxide (sCO2) Brayton cycles have the potential to attain higher cycle efficiencies than the conventional steam Rankine cycles. Using compact diffusion-bonded heat exchangers for thermal recuperation in sCO2 Brayton cycles can lead to cost-effective, simple, and compact cycle footprint. This study focuses on the experimental thermal-hydraulic performance evaluation of a set of chemically etched discontinuous offset rectangular and airfoil fin surface patterns for use in diffusion bonded heat exchangers. Local and average heat transfer coefficients and pressure drops were measured for a wide range of operating conditions relevant to the sCO2 Brayton cycles. Empirical correlations for the friction factor and the Nusselt number are proposed based on the experimental data. The friction factor correlations were able to reproduce the experimentally measured pressure drops with a standard deviation of ±13.5% and ±14.7% for the discontinuous offset rectangular and airfoil fins respectively. Nusselt number correlations were able to reproduce the experimental Nusselt numbers with standard deviation of ±15.4% and ±8% for the discontinuous offset rectangular and airfoil fins respectively.

Thermal Energy Processes in Direct Steam Generation Solar Systems: Boiling, Condensation and Energy Storage – A Review

Direct steam generation coupled is a promising solar-energy technology, which can reduce the growing dependency on fossil fuels. It has the potential to impact the power-generation sector as well as industrial sectors where significant quantities of process steam are required. Compared to conventional concentrated solar power systems, which use synthetic oils or molten salts as the heat transfer fluid, direct steam generation offers an opportunity to achieve higher steam temperatures in the Rankine power cycle and to reduce parasitic losses, thereby enabling improved thermal efficiencies. However, its practical implementation is associated with non-trivial challenges, which need to be addressed before such systems can become more economically competitive. Specifically, important thermal-energy processes take place during flow boiling, flow condensation and thermal-energy storage, which are highly complex, multi-scale and multi-physics in nature, and which involve phase-change, unsteady and turbulent multiphase flows in the presence of conjugate heat transfer. This paper reviews our current understanding and ability to predict these processes, and the knowledge that has been gained from experimental and computational efforts in the literature. In addition to conventional steam-Rankine cycles, the possibility of implementing organic Rankine cycle power blocks, which are relevant to lower operating temperature conditions, are also considered. This expands the focus beyond water as the working fluid, to include refrigerants also. In general, significant progress has been achieved in this space, yet there remain challenges in our capability to design and to operate high-performance and low-cost systems effectively and with confidence. Of interest are the flow regimes, heat transfer coefficients and pressure drops that are experienced during the thermal processes present in direct steam generation systems, including those occurring in the solar collectors, evaporators, condensers and relevant energy storage schemes during thermal charging and discharging. A brief overview of some energy storage options are also presented to motivate the inclusion of thermal energy storage into direct steam generation systems.

Techno-Economics of Cogeneration Approaches for Combined Power and Desalination From Concentrated Solar Power

For many decades, integration of concentrated solar power (CSP) and desalination relied solely on the use of conventional steam Rankine cycles with thermally based desalination technologies. However, CSP research focus is shifting toward the use of supercritical CO2 Brayton cycles due to the significant improvement in thermal efficiencies. Here, we present a techno-economic study that compares the generated power and freshwater produced from a CSP system operated with a Rankine and Brayton cycle. Such a study facilitates co-analysis of the costs of producing both electricity and water among the other trade-off assessments. To minimize the levelized cost of water (LCOW), a desalination facility utilizing multi-effect distillation with thermal vapor compression (MED/TVC) instead of multistage flash distillation (MSF) is most suitable. The techno-economic analysis reveals that in areas where water production is crucial to be optimized, although levelized cost of electricity (LCOE) values are lowest for wet-cooled recompression closed Brayton cycle (RCBR) with MSF (12.1 cents/kWhe) and MED/TVC (12.4 cents/kWhe), there is only a 0.35 cents/kWhe increase for dry-cooled RCBR with MED/TVC to a cost of 12.8 cents/kWhe. This suggests that the best candidate for optimizing water production while minimizing both LCOW and LCOE is dry-cooled RCBR with MED/TVC desalination.

Optimization and sensitivity analysis of the nitrogen Brayton cycle as a power conversion system for a sodium-cooled fast reactor

The sodium-cooled fast reactor (SFR) is a promising next generation reactor type. Existing prototype generation IV nuclear reactors use a steam Rankine cycle for power conversion. However, the reaction between sodium and water presents a major safety issue in the development of SFR. In this aspect, the nitrogen Brayton cycle can be a suitable alternative to the conventional steam Rankine cycle for SFR. Compared to the steam Rankine cycle, the nitrogen Brayton cycle is relatively simple; further, nitrogen does not react with sodium due to its chemically inert feature. Therefore, a nitrogen Brayton cycle coupled with SFR can be a good combination. In this work, the nitrogen Brayton cycle for KALIMER-600 has been studied. In addition, sensitivity analysis, optimization of the cycle, and the preliminary design of components were performed. Mathematical models for conducting sensitivity analysis of the cycles were developed using FORTRAN. Sensitivity studies were carried out by varying the cycle maximum temperature, turbine inlet pressure, and pressure ratio. The optimized results showed that the cycle efficiency is 38.26%. The preliminary design of components was performed to assess the viability of the proposed system. In order to improve cycle thermal efficiency, sensitivity studies of heat exchanger was performed to understand the effects of printed circuit heat exchanger (PCHE) channel shape. The analysis results show that a significant improvement in cycle efficiency (improve 1.3%) was obtained by changing the PCHE channel shape.