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

Entropy ◽  
2020 ◽  
Vol 22 (3) ◽  
pp. 305 ◽  
Author(s):  
Muhammad Ehtisham Siddiqui ◽  
Khalid H. Almitani
Keyword(s):  
Heat Exchangers ◽  
Heat Recovery ◽  
Exergy Analysis ◽  
Thermodynamic Assessment ◽  
Brayton Cycle ◽  
Efficiency Improvement ◽  
Exergy Destruction ◽  
Power Cycles ◽  
Recovery Mechanism ◽  
The Past

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 ( η t h   = 59.7% with reheat and η t h   = 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.

Simulation and Optimization of Combined Cycle Power Cycles Through HRSG’s Heat Exchangers Arrangement and Parameters for Exergy and Cost

2012 ◽  
Author(s):  
Ravin G. Naik ◽  
Chirayu M. Shah ◽  
Arvind S. Mohite
Keyword(s):  
Power Plant ◽  
Steam Generator ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Second Law Of Thermodynamics ◽  
Combined Cycle ◽  
Heat Recovery Steam Generator ◽  
Exergetic Efficiency ◽  
Power Cycles ◽  
Combined Cycle Power Plant

To produce the power with higher overall efficiency and reasonable cost is ultimate aim for the power industries in the power deficient scenario. Though combined cycle power plant is most efficient way to produce the power in today’s world, rapidly increasing fuel prices motivates to define a strategy for cost-effective optimization of this system. The heat recovery steam generator is one of the equipment which is custom made for combined cycle power plant. So, here the particular interest is to optimize the combined power cycle performance through optimum design of heat recovery steam generator. The case of combined cycle power plant re-powered from the existing Rankine cycle based power plant is considered to be simulated and optimized. Various possible configuration and arrangements for heat recovery steam generator has been examined to produce the steam for steam turbine. Arrangement of heat exchangers of heat recovery steam generator is optimized for bottoming cycle’s power through what-if analysis. Steady state model has been developed using heat and mass balance equations for various subsystems to simulate the performance of combined power cycles. To evaluate the performance of combined power cycles and its subsystems in the view of second law of thermodynamics, exergy analysis has been performed and exergetic efficiency has been determined. Exergy concepts provide the deep insight into the losses through subsystems and actual performance. If the sole objective of optimization of heat recovery steam generator is to increase the exergetic efficiency or minimizing the exergy losses then it leads to the very high cost of power which is not acceptable. The exergo-economic analysis has been carried to find the cost flow from each subsystem involved to the combined power cycles. Thus the second law of thermodynamics combined with economics represents a very powerful tool for the systematic study and optimization of combined power cycles. Optimization studies have been carried out to evaluate the values of decision parameters of heat recovery steam generator for optimum exergetic efficiency and product cost. Genetic algorithm has been utilized for multi-objective optimization of this complex and nonlinear system. Pareto fronts generated by this study represent the set of best solutions and thus providing a support to the decision-making.

Exergy Analysis of Part Flow Evaporative Gas Turbine Cycles: Part 2 — Results and Discussion

2002 ◽  
Author(s):  
Maria Jonsson ◽  
Jinyue Yan
Keyword(s):  
Gas Turbine ◽  
Heat Recovery ◽  
Exergy Analysis ◽  
Compressed Air ◽  
Cycle Performance ◽  
Exergy Destruction ◽  
Exergetic Efficiency ◽  
Recovery System ◽  
Heat Recovery System ◽  
Flow Case

This paper is the second part of a two-part paper. The first part contains an introduction to the evaporative gas turbine (EvGT) cycle and the methods used in the study. The second part contains the results, discussion, and conclusions. In this study, exergy analysis of EvGT cycles with part flow humidification based on the industrial GTX100 and the aeroderivative Trent has been performed. In part flow EvGT cycles, only a fraction of the compressed air is passed through the humidification system. The paper presents and analyzes the exergetic efficiencies of the components of both gas turbine cycles. The highest cycle exergetic efficiencies were found for the full flow case for the GTX100 cycles and for the 20% part flow case for the Trent cycles. The largest exergy destruction occurs in the combustor, and the exergetic efficiency of this component has a large influence on the overall cycle performance. The exergy destruction of the heat recovery system is low.

scholarly journals Advanced Exergy Analysis of Waste-Based District Heating Options through Case Studies

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4766
Author(s):  
Huseyin Gunhan Ozcan ◽  
Arif Hepbasli ◽  
Aysegul Abusoglu ◽  
Amjad Anvari-Moghaddam
Keyword(s):  
Real Time ◽  
Heat Exchangers ◽  
Exergy Analysis ◽  
Thermal Power ◽  
District Heating ◽  
Exergy Efficiency ◽  
Hot Water ◽  
Exergy Destruction ◽  
District Heating System ◽  
The Real

The heating of the buildings, together with domestic hot water generation, is responsible for half of the total generated heating energy, which consumes half of the final energy demand. Meanwhile, district heating systems are a powerful option to meet this demand, with their significant potential and the experience accumulated over many years. The work described here deals with the conventional and advanced exergy performance assessments of the district heating system, using four different waste heat sources by the exhaust gas potentials of the selected plants (municipal solid waste cogeneration, thermal power, wastewater treatment, and cement production), with the real-time data group based on numerical investigations. The simulated results based on conventional exergy analysis revealed that the priority should be given to heat exchanger (HE)-I, with exergy efficiency values from 0.39 to 0.58, followed by HE-II and the pump with those from 0.48 to 0.78 and from 0.81 to 0.82, respectively. On the other hand, the simulated results based on advanced exergy analysis indicated that the exergy destruction was mostly avoidable for the pump (78.32–78.56%) and mostly unavoidable for the heat exchangers (66.61–97.13%). Meanwhile, the exergy destruction was determined to be mainly originated from the component itself (endogenous), for the pump (97.50–99.45%) and heat exchangers (69.80–91.97%). When the real-time implementation was considered, the functional exergy efficiency of the entire system was obtained to be linearly and inversely proportional to the pipeline length and the average ambient temperature, respectively.

scholarly journals Testing Platform and Commercialization Plan for Heat Exchanging Systems for SCO2 Power Cycles

2013 ◽  
Author(s):  
Darryn Fleming ◽  
Jim Pasch ◽  
Thomas Conboy ◽  
Matt Carlson
Keyword(s):  
High Pressure ◽  
Heat Exchanger ◽  
Power Plant ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Brayton Cycle ◽  
Flow Temperature ◽  
Pressure Flow ◽  
Power Cycles ◽  
Capital Costs

Supercritical Closed Brayton Cycle (SCO2 CBC) systems have the potential to convert thermal energy to electricity at an efficiency significantly higher than traditional steam Rankine cycles. The primary difference in the Brayton cycle that enables higher efficiency is the availability of a useful temperature difference between the high temperature, low pressure flow exiting the turbine, and the low temperature, high pressure flow exiting the compressor. In the SCO2 CBC cycle, this temperature difference drives heat transfer through recuperation in heat exchangers. Overall cycle energy conversion efficiency increases as the extent of recuperation increases. Ideally, the low pressure flow temperature exiting the last heat exchanger before entering the compressor will equal the high pressure flow temperature exiting the compressor. Both heat exchanger capital costs and power plant operating income rise as this ideal is approached. The capital costs are considered in relation to their effect on profit from a SCO2 CBC power plant selling electricity. Sandia is currently designing a heat exchanger test platform to support research and development of heat exchanger technology for SCO2 power cycles. This platform will facilitate investigating performance characteristics of various new heat exchanger technologies, such as pressure drop, efficiency, failure modes, etc. The platform will be able to accommodate many types of exchangers of different physical sizes and flow rates. The purpose of this testing is to identify the correct heat exchanger for the many various SCO2 applications. Testing will be a focal point of the research and commercialization plan for Sandia to identify a path forward to develop a 10MW simple recuperated Brayton cycle. The platform, once commissioned, can test many types of heat exchangers to investigate performance characteristics and to select which application they will be best suited for. Characterizing these heat exchangers will facilitate understanding how they scale. Plant economics will be a major factor in the selection of these heat exchangers. It has been identified that at this time, up to 90% of the cost of the SCO2 Brayton Cycle will be in the heat exchangers. This percentage assumes the use of printed circuit heat exchangers. Although these heat exchanger are approximately 98% efficient and a relatively high cost, the use of a lower efficiency and less costly heat exchanger may make this SCO2 technology more attractive for a path forward commercialization.

Thermodynamic Evaluation of a Direct Expansion Ground-Sourced Heat Pump with Horizontal Ground Heat Exchangers Using Advanced Exergy Analysis

2021 ◽  
Author(s):  
Abdolazim Zarei ◽  
Mehran Ameri ◽  
Hossein Ghazizade-Ahsaee
Keyword(s):  
Heat Exchanger ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Exergy Analysis ◽  
Thermodynamic Evaluation ◽  
Ground Heat Exchanger ◽  
Exergy Destruction ◽  
Direct Expansion ◽  
Expansion Valve ◽  
System Improvement

This paper deals with the advanced exergetic analysis of a horizontal direct-expansion ground sourced CO2 heat pump operating in a transcritical cycle. The cycle is thermodynamically modeled in Engineering Equation Solver (EES) considering the pressure drops in both high and low temperature heat exchangers, and the system is to provide a fixed heating load. Conventional exergy analysis orderly suggests a compressor, expansion valve, gas cooler and ground heat exchanger to be considered for system improvement, while tracing exergy destruction of all components in detail demonstrates true improvement potential of each and all components and the system as a whole and offers a different order. Advanced exergy analysis points out that the compressor is directly and indirectly responsible for 56% of the overall exergy destruction generated in the cycle, confirming the detrimental role of this component in the system. The second influential component is recognized to be a ground heat exchanger accounting for 20% exergy destruction of the compressor as well as submitting 89% avoidability in its own exergy destruction, and expansion valve proves to be the last option for system improvement according to this analysis.

scholarly journals Exergy analysis of marine waste heat recovery CO2 closed-cycle gas turbine system

Pomorstvo ◽  
2020 ◽  
Vol 34 (2) ◽  
pp. 309-322
Author(s):  
Vedran Mrzljak ◽  
Igor Poljak ◽  
Jasna Prpić-Oršić ◽  
Maro Jelić
Keyword(s):  
Gas Turbine ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Exergy Analysis ◽  
Waste Heat ◽  
Exergy Efficiency ◽  
Mechanical Power ◽  
Closed Cycle ◽  
Marine Waste

This paper presents an exergy analysis of marine waste heat recovery CO2 closed-cycle gas turbine system. Based on the operating parameters obtained in system exploitation, it is performed analysis of each system component individually, as well as analysis of the whole observed system. While observing all heat exchangers it is found that combustion gases-CO2 heat exchangers have the lowest exergy destructions and the highest exergy efficiencies (higher than 92%). The lowest exergy efficiency of all heat exchangers is detected in Cooler (51.84%). Observed system is composed of two gas turbines and two compressors. The analysis allows detection of dominant mechanical power producer and the dominant mechanical power consumer. It is also found that the turbines from the observed system have much higher exergy efficiencies in comparison to compressors (exergy efficiency of both turbines is higher than 94%, while exergy efficiency of both compressors did not exceed 87%). The whole observed waste heat recovery system has exergy destruction equal to 6270.73 kW, while the exergy efficiency of the whole system is equal to 64.12% at the selected ambient state. Useful mechanical power produced by the whole system and used for electrical generator drive equals 11204.80 kW. The obtained high exergy efficiency of the whole observed system proves its application on-board ships.

Exergy Analysis of Heat Recovery Steam Generator: Effects of Supplementary Firing and Desuperheater

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Hanieh Khalili Param ◽  
Ofelia A. Jianu
Keyword(s):  
Steam Generator ◽  
Heat Recovery ◽  
Exergy Analysis ◽  
Exergy Efficiency ◽  
Exergy Loss ◽  
Water Spray ◽  
Exergy Destruction ◽  
Heat Recovery Steam Generator ◽  
Set Point ◽  
A Value

Abstract Comprehensive exergy analysis of a heat recovery steam generator (HRSG) with two levels of delivered pressure is presented. The effects of supplementary firing as well as desuperheater set-point are considered to evaluate the exergy destruction of HRSG components. Burner firing rate is limited to a value that corresponds to the maximum allowable temperature of tube metal of high-pressure (HP) superheater. According to the exergy analysis performed in the current study, the exergy efficiency of HRSG is about 80% which means 20% of flue gas exergy (entering HRSG) is dissipated by HRSG destruction (∼14%) and stack exergy loss (∼6%). The stack exergy loss drops continuously as supplementary firing raises. It has also been determined that increasing the rate of supplementary firing boosts the exergy efficiency in the absence of water spray and reduces it when desuperheater is working. In addition, the exergy delivered to steam turbine shows a linear growth with burner heat while it is hardly affected by the set-point of desuperheater. Also, it is found that exergy loss through the stack is not sensitive to desuperheater set-point while it is on the decrease as burner duty raises. HP steam flow will raise with increasing the firing and/or decreasing the desuperheater set-point. HP evaporator has the most contribution in exergy destruction among HRSG components (∼40%), whereas HP superheater and desuperheater are components with a maximum sensitivity of exergy destruction to the amount of water spray.

scholarly journals Exergy analysis of a reversible chiller

2021 ◽  
pp. 105-106
Author(s):  
Volodymyr Voloshchuk ◽  
Olena Nekrashevych ◽  
Volodymyr Voloshchuk ◽  
Pavlo Gikalo
Keyword(s):  
Heat Exchangers ◽  
Exergy Analysis ◽  
System Component ◽  
Space Heating ◽  
Exergy Destruction ◽  
Exergetic Analysis ◽  
Operational Modes

The work presents the results of exergetic analysis of a reversible chiller providing both cooling and space heating in varying operational modes. The year values of avoidable parts of exergy destruction occurring in each system component are used for the analysis. The outcomes obtained showed that the both inside and outside heat exchangers have the highest priority for improvement revealing more than 718 kW-hr avoidable year exergy destruction within the system.

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