Dual-loop Organic Rankine Cycle Research Articles

Techno-economic-environmental study and artificial intelligence-assisted optimization of a multigeneration power plant based on a gas turbine cycle along with a hydrogen liquefaction unit

According to the literature, there is a research gap concerning the practical heat recovery in solar-driven systems that have the capability to produce liquid hydrogen. In this study, an innovative combination of dual-loop solar-driven organic Rankine cycle and liquefied natural gas (LNG) heat recovery is designed to produce and liquefy hydrogen. The proposed system includes parabolic trough solar collectors (PTSCs), a Rankine cycle, a dual-loop organic Rankine cycle, LNG regasification process, proton exchange membrane (PEM) electrolyzer, and Claude hydrogen liquefaction cycle. A data-driven method is developed to analyze the system from techno-economic and environmental perspectives. The results show that LNG energy recovery improves the liquefaction work by as much as 7.96 kWh/kgH2. It is also concluded that the optimum compaction pressure range for the liquefaction cycle is 4.67 MPa, which is associated with better results. In these conditions, liquefaction work, liquefaction Coefficient of Performance (COP), and liquefaction exergy efficiency are 164.6 kJ/kg, 0.157 and 17.05%, respectively. To find optimum operating conditions, a supervised learning approach is applied to the developed code and the trained network is optimized using the genetic algorithm (GA). The optimization results reveal that a 10.98 $/h increase in total cost rate causes an 18% improvement in hydrogen production rate.

Environmentally friendly utilization of LNG regasification process and geothermal-based dual-loop power cycle for desalinated water and hydrogen production

The global scarcity of fresh water has prompted the development of innovative strategies for establishing affordable and efficient desalination systems that utilize waste heat from industrial processes. This study presents a novel combination of a geothermal-driven dual-loop organic Rankine cycle and liquefied natural gas (LNG) regasification process intended for electricity, desalinated water, and hydrogen production. The integration of diverse energy sources holds the capability to reduce dependence on traditional fossil fuels and promote a more sustainable and diversified energy portfolio, conducive to ecological well-being. In the suggested approach, a thermoelectric generator (TEG) is employed to harness the thermal contrast present between the residual heat of the geothermal process and the cold LNG stream, which reduces irreversibility and increases the system's power output. After examining the effect of key parameters on the system's performance, a data-driven approach is adopted in which the system's performance is predicted based on artificial neural networks (ANNs). According to the results, the primary generated power, desalinated water production rate, total cost rate, and cooling load are 5.15 MW, 127.31 m3/h, 188.22 $/h, and 2.92 MW, respectively. Also, the findings of the financial investigation demonstrate that the electrolysis unit, with an hourly cost rate of 85.2 $, constitutes more than 45 % of the total cost rate. In addition, the optimization of the system is performed in three distinct cases, wherein each case pertains to a different objective. In optimal conditions, the amount of produced desalinated water and the total cost rate are 153.89 m3/h and 153.58 $/h, respectively.

Thermo-economic optimization design of steam-water organic Rankine cycle with splitting flow

Aiming to address the potential scenario of waste heat recovery from a steam-water dual heat source, this paper proposes the thermo-economic models of split-flow dual-loop organic Rankine cycle (SFD-ORC) and split-flow triple-loop organic Rankine cycle (SFT-ORC) systems. The particle swarm optimization (PSO) algorithm is employed for single-objective optimization of the systems, with the goal of maximizing the net power output. The non-dominated sorting genetic algorithm-II (NSGA-II) algorithm is used to find the Pareto frontier by considering both the maximum net power output and the lowest cost of electricity production. The multi-objective optimization parameters are evaluated using the entropy weight method and TOPSIS method. The results show that the hot water split ratio and hot water outlet temperature of the high-pressure loop are higher in multi-objective optimization compared to single-objective optimization. The net output power of the SFT-ORC system after single-objective optimization can be up to 7.9% higher than that of the SFD-ORC system. From an economic perspective, it is recommended to use the SFD-ORC system at a hot water temperature of 85 °C–90 °C. In order to enhance the economic performance of the system, the steam outlet pressure should be as low as possible within the allowable range.

Comparison Study of Four Typical ORC Configurations for Different Waste Heat Characteristics of Engine

The organic Rankine cycle (ORC), as the most promising technology for engine waste heat recovery, has many configurations available to match the complicated engine waste heat conditions. This paper is aimed at revealing the characteristics of the engine waste heat condition for which different ORC configurations are matched so as to give selection guidance. The engine waste heat sources are characterized by the exhaust gas temperature (300°C-650°C) and the heat ratio of the high temperature waste heat to low temperature waste heat (0.5-1.5). Four mostly investigated configurations including the single-loop ORC, the cascade dual-loop ORC, the dual-pressure ORC, and the CO2 transcritical Rankine cycle (CTRC) are selected and modified to enable efficient utilization of all waste heat sources. Their thermodynamic performance is optimized for different waste heat characteristics. The results show improvements in net power for all configurations when exhaust gas temperature and heat ratio rise from 300°C, 0.5, to 650°C, 1.5, respectively, of which the high-temperature split CTRC (HTS-CTRC) recorded the largest increase of 183.58%, while the split regenerative ORC (SR-ORC), dual-pressure ORC (D-ORC), and split cascade ORC (SC-ORC) increased by 17.41%, 23.71%, and 35.45%, respectively. Two selection maps are established to provide general references for quickly selecting the configuration according to different waste heat characteristics whatever the engine type and operating conditions.

Thermo-economic performance comparison and advanced analysis using orthogonal experiment for organic Rankine cycle

To improve the thermo-economic performance of organic Rankine cycle (ORC) systems, a multi-level analysis method is proposed in this study. In the first level, the optimal configuration is determined based on the thermo-economic optimization. The exergy efficiency and electricity production cost are selected as the objective functions of optimization for three ORC configurations, including simple ORC, TORC (two-stage ORC), and DORC (dual-loop ORC). In the second level, the real potential of performance improvement for the optimal configuration is revealed through advanced exergy analysis method. Finally, the order of operating parameters to different performance indicators of the optimal configuration is determined by orthogonal experiment method. The results show that the TORC system exhibits better thermo-economic performance. Although the low-temperature condenser in the TORC system has the highest exergy destruction, the LTT (low-temperature turbine) contributes the largest avoidable-endogenous exergy destruction. Thus, the LTT has the greatest potential for technical improvement. The condensation temperature and pinch point temperature difference in the low-temperature evaporator are the primary factors for the thermodynamic and economic performance of the TORC system, respectively. While the evaporation temperature of the high-temperature evaporator has the greatest effect on the potential of technical improvement for the LTT.

Performance analysis of a dual-loop organic Rankine cycle system for waste heat recovery from engine coolant and exhaust of a heavy-duty truck

• Heat exchanger employed influences the system efficiency. • Significant heat loss observed from engine block at part-load. • Variable expander-to-engine speed gear ratio gives a small gain in power. • Performance comparison for unique Scandinavian motorway data. Strict legislations over emissions from heavy-duty trucks are pushing the manufacturers towards improving their brake thermal efficiency, thereby mitigating fuel consumption and reducing CO 2 emissions. Organic Rankine cycle-based waste heat recovery system has proven to be an inevitable technology in boosting the engine performance besides the other methods and approaches. In addition to recovering the exhaust heat from the engine, recovering heat from the engine coolant is also beneficial, provided its nominal temperature is raised. Thus, this work investigates the scope of improvement in performance of a heavy-duty truck engine when integrated with a dual-loop organic Rankine cycle system for recovering heat from its exhaust and coolant, simultaneously. The analysis has been performed as a simulation study on GT-SUITE using the one-dimensional model of the engine with its organic Rankine cycle heat recovery setup. The model was developed based on the components of a real commercial truck engine connected with a simple exhaust waste heat recovery system. For the work described in this paper, model of the single-loop exhaust waste heat recovery system was modified to a dual-loop circuit comprising of two scroll expanders and R1233zd(E) as the working fluid. Notably, performance investigation was carried out using a unique Scandinavian motorway road data retrieved from the truck. This paper addresses the challenges associated with simultaneous heat recovery from engine exhaust and coolant. Performance comparison at four steady-state engine operating points reveal that the low temperature radiator installed for the indirect condensation of the working fluid is the major influencing component on system efficiency. At higher engine loads, the overall system efficiency considerably decreased due to limited heat rejection capacity of this radiator. Moreover, on assessing the scope of improving the system’s performance by having variable gear ratio between the engine and the expanders, 1.6% points (0.12 kW) gain in power was observed by having the high-pressure expander’s speed fixed and the low-pressure expander’s speed varied. Furthermore, elevating the engine coolant temperature from 120 °C to 140 °C, significant heat loss from the coolant to the engine surroundings resulted in a substantial drop in net power at lower part loads although it had improved at higher engine operating points.

Thermo-economic-environmental optimization design of dual-loop organic Rankine cycle under fluctuating heat source temperature

Fluctuating heat source temperature leads to off-design operation of organic Rankine cycle systems, which is a challenge for its optimal design. For a dual-loop organic Rankine cycle, this study proposed a multi-objective optimization design framework, which integrates off-design optimization into design optimization to determine the optimal design point of the system under heat source temperature fluctuations. In the optimization design framework, we developed a multi-objective optimization model to maximize the exergy efficiency and annual CO2 emission reduction of the dual-loop organic Rankine cycle and minimize its payback period. Then, the effects of design heat source temperature Td,h on the lifetime performance of dual-loop organic Rankine cycle were investigated. To balance the conflict between different indexes, we proposed a comprehensive evaluation index based on the entropy method. The results show that the influence of actual heat source temperature on the performance of dual-loop organic Rankine cycle is greater than the Td,h. Compared with traditional research that ignore the off-design performance, the proposed design method can avoid 35.8% annual CO2 emission reduction overestimation and 58.7% payback period underestimation at Td,h of 573.1 K. In addition, the optimal Td,h is significantly influenced by the selected index. The optimal Td,h is 513.1 K for the dual-loop organic Rankine cycle to minimize its lifetime payback period. To maximize the comprehensive index, the optimal Td,h for the dual-loop organic Rankine cycle is 573.1 K, which is the temperature at 0.9 of the cumulative distribution curve of the heat source. The average exergy efficiency and annual CO2 emission reduction in the lifetime of the dual-loop organic Rankine cycle at the optimal Td,h of 573.1 K is 4.1% and 6.0% higher than that at the average Td,h of 529.1 K, respectively.

Investigation of a Dual-Loop ORC for the Waste Heat Recovery of a Marine Main Engine

As carbon dioxide emissions arising from fossil energy consumption and fossil fuels are gradually increased, it is important for the low-carbon operation of ships to recover diesel engine waste heat. A newly developed dual-loop organic Rankine cycle (ORC) system to recover waste heat from a marine main engine (M/E) was designed in this paper. The exhaust gas (EG) heat was recovered by the high-temperature (HT) loop. The jacket cooling water (JCW) heat and the condensation heat of the HT loop were recovered by the low-temperature (LT) loop. Toluene, cyclohexane, benzene, R1233zd (E), R245fa, and R227ea were selected as the working fluids. The influence of the condenser thermal parameters on the LT loop was analyzed using the pinch point method. The performance of the dual-loop ORC was investigated under various working fluid combinations. The maximum net power of the HT loop can reach 253.4 kW when using cyclohexane as the working fluid, and the maximum thermal efficiency of the HT loop can reach 18.5% with benzene as the working fluid. Meanwhile, higher condensation temperatures and levels of condensation heat of the HT loop have a positive effect on the performance of the LT loop. However, in most conditions, the HT loop condensation heat could not provide enough heat for the LT loop’s working fluid to start the boiling process. The total net power of the dual-loop ORC system was 410.6 kW with Cyclohexane in the HT loop and R1233zd (E) in the LT loop, resulting in a 10.9% improvement in the marine main engine thermal efficiency.

Flexibility concept in design of advanced multi-energy carrier systems driven by biogas fuel for sustainable development

In this paper, a new and comprehensive multigeneration system is developed exploiting biogas fuel. The system is examined from the perspective of energy, exergy, exergoeconomic, exergoenvironment, and safety for supplying the energy demands of large buildings such as modern hospitals located near industrial places. Multi-objective optimization is applied along with a new concept of flexibility in the system considering these five indicators. The Brayton cycle and closed Brayton cycle for power generation, dual-loop organic Rankine cycle and ejector refrigeration for power and cooling production, multi-effect distillation unit for freshwater production, carbon dioxide absorption unit by microalgae for biodiesel production, water heaters for domestic heating production, and PEM electrolyzer for hydrogen production are integrated into the devised system. From the environmental point of view, using biogas fuel and absorption of carbon dioxide leads to the best environmental efficiency in the proposed system. Moreover, the safety facet is analyzed to lower the level of damage and risk in the system. Based on the results of the optimization, the net output power, air conditioning refrigeration, freezing, and heating are reckoned at 1864, 286.6, 75.89, and 398.9 kW, and the production of freshwater, hydrogen, biodiesel, and glycerol is predicted to be 2.111, 0.00038, 0.0088, and 0.00091 kg/s, respectively. Also, the system performance ratio, unit cost of product, exergy efficiency, environmental effect of product, and overall system risk are equal to 1.828, 40.58 $/GJ, 31.11%, 6232 mPts/GJ, and 1656 $/year.

Comprehensive Performance Assessment of Dual Loop Organic Rankine Cycle (DORC) for CNG Engine: Energy, Thermoeconomic and Environment

The improvement of the overall utilization rate of compressed natural gas (CNG) engine fuel is the basis of efficient energy utilization. On the foundation of heat balance theory of internal combustion engines, this study fully considers the operation characteristics of CNG engines and systematically analyzes the distribution characteristics of different waste heat under variable working conditions. The nonlinear relationship between speed and intercooler heat source becomes evident with the increasing of intake mass flow rate. In accordance with the structural characteristics, the thermodynamic model, heat transfer model and environmental model of dual-loop organic Rankine cycle (DORC) are constructed. The system potential in full working environments is systematically evaluated. Compared with the speed, airmass flow has a significant effect on comprehensive performance of loop. The maximum power, heat transfer area and power output of per unit heat transfer area (POPA) of DORC are 36.42 kW, 23.34 m2, and 1.75 kW/m2, respectively. According to the operating characteristics of different loops, the variation laws of loop performance under the influence of multiple parameters are analyzed. The synergistic influence laws of multiple variables on system performance are also analyzed.

A novel investigation of waste heat recovery from a stationary diesel engine using a dual-loop organic Rankine cycle

A novel investigation of waste heat recovery from a stationary diesel engine using a dual-loop organic Rankine cycle

Rankine cycle waste heat recovery for a heavy-duty natural gas engine meeting China VI emission standards

The China VI natural gas engine is based on the theory of the air–fuel ratio method, leading to a high exhaust temperature, large heat load and difficult cooling. The paper carried out a thermal balance experiment of the China VI natural gas engine under different working conditions. A dual-loop organic Rankine cycle system is designed to reduce the difficulty of cooling system and improve the thermal efficiency. The high-temperature loop uses water as working fluid to recover the heat of engine exhaust gas and recirculation exhaust gas. The low-temperature loop recovers the heat from cooling water and waste heat of the high-temperature loop. The high-temperature and low-temperature loops are coupled through a shared heat exchanger. The results show that the China VI natural gas engine has a higher and more stable waste heat temperature than traditional engines and is more adaptable to waste heat recovery under variable operating conditions. For fixed evaporation temperature, with the increase of inlet temperature of the expander, the net output power of high-temperature loop increases first and then decreases, reaching the maximum value at about 800 K. In the low-temperature loop working fluids R601a, R601b, R600, R600a and R12333zd, The maximum net output power of the waste heat recovery system based on the combination of water and R12333zd is approximately 75.4 kW under the rated condition, which is 22.24% of the rated power of the engine.

Advanced Exergy Scrutiny of a Dual-loop Organic Rankine Cycle for Waste Heat Recovery of a Heavy-duty Stationary Diesel Engine

In this paper, the normal exergy scrutiny (NES) and advanced exergy scrutiny (AES) of a waste heat recovery (WHR) system was performed. The proposed system contains a dual-loop organic Rankine cycle (DORC) which recovers the available waste heat of the intake air, exhaust gas, and coolant streams of a 12-cylinder heavy-duty stationary diesel engine. A well-known method of the AES called the thermodynamic cycle approach is utilized to determine each component exergy destruction parts namely exogenous/endogenous, unavoidable/avoidable, etc. Results showed that 59.04 kW from the 258.69 kW total exergy destruction rate of the system could be eliminated (22.82% of the total exergy destruction rate). The total avoidable exergy destruction part of the low-temperature loop accounts for 46.62 kW, which indicates that it requires more attention than that of the high-temperature loop by 12.42 kW. Furthermore, it is revealed that to enhance the overall productivity of the system, there is a relatively significant difference in priority order regarding the improvement of system components. The AES has proposed this ranking for improvement priority of components: condenser, expander 2, expander 1, respectively. While the NES has specified the priority as the evaporator 1, condenser, expander 2, respectively.

Performance assessment of a dual loop organic rankine cycle powered by a parabolic trough collector for ammonia and hydrogen production purpose

Energy systems used in the future will need to be cleaner and more sustainable. The use of liquid ammonia as a potential medium for hydrogen storage is an efficient solution from an economic, practical and environmental point of view. In this work, a new approach linked to the production of hydrogen and ammonia using a system combining an alkaline water electrolysis, an air separation unit and a Haber Bosch reactor is proposed. The electricity necessary to carry out this process is provided by a dual loop organic rankine cycle supplied by a parabolic trough collector and an auxiliary heater system. The survey was carried out by developing mathematical models on the different components of the combined system. The discrepancies between numerical and experimental results did no exceed 2% for the parabolic trough solar collector. Results demonstrated that hydrogen and ammonia flow rates increased as evaporation temperature of working fluid in the high –thermodynamics cycle increased. Results also showed that the thermal performance of the parabolic trough collector increased as inlet temperature and concentration factor increased. It was pointed out that the overall electrical efficiency of the combined system ranged from 15 to 20.28%. The specific energy consumption of the Back-up heater decreased as mass flow rate of Therminol® VP-1 decreased and its values ranged from 0 to 35 kWh.kg-1 of ammonia. Ammonia production efficiency and electricity consumption ratio varied between 59 to 63% and 8.25 to 8.67 kWh.kg-1of ammonia, respectively. Overall results showed that Cyclohexane, Octane, Toluene and Benzene can be used effectively as working fluid for the high temperature loop organic rankine cycle supplied by parabolic trough collectors for hydrogen and ammonia production purpose.

Analyzing the dual-loop organic rankine cycle for waste heat recovery of container vessel

Increasing the efficiency of ships via waste heat recovery systems is one of the most effective methods to minimize emissions from ships, especially carbon dioxide emissions. The organic rankine cycle is a promising system. The purpose of this study is to analyze the dual-loop organic rankine cycle system using jacket cooling water, exhaust gas and scavenge air. Two model is designed to analyze the waste heat recovery system for the different main engine load. In the first model, while the exhaust gas is used as the heat source in the high temperature cycle, jacket cooling water and high temperature loop waste heat are used as heat sources in low temperature cycle. Scavenge air and exhaust gas and jacket cooling water are used as heat sources in the second model. Different working fluid combinations that have been familiar from literature and their alternatives are analyzed in two models and the net power output by using thermodynamics, reduction in carbon dioxide and fuel consumption are calculated. In low engine load, since the temperature range of scavenge air is low the second model is suitable for high main engine load. Results show that with the second model when benzene-R245fa(1,1,1,3,3-pentafluoropropane) combination is used as working fluid, 3373 kW net power can be produced, 13588,3 tonnes/year Carbon dioxide emissions can be reduced. However, since benzene is a flammable fluid, it is not recommended for use in the ship. Instead of benzene, R1233zd(E) (trans-1-chloro-3,3,3-trifluoro-1-propene) is more suitable for high temperature source.

Configuration Selection of the Multi-Loop Organic Rankine Cycle for Recovering Energy from a Single Source.

The Organic Rankine Cycle (ORC) is a well-established way to recover energy from a single waste heat source. This paper aims to select the suitable configuration, number of loops, and working fluids for the Multi-Loop ORC (MLORC) by using multi-objective optimization. The thermodynamic and economic performance of MLORC in three various configurations was analyzed. Multi-objective optimizations of the series and parallel MLORC using different working fluid groups were conducted to find the optimal configuration, number of loops, and working fluid combination. The analysis results show that the series–parallel MLORC performed the worst among the three configurations. The optimization results reveal that series MLORC has a higher exergy efficiency than the parallel MLORC. The exergy efficiency of the optimal solution in series dual-loop, triple-loop, and quadruple-loop ORC is 9.3%, 7.98%, and 6.23% higher than that of parallel ORC, respectively. Furthermore, dual-loop is the optimal number of cycles for recovering energy from a single heat source, according to the grey relational grade. Finally, the series dual-loop ORC using cyclohexane\\cyclohexane was the suitable configuration for utilizing a single waste heat source. The exergy efficiency and levelized cost of electricity of the series dual-loop ORC with the optimal parameters are 62.18% and 0.1509 $/kWh, respectively.

Cascaded dual-loop organic Rankine cycle with alkanes and low global warming potential refrigerants as working fluids

A cascaded dual-loop organic Rankine cycle (CD-ORC) consisting of a high-temperature ORC (HT-ORC) and a low-temperature ORC (LT-ORC) with a shared heat exchanger is studied. Thermal efficiency is investigated as a key indicator for system performance over a wide range of heat source temperature ranging from 170 °C to 330 °C. The relation between the thermal efficiency and the critical temperature of the working fluids is explored. For this purpose, six alkanes and 31 refrigerants with a low GWP (≤150) are considered as working fluids in the HT-ORC and the LT-ORC, respectively. Cyclohexane and cyclopentane are found to be suitable for the HT-ORC with a maximum thermal efficiency of 19.13% and 18.03%. The thermal efficiency of both loops is highly affected by the working fluids since it increases with the critical temperature. As a whole, the CD-ORC may achieve a total thermal efficiency of 25.24%, 24.88% and 24.60% when using the working fluid combinations cyclohexane-R1366mzz(Z), cyclohexane-R1233zd(E) or cyclohexane-butane. This indicates that low GWP refrigerants are well-suited for LT-ORC. Compared to regular ORC, CD-ORC systems may achieve a thermal efficiency that is better by around a quarter.

Dynamic Response Characteristics Analysis and Energy, Exergy, and Economic (3E) Evaluation of Dual Loop Organic Rankine Cycle (DORC) for CNG Engine Waste Heat Recovery

Frequent fluctuations of CNG engine operating conditions make the waste heat source have uncertain, nonlinear, and strong coupling characteristics. These characteristics are not conducive to the efficient recovery of the DORC system. The systematic evaluation of the CNG engine waste heat source and the comprehensive performance of the DORC system is conducive to the efficient use of waste heat. Based on the theory of internal combustion (IC) engine thermal balance, this paper analyzes the dynamic characteristics of compressed natural gas (CNG) engine waste heat energy under full operating conditions. Then, based on the operating characteristics of the dual loop organic Rankine cycle (DORC) system, thermodynamic models, heat transfer models, and economic models are constructed. The dynamic response characteristics analysis and energy, exergy, and economic (3E) evaluation of the DORC system under full operating conditions are carried out. The results show that the maximum values of net power output, heat exchange area, and the minimum values of EPC (electricity production cost) and PBT (payback time) are all obtained under rated condition, which are 174.03 kW, 25.86 kW, 37.54 kW, 24.76 m2, 0.15 $/kW·h and 3.46 years. Therefore, the rated condition is a relatively ideal design operating point for the DORC system. The research in this paper not only provides a reliable reference for the comprehensive analysis and evaluation of the performance of the DORC system, but also provides useful guidance for the selection of appropriate DORC system design operating points.

Thermodynamic analysis and high-dimensional evolutionary many-objective optimization of dual loop organic Rankine cycle (DORC) for CNG engine waste heat recovery

The complex and changeable working conditions of compressed natural gas (CNG) engines have brought great challenges to the efficient recovery of waste heat energy. The dual loop organic Rankine cycle (DORC) system can effectively recover and utilize CNG engine waste heat due to its structural advantages. Determining the nonlinear variations between operating parameters and thermodynamic performance serves as the basis for obtaining the thermodynamic performance limits of the DORC system. However, traditional analysis methods have obvious limitations in this area. Based on the bilinear interpolation algorithm, this paper comprehensively analyzes and evaluates the nonlinear and strong coupling characteristics between operating parameters and net power output, thermal efficiency, and exergy destruction. In addition, the comprehensive thermodynamic performance limits of the DORC system have a critical effect on its engineering application yet have not been thoroughly and comprehensively optimized. Therefore, this paper proposes an equilibrium-based thermodynamic high-dimensional evolutionary many-objective optimization (EMO) method for the DORC system. The optimal thermal efficiency, net power output, and total exergy destruction of the DORC system reached 37.11 kW, 14.27%, and 104.58 kW, respectively. Based on the optimization results under equilibrium and unequilibrium weight, the dominant relationship between the different thermodynamic performances of the DORC system is then analyzed. This research can provide a direct reference for analyzing and optimizing the comprehensive thermodynamic performance of the DORC system.

Thermodynamic Multi-Objective Optimization of an ORC-LNG Combined Cycle System

A thermodynamic model of a dual loop organic Rankine cycle (ORC) combined with liquefied natural gas (LNG) expansion system has been developed to analyze the thermodynamic performance for the purpose of recovering LNG cold energy and blast furnace slag water waste heat. Furthermore, a multi-objective genetic algorithm (GA) is employed to solve the optimal solutions from the viewpoints of maximizing thermal efficiency and exergy efficiency simultaneously over the whole operating range of the combined cycle system. The results show that the optimal evaporation temperature and the intermediate condensation temperature of the first ORC (cycle A) are 83 °C and 19 °C separately. The optimal condensation temperature of the secondary ORC (cycle B) is -63 °C . The optimal gasification pressure and the supply pressure of the LNG expansion are 3.92 MPa and 0.20 MPa. At the rated condition, the ORC-LNG combined cycle system has the maximum thermal efficiency of 46.12% and exergy efficiency of 51.67%, with a 4.39 MW total net power output.