Performance Assessments of Organic Rankine Cycle With Internal Heat Exchanger Based on Exergetic Approach

Yamankaradeni̇z, Nurettin; Bademlioglu, Ali Husnu; Kaynaklı, Ömer

doi:10.1115/1.4040108

Cited by 17 publications

(5 citation statements)

References 24 publications

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“…The best working fluid was R123, achieving a maximum exergy efficiency of 57%. Yamankaradeniz et al [32] analyzed the variation in the evaporator effectiveness in a G-ORC, and found that the energy and exergy efficiencies increased up to 6.87% and 6.21%, with the increment of the effectiveness. Invernizzi et al [33] studied a modified ORC including a flashing tank and a mixing chamber, as shown in Figure 7.…”

Section: Single-stage Orcmentioning

confidence: 99%

A Comprehensive Review of Organic Rankine Cycles

et al. 2023

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It has been demonstrated that energy systems driven by conventional energy sources like fossil fuels are one of the main causes of climate change. Organic Rankine cycles can help to reduce that impact, as they can be operated by using the industrial waste heat of renewable energies. The present study presents a comprehensive bibliographic review of organic Rankine cycles. The study not only actualizes previous reviews that mainly focused on basic cycles operating on subcritical or supercritical conditions, but also includes the analysis of novel cycles such as two-stage and hybrid cycles and the used fluids. Recuperative and regenerative cycles are more efficient than reheated and basic single-stage cycles. The use of two-stage cycles makes it possible to achieve higher thermal efficiencies and net power outputs of up to 20% and 44%, respectively, compared with those obtained with single-stage cycles. Theoretical studies show that hybrid systems, including Brayton and organic Rankine cycles, are the most efficient; however, they require very high temperatures to operate. Most organic Rankine cycle plants produce net power outputs from 1 kW up to several tens of kW, mainly using microturbines and plate heat exchangers.

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Section: Single-stage Orcmentioning

confidence: 99%

A Comprehensive Review of Organic Rankine Cycles

et al. 2023

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“…In this validation, only two points at a fixed radial position from the tube external wall, A (r = 3 mm) and B (r = 9 mm), have been considered. The heat transfer model considers the simultaneously solving of Equations ( 1), ( 4) and (5). Equation ( 1) is modified by removing the heat source and adjusting the thermophysical properties of hydrogen to the HTF (water).…”

Section: Model Validationmentioning

confidence: 99%

“…However, ORC and thermoelectric generators convert waste heat to electricity with very low energy efficiency in the range ca. 2-15% [3][4][5][6]. Besides, these methods need to be installed near the waste heat source, which can make the overall installation (e.g., heat source + heat recovery systems) very costly [1].…”

Section: Introductionmentioning

confidence: 99%

Optimal Design of Combined Two-Tank Latent and Metal Hydrides-Based Thermochemical Heat Storage Systems for High-Temperature Waste Heat Recovery

2020

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The integration of thermal energy storage systems (TES) in waste-heat recovery applications shows great potential for energy efficiency improvement. In this study, a 2D mathematical model is formulated to analyze the performance of a two-tank thermochemical heat storage system using metal hydrides pair (Mg2Ni/LaNi5), for high-temperature waste heat recovery. Moreover, the system integrates a phase change material (PCM) to store and restore the heat of reaction of LaNi5. The effects of key properties of the PCM on the dynamics of the heat storage system were analyzed. Then, the TES was optimized using a genetic algorithm-based multi-objective optimization tool (NSGA-II), to maximize the power density, the energy density and storage efficiency simultaneously. The results indicate that the melting point Tm and the effective thermal conductivity of the PCM greatly affect the energy storage density and power output. For the range of melting point Tm = 30–50 °C used in this study, it was shown that a PCM with Tm = 47–49 °C leads to a maximum heat storage performance. Indeed, at that melting point narrow range, the thermodynamic driving force of reaction between metal hydrides during the heat charging and discharging processes is almost equal. The increase in the effective thermal conductivity by the addition of graphite brings about a tradeoff between increasing power output and decreasing the energy storage density. Finally, the hysteresis behavior (the difference between the melting and freezing point) only negatively impacts energy storage and power density during the heat discharging process by up to 9%. This study paves the way for the selection of PCMs for such combined thermochemical-latent heat storage systems.

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“…On the one hand, if the heat is available at a constant temperature, therefore the selection of ORC and thermoelectric generators for heat recovery can improve the overall energy efficiency by generating extra electricity to the end-users. On the other hand, if the temperature of the waste heat fluctuates in a small or great range, domestic hot water or steam production using heat exchangers is the viable option [3][4][5][6][7] Although ORCs are attractive for waste heat to work conversion applications, it is noticed that they possess low thermal efficiency of approximately 5-10% [8]. This energy efficiency is greatly improved to 15-30% by identifying and optimizing the parameters affecting their performance [9,10].…”

Section: Introductionmentioning

confidence: 99%

“…It was also shown that the insertion of a recuperator at the downstream of the expander could improve the efficiency to up 30% [11]. However, the improvement of thermal efficiency cannot outweigh the capital cost of the installed ORC components, which make the ORC very prohibitive in Although ORCs are attractive for waste heat to work conversion applications, it is noticed that they possess low thermal efficiency of approximately 5-10% [8]. This energy efficiency is greatly improved to 15-30% by identifying and optimizing the parameters affecting their performance [9,10].…”

Section: Introductionmentioning

confidence: 99%

Metal Hydride Beds-Phase Change Materials: Dual Mode Thermal Energy Storage for Medium-High Temperature Industrial Waste Heat Recovery

2019

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Heat storage systems based on two-tank thermochemical heat storage are gaining momentum for their utilization in solar power plants or industrial waste heat recovery since they can efficiently store heat for future usage. However, their performance is generally limited by reactor configuration, design, and optimization on the one hand and most importantly on the selection of appropriate thermochemical materials. Metal hydrides, although at the early stage of research and development (in heat storage applications), can offer several advantages over other thermochemical materials (salt hydrates, metal hydroxides, oxide, and carbonates) such as high energy storage density and power density. This study presents a system that combines latent heat and thermochemical heat storage based on two-tank metal hydrides. The systems consist of two metal hydrides tanks coupled and equipped with a phase change material (PCM) jacket. During the heat charging process, the high-temperature metal hydride (HTMH) desorbs hydrogen, which is stored in the low-temperature metal hydride (LTMH). In the meantime, the heat generated from hydrogen absorption in the LTMH tank is stored as latent heat in a phase change material (PCM) jacket surrounding the LTMH tank, to be reused during the heat discharging. A 2D axis-symmetric mathematical model was developed to investigate the heat and mass transfer phenomena inside the beds and the PCM jacket. The effects of the thermo-physical properties of the PCM and the PCM jacket size on the performance indicators (energy density, power output, and energy recovery efficiency) of the heat storage system are analyzed and discussed. The results showed that the PCM melting point, the latent heat of fusion, the density and the thermal conductivity had significant impacts on these performance indicators.Energies 2019, 12, 3949 2 of 27 or combined cooling heating and power (CCHP), have been the predominant waste-heat recovery methods in power plants. These multi-generation processes allow for an improvement of thermal energy efficiency of up to 80%. On the other hand, for industrial process heat, the organic Rankine cycle (ORC), thermoelectric generators, heat pumps, and heat storage have been reviewed as potential methods for waste heat recovery [2]. However, the efficacy of either heat recovery method depends on the conditions at which heat is discharged (especially the temperature). There are mainly three factors affecting the implementation of waste heat recovery: the availability, the heat amount and quality (which is the temperature range). The temperature range depends on the waste heat source which ranges from thermal power plants (diesel engines, fossil fuels-fired power plants, PEM, and solid oxide fuel cells) to industrial processes (steel, cement, etc). On the one hand, if the heat is available at a constant temperature, therefore the selection of ORC and thermoelectric generators for heat recovery can improve the overall energy efficiency by generating extra electricity to the end-users. On the oth...

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Performance Assessments of Organic Rankine Cycle With Internal Heat Exchanger Based on Exergetic Approach

Cited by 17 publications

References 24 publications

A Comprehensive Review of Organic Rankine Cycles

A Comprehensive Review of Organic Rankine Cycles

Optimal Design of Combined Two-Tank Latent and Metal Hydrides-Based Thermochemical Heat Storage Systems for High-Temperature Waste Heat Recovery

Metal Hydride Beds-Phase Change Materials: Dual Mode Thermal Energy Storage for Medium-High Temperature Industrial Waste Heat Recovery

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