Exergy Concept and Determination

Querol, Enrique; Gonzalez-Regueral, Borja; Perez-Benedito, Jose Luis

doi:10.1007/978-1-4471-4622-3_2

Cited by 11 publications

(7 citation statements)

References 10 publications

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“…Table 2 summarizes exergy efficiency for some of the standalone and integrated processes. In contrast to MD, the majority of the exergy rates in RO are derived from the high pressures involved, i.e., 15-25 bars for brackish water and 60-80 bars for seawater, hence the related pressure drop as reflected in improved efficiencies when a pressure exchanger is considered [19]. The very low exergy efficiency of MD reported [4] was from the one powered by solar, and the high exergy losses were due to the MD and heat exchanger units.…”

Section: Exergy Efficiency Of the Agmd Modulesmentioning

confidence: 99%

Exergy Analysis of Air-Gap Membrane Distillation Systems for Water Purification Applications

Woldemariam

Santarelli

2017

Applied Sciences

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Exergy analyses are essential tools for the performance evaluation of water desalination and other separation systems, including those featuring membrane distillation (MD). One of the challenges in the commercialization of MD technologies is its substantial heat demand, especially for large scale applications. Identifying such heat flows in the system plays a crucial role in pinpointing the heat loss and thermal integration potential by the help of exergy analysis. This study presents an exergetic evaluation of air-gap membrane distillation (AGMD) systems at a laboratory and pilot scale. A series of experiments were conducted to obtain thermodynamic data for the water streams included in the calculations. Exergy efficiency and destruction for two different types of flat-plate AGMD were analyzed for a range of feed and coolant temperatures. The bench scale AGMD system incorporating condensation plate with more favorable heat conductivity contributed to improved performance parameters including permeate flux, specific heat demand, and exergy efficiency. For both types of AGMD systems, the contributions of the major components involved in exergy destruction were identified. The result suggested that the MD modules caused the highest fraction of destructions followed by re-concentrating tanks.

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Section: Exergy Efficiency Of the Agmd Modulesmentioning

confidence: 99%

Exergy Analysis of Air-Gap Membrane Distillation Systems for Water Purification Applications

Woldemariam

Santarelli

2017

Applied Sciences

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“…The chemical exergy of a material stream is the amount of exergy transferred over a chemical reaction at the ambient pressure and temperature until the chemical equilibrium is achieved. The specific molar chemical exergy ( ex ch ) of ideal gas mixtures or ideal liquids can be obtained using eq , as given below: …”

Section: Methodsmentioning

confidence: 99%

“…For nonideal liquids, it is preferred to calculate specific molar chemical exergy using eq where ex ch, i 0 , M i , and γ i introduce the standard molar chemical exergy, the molarity, and the molar activity of component i in the liquid mixture, respectively.…”

Section: Methodsmentioning

confidence: 99%

Performance Analysis and Simulation of the Gas Condensate Stabilization Process: Energy and Exergy Aspects

Hajizadeh

Mohamadi‐Baghmolaei

Azin

et al. 2022

Ind. Eng. Chem. Res.

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Gas condensate stabilization is a common process in gas refineries and petrochemical industries. This process is known as an energy consuming process because it uses distillation columns and furnaces for separating different cuts from the condensate feed. This study aims to improve the performance of the gas condensate stabilization unit in a large petrochemical company in terms of energy efficiency and loss prevention. The case study considered in this work is the gas condensate stabilization unit in the Nouri Petrochemical Company, treating 568 t/h of raw condensate feed. This plant includes two distillation columns, two furnaces, several pumps, heat exchangers, and air coolers. A hybrid energy and exergy analysis is conducted in this study. First, the validation of the simulation phase is performed. We then conduct a parametric sensitivity analysis to explore the effects of various parameters, such as operating temperature and pressure on the process performance. After that, the most influential variables are identified using a thermodynamic analysis for optimization and design purposes. An optimization method is employed to attain the maximum production improvement and exergy efficiency. The exergy analysis shows 187.4 MW total exergy destruction in the plant; the furnaces account for 79% of the total exergy destruction. The energy consumption of the process could be reduced by 33.7 MW, which leads to an 18% reduction in the energy consumption of the plant. The optimal process conditions outperform the current and design states in terms of exergy efficiency (4.6% improvement in exergy efficiency). The fuel gas consumption is reduced by 2.1 t/h, leading to a reduction of 136.8 t/d CO 2 emissions. The economic evaluation reveals that 7.3 × 10 5 USD/h could be saved at the optimum conditions. The current study could offer a proper platform for improving the energy efficiency of similar plants.

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“…Mixing exergy is always a negative value because the mixing of different components decreases the exergy continuously along the length of the reactor [ 28 ]. It can also be written in the form of

, where P i is the partial pressure of each component ( P i = χ i P total ) according to Dalton’s law [ 32 ].…”

Section: Process and Exergymentioning

confidence: 99%

Model Development and Exergy Analysis of a Microreactor for the Steam Methane Reforming Process in a CFD Environment

Rahman

Ahmad

Kano

et al. 2019

Entropy

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Steam methane reforming (SMR) is a dominant technology for hydrogen production. For the highly energy-efficient operation, robust energy analysis is crucial. In particular, exergy analysis has received the attention of researchers due to its advantage over the conventional energy analysis. In this work, an exergy analysis based on the computational fluid dynamics (CFD)-based method was applied to a monolith microreactor of SMR. Initially, a CFD model of SMR was developed using literature data. Then, the design and operating conditions of the microreactor were optimized based on the developed CFD model to achieve higher conversion efficiency and shorter length. Exergy analysis of the optimized microreactor was performed using the custom field function (CFF) integrated with the CFD environment. The optimized catalytic monolith microreactor of SMR achieved higher conversion efficiency at a smaller consumption of energy, catalyst, and material of construction than the reactor reported in the literature. The exergy analysis algorithm helped in evaluating length-wise profiles of all three types of exergy, namely, physical exergy, chemical exergy, and mixing exergy, in the microreactor.

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Exergy Concept and Determination

Cited by 11 publications

References 10 publications

Exergy Analysis of Air-Gap Membrane Distillation Systems for Water Purification Applications

Exergy Analysis of Air-Gap Membrane Distillation Systems for Water Purification Applications

Performance Analysis and Simulation of the Gas Condensate Stabilization Process: Energy and Exergy Aspects

Model Development and Exergy Analysis of a Microreactor for the Steam Methane Reforming Process in a CFD Environment

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