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Seawater desalination stands as an increasingly indispensable solution to address global water scarcity issues. This study conducts a thorough exergoenvironmental analysis of a multi-effect distillation with thermal vapor compression (MED-TVC) system, a highly promising desalination technology. The MED-TVC system presents an energy-efficient approach to desalination by harnessing waste heat sources and incorporating thermal vapor compression. The primary objective of this research is to assess the system's thermodynamic efficiency and environmental impact, considering both energy and exergy aspects. The investigation delves into the intricacies of energy and exergy losses within the MED-TVC process, providing a holistic understanding of its performance. By scrutinizing the distribution and sources of exergy destruction, the study identifies specific areas for enhancement in the system's design and operation, thereby elevating its overall sustainability. Moreover, the exergoenvironmental analysis quantifies the environmental impact, offering vital insights into the sustainability of seawater desalination technologies. The results underscore the significance of every component in the MED-TVC system for its exergoenvironmental performance. Notably, the thermal vapor compressor emerges as pivotal due to its direct impact on energy efficiency, exergy losses, and the environmental footprint of the process. Consequently, optimizing this particular component becomes imperative for achieving a more sustainable and efficient desalination system. [ABSTRACT FROM AUTHOR]

Vacuum membrane distillation (VMD) is an attractive method for water desalination due to its high pure water permeability under lower operating temperatures, resulting in less energy consumption, lower heat loss via conduction through the membrane surface, and negligible heat transfer by conduction due to the low pressure on the permeate side. The aim of this study is to establish a comprehensive numerical model that describes the water vapor transfer across a hydrophobic micro-porous membrane in single-stage and multi-stage VMD processes for seawater desalination. The numerical predictions are compared to previous experimental data, and a good correlation is observed. The investigation also conducted a sensitivity analysis of process variables and membrane specifications on VMD performance, as well as an assessment of the impact of temperature and concentration polarization. The obtained results showed that the permeation flux reached 18.42 kg/m²·h at 35 g/L feed concentration, 65°C feed temperature, 50 L/h feed flow rate, and 3 kPa vacuum pressure. Moreover, the findings revealed that feed temperature was the most significant factor, while feed flow rate was the least important in determining permeation flux. Additionally, the results indicated that the structure and porosity of support materials play important roles in determining the performance of VMD process. Finally, results confirmed that temperature polarization had a more significant effect on the reduction of permeate flux than concentration polarization. [ABSTRACT FROM AUTHOR]

Vacuum membrane distillation (VMD) is a compelling technique for desalinating water because it exhibits superior pure water permeability at lower operating temperatures compared to other membrane distillation technologies. This leads to reduced energy consumption, lower heat loss via conduction across the membrane surface, and minimal heat transfer through conduction due to the low pressure on the permeate side. Detailed modelling of heat and mass transfer in VMD is essential for optimizing the process as it provides valuable insights that contribute to the advancement and successful implementation of seawater desalination using VMD technology. The aim of this study is to establish a comprehensive numerical model that describes the water vapor transfer across a hydrophobic micro-porous membrane in single-stage and multi-stage VMD processes for seawater desalination. The numerical predictions were compared to experimental data in addition to numerical computations based on an existing literature database, and good agreement has been found. The investigation also conducted a sensitivity analysis of process variables and membrane specifications on the VMD performance, as well as an assessment of the impact of temperature and concentration polarization. The obtained results showed that the permeation flux reached 18.42 kg/m2·h at 35 g/L feed concentration, 65 °C feed temperature, 50 L/h feed flow rate, and 3 kPa vacuum pressure. Moreover, the findings revealed that the feed temperature was the most significant factor, while the feed flow rate was the least important in determining the permeation flux. Additionally, the findings suggested that the effectiveness of the VMD process heavily relies on the composition and permeability of the support materials. Finally, the results confirmed that temperature polarization had a more significant effect on the reduction of the permeate flux than the concentration polarization. [ABSTRACT FROM AUTHOR]

In this study, advanced exergy and exergoeconomic analysis are applied to an Organic Rankine Cycle (ORC) for waste heat recovery to identify the potential for thermodynamic and economic improvement of the system (splitting the decision variables into avoidable/unavoidable parts) and the interdependencies between the components (endogenous and exogenous parts). For the first time, the advanced analysis has been applied under different conditions: constant heat rate supplied to the ORC or constant power generated by the ORC. The system simulation was performed in Matlab. The results show that the interactions among components of the ORC system are not strong; therefore, the approach of component-by-component optimization can be applied. The evaporator and condenser are important components to be improved from both thermodynamic and cost perspectives. The advanced exergoeconomic (graphical) optimization of these components indicates that the minimum temperature difference in the evaporator should be increased while the minimum temperature difference in the condenser should be decreased. The optimization results show that the exergetic efficiency of the ORC system can be improved from 27.1% to 27.7%, while the cost of generated electricity decreased from 18.14 USD/GJ to 18.09 USD/GJ. [ABSTRACT FROM AUTHOR]

Multi-effect distillation with thermal vapor compression (MED-TVC) is a highly energy-efficient desalination technology that can provide a reliable and sustainable source of high-quality water, particularly in areas with limited energy infrastructure and water resources. In this study, a numerical model based on exergoeconomic approach is developed to analyze the economic performance of a MED-TVC system for seawater desalination. A parallel/cross feed configuration is considered because of its high energy efficiency. In addition, a parametric study is performed to evaluate the effects of some operational parameters on the total water price, such as the top brine temperature, seawater temperature, motive steam flow rate, and number of effects. The obtained results indicate that the total water price is in the range of 1.73 USD/m3 for a distilled water production of 55.20 kg/s. Furthermore, the exergy destructions in the effects account for 45.8% of the total exergy destruction. The MED effects are also identified to be the most relevant component from an exergoeconomic viewpoint. Careful attention should be paid to these components. Of the total cost associated with the effects, 75.1% is due to its high thermodynamic inefficiency. Finally, the parametric study indicates that adjusting the top brine temperature, the cooling seawater temperature, the motive steam flow rate, and the number of effects has a significant impact on the TWP, which varies between 1.42 USD/m3 and 2.85 USD/m3. [ABSTRACT FROM AUTHOR]

In this paper, exergoeconomic and exergoenvironmental analyses of a solar vacuum membrane distillation (VMD) desalination system were performed to evaluate the cost of exergy destruction and the environmental impact of each component of the desalination system. The analysis permits the identification and evaluation of inefficiencies in the plant as well as the determination of the most environmental friendly process components and opportunities for design improvements. The results showed that the solar collector has the largest irreversibility and cost of exergy destruction. Therefore, it is a very important component for improving solar VMD plant performance. In addition, it will be profitable to reduce exergy losses in the membrane module even at the expense of increased investment costs since the dominant factor in the total cost rate for this component is the cost of exergy destruction. Whereas, it would be advantageous to reduce capital costs in the condenser since it has a relatively high exergoeconomic performance. On the other hand, exergoeconomic factor and exergy efficiency for the heat exchanger are found to be 49.02% and 96.59%, respectively, indicating that the exergy and exergoeconomic performance of this component is satisfactory. Finally, the results revealed that the largest potential for reducing the overall environmental impact of the solar VMD system is associated with the solar collector, the membrane module, the condenser, and the heat exchanger. [ABSTRACT FROM AUTHOR]

In this paper, the performance of an organic Rankine cycle with a zeotropic mixture as a working fluid was evaluated using exergy-based methods: exergy, exergoeconomic, and exergoenvironmental analyses. The effect of system operation parameters and mixtures on the organic Rankine cycle's performance was evaluated as well. The considered performances were the following: exergy efficiency, specific cost, and specific environmental effect of the net power generation. A multi-objective optimization approach was applied for parametric optimization. The approach was based on the particle swarm algorithm to find a set of Pareto optimal solutions. One final optimal solution was selected using a decision-making method. The optimization results indicated that the zeotropic mixture of cyclohexane/toluene had a higher thermodynamic and economic performance, while the benzene/toluene zeotropic mixture had the highest environmental performance. Finally, a comparative analysis of zeotropic mixtures and pure fluids was conducted. The organic Rankine cycle with the mixtures as working fluids showed significant improvement in energetic, economic, and environmental performances. [ABSTRACT FROM AUTHOR]