Exergy Balance Research Articles

Development of a Small-Scale Electricity Generation Plant Integrated on Biomass Carbonization: Thermodynamic and Thermal Operating Parameters Study

Biomass has been known as a source of energy with a thermochemical process that produces heat and can be converted further into electricity. However, thermal energy losses are a huge problem during combustion. To overcome this problem, a system based on organic Rankine cycle (ORCs) was developed to recover and utilize them to generate electricity. The proposed ORCs include an evaporator, a turbine, a condenser, and a pump coupled with a biomass carbonizing system to create a promising technology for small-scale electricity generation. In this work, a thermodynamic modelling equation based on energy and exergy balances was briefly expressed for each subcomponent of the system. A case study with R134a as the working fluid is being investigated to validate the system’s performance. In addition to the effects of R134a on temperature at the turbine exit, the suitable operating pressures has been specially adopted from several valid journals that focused on the effects of a wide range of possible operating pressure on the working fluid characteristics, which have a significant effect on the system performance. Finally, the theoretical analysis shows that the turbine work is profitable at an inlet pressure of 5 bar and an outlet pressure of 2 bar. This system is recommended to be integrated into the thermochemical biomass process. Recommendations have been made for the future development of small-scale biomass-fuelled power generation systems. This study shows that the thermal losses of the biomass thermochemical processes can be theoretically recovered in the form of electricity by using ORC efficiently.

A parametric exergy and energy analysis of the municipal solid waste dryer system: With a comparative-analytic approach toward recent experimental methods

One of the major problems of assemblies is the increasing production of waste and how to manage the waste system. One of the best ways to manage waste is to convert waste into energy. In this way, waste can be converted hygienically and away from pollution into materials used. By producing energy from waste, another problem is human beings who need energy. This study was devoted to comprehensively investigating the exergetic performance of a municipal solid waste dryer. The main aim of the current research was to reveal the reasons and sources of thermodynamic losses occurring in the plant-based on simulation data and compare the performances of several thermodynamical models. The critical design data for the analysis were collected from the Tehran municipality Tehran, Iran. After writing energy and exergy balances for all unit components, their exergetic performance parameters were measured individually. An attempt was also undertaken to quantify the contributions of the products to the overall exergetic efficiency of the plant. The most important results show that the best model for drying MSW is the logarithmic model with a corresponding R 2 of 0.98. Also, the drying rate was 0.003 kg/m 3 s, and the dryer’s energy and exergy efficiency were 13.94% and 2.96%, respectively. The humidity of the hot inlet air has the most significant impact on the energy and exergy efficiencies of the MSW dryer. Generally, the exergetic analysis presented herein could provide important guidelines and methodological blueprints for future investigations to develop thermodynamically efficient and environmentally-benign waste-to-energy plants. • A Verma model was used, then the logarithmic model was selected as the most appropriate model for modeling the MSW drying process. • The parametric study shows that the humidity of the air entering the dryer has the greatest effect on the energy and exergy efficiencies of the MSW dryer. • With increasing dry air inlet temperature from 300 K to 500 K, energy and exergy efficiencies decrease about 28% and 58%, respectively. • Increasing the amount of moisture of inlet air, the amount of energy and exergy efficiencies decrease 56% and 95%, respectively. • Increasing the temperature of the waste entering the dryer shows an increase inenergy and exergy efficiencies.

A Novel Ocean Thermal Energy Driven System for Sustainable Power and Fresh Water Supply.

The ocean thermal energy conversion (OTEC) is a potential substitute for traditional power plants in tropical islands and coastal regions. However, the OTEC power generation cycle has low thermal efficiency and the integrated utilization is imperative, in which an OTEC coupled with seawater desalination is the most attractive option. Membrane distillation (MD) has distinct advantages making itself a competitive process for seawater desalination, especially the feature that the drained warm seawater from the OTEC power plant can be recycled, improving the integrated output of the OTEC system. In this study, an innovative OTEC system coupling a power generation sub-cycle (PGC) and a water production sub-cycle (WPC) was proposed, composed of the upstream organic Rankine cycle and the downstream membrane distillation modules. The mass, energy and exergy balance of the individual equipment, the sub-cycles and the whole system were performed by constructing the corresponding balance models. The thermal dynamic parameters were calculated, and the performance of power generation and water production was predicted. The results showed that by coupling with the MD desalination, the thermal efficiency of the OTEC system can be greatly improved from 2.19% to 25.38% while the exergy efficiency changed little. For a 100 kW OTEC power generation cycle, the water production rate approached 58.874 t/d. In addition, the economic analysis based on the electricity and water sale was carried out, and the profit can be improved by extra water production, especially in the Hawaii and Rainbow Beach by nearly 20%.

Energy and exergy analysis of a downstream single-row air washer at different droplet diameters for air cooling application

This study proposes a downstream single-row air washer for air cooling. The theoretical energy and exergy balance models were established at different droplet diameters and verified by the experimental data. Based on the abovementioned theoretical relationship, the single performance indicator of heat exchange efficiency (HEE) and exergy efficiency was quantitatively analyzed; a comprehensive analysis method of two indicators was proposed, combining HEE and exergy efficiency, and a numerical simulation was carried out. Results show that the smaller the droplet diameter and the larger the water–air ratio, the lower the dry-bulb temperature of the outlet air and the higher the HEE and exergy flux destruction. When the droplet diameter is less than 440 μm, the droplet diameter does not affect exergy efficiency and dry-bulb temperature. When the droplet diameter is larger than 440 μm, the droplet diameter is positively correlated with the air outlet dry-bulb temperature and exergy efficiency; in contrast, the water–gas ratio is negatively correlated with the air outlet dry-bulb temperature. An engineering case reveals that when the air outlet temperature is less than 34°C, the critical water–gas ratio can be set as 2.6 (mass ratio). At this time, the HEE is more than 90%, the exergy efficiency is more than 60%, and the critical value of droplet diameter is 440 μm. The research results provide an essential theoretical basis for the optimization of engineering design calculation.

Effects of water recirculation on microalgae assemblage and corresponding sustainability of the photobioreactor cultivation system

An algae photobioreactor (APB) was used to determine the effect of water recirculation on the growth of algal assemblage. CO2 in the flue gas from a power plant was the carbon source. Boiler water was used as the source water. The results showed that microalgae cultivation under recirculation conditions was stable over a period of four months. Biomass productivities during the 1st through 4th months of recirculation (0.26, 0.23, 0.20, and 0.18 g L−1 d−1, respectively) were not significantly different than freshwater (0.22 g L −1 d −1). Furthermore, the relationship between eukaryotic and bacterial domains in the assemblage remained consistent throughout the four months of recirculation (80.7, 87.1, 83.1, and 82.1%, respectively, and 19.2, 12.8, 16.9, and 17.8%, respectively). This was not significantly different than the abundance of each domain in the control freshwater cultivation (83.7% eukaryotic and 16.2% bacterial). A 1 m3 photobioreactor was then envisioned for a mass, energy, and exergy analysis to evaluate the water recirculation on sustainability of the culture system. The mass balance analysis concluded that 98% reduction in water usage, 25% reduction in nitrogen, and 12.5% reduction in phosphorus could be achieved during cultivation operating under recirculation for one year, while maintaining biomass productivity of 1.2 kg wet algal biomass and sequestration of 0.4 kg CO2 per day. The exergy balance analysis concluded that without considering solar irradiation, the culture with water recirculation greatly enhanced the rational exergy efficiency, which represents a more sustainable cultivation system for CO2 capture and utilization.

Exergy Analysis of Recycled Cooling System in a Process: A Case Study

Heat pumps are devices those allow to use the energy available in nature but cannot be used because of its low temperature. By raising its temperature, heat pumps do this with a cooling cycle similar to that of air conditioners. This study presents the performance analysis of an in-room heating system during mushroom compost fermentation using a heat recovery device with an air source heat pump, which is a type of heat pump. The study was carried out by setting up experimental equipment and providing measurement-based parameters in the university laboratory. The performance analysis of the system was calculated by considering all system elements (compressor, condenser, evaporator, expansion valve etc.) and the results were evaluated numerically. Performance analysis was made according to whether a heat pump is used in the system. Based on the results obtained by these calculations, when heat recovery device is added to the system, the work done by the compressor, loss of exergy, exergy balance and efficiency decrease. While the exergy balance of the condenser decreases, its efficiency increases. Also, while the exergy balance of the expansion valve increase, its efficiency decreases. Overall, the efficiency of the device increases.

OPTIMIZATION OF THE TECHNOLOGICAL PARAMETERS OF THE HEAT RECOVERY SYSTEM OF A BOILER PLANT WITH THE AIR PROTECTION METHOD OF GAS WATER TRACTS

The results of a study of the efficiency and optimization of technological parameters of the heat recovery system of a boiler plant, in which the method of mixing part of the heated air into the flue gases after the heat recovery unit, is implemented. The essence of the air method is to increase the temperature and decrease the relative humidity of the resulting mixture, which reduces the amount of condensate on the walls of the exhaust ducts. A gas-consuming boiler plant with a heat recovery system for heating heat supply water is considered. To optimize the technological parameters of the system in the implementation of this method, a complex technique based on exergy analysis was used. The technique combines structural-variant methods and balance integral methods of exergy analysis. This allows you to determine the exergy, heat engineering and technological characteristics that are included in the criteria for evaluating the efficiency of heat recovery systems. Due to the small number of parameters required for the calculation, and the simplicity of the calculation and analytical methods for obtaining exergy characteristics, the technique is convenient for research. The accuracy of the results obtained is 0.3-0.5%. A block diagram of a boiler plant with a heat recovery system in the implementation of the mixing method is given. In the block diagram, input and output excretory flows between individual elements are identified. The criteria for evaluating the efficiency of heat recovery and the main technological optimization parameters have been selected. Based on the general system of exergy, thermal and material balance equations in accordance with the structural scheme, an exergy balance equation was compiled, from which exergy losses and heat-exergy efficiency criteria were determined. The optimal values in the heat exchanger heat output and the amount of mixed air, which correspond to the high efficiency of the system, are determined.

АСПЕКТЫ ПРИМЕНЕНИЯ ЭКСЕРГИИ ДЛЯ АНАЛИЗА ЭНЕРГЕТИЧЕСКОГО КОМПЛЕКСА ПРЕДПРИЯТИЙ ПЕРЕРАБОТКИ УГЛЕВОДОРОДНОГО СЫРЬЯ

The paper describes methodological approaches of applying the thermodynamic analysis to assess the efficiency of complex chemical and engineering systems, as well as to identify the scientifically-based areas for improving the energy sector. Modern chemical and engineering systems including the hydrocarbon processing plants are characterized by the high specific energy intensity and complex engineering topology. The sophistication of such facilities can be objectively assessed based on the exergy analysis. The exergy analysis makes it possible to carry out a quantitative and qualitative assessment of any type of energy at the enterprise. Moreover, it provides an opportunity to adequately evaluate the potential of the energy utilization including secondary energy resources, combustible hydrocarbon gases, industrial wastes, and effluents. The paper presents methodological approaches to determine the exergy types and calculate the exergy balance, considering the specifics of hydrocarbon processing plants. The exergy balance of the study subject represented in the form of a Grassmann diagram has been calculated using the above provisions. Besides, the exergy of all types of fuel consumed has also been calculated, as well as the industrial processes consuming the largest amount of the fuel exergy for functioning have been determined. Finally, according to the data presented, the main directions for improving the efficiency of the hydrocarbon processing plants have been proposed.

Energy and exergy analysis during drying in rotary dryers from finite control volumes: Applications to the drying of olive stone

• An exergy and energy analysis during drying is performed from finites control volumes. • A big thermal shock is produced in the first third of the trommel due to evaporation. • Heat loss and exergy destruction is very high at the beginning of the drying process. • The dryer works in optimum conditions at low-medium air flows and low-medium temperatures. • This study will help improve aspects like design and control in rotary dryers. Nowadays, the design, control and development of rotary dryers are based on the study of the complete equipment. Rotary dryers are treated as a black box where only inlet and outlet parameters are known. This implies the need to know the main interactions of mass, energy and exergy throughout the trommel to help improve the drying process. In this paper, we carried out an analysis of energy and exergy during drying of olive stone from finites control volumes in an experimental rotary dryer. Mass, energy and exergy balances are applied to each control volume in the drying air. The design of experiments is based on three initial drying air temperatures (210 °C, 180 °C and 150 °C) and three drying air flows (576 kg/h, 425 kg/h and 280 kg/h), with a by-product mass flow of 40 kg/h and a rotational speed of 5.5 rpm. The results indicated that olive stone moisture content was reduced to less than half in the first third of the trommel where a big thermal shock is produced due to the interaction between the by-product and the drying air flow at high moisture contents and high temperatures, respectively. This fact led to the highest exergy destruction values, thereby diminishing the flow exergies for the following control volumes. Heat losses were considerable in all equipment, especially in the first two control volumes. Furthermore, drying process was analyzed from the energetic, exergetic and drying efficiencies and the unit energy consumption.

ANALYSIS OF EXERGY LOSSES IN HEAT RECOVERY SYSTEMS OF BOILER PLANTS WHEN IMPLEMENTING THE BYPASS METHOD TO PROTECT CHIMNEYS

The results of the analysis of exergy losses in the heat recovery systems of boiler plants during the implementation of one of the thermal methods of anticorrosion protection of gas exhaust ducts - the bypass method - are presented. Gas-consuming boiler plants with a heat recovery system for heating heat supply water are considered. The choice of a complex technique for the analysis of exergy losses in a heat recovery system with gas bypass is substantiated. The technique includes structural-variant and integral balance methods of exergy analysis and is effective due to the small number of parameters required for the calculation, the simplicity of the calculation and analytical methods for obtaining exergy characteristics, and the high accuracy of the results obtained. The principal and structural diagram of the heat recovery system in the implementation of the bypass method is given. In the block diagram, the input and output exergy flows between the individual elements of the heat recovery system are identified. According to the block diagram, an exergy balance equation was compiled, on the basis of which the exergy losses and the heat exergy efficiency criterion were determined. The exergy characteristics of the heat recovery system are given with an increase in the amount of bypassed gases and different values of the heat load of the heat recovery system. It is shown that the nature and extent of the impact of these parameters depend on the specified load. It has been established that an increase in the amount of bypassed gases at all values of the heat load of the heat recovery system leads to a decrease in exergy losses and the heat power criterion. The value of the heat load of the heat recovery system is determined, at which its exergy efficiency in the implementation of the bypass method is the highest.

Comparison of Thermodynamic Performances in Three Geothermal Power Plants Using Flash Steam

Abstract Three geothermal systems, including single-flash, double-flash, and double-flash connected turbine flash geothermal power plants, are compared in terms of electrical power production and exergy efficiency. In the double-flash connected turbine (double-T) geothermal electrical power production systems, the outlet stream from the first steam turbine is recovered in the mixing chamber and combined with the vapor product of the second separator. The thermodynamic model for the single-flash, double-flash, and double-T geothermal systems is developed using energy and exergy balances for each component of the systems. From the thermodynamic model, the optimum flash chambers pressures, at which the electrical power production is a maximum, can be determined. It is found that, for an input geothermal source temperature of 230 °C and an input geothermal water mass flowrate of 230 kg/s, the optimum pressures for the first flash chamber are 300 kPa, 350 kPa, and 350 kPa for the single-flash, double-flash, and double-T geothermal systems, respectively. The electrical power produced in these systems at their corresponding optimum flashing pressures, respectively, are 16,000 kW, 19,500 kW, and 20,600 kW. Also, for the single-flash, double-flash, and double-T geothermal systems, the exergy efficiency at the optimum flash chamber pressures are found to be 44.2%, 47.1%, and 48.5%, respectively.

A framework for exergy analysis of process control systems

In this study, a generic framework has been developed for using exergy as a dynamic measure for energy efficiency of process control systems. The proposed framework begins by restating the exergy balance in terms of nonlinear state space; followed by partitioning of input variables. The exergy balance is then linearized, and added to the plant model to construct an extended state space model which has unknown number of non-physical states. The numerical method of sub space state space system identification is applied to determine the extended model matrices along with the system order. Laplace transform is then applied to convert the extended state space into a multi-input-single-output (MISO) formula for estimating the lost work. In the next step, an scalar index is suggested for representing the steady and transient parts of the dynamic lost work. The proposed index which is defined in the time domain is transformed into Laplace domain for consistency with the formulated MISO lost work. The suggested framework is tested for two case studies; (1) selection of the control variables for a CSTR, and (2) selection of the tray number for inferential control of a distillation column. The results confirm the generality of the proposed framework not only for exergetical optimization of control systems but also for disclosing the thermodynamically unrealizable structures.

Exergy Analysis of the Electromagnetic Railgun

In this article, the energy conservation equation of a railgun is established by the Poynting theorem. The concept of exergy in thermodynamics is introduced, and the exergy calculation formula of electromagnetic (EM) energy, kinetic energy, and Joule heat as well as the exergy balance equation of the system are obtained. Using the experimental parameters of a medium-caliber railgun, the exergy of magnetic energy stored in the inductor of the system after a launch is calculated by dynamic simulation, and the exergy loss caused by friction and air drag as irreversible factors is obtained. The skin effect caused by time-varying EM field is considered when calculating the heat exergy of Joule heat of rails. Through the transient thermal simulation of the rail by the finite-element software, the temperature field distribution of the rail is obtained. On this basis, the qualitative temperature for calculating the heat exergy is obtained, and the heat exergy stored on the rail after the launch is calculated by the formula. Finally, how to reduce the exergy loss of the railgun is analyzed qualitatively.

A Thermodynamic Performance Analysis of Triple Effect Vapour Absorption Refrigeration System Using LiBr-H2O

Abstract: Being an eco-friendly system and a cheaper way to produce cooling effect absorption refrigeration system (ARS) is becoming more popular as it can produce higher cooling capacity than vapor compression refrigeration systems, and it can be powered by other sources of energy (like waste heat from gas and steam turbines, or can utilizes renewable source of heat by sun, geothermal, biomass) other than electricity. In the recent years, the interest in absorption refrigeration system is growing because these systems have environmentally friendly refrigerant and absorbent pairs. In this study, a detail energetic analysis of triple stage LiBr-H20 absorption system using First law of thermodynamics is done. An Energy Equation Solver code are used to simulate the computer program is developed for the cycle and results are validated with past studies available is also done. Mass, energy and exergy balance equations and the various complementary relations constitute the simulation model of the triple effect refrigeration system. Further, the effect of exit temperature of generator, absorber, condenser and evaporator on COP, solution concentration and other parameters are studied. It was found in the study that COP increases with increasing the generator exit temperature keeping the absorber exit temperature constant but when the absorber exit temperature is increased COP tends to decrease and the concentration of weak solution leaving HP generator (Xw3), MP generator (Xw2) and LP generator (Xw1) also increases with increase in generator exit temperature, while it decreases with increase in condenser exit temperature. Keywords: Absorption Refrigeration System (ARS), LiBr + H2O, COP, solution concentration, Energy Equation Solver code, energetic analysis, triple effect refrigeration system.

Thermal-exergy efficiency trade-off optimization of pressure retarded membrane distillation based on TOPSIS model

There has been an increasing interest in recovering low-grade heat and desalination simultaneously using pressure retarded membrane distillation (PRMD). As an energy-based process driven by temperature difference, the analysis of energy efficiency is significant. This work aims to analyze the effect of various operating parameters on thermal and exergy efficiencies of a counter-flow PRMD system. As the optimal value corresponding to the maximum thermal efficiency does not coincide with that leading to the maximum value of the exergy efficiency, a multi-objective optimization based on TOPSIS model and entropy weight method was conducted. A mathematical model including mass and heat transfer, and exergy balance for membrane module was firstly established to definite the effect of various parameters on PRMD performance. Then the highest scored condition was obtained, and thermal efficiency and exergy efficiency reached 78.75% and 43.4% respectively. Compared with the performance under the single-objective optimization for exergy efficiency, the exergy efficiency under the multi-objective optimization was reduced by only 5.73%, but the thermal efficiency is increased by 21.84%. Besides, the working conditions under multi-objective optimization with different feed solution concentrations are also presented. The PRMD system is trade-off optimized, which provides a reference for cost reduction and large-scale deployment.

Exergy-environment assessment for energy system: Distinguish the internal and total exergy loss, and modify the contribution of utility

Improving the efficiency of energy system is a way to reduce its environmental impact. However, high efficiency always means high system complexity and high expense, and will again increase the environmental impact. This work proposed an exergy-environment assessment method for energy system. With the exergy balance calculation, the method converted the internal and total exergy loss flows, as well as the life-cycle consumed material (including utility), to the values of environmental impact points. This work also proposed indexes to assess whether the energy transformation (exergy loss) or the life-cycle consumption dominates the environmental impact. Then, this work adopted a sludge digestion system to show the application of the proposed method. The exergy analysis and environmental impact points of the system were calculated. The entire system has a positive exergy output of digestion gas (4.18 GJ h−1). The objective exergy efficiency of system is 27.11%, and the general exergy efficiency of digester unit (80.10%) is over two times that of heating unit (35.00%). Heating unit also has a much higher environmental impact than digester unit (about 1.00: 0.15). Results show that the exergy-environment assessment does not breach the classical thermodynamic analysis and provides the understanding of environmental impact. Compared to previous studies, this work resolves the issue of unreasonable data for the exergy-environment impact factor in methodology by amending its value from <0 or ≈0 to 0.40, clarifying the significance and rationality of exergy-environment assessment. The case study result shows the feasibility and advantage of the proposed method, which can be flexibly selected by decision maker. Impact factor based on the internal exergy loss is relatively preferred from the perspective of sustainability.

Experimental study of the potential for thermal energy recovery with thermoelectric devices in low displacement diesel engines

Improving the thermal efficiency of internal combustion engines is essential to reduce the operating costs and complaints with the increasing environmental requirements. Thermoelectric generators came up as an opportunity to reuse part of the heat loss with the exhausts. This paper evaluates the performance of a thermoelectric generator to improve the efficiency of a stationary diesel engine under different rotational speeds and torques. The data was obtained through CFD simulations and validated with experiments. The proposed solution uses a cooling system to control the temperature of the thermoelectric modules. The results show that the torque and the rotational speed of the engine are the most significant performance parameters of the thermoelectric generator, while the influence of the cooling water temperature has a minor but still significant influence. Additionally, the results show a change from 1.3% to 6.2% in the thermoelectric generator efficiency, while the exergy efficiency varies between 1.8% and 7.9%. The exergy balance indicates that most of the exergy is loss because of the irreversibilities in the thermoelectric generator and of the exergy loss with the exhausts. The exergy loss can be reduced by optimizing the design of the heat exchanger. Since the thermoelectric generator improved the engine efficiency by a marginal 0.2%–0.8%. Therefore, it is important to further research how to improve the design of heat exchangers for thermoelectric generators to increase their energy conversion efficiency and their impact on the energy efficiency of internal combustion engines.

Exergy Analysis of Electrochemical Systems for Space Exploration

Human exploration of space, facilitated by electrochemical systems, will require integration of many seemingly disparate systems including but not limited to power systems, in situ resource utilization (ISRU), and environmental control and life support (ECLS). Through combining expressions of the First and Second Laws of Thermodynamics exergy quantifies the useful work that can be obtained from a system, subject to environmental limitations. This approach provides a means of integrating diverse systems and components based on one consistent and physically meaningful property: exergy. Using this property as a basis, diverse systems can be analyzed and integrated effectively based on the exergy destruction and exergy efficiency. Here, the applicability of exergy analysis to systems design and integration is demonstrated through two examples involving electrochemical systems that support human space exploration.First, analysis of the ECLS system aboard the International Space Station (ISS) is conducted to assess its overall performance in terms of exergy destruction rates and exergy efficiency. The ECLS system is divided into constituent subsystems which are further divided into key components. Based on this system decomposition, exergy balances are derived for each component and subsystem. Special focus is given to the Oxygen Generation Assembly (OGA) within the ECLS Atmospheric Revitalization Subsystem. The results of parametric studies of the OGA proton exchange membrane electrolyzer performance are presented with an emphasis on the impacts of operational conditions on exergy efficiency. This electrolyzer is a significant contributor to system exergy destruction and exhibits a low exergetic efficiency. It therefore presents an opportunity for improving overall ECLS system performance.Following the example of ECLS exergy analysis, the application of exergy analysis to the integration of power and ISRU systems for lunar exploration is presented through system level models. Exergy destruction and efficiency are quantified over the lunar diurnal cycle for power and ISRU systems. The power systems analysis focuses on photovoltaic arrays paired with battery and regenerative fuel cell systems. The ISRU system analysis focuses on production of oxygen from lunar regolith through the reduction of ilmenite combined with water electrolysis. Here the application of exergy analysis identifies key opportunities for the use of byproduct heat and the optimal sizing of system components.The studies presented demonstrate the capability of exergy analysis to support the design and integration of electrochemical systems within larger power, ISRU, and ECLS systems supporting space exploration. This approach can enable the full and efficient use of a system’s available work potential based on a consistent, physically meaningful property. Therefore, exergy analysis is shown to be a key tool for the future design and integration of electrochemical systems for space exploration.

Experimental Energy and Exergy Analysis of an Automotive Turbocharger Using a Novel Power-Based Approach

The performance of turbochargers is heavily influenced by heat transfer. Conventional investigations are commonly performed under adiabatic assumptions and are based on the first law of thermodynamics, which is insufficient for perceiving the aerothermodynamic performance of turbochargers. This study aims to experimentally investigate the non-adiabatic performance of an automotive turbocharger turbine through energy and exergy analysis, considering heat transfer impacts. It is achieved based on experimental measurements and by implementing a novel innovative power-based approach to extract the amount of heat transfer. The turbocharger is measured on a hot gas test bench in both diabatic and adiabatic conditions. Consequently, by carrying out energy and exergy balances, the amount of lost available work due to heat transfer and internal irreversibilities within the turbine is quantified. The study allows researchers to achieve a deep understanding of the impacts of heat transfer on the aerothermodynamic performance of turbochargers, considering both the first and second laws of thermodynamics.

Performance enhancement and multi-objective optimization of a double-flash binary geothermal power plant

Initiating cost-effective and technological frameworks to exploit geothermal energy is a fundamental incentive for scientists and engineers; in this regard, flash-binary geothermal power plants are plausible for high-temperature geothermal resources. Stemming from an in-depth literature review, it is conspicuous that the thermal and exergy losses of the expansion process are significant. To shed light on this matter, an ejector-expander is integrated into the conventional expansion valve of a double-flash binary geothermal power plant to enhance the plant performance. The feasibility of the contrived notion is scrutinized from energy, exergy, thermal, and cost balance standpoints and results converged in the increase in turbine output power, energy efficiency, and exergy efficiency of approximately 7.66%, 7.64%, and 7.69%, respectively. Among all components, the condenser constituted a 45.06% share of the overall exergy destruction, whilst the turbine had an exergy destruction ratio of 22.07%. An intensive parametric study is implemented that outlined that the turbine output power, energy efficiency, and exergy efficiency of the ejector-expander power system have a maximum in a specified pressure value of the first and second separator. Another merit was a marked decrease in the unit cost of power when ejector-expander is employed.