Exergetic Performance Research Articles

Exergetic performance evaluation of SAH with inclined ribs used as coarseness in triangular duct

Exergetic efficiency analysis is one of the important tools to determine the thermal performance of Solar Air Heater as it taken useful energy gain and the pumping power in the consideration. In this research, an analytical study is carried out to evaluate the exergetic performance of SAH with inclined rib coarseness attached to the underside of the absorber plate in a triangular duct. The exergetic efficiency were calculated and compared to smooth Solar Air heater. The exergetic efficiency is highest for Reynold number 10000, relative roughness height of 0.043, relative roughness pitch of 12 and angle of attack of 60°. The optimum value of temperature rise parameter is found to be 0.133 Km2/W for all operating and roughness variables. Design plots were also presented in order to help the designers in the design of SAH with inclined ribs for the given range of operating and roughness variables.

Exergetic performance analysis of high pressure air systems on ships

Exergetic performance analysis of high pressure air systems on ships

Thermodynamical study and Taguchi optimization of a two-stage vapor compression refrigeration system

This study?s primary purpose is to optimize the multistage refrigeration system with statistical methods. Taguchi optimization and ANOVA methods were applied to statistically determine the effects of components on system performance. The best operational conditions were defined for the maximum COP and exergy efficiency. Critical parameters have been determined to maximize the system?s performance. The evaporator temperature was defined as the most vital parameter (46.32%), and it is followed by condenser temperature (32.65%) for the maximum COP. The most important two parameters are determined as evaporator temperature with 29.14% and condenser temperature with 20.34% for maximum exergetic performance. As a result of 27 tests, the highest COP of the system was calculated as 2.67 and exergy efficiency as 55.22%. By using the optimum levels determined by Taguchi, it was ensured that the system?s COP was increased to 3.326 and its exergy efficiency to 71.23%. The ANOVA analyses indicate that the results? confidence level is relatively high, to be 99.9%. Another parameter examined in this study is the inter-stage level determination method and its effect on system performance. The method of determining the optimum inter-stage level may vary according to the objective function and system conditions.

Exergetic performance analysis of high pressure air systems on ships

Exergetic performance analysis of high pressure air systems on ships

Exergetic performance analysis of low GWP refrigerants as an alternative to R410A in split air conditioner

In the present analysis, five alternative refrigerants namely R32, R447A, R447B, R452B, and R454B have been analysed based on exergy to find an alternative of high global warming potential refrigerant R410A, in a split air conditioner. Evaporator temperature is considered as 4.5 °C whereas condenser temperature is taken from 40 °C to 60 °C in the interval of 4 °C. Different performance parameters have been calculated like total exergy destruction (TED), exergy destruction ratio (EDR), exergy efficiency, along with the coefficient of performance (COP) and efficiency defect. The result shows that R447A is found to be the potential alternative to replace R410A in the air conditioner as it has 9.24% higher COP and 15.38% less destruction of exergy along with 9.3% higher exergy efficiency compared to R410A at a condenser temperature of 60 °C. TED and EDR, are found to be minimum with the R447A system among all the considered refrigerants.

Investigation of the Energetic and Exergetic Performance of Photovoltaic Thermal Solar Collectors with Different Surface Areas and Various Mass Flow Rates

Investigation of the Energetic and Exergetic Performance of Photovoltaic Thermal Solar Collectors with Different Surface Areas and Various Mass Flow Rates

Performance evaluation of a rotary dryer in both co-current and counter-current configurations

A mathematical model was developed to simulate the process of superphosphates fertilizers drying in a rotary dryer in both co-current and counter-current configurations. Besides, the performance of the rotary dryer, installed in a local industrial unit, was assessed using the concept of energy and exergy analysis. Matlab software was used to develop the mathematical model, which is based mainly on mass and energy conservation equations. Good agreement between the simulated results and the experimental results from literature was obtained. The simulation results showed that the product’s moisture content was reduced from an initial value of 0,14 kgH2O / kg dry solid to 0.0912 and 0.0862 kgH2O / kg dry solid at the dryer's outlet for the co-current and the counter-current configurations, respectively. A parametric study was carried out to evaluate the effect of the length of the dryer and the inlet drying air temperature on the moisture content to compare both configurations. Energetic and exergetic indicators were formulated and then computed based on the inlet operating conditions. The energy efficiency and the specific energy consumption for the co-current and the counter-current configurations were, respectively, found to be 13% and 24% and 5762 and 3502 kJ per kg of water evaporated. The exergy indicators, namely the exergy loss, the exergy destruction rate, and the exergetic efficiency, were 11.37 and 17.82 kW, 1.026 and 1.098 kW, 25.86 and 41.38% for the co-current and the counter-current configuration, respectively. A sensitivity analysis was used to investigate the effect of varying the inlet drying air temperature on energetic and exergetic performance parameters.

Exergy based performance analysis of rice husk fuelled producer gas operated boiler for thermal application in parboiling mills

The utilization of rice husk to generate produce gas and run gas-fired boiler can enhance the overall efficiency of the rice parboiling system. Moreover, the exergy analysis of such a system maximizes the efficiency and helps to reduce the fuel requirement and environmental impact. To perform the exergy analysis in paddy parboiling mills, the properties of producer gas, air inflow to the combustor, water, steam, and flue gas must be needed. In this study, experiments are conducted to find these parameters and the exergetic performance has been analysed for different reference temperatures. 3D plots relating the important paraments are used to predict the performance of the boiler and its components. The exergy destruction is maximum at the combustor which is 65.5 %. The maximum exergetic efficiency achieved at the combustor, steam generator, and the total system is 33.45 %, 40.29 %, and 17.64 % respectively when the Equivalence Ratio (ER) of the gasifier is at 0.2. Whereas, the Potential Improvement is found to be a minimum of 49.21 kW and the Sustainability Index is a maximum of 1.21. The exergy efficiency of the boiler, heat exchanger, and combustor are found to be decreased up to 36.9 %, 21.06 %, and 29 % respectively when the reference temperature is increased from 280 K to 320 K.

Exergetic sustainability analysis of municipal solid waste treatment systems: A systematic critical review

The growing volume of municipal solid waste (MSW) generated worldwide often undergoes open dumping, landfilling, or uncontrolled burning, releasing massive pollutants and pathogens into the soil, water, and air. On the other hand, MSW can be used as a valuable feedstock in biological and thermochemical conversion processes to produce bioenergy carriers, biofuels, and biochemicals in line with the United Nations’ Sustainable Development Goals (SDGs). Valorizing MSW using advanced technologies is highly energy-intensive and chemical-consuming. Therefore, robust and holistic sustainability assessment tools should be considered in the design, construction, and operation phases of MSW treatment technologies. Exergy-based methods are promising tools for achieving SDGs due to their capability to locate, quantify, and comprehend the thermodynamic inefficiencies, cost losses, and environmental impacts of waste treatment systems. Therefore, the present review paper aims to comprehensively summarize and critically discuss the use of exergetic indicators for the sustainability assessment of MSW treatment systems. Generally, consolidating thermochemical processes (mainly incineration and gasification) with material recycling methods (plastic waste recovery), heat and power plants (steam turbine cycle and organic Rankine cycle), modern power technologies (fuel cells), and carbon capture and sequestration processes could improve the exergetic performance of MSW treatment systems. Typically, the overall exergy efficiency values of integrated MSW treatment systems based on the incineration and gasification processes were found to be in the ranges of 17–40% and 22–56%, respectively. The syngas production through the plasma gasification process could be a highly favorable waste disposal technique due to its low residues and rapid conversion rate; however, it suffers from relatively low exergy efficiency resulting from its high torch power consumption. The overall exergy efficiency values of integrated anaerobic digestion-based MSW processing systems (34–73%) were generally higher than those based on the thermochemical processes. Exergy destruction and exergy efficiency were the most popular exergetic indicators used for decision-making in most published works. However, exergoeconomic and exergoenvironmental indices have rarely been used in the published literature to make decisions on the sustainability of waste treatment pathways. Future studies need to focus on developing and realizing integrated waste biorefinery systems using advanced exergy, exergoeconomic, and exergoenvironmental methods.

Investigation of the effect of compression ratio on the energetic and exergetic performance of a CI engine operating with safflower oil methyl ester

This study examines the energy and exergy analyses for a single-cylinder, four-stroke, direct-injection, compression-ignition (CI) engine when it was run on the safflower (Carthamus tinctorius L.) oil methyl ester (SOME) and traditional diesel (as reference fuel) at various engine loading conditions (from 25% to full load in 25% steps) at a fixed speed of 1500 rpm. In addition, the compression ratio (CR) was changed between 12:1 and 18:1 in order to monitor its effect on the engine characteristics. The experimental outcomes obtained from the above-stated analyses showed that the tested engine spent more alternating fuel because of its lower energy content than that of diesel fuel in an effort to ensure the output power to be the same for the test fuels. Furthermore, the results exhibited that the energetic and exergetic efficiency enhanced with the increase of load and CR. In this contest, at the CR of 18:1 and full load, the maximum energy efficiency values for SOME and diesel fuel were found to be 28.67% and 29.78%, respectively meanwhile the related exergetic efficiency values were calculated to be 26.41% and 27.94%, respectively. The minimum exergy destruction figures were revealed at the CR of 18:1 and a load of 100% for tested fuels with the findings of 56.59% for SOME and 55.22% for diesel fuel. In conclusion, the results of the conducted analyses for the tested diesel engine powered by SOME appeared to be fairly close to those of diesel fuel at various loads and CRs. SOME will eventually be classified as an alternate fuel to petroleum-based diesel fuel.

Thermo-hydraulic and exergetic performance of a cost-effective solar air heater: CFD and experimental study

An experimental and computational fluid dynamics (CFD) study is carried out to investigate the impact of secondary flow strengthening the thermo-hydraulic performance of discrete multiple inclined baffles in a flat plate solar air heater (SAH) with semi-cylindrical sidewalls. Initially, for a fixed relative baffle height (Rh = 0.1), the relative baffle pitch (Rp) for continuous baffles is varied in the range of 0.6–1 to obtain the optimum baffle pitch for 6000 <Re < 14000. The impact of gaps at leading, trailing, and both leading and trailing apices are studied as three different configurations with the optimum Rp. A maximum thermo-hydraulic performance of 2.69 is obtained for the gap at the trailing apex. The proposed design has a higher collector efficiency, 55–70%, compared to the ribbed rectangular SAH design exhibiting 30–55%. With lower exergy losses, the present SAH design has higher exergetic efficiency (1.5%–2.2%)than ribbed rectangular SAH (0.9%–1.7%) for the range of Re studied. Further, at low Re, the present SAH design has a higher coefficient of performance, indicating that it is cost-effective than ribbed rectangular SAH designs.

Energy and exergy analyses of an innovative energy storage configuration using liquid air integrated with Linde-Hampson liquefaction system, molten carbonate fuel cell, and organic Rankine cycle

In this study, the peak shaving idea for storing energy during off-peak hours with low price and its use during peak hours with high price is investigated. The present work introduces an innovative storage-generation configuration for the distributed generation of energy through a combination of Liquefied Natural Gas regasification (LNG), Liquid Air Energy Storage (LAES), Molten Carbonate Fuel Cell (MCFC), and Organic Rankine Cycle (ORC). To compress and liquefaction of air, 108 MW electricity is required on the off-peak. The liquefied air and wasted heat from the intermediate cooling of the compressors are stored on the off-peak. The LNG stream after the regasification operation enters the MCFC cycle as fuel on the on-peak. The output heat from the fuel cell and the stored heat on the off-peak are used for preheating, the ORC, and the gas power system. At the on-peak condition, the MCFC, the gas power system and ORC generate 210.8 MW of power at a high price of electricity. The innovative system for peak shaving purposes and reduction of pollution by employing a fuel cell instead of combustion chambers is developed. The present work evaluated the thermodynamic and exergetic performances of each component and overall integrated system. The overall exergy efficiency of an integrated system, exergy efficiency in peak hours, and fuel cell efficiency decrease when methane content increases. Furthermore, with raising methane content, the irreversibility of the new structure and storage efficiency increase. Results show the highest exergy destruction is associated with the MCFC with 33.28% and heat exchangers with 25.41%. The system's round-trip efficiency is achieved to be 69.31% that improves 5.11%, whereas storage efficiency is obtained to be 86.22%, which increases 12.82% rather than the reference system. In addition, system exergy efficiency and storage exergy efficiency are obtained to 60.25% and 80.78%, respectively.

A review on converting plastic wastes into clean hydrogen via gasification for better sustainability

This review paper focuses on converting plastic wastes into clean hydrogen via gasification for better sustainability. In this regard, various aspects of hydrogen production from plastic wastes are discussed and comparatively evaluated, including the state-of-the-art and comparative evaluation, environmental and economical dimensions, global warming aspects, policies and strategies, a case study including energetic and exergetic performance evaluations, challenges and opportunities, and future directions possibly in the area. Additionally, this paper outlines what contributions it makes to the current literature about hydrogen production from plastic wastes by using gasification technologies. Moreover, this paper provides a detailed case study indicating exergetic sustainability aspects for hydrogen production from plastic wastes by applying plasma gasification whose data are taken from the literature. As a result of this case study, some exergetic sustainability indicators are studied for evaluation and comparison purposes. The exergetic sustainability index is found to be decreasing from 0.77 to 0.41 with the fact that exergetic efficiency drops from 0.43 to 0.28 while the environmental impact factor rises from 1.29 to 2.41 with the increase of waste exergy ratio from 0.56 to 0.70. Furthermore, plasma co-gasification can be recommended as an environmentally-benign solution for clean hydrogen production from plastic wastes. Highlights Plastic wastes is an important source of hydrogen. Gasification can efficiently be deployed for hydrogen production from plastic wastes. In order to evaluate potential gasification techniques, energetic, economic, environmental, and sustainability aspects should be considered. Plasma gasification appears to be more efficient and effective solution over other methods for higher amount of hydrogen production from plastic wastes.

Energy, Exergy and Economic Analysis of Absorption Chiller Systems: A Case Study for a Wood Pencil Factory

This study examines the use of absorption chiller systems in a designated industrial facility having waste heat by conducting energy, exergy and economic analyses. The absorption chiller systems namely single-effect, double-effect series, double-effect parallel and double-effect reverse parallel were analysed to determine the best alternative for the wood pencil factory. The results indicated that the COP of the single-effect absorption chiller systems is changed from 0.758 to 0.763 when the temperature of the generator was increased from 89 ºC to 125 ºC. However, the exergetic performance of the single-effect absorption chiller system decreased by 40% in the same generator temperature range. On the other hand, COP of all double-effect absorption chiller systems increased about 8 % when the generator temperature was changed from 116 ºC to 155 ºC while the exergetic performance of all double absorption chiller systems decreased by around 14% for the same generator temperature range. The COP and exergetic efficiency values of the double-effect parallel system were found to be higher than other absorption systems at all generator temperature values. Overall, this study recommends that the double-effect parallel absorption chiller systems can be preferred for the factories having waste heat source wood chips. The average payback period of the system was also found to be 1.4 years. Furthermore, this study shows that double-effect parallel absorption chiller systems can be proposed for the facilities having wood chips waste sources instead of double-effect reverse parallel absorption chiller systems since they are easy to operate and have lower maintenance costs.

Energy, Exergy and Economic Analysis of Absorption Chiller Systems: A Case Study for a Wood Pencil Factory

This study examines the use of absorption chiller systems in a designated industrial facility having waste heat by conducting energy, exergy and economic analyses. The absorption chiller systems namely single-effect, double-effect series, double-effect parallel and double-effect reverse parallel were analysed to determine the best alternative for the wood pencil factory. The results indicated that the COP of the single-effect absorption chiller systems is changed from 0.758 to 0.763 when the temperature of the generator was increased from 89 ºC to 125 ºC. However, the exergetic performance of the single-effect absorption chiller system decreased by 40% in the same generator temperature range. On the other hand, COP of all double-effect absorption chiller systems increased about 8 % when the generator temperature was changed from 116 ºC to 155 ºC while the exergetic performance of all double absorption chiller systems decreased by around 14% for the same generator temperature range. The COP and exergetic efficiency values of the double-effect parallel system were found to be higher than other absorption systems at all generator temperature values. Overall, this study recommends that the double-effect parallel absorption chiller systems can be preferred for the factories having waste heat source wood chips. The average payback period of the system was also found to be 1.4 years. Furthermore, this study shows that double-effect parallel absorption chiller systems can be proposed for the facilities having wood chips waste sources instead of double-effect reverse parallel absorption chiller systems since they are easy to operate and have lower maintenance costs.

Energy, Exergy and Economic Analysis of Absorption Chiller Systems: A Case Study for a Wood Pencil Factory

This study examines the use of absorption chiller systems in a designated industrial facility having waste heat by conducting energy, exergy and economic analyses. The absorption chiller systems namely single-effect, double-effect series, double-effect parallel and double-effect reverse parallel were analysed to determine the best alternative for the wood pencil factory. The results indicated that the COP of the single-effect absorption chiller systems is changed from 0.758 to 0.763 when the temperature of the generator was increased from 89 ºC to 125 ºC. However, the exergetic performance of the single-effect absorption chiller system decreased by 40% in the same generator temperature range. On the other hand, COP of all double-effect absorption chiller systems increased about 8 % when the generator temperature was changed from 116 ºC to 155 ºC while the exergetic performance of all double absorption chiller systems decreased by around 14% for the same generator temperature range. The COP and exergetic efficiency values of the double-effect parallel system were found to be higher than other absorption systems at all generator temperature values. Overall, this study recommends that the double-effect parallel absorption chiller systems can be preferred for the factories having waste heat source wood chips. The average payback period of the system was also found to be 1.4 years. Furthermore, this study shows that double-effect parallel absorption chiller systems can be proposed for the facilities having wood chips waste sources instead of double-effect reverse parallel absorption chiller systems since they are easy to operate and have lower maintenance costs.

A Comprehensive Thermoeconomic Evaluation and Multi-Criteria Optimization of a Combined MCFC/TEG System

In this study, an integrated molten carbonate fuel cell (MCFC), thermoelectric generator (TEG), and regenerator energy system has been introduced and evaluated. MCFC generates power and heating load. The exit fuel gases of the MCFC is separated into three sections: the first section is transferred to the TEG to generate more electricity, the next chunk is conducted to a regenerator to boost the productivity of the suggested plant and compensate for the regenerative destructions, and the last section enters the surrounding. Computational simulation and thermodynamic evaluation of the hybrid plant are carried out utilizing MATLAB and HYSYS software, respectively. Furthermore, a thermoeconomic analysis is performed to estimate the total cost of the product and the system cost rate. The offered system is also optimized using multi-criteria genetic algorithm optimization to enhance the exergetic efficiency while reducing the total cost of the product. The power generated by MCFC and TEG is 1247.3 W and 8.37 W, respectively. The result explicates that the provided electricity and provided efficiency of the suggested plant is 1255.67 W and 38%, respectively. Exergy inquiry outcomes betokened that, exergy destruction of the MCFC and TEG is 13,945.9 kW and 262.75 kW, respectively. Furthermore, their exergy efficiency is 68.22% and 97.31%, respectively. The impacts of other parameters like working temperature and pressure, thermal conductance, the configuration of the advantage of the materials, etc., on the thermal and exergetic performance of the suggested system are also evaluated. The optimization outcomes reveal that in the final optimum solution point, the exergetic efficiency and total cost of the product s determined at 70% and 30 USD/GJ.

Energy, exergy, economic and environmental (4E) analyses of a geothermal power plant with NCGs reinjection

In this study, a conceptual geothermal power plant with Non-Condensable Gases (NCGs) reinjection is analyzed from energy, exergy, exergo-economic, and environmental perspectives. The cycle is evaluated in considering both subcritical and supercritical working conditions. A sensitivity analysis comprising the variation of condensing temperature, turbine inlet pressure, and amount of NCGs within the geofluid is performed to assess the system performance from the thermodynamic, economic, and environmental points of view. The exergy efficiency results for the supercritical and the subcritical cycles are 52% and 50.5%, respectively. Results showed increasing the condensing temperature decreases exergy efficiency, net power, and exergetic performance parameters and increases total exergy destruction, exergo-destruction impact, and specific power cost in both working cases. According to the obtained results, an increase in the inlet pressure of the turbine in the supercritical case study reduces exergy efficiency and exergetic performance and increases the exergo-destruction impact factor. However, it increases the cycle exergy efficiency and exergetic performance criteria first and then decreases in a subcritical case. The LCOE for the supercritical cycle is 6.96 (c€/kWh) and for the subcritical is 5.52 (c€/kWh). The highest exergy destruction rates are related to the main heat exchanger, condenser, and turbine, respectively.

Energetic and Exergetic Performances of a Retrofitted, Large-Scale, Biomass-Fired CHP Coupled to a Steam-Explosion Biomass Upgrading Plant, a Biorefinery Process and a High-Temperature Heat Network

This paper aims at assessing the impact of retrofitting an existing, 730 MWe, coal-fired power plant into a biomass-fired combined heat and power (CHP) plant on its energetic and exergetic performances. A comprehensive thermodynamic model of the power plant was developed and validated against field data, resulting in less than 1% deviation between the model and the measurements for the main process parameters. The validated model was then used to predict the behaviour of the biomass CHP after retrofitting. The modelled CHP unit is coupled to a steam-explosion biomass upgrading plant, a biorefinery process, and a high-temperature heat network. 13 scenarios were studied. At constant boiler load, delivering heat to the considered heat clients can increase the total energy efficiency of the plant from 44% (electricity only) to 64%, while the total exergy efficiency decreases from 39% to 35%. A total energy efficiency of 67% could be reached by lowering the network temperature from 120∘C to 70∘C. Identifying the needed heat clients could, however, represent a limiting factor to reach such high efficiencies. For a constant power demand, increasing the boiler load from 80 to 100% in order to provide additional heat makes the total energy efficiency increase from 43% to 55%, while the total exergy efficiency decreases from 39% to 36%.

Highly-integrated and Cost-efficient Ammonia-fueled fuel cell system for efficient power generation: A comprehensive system optimization and Techno-Economic analysis

Ammonia (NH3) has been considered as a promising hydrogen storage media due to the features of low saturated vapor pressure at room temperature, high hydrogen content, low costs of transportation and storage, and carbon-free emission·NH3 can decompose into a gaseous mixture compromising of 75 vol% H2 and 25 vol% N2 in an NH3 decomposition reactor, which can integrate with a proton exchange membrane fuel cell (PEMFC) into one compact system, called as an indirect ammonia PEMFC (IA-PEMFC) system. IA-PEMFC systems are applicable for distributed power systems, vehicle and marine applications. In this study, we develop a physical–chemical model of an IA-PEMFC system, and perform a comprehensive techno-economic analysis to optimize IA-PEMFC system layout and improve its energetic, exergetic and economic performance. Results indicate that using our self-developed Ru/C NH3 decomposition catalyst can reduce operating temperature to less than 500 °C with remarkable stability, at least 300 °C lower than current commercially-available Ni-based catalyst, which can help the IA-PEMFC system to save heat supply by 29%, leading to an improvement of 2 points of percentage in energy efficiency. Recycling and burning tail gas from PEMFC anode are an effective pathway for better heat integration, and can significantly enhance system efficiency by about 11% to 56.1% when average cell voltage is 0.7 V. An auto-thermal reactor integrating NH3 decomposition and H2 catalytic combustion can further improve system efficiency by 0.5 points of percentage to 56.6%, and the exergy efficiency increases to 49% correspondingly. Economic estimation reveals fuel cost of our optimized IA-PEMFC system reaches 0.13 $/kWh for power generation and 0.024 $/km for vehicle application, respectively. In contrast, a carbon-free IA-PEMFC system is more economically efficient than ones using gasoline-fueled heat engines and H2-fueled PEMFC, and highly competitive in both energy efficiency and economic feasibility to indirect methanol PEMFC system (with end-user CO2 emission).