International Journal of Exergy (17 papers in press)

Regular Issues

• Performance and sustainability assessment of a geothermal district heating and cooling system through energy and exergy analyses  
  by Ebru Hanc?o?lu, Arif Hepbasli 
  Abstract: A comprehensive thermodynamic analysis of a geothermal energy-supported heating and cooling system for a model building was presented in this study, employing energy, exergy, and sustainability evaluation methods. The heating and cooling systems achieved energy efficiencies of 0.81 and 0.47, respectively, while their corresponding exergy efficiencies were determined as 0.52 and 0.11. The coefficient of performance (COP) of the cooling system was calculated as 0.56. The results indicate that, in cooling mode, the condenser and absorber exhibit the greatest potential for performance and environmental improvement, whereas in heating mode, the heat exchanger (HE1) represents the principal component for enhancement.
  Keywords: geothermal district; geothermal cooling; energy analysis; exergy analysis; sustainability analysis.
  DOI: 10.1504/IJEX.2026.10079337
   
  
• Combustion-Zone Driven Irreversibility in a Heavy-Duty Diesel Engine under Injection Timing Variations  
  by Eihab A. Raouf 
  Abstract: The effect of injection timing on combustion-zone and thermodynamic irreversibility in a heavy-duty diesel engine was analysed. Simulations at 2,000 rpm across different loads showed that advancing injection shifted combustion toward top dead centre and increased the in-cylinder pressure rise rate. Peak cylinder pressure increased from about 58 to 62 bar at 25% load and from 105 to 114 bar at full load. The maximum pressure rise rate increased from 1.3 to 4.4 bar per crank-angle degree at low load and from 2.4 to 6.7 bar per degree at full load. Exergy analysis showed that 8-12 degrees before top dead centre (BTDC) provided the optimal balance between useful work and thermodynamic irreversibility. Injection timing shifts the combustion zone relative to top dead centre. Combustion-zone width varies strongly with engine load and injection timing. Advanced injection intensifies pressure development and heat transfer to cylinder walls. Exergy redistribution identifies an optimal injection range near SOI = 812 degrees BTDC. Combustion-zone evolution governs thermodynamic irreversibility in diesel engines.812
  Keywords: diesel engines; injection timing; combustion zone; exergy destruction; second law analysis.
  DOI: 10.1504/IJEX.2026.10079411
   
  
• Exergy-Based Four-Dimensional Sustainability Assessment of Energy Systems Integrating Entropy, Economy, and Environment: A Case Study of T  
  by Mert Ökten 
  Abstract: This study introduces the E4S index, a four-dimensional framework integrating exergy, entropy, economy and environment into a single dimensionless sustainability score (01). Applied to 14 energy technologies in Turkiye across four policy scenarios, the index employs Dirichlet-based Monte Carlo simulations to account for weighting uncertainty. Hydroelectric power achieves the highest score (E4S > 0.90) across all scenarios. The Environment First scenario yields the strongest alignment with UN sustainable development goals (R = 0.92), while the Economy First scenario diverges markedly (R = 0.18), demonstrating that cost-centric planning undermines long-term sustainability.
  Keywords: Energy Sustainability; E4S Index; UN SDG Validation; Monte Carlo Simulation; Energy Policy; Sustainable Development.
  DOI: 10.1504/IJEX.2026.10079731
   
  
• Exergy analysis of a Fresnel Lens integrated Flat Plate Collector  
  by Sunil Kumar, G.N. Tiwari, Madhu Sudan 
  Abstract: The primary goal is to enhance beam radiation with a top-mounted Fresnel lens, thereby improving energy and exergy performance. The energy balance for each component of the proposed system was derived in accordance with the first law of thermodynamics, forming the fundamental basis of the analysis. The impact of mass flow rate (m ?_f) and concentration ratio (C) on the rate of thermal, electrical, and overall energy and exergy produced by FLi-FPC-TEC has been evaluated. The proposed system achieved a maximum thermal gain of 1004 W and a peak electrical power output of 201 W under the operating conditions at (m ?_f=0.025kg/s, C=8, packing factor =1).
  Keywords: Flat plate collector (FPC); thermoelectric cooler; Fresnel lens; solar energy and Exergy.
  DOI: 10.1504/IJEX.2026.10079766
   
  
• Tray-by-Tray Exergy Analysis of the Stripper Column of the Catalytic-Conversion Unit of Abadan Refinery  
  by Morteza Yaghoobi, Ali Saeedi, Fatemeh Deymeh, Kazem Mokaffa 
  Abstract: Distillation columns are among the most energy-intensive units in refineries. This study presents a tray-by-tray exergy analysis of the catalytic-reforming stripper column at Abadan Oil Refinery under steady-state conditions using Aspen Plus v12. The feed tray, condenser, and reboiler were identified as the main sources of exergy destruction, accounting for 28%, 20-28%, and 15% of total losses, respectively. Sensitivity analysis showed that feed temperature and reflux flow have the greatest influence on exergy efficiency. Their simultaneous optimization reduced total exergy destruction by up to 34% and improved exergy efficiency by approximately 8.5%.
  Keywords: Exergy analysis; Stripper Column; Catalytic Reforming Unit; Aspen Plus; Exergy Destruction.
  DOI: 10.1504/IJEX.2026.10080065
   
  
• Metaheuristic Modelling of Exergy and Sustainability Parameters in High-Bypass Turbofan Engines: A Comparative Study of Cuckoo Search, PSO, and GA  
  by Ridvan Oruc 
  Abstract: This paper presents a comprehensive modeling approach to predict the exergy and sustainability parameters of high-bypass turbofan engines using the Cuckoo Search Algorithm (CSA), Particle Swarm Optimization (PSO), and Genetic Algorithm (GA). Engine data were obtained from the ICAO emissions databank. Exergy efficiency, wasted exergy ratio and environmental effect factor are modeled as functions of design variables such as bypass ratio and overall pressure ratio. The results show that all metaheuristic models provide satisfactory prediction accuracy, with the CSA-based model slightly superior in most cases. R? value greater than 0.92 for all methods indicates the robustness of the developed models.
  Keywords: Cuckoo search algorithm; particle swarm optimization; genetic algorithm; turbofan; exergy.
  DOI: 10.1504/IJEX.2026.10080109
   
  
• Exergy and Thermoeconomic Assessment of a Multifuel Engine-Driven ORC?VCR?District Water Heating System  
  by D. Manivannan, Shankar Ganesh Narayanan, A. R. Pradeep Kumar, T. Srinivas 
  Abstract: An integrated Organic Rankine Cycle?Vapor Compression Refrigeration?District Water Heating (ORC?VCR?DWH) system driven by a multifuel engine is analyzed using exergy and thermoeconomic methods. O-xylene, M-xylene, and ethylbenzene are evaluated under diesel, petrol, and biofuel operation at varying loads and compression ratios. O-xylene with biofuel achieves the highest ORC exergetic efficiency of 48.34% at 80% load, while the combined ORC?VCR efficiency reaches 44.7% at 150 ?C heat-source temperature. The turbine and high-temperature heat exchanger account for 50?55% of total exergy destruction. The evaporator exhibits the highest relative cost difference (~20%), indicating priority for thermoeconomic improvement.
  Keywords: Combined cycle; organic Rankine cycle; Vapor compression refrigeration; Energy and Exergy.
  DOI: 10.1504/IJEX.2026.10080139
   
  
• Exergy Analysis and Predictive Modelling of a Hybrid Solar Photovoltaic Thermoelectric Collector for Refrigeration Application  
  by Abhishek Tiwari, Shruti Agarwal 
  Abstract: This study investigates a hybrid solar collector integrating a semi-transparent photovoltaic (SPV) module and thermoelectric generator (TEG) coupled with a vapour absorption refrigeration (VAR) system. Five photovoltaic technologies, namely amorphous silicon (a-Si), polycrystalline silicon (poly-Si), monocrystalline silicon (mono-Si), cadmium telluride (CdTe), and copper indium gallium selenide (CIGS), were evaluated using a MATLAB-based simulation framework. System performance was analysed in terms of overall exergy output, overall exergy efficiency, and refrigeration coefficient of performance (COP). An equivalent multilayer perceptron artificial neural network (MLP-ANN) model achieved high predictive accuracy (mean squared error (MSE) = 0.088, correlation coefficient (R) = 0.999, mean bias error (MBE) = 0.2363, mean absolute percentage error (MAPE) = 1.89%). Poly-Si yielded the highest COP (0.92), while mono-Si achieved the maximum overall exergy efficiency (32.09%).
  Keywords: Artificial Neural Network; Hybrid System; Vapor Absorption Refrigeration System; Mean Squared Error; Thermal Modelling; Exergy Analysis.
  DOI: 10.1504/IJEX.2026.10080179
   
  
• Energy and Exergy Assessment of a Natural Gas-Fired Fire Tube Boiler with Humidity-Induced Heat Loss Identification  
  by Hablinur Al Kindi, Yogi Sirodz Gaoz, Qowiyu Haryo Bimoseno, Edi Sutoyo, Budi Hartnono 
  Abstract: This study evaluates the energy and exergy performance of a 4,000 kg/h natural gas-fired firetube boiler under real tropical industrial conditions in Bogor, Indonesia. Using the indirect heat-loss method, thermal efficiency was determined to be 88.97%, with total heat losses of 11.03% comprising ambient humidity-induced loss (4.83%), moisture from hydrogen combustion (4.03%), and dry flue gas loss (2.17%). Exergy analysis yielded an efficiency of 43.4%, with 56.6% of available work potential irreversibly destroyed through combustion and heat transfer processes. A component-level exergy destruction breakdown revealed that ambient humidity constitutes the dominant recoverable loss source ? a finding particularly significant in tropical operating environments. Improvement strategies including flue gas heat recovery, combustion air preheating, and inlet air dehumidification are recommended. This work addresses a gap in prior literature by systematically quantifying humidity-induced losses within a unified energy?exergy framework for natural gas fire-tube boilers.
  Keywords: fire tube boiler; exergy; energy efficiency; heat loss; combustion.
  DOI: 10.1504/IJEX.2026.10080256
   
  
• Exergy Analysis of a Double Absorption-Resorption Heat Transformer  
  by Abdullah Sabir, Runfa Zhou, Zeenat Ullah, Muhammad Aurangzeb, Sibtain Waheed, Shuhong Li 
  Abstract: Industrial waste heat is a massive, underutilized resource. To address this, the study evaluates an ammonia-water Double Absorption-Resorption Heat Transformer (DARHT) through extensive thermodynamic exergy analysis to identify inefficiencies. The system achieves a peak Coefficient of Performance (COP) of 0.2810 and maintains a stable 32% exergetic efficiency. Analysis identifies the desorber (25.4%) and generator (22.9%) as primary sources of exergy destruction, emphasizing them as key redesign targets. A key finding is that, DARHT significantly outperforms traditional single-stage systems at delivering high-grade heat above 125 ?-?C. These results demonstrate that the DARHT is a reliable and scalable technology for sustainable industrial energy conservation.
  Keywords: Absorption heat transformer; ammonia-water; exergy analysis; double absorption-resorption; thermodynamic optimization; waste heat recovery; industrial energy efficiency.
  DOI: 10.1504/IJEX.2026.10080502
   
  
• Analysis of entropy production in electro-osmotic peristaltic flow of Jeffrey fluid through single- and multi-walled carbon nanotubes with convective heating  
  by Mahadev Channakote, Muthumeenakshi S, Asha S. K 
  Abstract: This speculative study investigates the behaviour of Jeffrey fluid flowing through carbon nanotubes, including single-walled and multi-walled carbon nanotube (CNT). These nanotubes are widely utilised in advanced technologies and medical applications due to their unique structure and transport properties. The flow is induced by electro-osmotic peristalsis, a process that combines an electric field with wave-like pumping of the nanotube walls. Heat transfer, focusing on entropy generation as a measure of energy loss and system inefficiency, is also examined. The study assesses how factors such as electric field strength, fluid properties, and convective heat transfer conditions impact flow performance and thermal behaviour. A comparison between single-walled and multi-walled nanotubes reveals their distinct effects on energy efficiency. The results provide valuable insights for designing electro-osmotic peristaltic nanofluidic systems, particularly in biomedical microdevices, controlled drug delivery platforms, and micro-nano-scale cooling technologies. Minimising entropy production, reducing energy losses, and enhancing thermal-flow efficiency are crucial for achieving reliable and optimised performance in these applications.
  Keywords: Electro-osmotic flow; Peristaltic transport; Jeffrey nano fluid; Entropy generation Carbon nanotubes; Convective heat transfer.
  DOI: 10.1504/IJEX.2026.10080541
   
  
• A Topology Consistent Comparative Exergy and Technoeconomic Assessment of Advanced Brayton Cycle Configurations with Noncoincident Design Optima  
  by Hayati Tore 
  Abstract: This study reassesses four Brayton-cycle topologies using a fuel-based combustion-products model. Methane combustion, fuel chemical exergy, component pressure losses, CO2 intensity, specific fuel consumption (SFC), carbon tax, one-at-a-time economic scenarios, and topology-complexity, pressure-loss, and component-parameter sensitivities are included. Within the screening-level economic model and the investigated pressure-ratio interval, the intercooled, reheated, and regenerated (IC + RH + REG) cycle gives the lowest base product cost, 72.02 USD/MWh, among the investigated configurations, with CO2 intensity of 461.10 kg/MWh. Its maximum thermal and exergy efficiencies are 42.85% and 41.20%.
  Keywords: Brayton cycle; exergy analysis; technoeconomic assessment; regeneration; intercooling; reheating; temperature dependent properties.
  DOI: 10.1504/IJEX.2026.10080622
   
  
• Energy, Exergy and Economic (3E) analysis of liquid air energy storage system based on different liquefaction cycles: a comparative study  
  by Ruifeng Cao, Hailong Jia, Qizhen Guan, Ye Ji, Fangxu Li 
  Abstract: This paper examines how four different liquefaction cycle affect the LAES system performance from the energy, exergy, and economic perspectives. For a system of 10MW, it is found that the Linde-Hampson-cycle-based LAES system performs best thermodynamically with an RTE of 77.91% and an ESD of 207.98 kWh/m3. The exergy analysis shows that heat exchangers account for the largest proportion of exergy loss in the liquefaction process, taking 30.6% - 41% of total. In terms of economic performance, the Claude-cycle-based LAES system performs best with the lowest initial investment, achieving a DPP of 3.33 years, and a LCOE of 0.1152 $/kWh.
  Keywords: liquid air energy storage; liquefaction cycles; energy analysis; exergy analysis; economic analysis.
  DOI: 10.1504/IJEX.2026.10080647
   
  
• Exergoeconomic Comparative Study of Solar-Ground Source Heat Pump Systems for Crude Oil Heating  
  by Qinglin Cheng, Zezhong Qu, Haiying Sun, Tao Liang, Lu Lu, Xishan Liu, Bozhi Liu 
  Abstract: This study proposes a solar-ground source heat pump (SGSHP) system for crude oil heating. An exergoeconomic model utilising the energy level coefficient () was constructed via TRNSYS. Validated against empirical data (RMSE 1.24
  Keywords: Solar-Ground Source Heat Pump System (SGSHP); Crude Oil Heating; Exergoeconomics; Energy Level Coefficient; Life cycle cost.
  DOI: 10.1504/IJEX.2026.10080696
   
  
• Energy, Exergy and Economic Analysis of an Enhanced Ejector assisted Vapor Compression Double Effect Absorption Cascade Cycle  
  by Billal Mebarki 
  Abstract: An enhanced ejector-assisted vapor compression double-effect absorption cascade cycle is proposed to improve thermodynamic and economic performance. A liquidvapor heat exchanger integrated between the ejector and compressor enhances the entrainment ratio and reduces compressor power consumption. A thermo-economic model incorporating energy and exergy analyses was developed and validated against published data. Using R744 as the refrigerant, the proposed cycle achieved 19.2% higher coefficient of performance and exergy efficiency, together with a 32% reduction in annual operating cost compared with the conventional cycle. These results demonstrate the thermodynamic and economic advantages of the proposed configuration for refrigeration applications.
  Keywords: Absorption; Cascade; Ejector; Exergy; Vapor compression; double effect; COP; exergy efficiency.
  DOI: 10.1504/IJEX.2026.10080716
   
  
• Comparative Thermodynamic, Exergy and Sustainability Assessment of Alternative Refrigerants for Vapour Compression Refrigeration Systems  
  by Moti Lal Roy, Raju Kumar, Arvind Patel 
  Abstract: A REFPROP-based thermodynamic, exergy, and sustainability assessment of eight refrigerants (R-1234yf, R-717, R-32, R-290, R-134a, R-600a, R-410A, and R-436A) was conducted for a single-stage vapour compression refrigeration system (VCRS). Performance was evaluated over an evaporator temperature range of 238263 K at a condenser temperature of 313 K. Increasing evaporator temperature improved COP, exergetic efficiency, and sustainability while reducing compressor work, refrigerant mass flow rate, and exergy destruction. Among the refrigerants, R-717 exhibited the best overall thermodynamic and exergy performance, demonstrating its potential as an environmentally sustainable and energy-efficient refrigerant for future refrigeration applications.
  Keywords: Vapour compression refrigeration system; Exergy analysis; Sustainability index; Coefficient of performance; Thermodynamic assessment; REFPROP.
  DOI: 10.1504/IJEX.2026.10080724
   
  
• Exergoeconomic and Exergoenvironmental Analysis of TiO2 Nanoparticles in Diesel-Fusel Oil Blends  
  by Nisa Atak, Battal Doğan, Murat Yeşilyurt, Hayri Yaman 
  Abstract: The present study investigates the exergy, exergoeconomic, and exergoenvironmental impact of diesel-fusel oil blends enriched with TiO2 nanoparticles in a single-cylinder compression-ignition engine. Tests were conducted at a constant speed of 1500 rpm at different engine loads by adding 100, 300, and 500 ppm TiO nanoparticles to 90% diesel-10% fusel oil. As the engine operated at 50%, the exergy destruction in diesel was measured at 8.372 kW, whereas it was recorded as 9.067 kW for F10Ti100. The exergy efficiency of binary blend at full load was 23.08%, while it was obtained with the addition of 500 ppm nanoparticles was 21.49%.
  Keywords: Diesel engine; fusel oil; nanoparticles; exergy; exergoeconomic; exergoenvironmental.
  DOI: 10.1504/IJEX.2026.10080768