International Journal of Exergy (14 papers in press)

Regular Issues

• Energy and Exergy Analysis of a Solar Air Collector with Evacuated Tubes under Different Flow and Reflector Configurations  
  by Nitin Panwar, Rajesh Attri 
  Abstract: This study investigates the energy and exergy performance of a solar air collector (SAC) integrated with evacuated tubes under varying air flow rates and reflector configurations. Experiments conducted from 08:0018:00 h showed outlet air temperatures up to 105.2. This study investigates the energy and exergy performance of a solar air collector (SAC) integrated with evacuated tubes under varying air flow rates and reflector configurations. Experiments conducted from 08:0018:00 h showed outlet air temperatures up to 105.2C. Energy efficiency ranged between 3571%, while exergy efficiency varied from 2.165%. Exergy input, output and loss averaged 104.6, 3.0 and 101.6 kJ/kg, respectively. Efficiency decreased near midday but improved later. Overall, the reflector-assisted high-flow system demonstrated superior thermal and exergy performance, highlighting its potential for sustainable and efficient solar air heating applications.
  Keywords: Evacuated tube; Solar air collector; Thermal Performance; Exergy; flow rates.
  DOI: 10.1504/IJEX.2026.10075494
   
  
• Exergy, Energy, and Exergoeconomic Assessment of a Solar Based Novel Power Generation System using Helium Brayton Cycle  
  by Achintya Sharma, Anoop Shukla, Onkar Singh, Meeta Sharma 
  Abstract: This study presents a novel solar power tower (SPT)-based power plant integrating a helium Brayton cycle (HBC) as the topping cycle and a recuperative organic Rankine cycle as waste heat recovery cycle. Energy, exergy, and exergoeconomic analyses were performed numerically. Results demonstrate that the proposed system achieved improvements of 19.86% in energy efficiency and 19.85% in exergy efficiency, however, at a 9.41% increase in overall plant cost compared to the conventional SPT-HBC configuration. Therefore, the proposed system achieved energy and exergy efficiencies of 34.45% and 36.89%, respectively, and a levelised cost of electricity of 43.23 $/MWh.
  Keywords: solar power tower; recuperative ORC; working fluid selection; helium Brayton cycle; exergoeconomic analysis.
  DOI: 10.1504/IJEX.2026.10075560
   
  
• Exergy Efficiency and Simulation of Novel Parabolic Solar Collector Influence of Turbulence Hybrid Nanotube  
  by Samaneh Baharloui, Mohammad Mohsen Peiravi, Mofid Gorji Bandpy 
  Abstract: The novelty stems from the original combination of a new collector design, interchangeable rib geometries, and advanced hybrid nanotube-based nanofluids. Determine how changeable rib geometries (square vs. triangular) combined with turbulent flow of hybrid nanotube-based nanofluids can improve the thermal efficiency of a newly designed PTSC, using 3D CFD simulations for performance analysis and optimisation. As regards the square collector increases surface incident radiation up to 0.36%. Furthermore, for the PTSC with square ribs and hybrid nanotube fluid demonstrated 0.22% to 0.81% better performance in total energy output, the triangular-rib collector showed 0.78% better performance under turbulent fluid flow conditions. At last, the use of triangular baffles improved collector thermal efficiency by 0.11%.
  Keywords: Exergy efficiency; Parabolic trough solar collector; Renewable Energy; Turbulence hybrid nanotube.
  DOI: 10.1504/IJEX.2026.10076082
   
  
• Energy and Exergy Analyses of a Novel Trans-critical CO2 Booster Refrigeration System with Internal Subcooling for Supermarket  
  by Xuyang Cui, Yunzhe Zhang, Junlan Yang 
  Abstract: In order to optimize supermarket refrigeration systems, a novel transcritical CO2 system was developed. Simulation results indicate that under high-temperature conditions, the optimal discharge pressure ranges from 9 to 11 MPa, corresponding to the best COP value of 2-2.4, while receiver pressures above 5 MPa reduce COP by 3.7-4.7%. Advanced exergy analysis reveals the high-pressure compressor has the highest avoidable exergy destruction (12.05 kW at 30C), followed by the gas cooler and medium-temperature evaporator, indicating significant optimisation potential.
  Keywords: transcritical CO2 booster refrigeration system; internal subcooling; COP; advanced exergy analysis.
  DOI: 10.1504/IJEX.2026.10076204
   
  
• Exergy Analysis of Biomass Polygeneration System for Power, Hydrogen, and Heat Production  
  by Mojtaba Babaelahi, Seyyed Mohammad Hasan Ghiasi 
  Abstract: This study presents energy and exergy analysis of an integrated biomass-based polygeneration system comprising a gasifier, PEM electrolyser, and absorption refrigeration cycle for simultaneous power, hydrogen, and cooling production. Multi-objective optimisation using NSGA-II maximizes energy and exergy efficiency. Results show 6.65% exergy efficiency and 6.95% energy efficiency improvements through optimisation. Optimal design parameters include gas turbine inlet temperature of 1,030C, condenser pressure of 110 kPa, and biomass mass flow rate of 4.2 kg/s. The system demonstrates significant performance enhancement through careful parameter optimisation.
  Keywords: Polygeneration; Biomass; Exergy Analysis; Energy Efficiency; Thermodynamic Optimisation; PEM Electrolyser.
  DOI: 10.1504/IJEX.2026.10076207
   
  
• Exergy-Based Analysis of Polymer Recycling in the Automotive Sector  
  by Cemil Koyunoğlu, Tamer Çınar 
  Abstract: In this study, the exergy performance of a biomass drying system was analysed using MATLAB-based simulations under varying operating conditions. Maximum exergy efficiency was 42.3%, while maximum exergy destruction occurred at elevated inlet air temperatures. These results emphasise the reliance of system performance on operating parameters, and the relevance of critical points for improvement regarding energy efficiency. The results presented herein are anticipated to stimulate the development of more effective and sustained biomass drying technologies.
  Keywords: Polymer Recycling; automotive sector; exergy approach; energy use; sustainability; environmental impact; recycling level; polymer type; resource conservation; sustainable practices.
  DOI: 10.1504/IJEX.2026.10076209
   
  
• Energetic and exergetic investigations on a new PTSC supported triple-staged greener cooling system  
  by Tawfiq Al-Mughanam, Abdul Khaliq 
  Abstract: This paper attempted to develop a new configuration of a solar based triple-staged system producing greener cooling at three different levels of temperature (air conditioning, refrigeration, and deep freezing). The system integrates PTSC, Kalina cycle, ERC, cascaded refrigeration cycle (CRC), and a double-effect absorption refrigeration cycle (DEARC). The suggested configuration is comprehensively inspected by employing the steady-state energy-exergy model, encompassing a detailed parametric investigation. The exergetic evaluation show solar collector (30.26%) has the uppermost irreversibility rate among the components, followed by ejector (12.5%) and VGSS (7.61%). Findings revealed that change in DNI has a direct effect on system outcomes, and its variation from 850 W/m2 to 1200 W/m2 increases the cooling exergy efficiency of combined system from 6.72% to 9.52% when CRC employs NH3-propylene at fixed evaporator temperature -45. However, cooling exergy is found negatively correlated with concentration of ammonia-water basic solution.
  Keywords: Exergetic; Triple-staged cooling; PTSC; Cascaded refrigeration cycle.
  DOI: 10.1504/IJEX.2026.10076442
   
  
• Tubes in cross-flow with splitter plate- Second law aspects  
  by Anil Kumar Patil, Manoj Kumar 
  Abstract: Cross-flow geometry is commonly used in industrial heat exchangers due to high energy transfer efficiency Vortex formation on the downstream of tube becomes a challenge for heat transfer and energy loss perspective In the present study, novel splitter plates with perforations are used on the downstream of tubes to improve the overall scenario of energy transfer in the cross-flow heat exchangers The entropy generation analysis has been carried out for the tubes in cross-flow with and without perforated splitter plates for the splitter plate length ratio (RL) of 0.5 to 1.5, perforation ratio (RP) of 0.1 to 0.3, in the Reynolds number (Re) range of 9600 - 41600 The minimum values of the entropy generation (Sgen) and the entropy generation number (Ns) correspond to the tube with the perforated splitter plates having splitter plate length ratio of 0.5 and perforation ratio of 0.1.
  Keywords: Tube bank; Splitter plate; Entropy generation; Reynolds number.
  DOI: 10.1504/IJEX.2026.10076443
   
  
• Exergy Destruction Associated with Maximising C2 Recovery in an Existing NGL Facility  
  by Karim Zaki, Ahmed Fayez Nassar, Reem S. Ettouney, Mahmoud A. El-Rifai 
  Abstract: This study addresses increasing C2 recovery in an existing NGL plant through a set of operating conditions modifications targeting the decrease of the demethaniser temperature. The CO2 freezing problem associated with the reduction in temperature is first studied. Reducing the demethaniser pressure and temperatures of the low-temperature separator and reflux enabled to increase the C2 recovery from 59% to 94% with an increase in energy consumption by 16.5 MW. This however required the addition of a sweetening unit and a consequent additional increase in energy consumption by 31.8 MW. The exergy destruction and efficiency associated with revamp were also studied.
  Keywords: demethaniser; CO2 freeze; C2 recovery; NGL; exergy; simulation; retrofitting; cryogenic separation; cold energy recovery; thermal integration.
  DOI: 10.1504/IJEX.2026.10076444
   
  
• Sustainable biodiesel production from waste cooking oil: a thermodynamic study with process simulation and optimisation  
  by Md Nazeem Khan, Mohammad Zunaid, Amit Pal 
  Abstract: This research conducts a comprehensive simulation and optimisation of biodiesel production from waste cooking oil using DWSIM® software, involving acid pretreatment with sulphuric acid to lower free fatty acids and subsequent base-catalysed transesterification with potassium hydroxide. The study investigated various operational parameters, and their impacts on yield, exergetic efficiency, and exergy destruction, identifying optimal conditions that achieved a maximum yield of 90.85%. The investigation into thermodynamic principles provided valuable insights into system efficiency, revealing energy and exergy efficiencies of 92.97% and 91.02%, respectively. Furthermore, employing response surface methodology for optimisation revealed the ideal conditions, resulting in a yield of 92.88%.
  Keywords: biodiesel production; waste cooking oil; thermodynamic analysis; DWSIM simulation; optimisation; potassium hydroxide.
  DOI: 10.1504/IJEX.2026.10076116
   
  
• Energy exergy and environmental analyses of mango leather drying in greenhouse solar dryer with evacuated tube collector and finned tray  
  by Amit Shrivastava, Manoj Kumar Gaur, Parul Saxena 
  Abstract: This research evaluates the performance of a hybrid greenhouse solar dryer (HGSD) combined with an evacuated tube collector (ETC) for drying mango pulp. The experiments were conducted in June 2021 using a finned aluminium tray placed inside the drying chamber. The system demonstrated significant environmental advantages, including the mitigation of approximately 86.21 tons of CO₂ emissions. The average exergy efficiency was 4.62%, with a corresponding sustainability index of 1.048. The energy payback period was calculated as 3.98 years, and the carbon credit earned $817.31. The findings highlight the system's potential for optimisation to improve efficiency and sustainability.
  Keywords: mango leather; energy balance; exergy balance; solar energy; greenhouse.
  DOI: 10.1504/IJEX.2026.10074718
   
  
• Enhancing performance by incorporating solar feedwater heating instead of steam bleeding of an existing steam power plant: energy and exergy analyses  
  by Sayan Mandal, Sudip Simlandi, Nilkanta Barman 
  Abstract: This study presents energy and exergy analyses to improve the performance of a 500 MW thermal power plant by adding a direct solar feedwater heating system, rather than steam bleedings, resulting in a significant increase in energy efficiency. The energy efficiency increases from 44.33% to 48.50%, if off-bleeding is considered at the reheater inlet or at low- and intermediate-pressure turbines. A lower solar energy requirement of 134 MW is found when off-bleeding is established at the reheater inlet, but it demands an increase in temperature to 337.40°C. The approach enhances energy efficiency and introduces a new concept.
  Keywords: existing thermal power plant; reduce bleedings; direct solar heating; increasing efficiency; energy and exergy analyses.
  DOI: 10.1504/IJEX.2026.10075150
   
  
• Reinforcement learning-based exergetic analysis and assessment of a novel cogeneration system for smart urban energy applications  
  by Asli Tiktas 
  Abstract: This paper presents a novel Kalina-based geothermal cogeneration system for smart urban energy applications, integrated with a reinforcement-learning-based exergetic analysis and control framework implemented in a digital twin environment coupling EES, TRNSYS and COMSOL. The configuration exploits absorber-integrated internal heat regeneration to raise the working-fluid temperature above the geothermal source without auxiliary energy input. The optimisation results indicated that the reinforcement learning (RL)-based control strategy improved overall energy and exergy efficiencies by 0.066 and 0.058, respectively while simultaneously reducing CO₂ emissions by 0.126, levelised cost of electricity by 0.191, and the levelised cost of heating by 0.133.
  Keywords: reinforcement learning optimisation; digital twin modelling; exergy-aware control; low-grade heat recovery; geothermal energy; cogeneration systems; exergy analysis; exergoeconomic analysis.
  DOI: 10.1504/IJEX.2026.10075882
   
  
• Investigating the sectional thrust and exergy efficiency of a turbojet engine  
  by Mustafa Akbas, Onder Altuntas, Arif Hepbasli 
  Abstract: This study delves into the performance characteristics of a turbojet engine, focusing on the impact of varying compressor pressure ratios and component geometries on thrust and exergy efficiency. The effects of Mach number and compressor pressure ratio on exergy utilisation efficiency at varying altitude values are also examined. Utilising the MATLAB, the analysis was conducted within a range of sea level to 12,000 m altitude. The results obtained provide valuable insights into the potential for optimising turbojet engine performance through strategic adjustments to pressure ratios and component geometries.
  Keywords: exergy analysis; energy analysis; exergy utilisation efficiency; EUE; aeroengine performance; turbojet engine.
  DOI: 10.1504/IJEX.2026.10075252