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This study dealt with evaluating the (J85-GE-5H) military turbojet engine (TJE) in terms of exergetic and advanced exergetic analyses at Military (MIL) and Afterburner (AB) process modes by utilizing kerosene (JP-8) and hydrogen (H2) fuels. First, exergy and advanced exergy analyses of the engine were performed using JP-8 fuel as per actual engine operating conditions. These analyses of the turbojet engine using hydrogen fuel were also examined parametrically. The performance evaluation of the engine was lastly executed by comparing the obtained results for both fuels. Based on the parametric studies undertaken, the entire engine’s exergetic efficiency with JP-8 was reckoned 30.85% at the MIL process mode while it was calculated as 16.98% at the AB process mode. With the usage of H2, the efficiencies of the engine decreased to 28.62% and 15.33% for the above mentioned two modes, respectively. As the supreme exergy destructions occurred in the combustion chamber (CC) and afterburner exhaust duct (ABED) segments, the new technological developments should be considered to design more efficient engines. As a result, the engine worked less efficiently with hydrogen fuel due to the enhancement in exergy destructions. Conversely, the greenhouse gas (GHG) emission parameters lessened with the utilization of H2 fuel.

This research paper figures out thermal performance analysis for vapor compression refrigeration (VCR) driven by the organic Rankine cycle (ORC) implementing MATLAB software. The ORC system is powered by improved evacuated tubes and compound parabolic collectors. The paper evaluates the overall exergetic efficiency and coefficient of performance using the working fluid Pentane/R245fa. The result of the present paper indicates that optimum COP of 0.75 and exergetic efficiency of 28% is obtained at 340 K of collector output temperatures, 0.1/0.9 of fractional mass of the working fluid, and 285, 300 K for VCR condenser and evaporator temperature, respectively. Sensitivity analysis pointed out that condenser temperature was the most impactful parameter for both exergetic efficiency and COP owing to higher F -value ‘of 156.06’ and ‘89.28,’ respectively. Further, collector output temperature and fractional mass of the working fluid were the least impactful parameters owing to lower F -value ‘1.95’ and ‘1.02’ for exergetic efficiency and COP, respectively.

This article deals with the thermodynamic assessment of supercritical carbon dioxide (S-CO2) Brayton power cycles. The main advantage of S-CO2 cycles is the capability of achieving higher efficiencies at significantly lower temperatures in comparison to conventional steam Rankine cycles. In the past decade, variety of configurations and layouts of S-CO2 cycles have been investigated targeting efficiency improvement. In this paper, four different layouts have been studied (with and without reheat): Simple Brayton cycle, Recompression Brayton cycle, Recompression Brayton cycle with partial cooling and the proposed layout called Recompression Brayton cycle with partial cooling and improved heat recovery (RBC-PC-IHR). Energetic and exergetic performances of all configurations were analyzed. Simple configuration is the least efficient due to poor heat recovery mechanism. RBC-PC-IHR layout achieved the best thermal performance in both reheat and no reheat configurations ( η t h   = 59.7% with reheat and η t h   = 58.2 without reheat at 850 °C), which was due to better heat recovery in comparison to other layouts. The detailed component-wise exergy analysis shows that the turbines and compressors have minimal contribution towards exergy destruction in comparison to what is lost by heat exchangers and heat source.

In this research, we performed energy and exergy assessments of a solar driven power plant. Supercritical carbon dioxide (S-CO2) Brayton cycle is used for the conversion of heat to work. The plant runs on solar energy from 8 a.m. to 4 p.m. and to account for the fluctuations in the solar energy, the plant is equipped with an auxiliary heater operating on hot combustion gases from the combustion chamber. The capital city of Saudi Arabia (Riyadh) is chosen in this study and the solar insolation levels for this location are calculated using the ASHRAE clear-sky model. The solar collector (central receiver) receives solar energy reflected by the heliostats; therefore, a radially staggered heliostat field is generated for this purpose. A suite of code is developed to calculate various parameters of the heliostat field, such as optical efficiencies, intercept factors, attenuation factors and heliostat characteristic angles. S-CO2 Brayton cycle is simulated in commercial software, Aspen HYSYS V9 (Aspen Technology, Inc., Bedford, MA, USA). The cycle is mainly powered by solar energy but assisted by an auxiliary heater to maintain a constant net power input of 80 MW to the cycle. The heliostat field generated, composed of 1207 rows, provides 475 watts per unit heliostat’s area to the central receiver. Heat losses from the central receiver due to natural convection and radiation are significant, with an average annual loss of 10 percent in the heat absorbed by the receiver. Heat collection rate at the central receiver reveals that the maximum support of auxiliary heat is needed in December, at nearly 13% of the net input energy. Exergy analysis shows that the highest exergy loss takes place in the heliostat field that is nearly 42.5% of incident solar exergy.

Traditional biomass cookstoves (TCS) are very popular among rural areas and street vendors especially in developing and underdeveloped nations due to their conventional process and simple construction. However, this direct combustion technique is not suitable due to poor efficiency and harmful gaseous-particular emission. Improved biomass cookstoves (ICS) have the potential to overcome the health and environmental problems that are common in the case of TCS. In the present study, investigations were carried out on 3.5 kWth ICS based on gasification design with four different air conditions. The opening to the closing ratio of primary to secondary air vents are taken at 50/50, 50/100, 60/100, and 80/100, respectively for the experiments. Performance of TCS and different ICS cases were compared in terms of burning rate, specific fuel consumption, firepower, useful firepower, thermal efficiency, total particulate matter, and gaseous emissions (CO, CO 2 , O 2 , NO x , CC, HC). Apart from that, thermal analysis such as mass balance, energy balance, and exergy efficiency was also calculated. 50/100 opening to the closing ratio of primary to secondary air offers the better performance in terms of higher thermal efficiency and lower gaseous and particulate emission is the major conclusion from this study.