This paper considers the criterion of minimum compression work to derive an expression for the interstage pressure of a multistage compressor with intercooling that includes the gas properties, pressure drops in the intercoolers, different suction gas temperatures, and isentropic efficiencies in each compression stage. The analytical expression for the interstage pressures is applied to estimate the number of compression stages and to evaluate its applicability in order to estimate interstage pressures in the operation of multistage compressors, which can be especially useful when their measurements are not available.

Vapour-compression refrigeration and cooling systems represent a significant share of global electricity consumption, being estimated to account for approximately 10% to 20% of the worldwide electricity demand, which highlights their critical impact on energy efficiency and sustainability. In this context, improving the thermodynamic and exergoeconomic performance of refrigeration cycles, as well as the appropriate selection of the refrigerant, has become a key research priority. Therefore, this work aims to comparatively evaluate the energy, exergy, exergy cost, and exergoeconomic performance of three vapour-compression refrigeration cycle configurations: a simple cycle, a two-stage cycle with a flash tank, and a two-stage cycle with a flash tank and a mixing chamber. Six refrigerants (R134a, R600a, R290, R1234yf, R1234ze (E), and R717) were analysed under evaporation temperatures of 228–238 K and condensation temperatures of 298–308 K. The performance evaluation was carried out using the Fuel–Product–Residue (FPR) methodology, considering the coefficient of performance (COP), exergy efficiency, system irreversibilities, and exergy and exergoeconomic costs. The results indicate that the incorporation of the mixing chamber increases the COP by up to 7% and the exergy efficiency by up to 6% compared to the simple cycle, while reducing exergoeconomic costs by up to 10% for the most favourable refrigerants. Among the working fluids analysed, R600a exhibits the best overall performance (COP up to 4.3 and an exergy efficiency of 33%), followed by R290 and R717, whereas R1234yf shows the lowest efficiencies (COP ≈ 3.7 and exergy efficiency ≈ 28%) and the highest exergoeconomic costs. These findings demonstrate that the design of vapour-compression refrigeration systems should involve the joint selection of the cycle configuration and the refrigerant based on integrated energy, exergy, and exergoeconomic criteria. Overall, the results highlight that both the refrigerant and the cycle configuration must be selected simultaneously, considering energy, exergy, and exergoeconomic criteria, to achieve more efficient and sustainable industrial applications.

This work presents an energetic, exergoeconomic, environmental, and toxicity analysis of the simple gas turbine M501F3 based on a parametric analysis of energetic (thermal efficiency, fuel and air flow rates, and specific work output), exergoeconomic (exergetic efficiency and exergoeconomic operation costs), environmental (global warming, smog formation, acid rain indexes), and human toxicity indexes, by taking the compressor pressure ratio and the turbine inlet temperature as the operating parameters. The aim of this paper is to provide an integral, systematic, and powerful diagnostic tool to establish possible operation and maintenance actions to improve the gas turbine’s exergoeconomic, environmental, and human toxicity indexes. Despite the continuous changes in the price of natural gas, the compressor, combustion chamber, and turbine always contribute 18.96%, 53.02%, and 28%, respectively, to the gas turbine’s exergoeconomic operation costs. The application of this methodology can be extended to other simple gas turbines using the pressure drops and isentropic efficiencies, among others, as the degradation parameters, as well as to other energetic systems, without loss of generality.

Modern power generation aims to maximize the extraction of thermal energy from fossil fuels to produce electricity. Combined cycle power plants, leaders in efficiency, sometimes require an additional steam generator to compensate for insufficient exhaust gas energy in the heat recovery steam generator (HRSG), leading to hybrid combined cycles. This study presents a comprehensive thermodynamic analysis of the hybrid combined cycle power plant located in the Valley of Mexico, operating under both full-load and partial-load conditions. The investigation begins with an energy analysis evaluating key performance parameters under real operating conditions, including the power generation, heat flow supply, thermal efficiency, fuel consumption rates, steam flow, and specific fuel consumption. Subsequently, the analysis examines the performance of the steam cycle using the β factor, which quantifies the relationship between heat flows in the steam generator and the HRSG, to maintain a constant steam flow. This evaluation aims to determine the potential utilization of exhaust gas residual energy for partial steam flow generation in the steam turbine. The study concludes with an exergy analysis to quantify the internal irreversibility flows within the system components and determine the overall exergy efficiency of the power plant. The results demonstrate that, under 100% load conditions, the enhanced utilization of exhaust gases from the HRSG leads to fuel savings of 33,903.36 tons annually and increases the exergy efficiency of the hybrid combined cycle power plant to 54.08%.

Direct steam generation (DSG) is a promising technology for introducing solar energy into industrial applications, yet it still faces significant challenges. This work analyzes two critical issues associated with DSG: temperature gradients on the receiver tube wall caused by direct and concentrated radiation and flow instability resulting from the phase transition of the working fluid from liquid–vapor to vapor. These phenomena can reduce the mechanical strength of the receiver tube and lead to sudden pressure increases, deformation, or rupture, which hinder the implementation of DSG in solar thermal plants. To address these challenges, the behavior of a receiver tube composed of copper on the inside and an Al₂O₃ envelope is studied. A 50 MWe hybrid solar thermal plant is proposed for Mulegé, Baja California Sur, Mexico, including a solar field designed to analyze the production of superheated steam during peak solar irradiance hours. The effect of the Cu-Al₂O₃ ratio on the receiver tube is evaluated, with Al₂O₃ serving as a thermal regulator to reduce temperature gradients and mitigate flow instability. This combination of materials improves the receiver tube’s performance, ensuring mechanical stability and enhancing the viability of DSG systems. By reducing temperature gradients and flow instability, DSG-based plants can double thermal efficiency and significantly lower environmental impact by eliminating the need for thermal oils, which require frequent replacement. These findings demonstrate the potential for hybrid solar thermal plants to provide sustainable and efficient solutions for industrial energy needs.