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Despite being a cutting‐edge technology, the proton exchange membrane fuel cell (PEMFC) generates a lot of heat as it works, which makes it wasteful with energy. In order to enhance energy efficiency via waste heat recovery, we provide and analyze a novel integrated energy system that utilizes PEMFC and ORC technology. There are a lot of ways to put the waste heat from fuel cells (FCs) to good use, but the most efficient one is the organic Rankine cycle (ORC) with the right working fluid. This research aims to find the optimal way to use the waste heat of the FC by testing several working fluids. The optimal solution is derived using a genetic algorithm by monitoring the objective functions that characterize the system's overall performance as they vary across different system parameters. The results show that the proposed efficient integration achieves high energy and exergy efficiency levels and achieves rates of total cost and environmental impact that are within acceptable limits. Since the fuel usage element's content significantly affects the system indicators in several ways, the results also demonstrate that it is quite relevant. Since the exergo‐environmental metric and the exergy efficiency meter are always moving in different directions, choosing a design condition that meets several requirements is crucial. According to the results, fuel cells had the highest irreversibility rate at 12.2, making them the most energy‐conserving piece of machinery. [ABSTRACT FROM AUTHOR]

Solar energy exploitation is growing consistently, as it is the cheapest and most accessible amongst all forms of renewable energies. Increasing the performance of solar air heaters can aid in developing clean energy use and subsiding the greenhouse gas emissions in the world. This study, therefore, seeks to improve the thermo-hydraulic performance of solar air heaters using sinusoidal extended surfaces. The results show that the Reynolds number increment contributes to the enhancement of Nusselt number and thermo-hydraulic performance, while it does not affect the friction factor considerably. The highest value of the Nusselt number belongs to the case with the highest fin amplitude and wavy fins configuration by about 7 times higher value in comparison to the simple solar air heater. It is shown that the wavy configuration can render higher thermo-hydraulic performance than that of raccoon fins, by about 10 percent. The finned configurations feature better fluid flow mixing at the outlet and lower maximum and gradient of temperature on the absorber plate compared to those of simple and common solar air heaters. [ABSTRACT FROM AUTHOR]

The present paper strives for optimization of the cooling system of a liquid‐propellant engine (LPE). To this end, the new synthetic metamodel methodology utilizing the design of experiment method and the response surface method was developed and implemented as two effective means of designing, analyzing, and optimizing. The input variables, constraints, objective functions, and their surfaces were identified. Hence, the design and development strategy of combustion chamber and nozzle was clarified, and 64 different experiments were carried out on the RD‐161 propulsion system, of which 47 experiments were approved and compatible with the problem constraints. This engine used all three modes of cooling: the radiation cooling, the regenerative cooling, and the film cooling. The response surface curves were drawn and the related objective function equations were obtained. The analysis of variance results indicate that the developed synthetic model is capable to predict the responses adequately within the limits of input parameters. The three‐dimensional response surface curves and contour plots have been developed to find out the combined effects of input parameters on responses. In addition, the precision of the models was assessed and the output was interpreted and analyzed, which showed high accuracy. Therefore, the desirability function analysis has been applied to LPE's cooling system for multiobjective optimization to maximize the total heat transfer and minimize the cooling system pressure loss simultaneously. Finally, confirmatory tests have been conducted with the optimum parametric conditions to validate the optimization techniques. In conclusion, this methodology optimizes the LPE's cooling system, a 2% increase in the total heat transfer, and a 38% decrease in the pressure loss of the cooling system. These values are considerably large for the LPE design. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is to investigate how to optimize gasoline in order to reduce the emitted pollutants caused by combustion, while the torque and power of the engine reach the maximum capabilities. To optimize gasoline formulation, an ethanol and magnesium oxide (MgO) or cerium oxide (CeO2) mixture was added to gasoline. This study explores the role of main variables such as type of metal nanoparticle additive, engine speed, and throttle on engine performance and exhaust gas emissions through the modeling and optimization methods. Experimental design conducted through the implementation of D-optimal design, taking into account the three main parameters. To review the efficiency of this novel fuel, it was tested by a four-stroke engine connected to a dynamometer and an analyzer, under different controlled environments: speeds of 1500, 2000, 2500, and 3000 rpm at both half and full throttle conditions. The analyzed data are the power and torque of the engine, the amount of emitted CO, CO2, HC, and NOx, the octane index, and the viscosity. The analyzed data were calculated and turned into models. Applying the models to data (the optimization process), close correlation between predicted and actual outcomes was found, highlighting the validity of the work. A secondary finding is that the CeO2 mixture used at higher speeds and throttles produces less emissions, while lower speeds and throttles using the MgO mixture produce less emissions. [ABSTRACT FROM AUTHOR]

Atomizers are widely used for fuel injection in aircraft engines and gas turbine power plants. Improvement in fuel atomization can lead to the reduction of pollutant emissions resulting from the fuel combustion such as NOx gases. Air-blast atomizers provide excellent atomization over a large range of fuel flow rates and very good patternation. In this study, we consider an annular liquid sheet emanating from an air-blast atomizer subjected to inner and outer swirling air streams. The final dispersion equation is solved numerically usingMathematicaTM. We solve for the root with the maximum imaginary part that represents the maximum growth rate of disturbance corresponding to the most unstable wave number. [ABSTRACT FROM PUBLISHER]