Helical or spiral coiled heat exchangers, prevalent in industries such as power generation, heat recovery systems, the food sector, and various plant processes, exhibit potential for performance enhancement through optimal fluid selection. Notably, nanofluids, distinguished by their superior thermophysical properties, including enhanced thermal conductivity, viscosity, and convective heat transfer coefficient (HTC), are considered viable candidates. In this study, the thermo-physical attributes of helical coil heat exchangers (HCHEs), when subjected to nanofluids, were meticulously examined. During the design phase, Creo parametric design software was employed to refine the geometric configuration, subsequently enhancing fluid flow dynamics, thereby yielding a design improvement for the HCHE. Subsequent computational fluid dynamics (CFD) simulations of the heat exchanger were conducted via the ANSYS CFX program. A CuO/water nanofluid, at a 1% volume fraction, served as the basis for the CFD analysis, incorporating the Re-Normalisation Group ($k-\varepsilon$) turbulence model. From these simulations, zones exhibiting elevated temperature and pressure were discerned. It was observed that the wall HTC value for the CuO/water mixture surpassed that of pure water by 10.01%. Concurrently, the Nusselt number, when the CuO/water nanofluid was employed, escalated by 6.8% in comparison to utilizing water alone. However, it should be noted that a 5.43% increment in the pressure drop was recorded for the CuO/water nanofluid in contrast to pure water.

A hybrid procedure FLT-HPM was proposed in this study, by combining the homotopy perturbation method (HPM) with Fourier transform and Laplace transform which aimed to find an approximate analytical solution to the problem of two-dimensional transient natural convection in a horizontal cylindrical concentric annulus bounded by two isothermal surfaces. The effect of the Grashof number, Prandtl number, and the radius ratio on fluid flow (air) and heat transfer with different values awreas discussed. Moreover, the velocity distributions and the mean Nusselt numbers were studied, and the Nusselt numbers were used to represent local and general heat transfer rates. Finally, the convergence of FLT-HPM was tested theoretically through the proof of some theorems. In addition, these theorems were applied to the results of the new solutions obtained using FLT-HPM.

This study examines the energy and exergy performance of the Khoy dual fuel combined cycle power plant, focusing on dual pressure heat recovery steam generators (HRSGs). The aim is to identify an optimal design through the development of a thermodynamic model using ASPEN PLUS software. In the simulation, isentropic efficiencies of high-pressure and low-pressure steam turbines, gas turbines, and compressors are assumed to be 0.85, 0.80, 0.85, and 0.85, respectively. Various practical parameters, such as compressor pressure, condenser pressure, high-pressure steam turbine pressure, and outlet and inlet temperatures of superheaters and turbines, are investigated for their effects on energy and exergy efficiencies. The analysis reveals that combustion chamber I and combustion chamber II contribute the highest amounts of exergy destruction, accounting for 21.80% and 21.50% of the total exergy destruction, respectively. These areas are identified as requiring improvement. Based on the findings, an optimal design is presented, resulting in significant enhancements in energy and exergy efficiencies. The energy efficiency experiences a remarkable increase of 8.75%, while the exergy efficiency demonstrates a substantial improvement of 22.04%. This underscores the superiority of the optimized power plant configuration and provides valuable insights for designers, engineers, and power plant operators. In conclusion, this study advances the understanding of the energy and exergy performance of the Khoy dual fuel combined cycle power plant and offers guidance for optimizing its design and operation.

The development of an effective cooling system is paramount for the optimal design of high altitude Unmanned Aerial Vehicles (UAVs). These vehicles often operate at or near supersonic speeds in thin atmospheric conditions to generate sufficient lift. It is emphasized that the necessity for air-cooling mandates the incorporation of cooling ducts into the initial design, striving for a balance between low-speed, high-density cooling air for efficient heat rejection, minimal drag, or even potential thrust augmentation. The proposition is that dedicated, meticulously optimized cooling air pathways may facilitate superior performance at high altitudes. The abstract further underscores that the longevity and efficiency of solar panels, commonplace in solar-powered UAVs, are substantially temperature-dependent. As such, high-altitude cooling poses a complex challenge. For conventionally fueled jet-powered UAVs, fuel may serve as a viable heat sink, necessitating a design approach that integrates Peltier cells within electronic components. An alternative approach involves the installation of a subsonic Meredith duct within the primary air intake of the main turbo engine. This duct operates by reducing air speed at the face of a high-efficiency air-to-liquid radiator and then expanding the heated air into a nozzle, making the application of radiators feasible, even for supersonic UAVs. The feasibility of deploying the Meredith duct with direct exposure to external air in subsonic UAVs is also explored. This investigation thus sheds light on innovative cooling mechanisms for UAVs operating at high altitudes, potentially leading to improved efficiency and lifespan of critical components. The findings are poised to enhance the understanding of UAV design and operation, contributing to their overall performance and effectiveness.

This paper aimed to analyze the properties of rubber agglomerate panel, a heterogeneous material. After making three adjustments using three classical differential fractional models, namely, the Scott-Blair model, the generalized fractional Maxwell model (FMM), and the 1D standard fractional viscoelastic order for fluids (SFVOF), this paper assessed the number of parameters in those models for rubber agglomerate panel, made from rubber grains and urea thermoplastic elastomer (TPE). Combining data published from an undergraduate thesis with Microsoft Excel software and the solver command, this paper obtained better sample results using four parameters, rather than two or three complicated material function equations. Data of Ribeiro Alves in 2019 came from hardness experiments. Then this paper transformed deformation data into creep compliance in accordance with equation $J(t)=\varepsilon / t$ (mm/s), and obtained graphical adjustment representations, parameter values, and eventually adjustment equations. However, results from the modified FMM and 1D SFVOF were more comparable, and certain hypotheses were investigated to choose the better model. It was determined that the generalized FMM fit the data the best for this time period. With a certain margin of error, this model could be used for constructing new recycled materials and rubber agglomerate panel using Salvadori equipment. However, it is suggested that new and recent materials should be tested in order to solve environmental problems.

Thermal Energy Storage (TES) system has emerged as a promising solution of energy demand and supply management, which stores excess thermal energy and releases it when energy demand is high, making it an efficient and cost-effective energy storage solution when combined with renewable energy sources, such as solar and wind power. This study aimed to evaluate the thermal performance of TES units using Computational Fluid Dynamics (CFD) simulations in the ANSYS CFX software package. After comparing the heat storage capacity of conventional Phase Change Material (PCM) and iron oxide/paraffin wax composite (2%) using industrial residual water, temperature distribution plots and heat flux data were generated in simulations for both cases. Addition of iron oxide nanoparticles significantly improved the heat absorption performance of TES units. Both materials initially exhibited a higher heat absorption rate, which gradually decreased over time. CFD data analysis revealed that iron oxide/paraffin wax material enhanced heat absorption performance by up to 1.3%, which demonstrated the potential of iron oxide nanoparticles in improving the efficiency of TES system and highlighted the advantages of TES system combined with renewable energy sources. By improving heat absorption properties, the incorporation of iron oxide nanoparticles had the potential to increase the lifespan of TES units and significantly reduced maintenance and replacement expenses. This breakthrough, along with the cost savings and energy efficiency offered by TES technology, may encourage its widespread application, thus reducing reliance on fossil fuels and promoting sustainable energy practices.

Unsustainable fossil fuels are mainly used to generate power in compression ignition (CI) engines in industry now. Due to fossil fuel depletion and potential environmental hazards, it is necessary for researchers to find alternative energy resources to adequately substitute hydrocarbon fossil fuels in current engines. A huge number of studies have focused on the use of renewable fuels in CI engines along with conventional petroleum fuels. Therefore, this paper aimed to analyze the effect of gaseous fuels added to CI engines as a supplement, such as H₂, biogas and syngas, in dual fuel mode with diesel as an alternative fuel. This paper analyzed several important characteristics, on which engine evaluation of CI engines using gaseous fuel as an additive is based, such as combustion, performance and emissions, and compared them with those of CI engines operating in single-fuel mode. The findings of numerous empirical studies are shown in graphs of particular parameters, which were crucial for investigating and assessing the case. The main conclusions indicated that gaseous fuel enrichment caused slight decline of performance in CI dual-fuel engine but actually improved emissions. In addition, this paper thoroughly analyzed various methods to assess the performance of biogas in CI dual-fuel engines and investigated dangerous emission pollution.

In an oil-film lubricating system, fit clearance and the different types of lubricating oil can result in changes in the orbit of shaft center, thereby affecting the stability of the system. Subject of this paper is the camshaft lubricating system of airspace engine, to figure out the effects of fit clearance and the type of lubricating oil on the shaft center orbit of camshaft, in this study, a 3D model of the camshaft lubricating system was built for simulation purpose based on Reynolds equation, and the calculation results suggest that, as the fit clearance grows larger, the convergence position of shaft center gradually moves away from the starting position, and the stability of shaft center declines; in terms of the type of lubricating oil, the higher the viscosity of the lubricating oil, the closer of the position of shaft center to the starting point, and the higher the stability. Our research method can be applied to common oil-film lubricating systems and we hope it could provide a theoretical evidence for the selection of fit clearance and type of lubricating oil for such systems.

Turboprop engines are widely used in the commuter or light transport aircraft (LTA) turboprop engines, because they are more fuel efficient than the propeller, which has a low jet velocity, at flight velocities below 0.6 Mach. For short distances, turboprop engines are more fuel efficient than jet engines, because the light weight assures a high power output per unit of weight. In addition, turboprops are known for their efficiency at medium and low altitudes. Turboprop engines require an exhaust stub (or nozzle) to duct the engine exhaust flue gas outboard of the aircraft. The design of these exhaust stubs is dictated primarily by the aircraft configuration. During the exhaust stub design, full flow at bends and in diffusing sections must be realized by following the established practice for the design of internal flow ducts. Otherwise, the flow will separate from the wall, causing unnecessary pressure loss and reducing the effective flow area. This paper discusses some of the many variations in exhaust stub design, and examines how they influence the performance of the engine, the performance of the aircraft, and the manufacturing aspect. The authors carried out a detailed analysis on the influencing parameters, such as the location, orientation, flange dimension, and geometric effective area of exhaust port. On this basis, the authors determined the jet temperature at exhaust stub exit and temperature at exhaust stub exit plane and nacelle midsection were determined at both static and cruise condition, laying the data basis for further analysis on the exhaust temperature effects over the nacelle and aircraft surfaces.

The world is presently confronted with the twin crisis of resource restriction and environmental degradation. The search for solutions that promise a harmonious correlation with sustainable development, energy conservation, efficiency, and environmental preservation has become highly important. The main purpose of innovative studies on fuel refinement and combustion engines is to improve fuel properties by adding fuel additives. In this study, the impact of Titanium dioxide, TiO₂, nanoparticles solution blended with diesel fuel on the performance and emission characteristics of four-stroke combustion engine OM 364 EU III, manufactured by IDEM Co and licensed by Daimler Benz, has been investigated. The selection of TiO₂ nanoparticles is based on the easy access in the market and the gap recognized; in previous literature, these nanoparticles were added to biodiesel or n-butanol blends. The proposed combined fuel in this study contains 2.5 ppm TiO₂ nanoparticles dissolved in 1200 [ml] water and added to 60 [Lit] base diesel fuel. The results of the aforementioned combined fuel have been compared with the base diesel fuel. It has been observed that applying nano-additives improves the mechanical performance of the diesel engine, such as power, torque, brake-specific fuel consumption, and thermal efficiency. Moreover, soot, unburned hydrocarbons, and carbon monoxide have declined by 2.78%, 3.55%, and 3.32%, respectively, due to TiO₂ nanoparticles' catalytic effect on fuel combustion. However, the amount of NOx has increased up to 3.09% because of the high cycle temperature.

Convectional refrigeration is one of the causes of global warming as carbon dioxide is emitted from its refrigerant to the environment. Semiconductor-based refrigeration is one of the alternative technologies that can lower the carbon dioxide emissions to the atmosphere as it uses electron gas instead of a refrigerant as its working fluid. The present work aims to design and construct a semiconductor-based refrigerator and test its performance. The refrigerator was designed to cool 4×10^-3 m^-3 of water from a temperature of 30℃ to 0℃. The tests performed on the refrigerator were retention time of the temperature of the water, change in the water temperature at different intervals of time, and the cooling rate of the water. The results of the tests indicated that the temperature of the water dropped from its initial value of 30℃ to 0℃ after 225 minutes, and maintained the temperature of 0℃ for 15 minutes. After the refrigerator was switched off, the temperature of 0℃ was retained for approximately 30 minutes, and then took 192 minutes to rise from 0℃ to its initial value of 30℃. The average cooling rate for the duration of 225 minutes was 0.133℃/min. The current work widens the studies on the use of alternative technologies for convectional refrigeration.

In the process of robot bone grinding, a large amount of heat is generated, which will cause mechanical and thermal damage to bone tissues and nerves. It is necessary to study the influence of cooling and lubrication parameters on the robot bone grinding temperature and establish the prediction models among them. The FE model of single abrasive bone grinding was established to explore the influence of cooling and lubrication parameters on the bone grinding temperature. Response surface design of experiment was carried out to obtain the simulation results, and Design-Expert was used to establish a multiple regression prediction models of grinding temperature under the condition of different cooling and lubrication. Through the variance and response surface comparative analysis of the prediction model, the influence rules of the bone grinding parameters and the cooling and lubrication parameters on the bone grinding temperature was obtained. A robot bone grinding experiment was performed to prove the accuracy of FE simulation and prediction model. The research results show that the relationship between grinding temperature and cooling lubrication parameters obtained by FE simulation, RSM prediction and experiment verification is consistent, and the simulation model and prediction model of cooling and lubrication parameters are proven to be correct and effective. The influence rules and prediction effects obtained in this study will provide a reasonable scheme for doctors to implement robot bone grinding with high efficiency and low damage, and establish the theoretical basis for the effective control of robot bone grinding force thermal damage.

Although many fluidized systems are not vertically oriented, little research has been done on fluidization within inclined channels. The fluidization of the gravitational force and the tensile force may be substantially opposing in the vertical system. The theory of gravitational field fluidization, which is related to industrial fluidization processes like coal gasification, iron ore reduction, and catalytic cracking and calls for the use of standing tubes or angled risers, has to be developed in order to encompass various orientations. Without underlying theories, engineers must rely on vertical fluidization equations to build these sloping systems. A significant barrier to improving the design and optimization of new solid circulation systems is the tendency of fluidization. Based on historical developments and theoretical progress, the study presents an overview of recent advancements of liquid-solid fluidized beds in inclined columns. The fluidized bed is investigated as a whole by looking at the governing factors.

This paper intends to improve the hydrogen production efficiency of the electrolysis cells, fully utilize wind energy, and ensure the reliability of power supply. For this purpose, the authors put forward a capacity optimization configuration for non-grid-connected wind-hydrogen hybrid energy storage system, in view of the features of hydrogen production efficiency. The working interval of the electrolytic cell was optimized by analyzing the said features. Considering the features of battery charge/discharge, equipment capacity and power, the authors formulated the energy management strategy applicable to six working conditions, established the quantitative multi-objective function of system cost and reliability, and solved the optimization model by the fast non-dominant sorting genetic algorithm (NSGA)-II. In this way, the optimal combination of energy storage capacity was determined. Next, the wind velocity data of a pastoral area in Inner Mongolia was measured, and analyzed in details. The analysis results show that the electrolytic cell always operates in the optimal working area, and the optimized wind-hydrogen system is economic and reliable in power supply. The research provides a reference for practical engineering applications.

During the operation of the ground source heat pump (GSHP) system, the operations of the chiller system should be controlled by adjusting the difference between water temperature and wet bulb temperature. Therefore, it is important to consider the control strategy for the switch time (ST) and wet bulb temperature difference (WBTD) of the chiller system. This paper sets up two control strategies, namely, the strategy to control the ST of system operations, and the strategy to control the WBTD. Then, theoretical modeling was carried out to compare the system energy consumption and borehole wall temperature under different strategies. The modeling results were referred to optimize the control strategy for composite GSHP systems. It was found that, under the ST control strategy, the best wet bulb temperature is 2℃, and the best chiller operation hours are 3h; under the WBTD control strategy, the best wet bulb temperature is 3.5℃, and the best WBTD is 1.5℃. In addition, the ST control strategy is superior to the WBTD control strategy, in terms of system energy consumption, borehole wall temperature and initial investment.