Increase In Thermal Efficiency Research Articles

INVESTIGATION OF HYBRID PHOTOVOLTAIC /THERMAL SOLAR SYSTEM PERFORMANCE UNDER IRAQ'S CLIMATE CONDITIONS

The research investigates the use of fins fastened to a solar panel's rear surface for passive cooling. The research compared solar modules with air cooling against modules with connected fins acting as a heat sink. The comparison was based on the former. The research studies the cooling of modules with fins using two different types of air: ventilation air and still air. By comparing the heat transmission by photovoltaic panels with and without fins, the research sought to analyses the effects of the environment and solar radiation on the performance of solar cells. The inquiry was done hypothetically. According to the findings, using fins for cooling reduced cell temperature and improved electrical and thermal efficiency. The estimated performance values of the PVT solar cell obtained by using the COMSOL program and the experimental measurements carried out during the daytime were reasonably in accord. The biggest reduction in cell temperature is (3.7ºC at noon), while the greatest increases in electrical and thermal efficiency are (16.54% and 58.3%, respectively). There is good agreement between experimental and numerical results.

Development of a novel multi-fidelity meta modeling approach for robust multi-objective optimization of a natural gas-hydrogen/diesel dual fuel engine

Multi-fidelity modeling (MFM) is an evolving field that matches low-fidelity models (LFM) and high-fidelity models (HFM) to get better solutions with low computational cost. However, improving the duality between accuracy and computational cost remain challenging, particularly for complex problems such as dual fuel engines. This paper contributes to the MF modeling cost-effectiveness improvement by proposing a new approach to solve large-dimensional multi-objective optimization problems. The first step is to build a meta-model based on the LF model, which will be subjected to a comet-governed analysis to detect potential areas where the uncertainty on the LF model is relatively high. Then, a design of experiment (DOE) will be developed based on the results of this analysis to construct an initial HF model. Finally, an iterative loop will be activated to improve the accuracy of the MF model using a well-weighed combination of the details delivered by the LF model correction via the HF model and the HF meta-model. The developed approach is validated on four different mathematical benchmarks with different difficulties, compared with four different MF modeling strategies. This validation shows that the proposed MF modeling is competitive and can produce solutions as accurate as the HF model while reducing significantly the overall computation time by up to 50%. As an engineering application, the operating conditions in a natural gas-hydrogen/diesel dual fuel engine in terms of compression ratio, pilot injection timing, and EGR are optimized. A reduction of 46%, 68%, and 96% was achieved for HC, NOx, and the knocking index, respectively, while an increase in thermal efficiency of about 5% was obtained.

Experimental determination for optimal position of reflector in solar water heater

An experimental investigation was carried out on novel solar water heater that utilizes a flat reflector positioned underneath the absorber tubes. Experiments were conducted at National Institute of Technology Patna, India, having latitude 25.61°N and longitude 85.14° E and constant insolation of 1000 The experimental data were collected for different reflector positions i.e. δ = 0 mm, 15 mm, 30 mm, 45 mm, and 60 mm and six mass flow rates of working fluid i.e. 0.0056 kg s−1, 0.0097 kg s−1, 0.0138 kg s−1, 0.0207 kg s−1, 0.0277 kg s−1, and 0.0346 kg−1s. The obtained experimental results exhibited that the location of the reflector relative to the absorber tubes significantly affects the thermal performance of the system. The effect of the mass flow rate on the outlet temperature, thermal performance, and overall performance has also been studied. For the present system under energy and exergy analysis, the optimal position of the reflector was found of δ = 30 mm. The results showed that the solar water heater with an optimally positioned reflector has a 23% increase in thermal efficiency compared to the solar water heater without a reflector. The novelty of using a flat reflector underneath absorber tube is to provide heat to rear side of the absorber tubes after reflecting the insolation falling on the reflector and hence improvement in the thermal performance of the solar water heater. The scope of present system includes providing an eco-friendly and energy-efficient solution for residential and commercial hot water needs. Limitations of the present study are requirement of sufficient roof space and direct sunlight. The use of reflectors has implications for energy savings, more efficient system designs, and enhanced thermal performance.

Sensitivity analysis of the thermal performance of a parabolic trough concentrator using Al2O3 and SiO2/Vegetable oil as heat transfer fluid

This paper aims to highlight the use of different heat transfer fluid (HTF) configurations based on vegetable oils in Parabolic Trough Solar Concentrator (PTSC). Rapeseed and jatropha oils as innovative heat transfer materials combined with SiO2 and Al2O3 to obtain six (6) HTF configurations are used in a 1-dimensional PTSC model. The thermophysical properties of the nanofluids are determined from correlations derived from the literature, using Gauss-Seidel method from a numerical code developed in Matlab software. Model validation is obtained. Thermal sensitivity analysis shows that the use of rapeseed increases the thermal efficiency of the PTSC by around 4.21 % compared with jatropha. The use of nanofluids reduces thermal losses within the system due to thermal gradients. For a fixed irradiance and each 1 %–4 % increase in volume fraction, thermal efficiency increases by around 1.96 % when Al2O3/rapeseed is used and by 0.47 % when SiO2/rapeseed is used compared with rapeseed. Similarly, thermal efficiency increases by around 1.98 % when Al2O3/jatropha is used and decreases by around 0.20 % when SiO2/jatropha is used compared with jatropha. However, the positive effects of nanoparticles on thermal conductivity alone are not always sufficient to improve thermal efficiency, and thermal effects on heat capacity should also be considered.

Thermodynamic Analysis of Once-through Heat Recovery Steam Generator in a Combined Cycle Power Plants Fueled with Biogas

The working principle of the combined cycle in the combined cycle power plant (CCPP) is to utilize a certain amount of waste heat in the gas turbine, which reaches temperatures of 1650°C, to generate steam in the steam turbine. Due to the high temperature of the exhaust gas in the gas turbine, a device is needed to recover this waste heat, known as a Heat Recovery Steam Generator (HRSG). Compared to conventional HRSG, a once-through heat recovery steam generator (OTHRSG) offers the advantages of faster design time (25% faster than conventional) and lower design costs because it does not require a drum which contributes to an increase in thermal efficiency. This study aims to model and simulate the CCPP system with an OTHRSG to achieve maximum thermal efficiency by using biogas from the degradation of organic waste as the input fuel for CCPP using Cycle Tempo software. The thermal efficiency of the CCPP system was achieved at 57% by applying turbine inlet temperature (TIT) of 1500°C and compression ratio of 46. These results proved that the CCPP system by using biogas as fuel could increase the thermal efficiency of a single cycle power plant.

INVESTIGATING THE IMPACT OF USING MAGNETIC-TYPE NANOFLUID ON THE THERMAL PERFORMANCE OF A SOLAR WATER COLLECTOR WITH HELICALLY COILED TUBE ABSORBER

In recent years, solar water collectors are commonly preferred for supplying heated water to be utilized in various processes. In the present study, a solar water collector equipped with a helically coiled absorbing surface has been manufactured and experimented under various working conditions to determine its general behavior. The main goal of using a helically coiled absorber is enhancing energy harvest in the collector by ensuring vertical angle between the absorbing area and incident radiation. In addition, for providing greater increase in thermal efficiency, magnetic type nanofluid has been used as a working fluid. In this context, NiFe<sub>2</sub>O<sub>4</sub> nano-sized particles have been mixed with water at the ratio of 2% (wt./wt.). Accordingly, the performance of the collector has been empirically examined using both water and magnetic nanofluid at two different flow rates. The overall results of the present survey exhibited successful use of magnetic type nanofluid in a solar collector equipped with a helically coiled absorbing surface. Utilizing magnetic nanofluid in the collector as circulating fluid raised the thermal efficiency on an average of 20.29% and 23.59% at volumetric flow rates of 0.5 lpm, and 0.9 lpm, respectively. Moreover, utilizing NiFe<sub>2</sub>O<sub>4</sub>/water nanofluid in the water collector enhanced the exergy efficiency on an average of 44.53% and 40.04% at volumetric flow rates of 0.5 lpm and 0.9 lpm, respectively.

INVESTIGATING THE PERFORMANCE OF A FLAT-PLATE SOLAR WATER-HEATING SYSTEM USING CeO2/WATER NANOFLUID: A HOLISTIC APPROACH

The efficiency of a solar water heater with a flat-plate collector, which had an absorber area of 2 m<sup>2</sup> and utilized a cerium oxide-water nanofluid as the working medium with a fixed volume fraction of 0.01%, was analyzed using a holistic approach. To assess the impact of flow rate on its heat transfer characteristics, the working fluid was systematically circulated through a pump-circulation system at various flow rates ranging from 1 to 3 liters per minute (LPM). The system underwent analytical and field testing, which revealed that it achieves a maximum thermal efficiency of 78.2% at a flow rate of 2 LPM. The heat transfer coefficient underwent a notable enhancement, leading to a 21.5% increase in thermal efficiency compared to a system operating with plain water. A refined artificial neural network (ANN) model was created to forecast thermal performance and outlet temperature. The optimized ANN model is structured with a 3-10-2 architecture and achieves a mean squared error of 8.2 × 10<sup>-3</sup>. The performance of the optimized ANN model was assessed by testing its generalization capacity against experimental results. It was determined that the ANN model predictions aligned closely with the experimental data, exhibiting correlation coefficients ranging from 0.96 to 0.98. This study conclusively demonstrates that the analytical model and ANN can serve as a highly effective design tool for evaluating the performance of innovative solar collectors.

Subcritical and supercritical Rankine steam cycles, under elevated temperatures up to 900°C and absolute pressures up to 400 bara

The Rankine cycle is a conceptual arrangement of four processes as a closed vapor power thermodynamic cycle, where a working fluid (especially water as a liquid, as a vapor, and as a liquid-vapor mixture) can be used to convert heat into mechanical energy (shaft rotation). This cycle and its variants are widely used in electric power generation through utility-scale thermal power plants, such as coal-fired power plants and nuclear power plants. In the steam-based Rankine cycle, water should be pressurized and heated to be in the form of very hot high-pressure water vapor called “superheated steam,” before the useful process of expansion inside a steam turbine section occurs. If the absolute pressure and temperature of the superheated steam are both above the critical values for water (220.6 bara and 374.0°C), the cycle is classified as “supercritical.” Otherwise, the cycle is classified as “subcritical.” This study considers the impact of the temperature and pressure, independently, on the performance of a steam Rankine cycle. Starting from a representative condition for a subcritical cycle (600°C peak temperature and 50 bara peak absolute pressure), either the peak temperature or the peak absolute pressure of the cycle is increased with regular steps (up to 900°C, with a temperature step of 50°C, and up to 400 bara, with a pressure step of 50 bar). The variation of five scale-independent performance metrics is investigated in response to the elevated temperature and the elevated pressure. Thus, a total of 10 response curves are presented. When the temperature increased, all the five response variables were improved in a nearly linear profile. On the other hand, increasing the pressure did not give a monotonic linear improvement for each response variable. In particular, the cycle efficiency seemed to approach a limiting maximum value of 45% approximately, where further increases in the pressure cause diminishing improvements in the efficiency. When varying the peak pressure, an optimum minimum ratio of (water-mass-to-output-power) is found at 203 bara, although the cycle efficiency still increases beyond this value. In the present research work, the web-based tool for calculating steam properties by the British company Spirax Sarco Limited, and the software program mini-REFPROP by NIST (United States National Institute of Standards and Technology) were used for finding the necessary specific enthalpies (energy content) of water at different stages within the steam cycle. Both tools were found consistent with each other, as well as with the Python-based software package Cantera for simulating thermo-chemical-transport processes. The results showed that if the peak temperature reaches 900°C, a gain of about 5 percentage points (pp) in the thermal cycle efficiency becomes possible (compared to the case of having a base peak temperature of 600°C), as the predicted efficiency was found to increase from 38.60% (base case) to 43.67%. For the influence of the steam peak pressure, operating in the subcritical regime but close to the critical point appears to be a good choice given the gradual decline in efficiency gains at higher pressures. About 4.7 percentage point increase was found at the high subcritical peak pressure of 200 bara (compared to a base subcritical peak pressure of 50 bara). The results of this study also showed that the liquid water droplet mass fraction at the steam turbine exit diminishes from 11.00% at 600°C to only 1.48% at 900°C, which is favorable. This mass fraction grows from 11.00% at 50 bara to 27.89% at 400 bara, which is not acceptable. Every 100°C increase in the superheating temperature between 600°C and 900°C was found to cause aa increase in the cycle thermal efficiency by about 1.69 percentage points, and simultaneous a beneficial increase in the steam quality at the turbine exit by about 3.17 percentage points.

Carbon neutrality with ammonia: An analysis of its feasibility as a fuel for diesel engines fuelled with spirulina microalgae and oxygenated additives

Ammonia has emerged as a promising gaseous fuel for replacing conventional fossil fuels and achieving carbon neutrality. This research explores the viability of using ammonia as a fuel in compression ignition diesel engines operating in dual-fuel mode. The study investigates the performance and emission characteristics of diesel engines fueled with ammonia, microalgae-based biodiesel, and their combinations, with the addition of Fe2O3 nanoparticles to enhance combustion efficiency. A series of experiments were conducted using various blends of ammonia, biodiesel, and nanoparticles in a single-cylinder engine. The objective was to assess the impact of ammonia and biodiesel on thermal efficiency and carbon-based emissions. Comparative analysis revealed that ammonia-based fuels exhibited higher brake thermal efficiency and lower carbon emissions compared to traditional diesel fuel. The combination of ammonia, biodiesel, and nanoparticles resulted in an 8.5% increase in thermal efficiency compared to diesel fuel. However, the fuel consumption increased by 18% due to the lower energy density and higher viscosity of the biodiesel blends. Furthermore, the study examined the emissions profile of the tested fuels. The use of ammonia and nanoparticles led to significant reductions in carbon monoxide, hydrocarbon, and smoke emissions. However, there was a slight increase in nitrogen oxides and carbon dioxide emissions, regardless of engine loading conditions. It was observed that the emission of NOx was influenced by combustion delay and autoignition temperature. To mitigate NOx emissions, optimizing the combustion delay and avoiding premixed combustion phases are crucial. Based on the findings, the study concludes that ammonia has the potential to serve as a viable substitute for diesel fuel in engines. Ammonia-based fuels exhibit higher brake thermal efficiency and lower carbon emissions. Future research should focus on optimizing combustion parameters to minimize NOx emissions, thereby facilitating the widespread adoption of ammonia in diesel engines and contributing to the decarbonization of the transportation sector.

The Effect of Upstream Unsteadiness on the Unstarting of a Supersonic Inlet Turbine

Abstract A 15% increase in thermal efficiency at medium pressure ratios is promised by rotating detonation engine technology over conventional Joule–Bryton cycles. A supersonic inlet turbine is a viable option to extract substantial work from the highly fluctuating and supersonic flow delivered by the detonating combustor. However, an additional unstarting mechanism based on the generation of a collective shock from the coalescence of leading-edge bow-shock waves further restricts the available design space. First, the effect of unsteady inlet conditions with variable frequency, amplitude, and mean value on collective shock generation is investigated. Then, a fast and cost-effective tool was developed and verified to predict bow-shock wave motion from a prescribed inlet Mach trend; the parameters of the transfer function were estimated with a classical identification method based on a step-response computational fluid dynamics (CFD) simulation. The model was employed to rapidly calculate the maximum amplitude of fluctuations accepted by the supersonic blade row for each frequency and average inlet Mach number. Finally, the influence of the inlet geometric angle, pitch to leading-edge thickness ratio, and static temperature on the model parameters is studied. The preliminary observations of the parametric analysis were confirmed by the rigorous quantitative approach of a global sensitivity analysis based on Sobol sensitivity indices.

Venturi effect-based simulation of air-based PVT optimization

ABSTRACT Air-based photovoltaic thermal(PVT) solar collectors can convert solar energy into both electrical and thermal energy. However, the output efficiency was often low due to the limitation of the heat transfer capacity for air. Therefore, in this paper, an air-based PVT with the application of a novel rib was modeled and numerically simulated. The innovation of this paper was proposing a novel rib, which was based on the Venturi effect. First, the effects of the new rib control parameters on the performance of the PVT system were analyzed using orthogonal design tests. The result showed that the thermal efficiency of the best factors combination test was 51.16% when the solar radiation was 500 W / m 2 and the air inlet rate was 0.09 m / s . Second, analyzing the fluid flow characteristics and the enhanced heat transfer mechanism, this study found that the increased air velocity under the novel rib and the low-velocity vortex formed between the rib both negatively affected heat transfer. Consequently, this paper proposed a novel fin design coupled with curved fins to address the issues with the novel rib design, which achieved 55.12% thermal efficiency with the combination structure. Finally, we applied the combined structure to the PVT system, studied its thermal efficiency under real-world conditions, and compared it with the empty channel collector. The results showed significant improvement, with a 16.38% increase in thermal efficiency and the model exhibited excellent, stable performance.

Experimental investigation of the influence of pre-chamber structural parameters on combustion and emission characteristics of a high compression ratio SI engine

The passive pre-chamber exhibits great potential for practical applications in the internal combustion engine due to its simple structure. However, it faces difficulties in scavenging process, making optimization of pre-chamber structure particularly important. In this study, the effects of pre-chamber ignition systems with different structures and original spark ignition were conducted on a high compression ratio direct-injection SI engine to investigate the combustion, performance, and emission characteristics. The results show that the increase in pre-chamber volume weakens the in-cylinder combustion process and engine performance, while increasing the pre-chamber orifice diameter can enhance the combustion stability at medium to high loads, but will weaken the engine performance at low load. Compared to spark ignition, pre-chamber ignition results in an earlier 50% combustion position, a shorter combustion duration and lower COVIMEP, with these effects becoming stronger as load increases. At high load, the pre-chamber ignition (PC1) advances the 50% combustion position by 5.6°CA and shortens the combustion duration by 16.7%. In addition, the indicated thermal efficiency of the pre-chamber ignition achieves an increase of 0.84% at the optimal point and 2.5% at high load. Overall, using the smaller orifice diameter and volume in the pre-chamber can improve in-cylinder combustion process and increase thermal efficiency across the load range. For emission analysis, the pre-chamber ignition leads to an increase in NOx and HC emissions due to the influence of in-cylinder combustion temperature and quenching effect, while the CO emissions are similar to spark ignition.

Artificial Neural Network and Genetic Algorithm-based prediction of photovoltaic panel performance with porous foam gradient and nano-enhanced phase change material

Photovoltaic panels (PV) become less efficient as the temperature rises. The use of porous foam gradient, phase change materials (PCMs), and nanoparticle-PCM (nePCM) can effectively lower the temperature of PV panels. This study employed numerical analysis using the finite volume method to investigate the effects of different types of PCMs (n-octadecane, decanoic acid natural, lauric acid, paraffin wax, and RT-42), mono and hybrid nanoparticles/PCM, and the position of PCM in the design system. The results indicate that the highest electrical efficiency of 9 % is achieved when the PCM is placed under the PV panel and the thickness of the PCM layer is 0.6 times the height of the microchannel. Furthermore, the use of a porous medium with a variable porosity coefficient that increases along the y-direction can significantly improve thermal and electrical efficiency (approximately 5–42 % and 5–48 % respectively). Additionally, incorporating PCM and hybrid nanoparticles-PCM enhances PV performance compared to the absence of nanoparticles. For TiO2, Ag, Al2O3, GO, and MWCNT nanoparticles, the thermal efficiency, electrical efficiency, and exergetic efficiency increase by approximately 24.18 %, 26.15 %, 26.28 %, 26.30 %, and 26.33 % respectively. Similarly, for hybrid nanoparticles such as GO-Al2O3, GO-Al2O3-MWCNT, MWCNT-GO, and MWCNT-Al2O3, these values increase by approximately 26.32 %, 26.3419 %, 26.3432 %, and 26.335 % respectively for thermal efficiency, and 5.16 %, 5.1702 %, 5.1704 %, and 5.1689 % respectively for electrical efficiency. Moreover, n-octadecane exhibits the highest melting fraction, while paraffin wax has the lowest melting fraction. Lastly, the genetic algorithm-neural network method was employed to estimate the PV electrical efficiency.

Experimental examination of the effect of thermal barrier coating in a 2-stroke gasoline engine on recovery performance in exhaust waste heat recovery system with thermoelectric generator and engine performance

In internal combustion engines, while the decrease in in-cylinder wall temperature increases the amount of energy passing towards the cooling system, it decreases temperature and pressure at the end of compression and accordingly reduces thermal efficiency of the engine. Moreover; combustion chamber elements are exposed to chemical corrosion and deformation as a result of uncompleted combustion in the cylinder. With thermal barrier coating application, the energy lost in cooling system will decrease and exhaust temperatures will increase in 2-stroke engines. Placement of a waste heat recover system with thermoelectric generator into the exhaust system can provide exhaust waste heat recovery and increase thermal efficiency of the engine. There is no study in the literature, which examines waste heavy recovery systems with thermal barrier and thermoelectric generator altogether. In this article, yttria stabilized zirconia coating has been applied by means of plasma spraying method in the combustion chamber of a 2-stroke gasoline engine, and effect of thermal barrier coating application on engine performance and exhaust waste heat recovery system has been examined experimentally. According the results of the experiment, maximum engine power has increased by 6.23%, maximum engine torque has increased by 6.02%, and specific fuel consumption decreased by 5.56%. While the exhaust temperatures have increased by 78.5 °C at maximum by means of thermal barrier coating application; by means of thermal barrier coating application with waste heat recovery system with thermoelectric generator, a higher waste heat recovery has been obtained by 64.8%.

Evaluation of an integrated electric power generation system with natural gas engines operating in dual mode through heat recovery with thermoelectric devices for hydrogen production

In the present investigation, an environmental, thermal, economic, and social analysis of an integrated system is carried out, which has as its function the production of hydrogen through the recovery of residual thermal energy from exhaust gases. The proposed integrated system consists of a thermoelectric generator and a hydrogen production bench based on the water electrolysis process. For the development of the research, an internal combustion engine fueled with natural gas was used, operating under four load conditions (25%, 50%, 75%, and 100%). From the environmental assessment, it is demonstrated that the implementation of the integrated system allows a decrease of 12.30%, 6.26%, and 7.90% in CO, CO2, and HC emissions. However, the addition of hydrogen causes a 9.9% increase in NOx emissions. Additionally, the implementation of the integrated system allows a 4.9% decrease in brake specific fuel consumption and a 4.9% increase in engine thermal efficiency. The improvement in engine thermal performance contributes to the 7% reduction in engine operating costs. On the other hand, it demonstrates an 8.7% reduction in the environmental and social impact cost and a 9% reduction in the ecological cost. Additionally, the integrated system minimizes the cost of environmental and social impact, as well as the ecological cost of polluting gases CO, CO2, and HC. The mixture of natural gas and hydrogen allows for a 4.70% and 7.59% increase in pressure and maximum heat release rate. In general, the proposed integrated system is a way to harness the thermal energy of exhaust gases for hydrogen production. In this way, it is possible to obtain an auxiliary fuel that improves the efficiency of the combustion process of the natural gas engine. This allows for minimizing energy losses in self-generation activities in Colombia, achieving better energy management and a reduction in operating costs.

Thermodynamic evaluation of 2026 Power Unit technical regulation changes in Formula 1

Federation Internationale de l'Automobile (FIA) has announced a Power Unit (PU) Regulation change for its Formula 1 (F1) Championship that will become valid from the 2026 season in pursuit of carbon neutralization and a higher commercial value. The change includes a full switch to sustainable fuel and an increase in the power of the electric power output to the cars axles but removed energy retrieving and recovery from the turbocharger. The choice to use fully sustainable fuel will lead to a richer burn. On the other hand, the increase in the hybrid system capacity will outweigh the removal of energy retrieving and recovering from the turbocharger and cause an overall increase in thermal efficiency. Also, the changes are bringing a cost reduction for PU suppliers, which is an attraction for them. The increase in electric power will also integrate the car with new driving characteristics. This paper focuses on respective reviews of the 2023 and 2026 F1 PU Technical Regulations and gives an evaluation of the process for the improvements.

3D thin-film nanofluid flow with heat transfer on an inclined disc by using HWCM

Abstract Momentum and heat transmission influence the coated physical characteristics of wire product. As a result, understanding the polymeric movement and heat mass distribution is crucial. An increase in thermal efficiency is necessary for the wire covering technology. So, the aim of this work is to investigate the influence of nanomaterials on the heat and mass transport processes in wire coating analyses. A thin film nanofluid is used to investigate heat and mass transfer in three dimensions over a rotating inclined disc. Both the suction and injection effects of nanofluids and the thermal radiation of their fluxes are taken into account. By employing similarity variables, the set of governing equations can be transformed into a differential equation system. The necessary differential equation system is solved using the Haar wavelet collocation method. Plots and observations of the velocity distribution, concentration, and thermal fields within the boundary layer across an inclining, steadily rotating plane are made. Flow characteristics change as a result of varying embedded factors such as S , Sc , N b , Pr , S,{\rm{Sc}},{N}_{{\rm{b}}},\Pr , and thermophoretic parameters. Evidence suggests that as the number of rotation parameters grows, the thermal boundary layer weakens.

A novel solar-driven waste heat recovery system in solar-fuel hybrid power plants

Solar-fuel hybrid power generation can effectively reduce pollutants in fuel power plants and facilitate the efficient utilisation of solar energy. This study proposes a novel solar-driven waste heat recovery system for solar–fuel hybrid power plants. New system is integrated with parabolic-trough solar collector to drive the heat pump and optimise air pre-heating, offering unique advantages: solar energy amplification and upgraded utilisation. For a 600 MW unit, solar energy in new system generates an electric power of 9.0 MWe with a 0.67 % increase in thermal efficiency, almost twice that of conventional system. With waste heat recovery, the new system exhibits a solar-to-electricity efficiency of 42.12 %. The new system can increase boiler exergy efficiency from 47.78 % to 48.35 %, and decrease exergy loss of air pre-heating to 7.6 MWe. The essential energy saving mechanism of the new system can be attributed to the optimisation of air preheating. Owing to high thermal performance, new system can yield a net benefit of 13.82 million CNY/y, which is 2.6 times that of conventional system. The findings of this study can help for better understanding of solar energy amplification and and upgraded utilisation, thus opening new avenues for solar conversion in solar-fuel hybrid power generation systems.

Energy analysis and control scheme optimizations for a recuperated gas turbine with variable power offtakes/inputs

An innovative hybrid electric propulsion system (HEPS) is used for recuperated gas turbine (RGT) to avoid partial-load efficiency deterioration. Power offtakes/inputs of high and low-pressure shafts can be regulated by electric machines to achieve decoupling control in the innovative HEPS. The HEPS brings higher heating temperature in the combustor and significantly higher thermal efficiency at partial-load by optimizing the control scheme. A component-level model is used to conduct energy and performance analyses for RGT. The control scheme is optimized to enhance partial-load efficiency and protect RGT from temperature overrun, rotational speed overrun, and compressor surge.The optimal control scheme keeps the combustor exit temperature constant at the maximum restricted value to attain minimum combustor exergy loss under partial-load. The optimal control scheme brings smaller surge margins, but it successfully reverses the deterioration trend of efficiency with decreased load. The thermal efficiency of the original RGT decreases by 8.2 % as the load decreases from 100 to 40 %. The HEPS makes the efficiency curve of the RGT almost keep horizontal as the load ranges from 100 to 40 %. The specific fuel consumption decreases by 29.1 %, and the thermal efficiency increases by 11.5 % at 40 % load, compared to the original RGT.

Prediction of RCCI combustion fueled with CNG and algal biodiesel to sustain efficient diesel engines using machine learning techniques

This study used microalgae biodiesel as a high-reactive fuel directly injected along with various Compressed Natural Gas (CNG) energy shares (10, 20, 30, and 40%) as low-reactive fuel injected into the intake system. The experiments are performed in a single-cylinder, water-cooled, 1500 rpm, 3.5 kW power Compression Ignition (CI) engine under various loading conditions to examine the effects of CNG energy share on performance and emissions in Reactivity Controlled Compression Ignition (RCCI) combustion mode. The study found that the 30%CNG share decreased Nitrogen oxides (NOx) and smoke by 25 and 31%, as well as an increase in thermal efficiency of 4.35% in comparison to traditional biodiesel combustion. Finally, two machine learning (ML) models, namely the Gradient Boosting Regressor (GBR) and LASSO (Least Absolute Shrinkage and Selection Operator) Regression, were developed for predicting the dependent variables individually from the independent variables. Both the LASSO and GBR models achieved high accuracy with R2 values of 0.98–0.99 and relatively low Root Mean Square Error (RMSE) values.