Increase In Thermal Efficiency Research Articles

Effect of Ceramic Matrix Composites on the Thermal Efficiency of a Power Generation Turbine

Abstract Ceramic matrix composites (CMCs) offer higher allowable temperatures and reduced weight, making them an attractive prospect for parts in the hot section of a gas turbine engine. As CMCs are increasingly adapted into aero and land-based engines, there is a need to quantify the performance increase based on the potential for reduced cooling and increased firing temperatures. In this work, two static hot section components—the first-stage turbine vane and the first-stage turbine tip shroud (outer casing above the blade)—of a mid-sized power generation engine were modeled. Informed approximations about part geometry and cooling architectures were made to determine the cooling requirements of each part. Thermal boundary conditions for the turbine tip shroud and turbine vane were generated as a function of coolant mass flowrate using data from literature and applied to a 2D finite element analysis of the parts to determine maximum temperatures for both metallic and ceramic materials. A gas turbine cycle model was developed to simulate the performance of a mid-sized power generation turbine and used to determine the increase in efficiency due to a reduction in the cooling requirement for the CMC part compared to a conventional metal superalloy-based part. The potential reduction in chargeable cooling seen for the tip shroud ring was between 0.09% and 0.4% of the compressor mass flowrate, which corresponds to an increase in thermal efficiency between 0.11% and 0.45%. A similar analysis of the turbine vane resulted in a cooling reduction of 10.71% at the maximum turbine entry temperature considered which corresponds to a 3.4% increase in thermal efficiency.

Optimization of Thermal Performance by Enhancing Natural Convection of Diverse Configurations of Fin Heat Sink Filled With Nano‐Enhanced Phase Change Materials: A Numerical Study

ABSTRACTElectronic components require faster propagation of heat to prevent overheating as well as to maintain a stable operating condition. Incorporating phase change materials (PCMs) in fin heat sinks (FHSs) can be a viable solution to enhance natural convection. In the present work, an extensive investigation has been carried out on three types (square, circular, and triangular) of FHSs filled with PCMs to find the best combinations for the thermal cooling of a heat sink. To increase the thermal conductivity of the PCMs, Cu–water nanofluid is added. The effects of three types (paraffin wax, stearic acid, and polyethylene glycol) of PCMs have been studied. Nondimensional equations have been solved numerically by using Galerkin's finite element method. A parametric investigation has been conducted by varying the Rayleigh number within the range of 103–106 to calculate the Nusselt number. Results reveal that a heat sink with PCMs can reduce the temperature rise by 6.41% and increase the Nusselt number by 4.6% compared to a heat sink without PCMs. As the height of the fins increases from 10 to 16 mm, thermal efficiency increases. Moreover, square FHSs show the best thermal performance by reducing the temperature rise by as much as 13.41% compared to circular and triangular FHSs. Therefore, this comparative study shows that the dimensional configurations of FHSs with varying PCMs have a great impact on thermal performance and thus provide one the opportunity to obtain an effective arrangement of heat sinks.

0-D Dynamic Performance Simulation of Hydrogen-Fueled Turboshaft Engine

In the last few decades, the problem of pollution resulting from human activities has pushed research toward zero or net-zero carbon solutions for transportation. The main objective of this paper is to perform a preliminary performance assessment of the use of hydrogen in conventional turbine engines for aeronautical applications. A 0-D dynamic model of the Allison 250 C-18 turboshaft engine was designed and validated using conventional aviation fuel (kerosene Jet A-1). A dedicated, experimental campaign covering the whole engine operating range was conducted to obtain the thermodynamic data for the main engine components: the compressor, lateral ducts, combustion chamber, high- and low-pressure turbines, and exhaust nozzle. A theoretical chemical combustion model based on the NASA-CEA database was used to account for the energy conversion process in the combustor and to obtain quantitative feedback from the model in terms of fuel consumption. Once the engine and the turbomachinery of the engine were characterized, the work focused on designing a 0-D dynamic engine model based on the engine’s characteristics and the experimental data using the MATLAB/Simulink environment, which is capable of replicating the real engine behavior. Then, the 0-D dynamic model was validated by the acquired data and used to predict the engine’s performance with a different throttle profile (close to realistic request profiles during flight). Finally, the 0-D dynamic engine model was used to predict the performance of the engine using hydrogen as the input of the theoretical combustion model. The outputs of simulations running conventional kerosene Jet A-1 and hydrogen using different throttle profiles were compared, showing up to a 64% reduction in fuel mass flow rate and a 3% increase in thermal efficiency using hydrogen in flight-like conditions. The results confirm the potential of hydrogen as a suitable alternative fuel for small turbine engines and aircraft.

Maximizing thermal management of photovoltaic-thermal systems with proper configuration of porous fins and phase change materials

Effective thermal management is crucial to enhance the performance and longevity of photovoltaic-thermal (PVT) systems. Phase change materials (PCMs) offer a promising solution for absorbing excess heat from PV modules; however, their poor thermal conductivity limits their effectiveness. This work explores the incorporation of porous fins within PCMs to improve heat absorption and thermal regulation in PVT systems. A detailed mathematical model is developed to analyze the effects of varying fin porosity (0.85 to 0.95), fin thickness (7 to 21 mm), fin height (7 to 21 mm), and fin inclination (-15° to 30°) on PCM melting and PVT cooling performance. Results show that optimally configured porous fins significantly enhance PCM melting rates and heat extraction from PV cells. Incorporating optimal fins reduces peak PV temperatures by up to 5°C compared to PCM alone at irradiation rate of 1000 W/m2. Meanwhile, reducing the fin thickness from 21 to 7 mm accelerates the overall PCM melting rate by 14%. The cooling performance also shows a nonlinear increase with fin tilt angle, with maximum enhancement occurring at 15° downward tilt for the studied configuration. The optimized fin-enhanced PVT design achieves 3.1% higher electrical efficiency and 15% increase in thermal efficiency compared to conventional PCM-PVT systems without fins. Findings provide design guidance to harness porous fins for maximized PCM-based cooling of PVT systems.

FLUE GAS RECIRCULATION AS A WAY TO IMPROVE THERMAL EFFICIENCY AND REDUCE EMISSIONS IN POWER BOILERS

This study investigates the impact of flue gas recirculation on key parameters of the fuel combustion process, such as heat release and adiabatic combustion temperature. Based on the mathematical processing of experimental data, equations were obtained that reflect the dependence of useful heat release and adiabatic combustion temperature on the gas recirculation coefficient. According to the results of the study, the useful heat release in the furnace increases proportionally with the growth of the recirculation coefficient. This indicates that an increase in the level of recirculation contributes to an increase in combustion thermal efficiency, improving heat exchange processes within the furnace. A similar trend is observed for the adiabatic combustion temperature. It was found that the adiabatic combustion temperature also increases with an increase in the recirculation coefficient, which indicates the significant influence of recirculation on raising the temperature parameters of the combustion process. The rise in combustion temperature is associated with improved fuel combustion and more complete utilization of its energy potential. This, in turn, can contribute to a reduction in emissions of harmful substances such as nitrogen oxides and carbon, which is an important factor for environmental safety.Thus, the results of the study demonstrate that flue gas recirculation has a significant impact on heat exchange processes and combustion temperature. This makes recirculation an effective tool for increasing thermal efficiency and reducing the environmental impact. The application of this method in modern energy systems not only improves production performance but also ensures compliance with environmental requirements. The study results confirm the feasibility of implementing flue gas recirculation to enhance overall efficiency and environmental safety in energy installations.

A new track for high-efficiency marine diesel engines: Initiative air jet and post-split injection combined

In pursuit of adequate mixing with a high volume of fuel injection, a re-intake scheme is proposed to promote the diffusion of combustibles and flames by using the disturbance of high-pressure air jets after the pressure peak. The results indicate that during the power stroke, an additional air jet enhances combustion by penetrating the spray and disturbing the flame front. The high-pressure air jet's obstruction of the atomization of local sprays achieves a longer combustion duration, while intensifying the vortex and temperature at the cylinder center, which enhances the evaporation of fuel near the nozzle. However, excessively high fuel injection pressure brings in more cold air, causing a temperature drop. It is necessary to have sufficient flame expansion before re-intake to eliminate the impact on pressure. By adjusting the re-intake pressure and timing, the air jet, when it reaches half the cylinder diameter, can exert its maximum advantage. By introducing post-injection and increasing the pressure of the first fuel injection, the air-spray impingement duration is extended, thereby improving thermal efficiency. This work, at 190 MPa injection pressure without changing the duration, and combined with a 5°CA re-intake, achieved a 1.82 % increase in thermal efficiency.

Combustion Process of Coal–Açai Seed Mixtures in a Circulating Fluidized Bed Boiler

This study investigates the effects of the co-combustion of coal and açai seed in circulating fluidized bed (CFB) boilers, highlighting the increase in thermal efficiency and relevance of a less-polluting source of energy. Using the computer software 1.5D CeSFaMB™® v4.3.0, simulations of the co-combustion process of coal and biomass were carried out in a CFB boiler, obtaining results such as the temperature profile, boiler efficiency and emissions. The work acquired data regarding the equipment in real operational conditions, consisting of the fundamental geometric and operational parameters used in the simulation campaign. The thermal and chemical properties of the fuels were analyzed by carrying out proximate, ultimate, heating value, particle size and specific mass analyses. The model validation was achieved by simulating the boiler in its real operating conditions and comparing the obtained results with the real data; the obtained error was below 10%. Simulations with different fractions of açai seed for energy replacement (10% and 30%) were carried out. As a result, an increase in the average temperature of the bed was observed, highlighting the region immediately above the dense bed. An increase in boiler efficiency was verified from 56% to 85% with 10% açai and to 83% with 30% açai seed. Decreases in SO2 and CO emissions with the insertion of açai were obtained, showing that co-combustion is more complete, while CO2 emissions were increased due to the higher quantity of fuel inserted into the equipment. The fossil CO2 emissions were reduced.

An experimental investigation on performance, emission and combustion characteristics of IC engine using liquid fuel produced through catalytic co-pyrolysis of pressed oil cake and mixed plastics with the addition of nanoparticles

The study focuses on using a combination of diesel and a liquid fuel derived from the co-pyrolysis of pressed neem cake (PNC) and mixed waste plastics (MWP) containing waste polyethylene terephthalate (PET) and low density polyethylene (LDPE) in equal amounts with the help of cupric oxide (CuO) catalyst. The engine analysis was carried out using diesel and five different blends of co-pyrolysis oil with diesel in proportions of 20 % (20 % pyrolysis oil + 80 % diesel = PD20), 40 % (PD40), 50 % (PD50) and 100 % pyrolysis oil (PD100), respectively. Initially, the co-pyrolysis oil was produced using PNC and MWP in a ratio of 1:2 under different operating temperatures between 350 °C and 650 °C. The process temperature was optimized to yield maximum liquid oil, and the characterization study was performed. In addition to that, CeO2 nanoadditives were used to improve the properties of PD20 fuel. Different dosages of nanoadditives were blended with PD20 to prepare PD20@25 (PD20 + 25 ppm CeO2), PD20@50, PD20@75, and PD20@100. The objective of the study is to assess the performance, emission, and combustion characteristics of a diesel engine utilizing co-pyrolysis oil-diesel blend by including the nanoadditives. The analysis was carried out on a single-cylinder water-cooled diesel engine mounted with an eddy current dynamometer. The experiments demonstrated that the combination of PD20 and 50 ppm CeO2 resulted in a 6 % increase in thermal efficiency when compared to other blended fuels and diesel. When compared to all fuels, the PD20@50 produced a higher decrease in CO and HC emissions by roughly 30 and 6.2 %, respectively. The combustion analysis showed that the heat release rate (HRR) and maximum cylinder pressure were also found to have improved by adding nanoparticles.

Alcohols as Biofuel for a Diesel Engine with Blend Mode—A Review

In the era of decarbonization driven by environmental concerns and stimulated by legislative measures such as Fit for 55, the industry and transportation sectors are increasingly replacing petroleum-based fuels with those derived from renewable sources. For many years, the share of these fuels in blends used to power compression ignition engines has been growing. The primary advantage of this fuel technology is the reduction of GHG emissions while maintaining comparable engine performance. However, these fuel blends also have drawbacks, including limited ability to form stable mixtures or the requirement for chemical stabilizers. The stability of these mixtures varies depending on the type of alcohol used, which limits the applicability of such fuels. This study focuses on evaluating the impact of eight types of alcohol fuels, including short-chain (methanol, ethanol, propanol) and long-chain alcohols (butanol, pentanol, hexanol, heptanol, and octanol), on the most critical operational parameters of an industrial engine and exhaust emissions. The engines being compared operated at a constant speed and under a constant load, either maximum or close to maximum. The study also evaluated the effect of alcohol content in the mixture on combustion process parameters such as peak cylinder pressure and heat release, which are the basis for parameterizing the engine’s combustion process. Determining ignition delay and combustion duration is fundamental for optimizing the engine’s thermal cycle. As the research results show, both the type of alcohol and its concentration in the mixture influence these parameters. Another parameter important from a usability perspective is engine stability, which was also considered. Engine performance evaluation also includes assessing emissions, particularly the impact of alcohol content on NOx and soot emissions. Based on the analysis, it can be concluded that adding alcohol fuel to diesel in a CI engine increases ignition delay (up to 57%), pmax (by approximately 15–20%), HRRmax (by approximately 80%), and PPRmax (by approximately 70%). Most studies indicate a reduction in combustion duration with increasing alcohol content (by up to 50%). For simple alcohols, an increase in thermal efficiency (by approximately 15%) was observed, whereas for complex alcohols, a decrease (by approximately 10%) was noted. The addition of alcohol to diesel slightly worsens the stability of the CI engine. Most studies pointed to the positive impact of adding alcohol fuel to diesel on NOx emissions from the compression ignition engine, with the most significant reductions reaching approximately 50%. Increasing the alcohol fuel content in the diesel blend significantly reduced soot emissions from the CI engine (by up to approximately 90%).

Performance evaluation of a novel parabolic trough solar collector with nanofluids and porous inserts

In this study, the thermal performance enhancement of parabolic trough solar collector (PTSC) with porous strips and nanofluid is visited computationally. The research investigates the effect of variation of the geometry angle of the porous protrusion and nanoparticles on the thermal performance of PTSC system. The tests are performed by varying geometry angles from 5° to 15°, porosity from 0 to 0.7, solar radiation from 400-1000 W/m2, Reynolds number (Re) of 477–1906, and at a fixed height-to-diameter (h/D) ratio of 0.25. The study is also extended by considering copper oxide (CuO) and aluminum oxide (Al2O3) based nanofluids with a volume fraction of 3–7 %. Results indicate the presence of nanofluids increases the average Nusselt number ratios by up to 51.39 % compared to water. The research also emphasizes that adding porous obstacles results in a 9.86% enhancement in the average Nusselt number compared to a non-porous version. The thermal performance factor is found to be augmented by 5.32 % and 5.75 % with a change in geometry angle from 5° to 15° for Al2O3 and CuO nanofluids, respectively. Further, at a geometry angle of 15°, h/D=0.25, Re = 1428, and solar radiation of 800 W/m2, the highest thermal performance factor of 1.368 is obtained for CuO nanofluids. With the change in geometry angle from 5° to 15° with Al2O3 and CuO nanofluids, the thermal efficiency increases by 7.73 % and 8.59 %, respectively. At an h/D ratio of 0.25 and a geometry angle of 15°, the absorber tube provides maximum thermal efficiency of up to 59.75 % and 62.96 %, respectively, with a 7 % volume fraction of Al2O3 and CuO nanofluids.

Enhancing reactivity-controlled compression ignition engine performance: A response surface methodology approach with ammonium hydroxide-waste cooking oil biodiesel optimization

The focus on ammonium hydroxide, biodiesels and their combustion technology has garnered significant attention in pursuing carbon-neutral and carbon-free fuels to address greenhouse gas emissions (GHG) and mitigate global warming. Low-temperature combustion (LTC) has been introduced as an alternative method to conventional compression ignition (CI) combustion. Reactivity controlled compression ignition (RCCI) can be achieved by introducing highly reactive waste cooking oil methyl ester (WCOME) oil directly into the manifold in intervals of 10% energy and injecting low-reactive ammonium hydroxide at 20%–50%. Utilizing the response surface methodology (RSM) approach, it was determined that for optimal operation in RCCI mode, an ideal ammonium hydroxide energy sharing (AHES) of 43% would account for the varying parameters and their effects on emissions and performance. The results of the experiments predicted a brake thermal efficiency (BTHE) of 34.85% and a brake specific energy consumption (BSEC) of 10.69 MJ/kWh. Meanwhile, a notable decrease in exhaust emissions was observed for HC, CO, CO2, NO x and smoke by 41.54%, 38.89%, 48.89%, 51.27% and 65.80% respectively when compared to conventional biodiesel combustion (CBC). The experimental result at maximum load operation with an AHES of 50% indicates that RCCI combustion led to an increase in thermal efficiency from 30.36% to 35.42%, and the in-cylinder pressure and heat release rate dropped from 83.42 bar to 59.64 bar and 78.68 kJ to 60.92 kJ, respectively. There was a significant reduction in HC, CO, CO2, NO x and smoke emissions recorded as 58.76 ppm, 0.11%v, 1.61%v, 442 ppm and 6.64 N, respectively, compared to CBC.

Effects of hydrogen volume fraction, air fuel ratio, and compression ratio on combustion and emission characteristics of an SI ammonia-hydrogen engine

An effective approach to reducing greenhouse gas emissions is to utilize low/zero carbon fuels. This study simulated the combustion of a marine spark ignition (SI) ammonia-hydrogen engine, focusing on the effects of hydrogen volume fraction (XH2), air fuel ratio (λ), and compression ratio (CR) on the combustion and emission characteristics. The pathways of nitrogen-based pollutants such as NH3, NO, and N2O were explained. The results show that increasing XH2 improves Pmax, heat release rate, thermal efficiency, and power. Regarding emission characteristics, when XH2 rises, NH3 emissions drop; NOx emissions remain almost constant at λ ≤ 1 (2100 ppm at λ = 1) and considerably increase at λ > 1, peaking at 5245 ppm. Moreover, as CR rises, the engine power and thermal efficiency increase, NOx emissions decrease by 10%, and N2O emissions are below 20 ppm. Furthermore, chemical kinetic analysis shows that NO comes from N and N2, diffuses from the flame front toward the center in the cylinder under λ = 1.2. And NO comes from HNO and is generated in the flame front and the center under λ = 0.9, respectively. N2O is produced by NH and NH2 and is only generated in the flame front.

Heat pump assisted sorption carbon capture with steam condenser heat recovery in a decarbonised coal-fired power plant

More than 50% energy input of coal-fired power plant is lost in the condensation of steam turbine in a temperature range of 30–35 ℃. Carbon capture technology has a negative influence on power generation efficiency of coal-fired power plant. Thus, it is essential to find an efficient method for waste heat recovery and increase the overall energy efficiency in coal-fired power plant with carbon capture. A novel integrated system including absorption heat pump and adsorption carbon capture based on coal-fired power plant is then presented. Waste heat from steam condenser is recovered by absorption heat pumps driven by steam extracted from low pressure steam turbine. The output hot medium from the absorption heat pumps is further heated to desorption temperature for the regeneration process of adsorbents by the extracted steam. The results show that heat penalty increases with the increase of the desorption temperature, and the heat recovery amount has an opposite trend. Compared with the conventional coal-fired power plant, thermal efficiency of the integrated system increases by 0.854%. The efficiency decrease of the compression work accounts for over a half of the total efficiency decrease due to the compression and the capture process. External heat recovery is applied in flue gas and the multi-compression process, and the thermal efficiency increase can be improved to 1.453% when compared with 0.725% of the system without external heat recovery. It proves that absorption heat pump could play a significant role in the energy saving of adsorption carbon capture system.

4E experimental investigation of concentrated solar cell cooling via system of heat dissipator-phase change material

Low-concentrator solar cell (SC) experimentally cooled using a new composite thermal regulation system of heat dissipator (HD) and phase change material (PCM) is investigated. The impact of area ratio (AR; HD area/SC area) of 1.5 and 2 at different HD thicknesses (h) on the system performance is reported. An energy, exergy, economic, and enviroeconomic assessments for the different cooling systems used for the SC thermal regulation are presented. The results show that the SC temperature reduction increases with increasing the HD thickness and AR. Compared with reference SC, SC-PCM/HD (AR=2/h = 3) achieves a maximum temperature reduction of 24 °C compared with 9.1 °C and 21.8 °C for SC-PCM and SC-HD, respectively. Moreover, SC-PCM/HD cooling system achieves the maximum enhancement in the average electrical efficiency and power output of 11.88 % and 12 %, respectively, compared with reference SC. The PCM thermal energy storage rate and PV system efficiency increase with increasing area ratio and decreasing the HD thickness. Using HD of (AR=2/h = 1) in conjunction with PCM yields the most favorable PCM thermal performance where it enhances the thermal energy storage, rate of energy storage, and overall thermal system efficiency by 9.5 %, 40 %, and 20.36 %, respectively, compared with using PCM only. Moreover, the PCM/HD cooling system is more economical than using PCM or HD only, and reference SC, with a maximum cost saving of 41.7 % compared with reference SC. The SC-PCM/HD cooling system is the most eco-friendly option with net CO2 mitigation and ψCO2 of 146.2 kg and 5.84$, respectively compared with 143.7 kg and 5.74$, respectively for SC-PCM.

Experimental and numerical investigations on jet impingement heat transfer with different nozzles and enhanced surfaces

Hot air anti-icing systems are essential in aviation engines, preventing ice formation on inlet components during high-altitude flights. A critical factor in enhancing these systems' effectiveness is the application of jet impingement technology. In order to further enhance the performance of jet impingement heat transfer in this application scenario, the research assesses the impact of nozzle type and surface protrusion type on the anti-icing system's performance by integrating experimental and numerical approaches. Findings reveal that circular nozzles outperform swirl and satellite nozzles in heat transfer efficiency in the application of aviation anti-icing system with high jet Reynolds number. The average Nusselt number, indicative of heat transfer rate, can be increased by up to 10.54 % with protrusions. For surface protrusions, sequentially-arranged cylinder protrusions are more effective at Reynolds numbers between 8000 and 48000. Cross-arranged circular truncated cone protrusions do better at higher Reynolds numbers, from 48000 to 80000 which is the range relevant to the hot air anti-icing system. Comparing concave and flat plates with the same type of protrusions, the former shows superior heat transfer performance. The study also establishes correlations for convective heat transfer coefficients and attenuation coefficients on the concave plate with sequentially-arranged cylinder protrusions. By applying the cross-arranged circular truncated cone protrusions, which proved to be the best in our experiments, to the engine nacelle's anti-icing section, the numerical results indicate a 6.21 % increase in anti-icing thermal efficiency and an 8.31 % decrease in air bleed capacity, all under the same heat transfer conditions. The use of protrusion structures in the anti-icing system of an engine nacelle boosts thermal efficiency, lowers air bleed capacity, and reduces the fuel penalty, thereby optimizing overall performance.

Irreversible mechanism and thermal cross-radiative flow in nanofluids driven along a stretching/shrinking sheet with the existence of possible turning/critical points

The significant increase in thermal efficiency and the rate of energy exchange used in fuel dynamics and automobile coolants are leading to a better understanding of nanofluids. This computational analysis explores the thermal conductivity performance for radiative cross-flow of a nanofluid across an expanding/constricting sheet with a suction effect as a result of its application. To compute or calculate the magnificent point of nanofluid flow, the entropy, and asymmetrical heat source/sink effects are also elicited. The boundary layers traverse a stream-wise procedure for expanding and contracting sheets. Additionally, the study examines the features of heat transfer and cross-flow of nanofluids using numerical simulations. By employing similarity variables, the basic PDE equations of the current model are transformed into ODEs, and they are subsequently evaluated using the bvp4c method. Therefore, the effects of embedded flow variables on drag force, heat transfer rate, and entropy generation profiles have been framed using parametric research. Multiple solutions are offered for a specific range of the contracting parameter as well as the mass suction parameter. In addition, the heat transfer rate accelerates due to the heat source and decelerates due to the heat sink. The literature that is already published has been compared favorably, and it reveals many commonalities.

Performance test of a heliostat field integrated PVT solar collector using organic phase change material and carbon black additives

The rising global awareness of environmental issues has brought about a rise in the adoption of green energy throughout our daily activities in recent decades. The radiation from the sun is utilized for thermal heating, electrical generation, and agriculture by Phase change materials (PCM) integrated PVT collector. However, the lower concentration ratio of solar radiation on flat plate collectors and the lower thermal conductivity of PCMs are the major drawbacks. In this present study, a Heliostat field concentrator was designed to integrate with a hybrid photovoltaic thermal (PVT) collector for the increase of the solar irradiance, and carbon black additives incorporated stearic acid (SA) were used in the underneath PVT collector to enhance the thermal conductivity of SA as well as the thermal efficiency of the system. The performance tests were carried out for both SA with carbon black and SA without carbon black additives for varying water flow rates of 0.0025 kg/s, 0.0035 kg/s, 0.0045 kg/s, and 0.0055 kg/s. The efficiency of the PV panels ranged from 10 % to 13 %. The maximum thermal efficiency was found to be 46.56 % when using SA with carbon black for the water flow rate of 0.0035 kg/s whereas the maximum thermal efficiency was 45.45 % in the case of SA without carbon black for that water flow rate. Especially contrasted with the other flow rates throughout the investigation, the average thermal efficiency increases by 6.83 % for the flow rate of 0.0035 kg/s after integrating carbon black with PCM. The experimented results showed the outlet temperature of water in the range of 50 °C-59 °C throughout the day which is sufficient for domestic hot water applications.

Thermal performance improvement for parabolic trough solar collectors integrated with twisted fin and nanofluid: Modeling and validation

The low thermal efficiency of parabolic trough solar collectors (PTSCs) is a major drawback that has hindered their development as a viable renewable energy resource. Among the available methods to enhance the thermal performance of PTSCs, installing internal fins within the collector tube is one of the most reliable, economical, and straightforward passive techniques. However, while internal fins can significantly improve thermal performance in turbulent flows, they also lead to a substantial increase in pumping work. Here, we demonstrate that with an optimal design of helical fins, the thermal efficiency of PTSCs can be improved without causing significant pressure losses through the receiver tube. The results proved that higher thermal efficiency and lower pressure losses were achieved when annular fins are replaced by an axial helical insert. Installation of a helical fin with 4 turns and a height of 4 mm led to a 4.5 % increase in thermal efficiency (η) while raising the friction factor (f) by 30 %. Optimal performance was observed with helical fins having 10 turns. For instance, at Re = 105, switching from 16 to 4 turns of 8 mm helical fins resulted in η and Nu enhancements, and f reduction of 1.6 %, 33 % and 64 %, respectively. While these changes were 2.0 %, 55 % and 54 % when n reduced from 16 to 10.

Enhancement and evaluation of solar still performance using internal reflectors and woven wire mesh: An experimental approach

In recent years, the urgency for harnessing solar energy for water desalination has grown significantly, driven by the escalating costs and the increasing scarcity of clean water sources. Numerous research efforts were dedicated to enhance the productivity of solar still, including the thermal energy storage materials, solar concentrators, nanofluid, and more. The main objective of this research is to improve the solar still performance by using wastes of workshops and factories so, their actual cost can be assumed to be zero. The experimental setup placed at faculty of Engineering Suez Canal University. Two solar still were included: one representing the conventional and the second one is modified with internal reflectors and woven wire mesh. The performance of the stills was assessed under identical climate conditions, considering water depths of 1, 2, 3 and 4 cm using both fresh and saline water with Total dissolved Solids of 18,562 and 35643 ppm. The obtained results indicated that the incorporation of internal reflectors and woven wire mesh led to a notable percentage increase in daily thermal efficiency and accumulative productivity ranged from 42.49 % to 45.04 % and from 43.0 % to 46.8 % respectively. The economic analysis demonstrated that the cost per liter for conventional and modified solar still was about 0.0018 and 0.0011$ per liter per m2 respectively. This study’s findings suggested that the integration of internal reflectors and woven wire mesh into solar stills to obtain high productivity potable water with low cost. These results align with and reinforce previous publications in this field, highlighting the potential of this approach for addressing the pressing challenges of affordable and efficient water desalination.

Evaluating potential of increasing flow intensity and reducing crevice volume to improve thermal efficiency and hydrocarbon emission in spark-ignition natural gas engines

Low thermal efficiency and high hydrocarbon emissions caused by slow combustion rates and high methane emissions hinder the development of natural gas (NG) engines. Engine structure modifications have always been an important means of improving the combustion effects of engines. This study investigates the effects of combustion chamber improvements on the thermal efficiency and hydrocarbon emissions of stoichiometric spark-ignition NG engines through numerical simulations. The improvements aimed to enhance squish flow, organize high tumble flow, and reduce crevice volume. The results indicate that strengthening the squish intensity by increasing the squish area of the piston can accelerate flame propagation and reduce exhaust loss. However, this improvement is hindered by a significant rise in heat transfer loss, which limits further gains in thermal efficiency. Compared to the traditional high swirl combustion chamber, a high tumble combustion chamber (dual straight intake port combined with a hemispherical piston) can promote flame propagation in the early stages of combustion and increase thermal efficiency by 1.43%. However, the accelerated flame propagation rate resulting from increased flow intensity has little potential to reduce hydrocarbon emissions due to the small contribution of flame quenching to unburned hydrocarbon production. The primary source of hydrocarbon emissions from NG engines is unburned methane in the piston crevice. Therefore, when addressing hydrocarbon emissions from NG engines, the first consideration should be to minimize the volume of the piston crevice, which will significantly reduce methane emissions and incomplete combustion loss.