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This study examines the generation of irreversibility and the behavior of stagnation point hybrid nanofluid flow on a Riga plate. The effects of nonlinear thermally convective and solar radiation are incorporated in the modeled equations. The nanoparticles of (Cu) and (Al2O3) are mixed with Glycol (C3H8O2) to hybridized it. The leading equations have been changed to dimension-free form by using the set of appropriate variables and then have been evaluated by Artificial Neural Network (ANN) approach. It is revealed in this work that, the velocity panels are amplified with expansion in Grashof number and electromagnetic factor while declined with escalation in magnet/electrode factor and nanoparticles concentration. Upsurge, in Eckert number for both the scenarios (Ec < 0) and (Ec > 0), the radiation factor and nanoparticles concentration cause augmentation in thermal characteristics. Radiation factor has positive impacts on Bejan number and generation of Entropy. Moreover, Bejan number is retarded while entropy is augmented with growth in Brinkman number. It is also established in this work that the principle of entropy generation for hybrid nanoparticles supports the efficient delivery of drug in cancer treatment.

This study introduces innovative turbulators with unique geometries, namely the Conical Simple Wire Turbulator (CSWT) and Conical Braided Wire Turbulator (CBWT), designed to enhance heat transfer in a constant temperature tube. These turbulators resemble a conical shape in appearance but are constructed by interconnecting multiple wires, enabling fluid flow to pass through. The distinct geometry of these turbulators not only disrupts the thermal boundary layer for improved heat transfer and Thermal Enhancement Factor (TEF), and results in a favorable pressure drop. The study explored various geometrical parameters of the turbulator, including wire diameters (a) ranging from 0.5 to 1.5 mm and turbulator gaps (TG) ranging from −10 to 30 mm. Using the RNG k–ε model, the finite-volume scheme is utilized to discretize the turbulence flow equations. A numerical investigation was conducted across Reynolds numbers ranging from 5500 to 12375. The results show that increasing the wire diameter and reducing the turbulator gaps simultaneously enhanced heat transfer, pressure drop, and TEF. The highest heat transfer and TEF were achieved with the CBWT featuring a 1.5 mm wire diameter and a −10 mm TG. In this configuration, Nusselt was 2.84 times greater than a plain tube, with a maximum TEF recorded at 1.4.

This experimental study proposes a new approach to enhance heat transfer performance inside heat exchangers of engine by tandem utilization of bubble injection and a punched zigzag strip turbulator. The side edges of the zigzag turbulator underwent two distinct geometry modifications, involving V and U shape cuts. These cuts were made at varying zigzag angles, ranging from 60° to 150° and four diffirent surface area. The potential improvement in thermal efficiency of the heat exchanger was evaluated at different inlet Reynolds number ranging from 5390 to 10860. Based on survey results, it has been demonstrated that at a Reynolds number of 5390, the Nusselt number and friction factor increase by 48 % and 154 % for U-Cut with a bending angle of 150°, and by 61 % and 170 % for V-Cut, respectively. Hence, V-cut boasts a TEF of 1.15, representing a 6.5 % improvement over U-cut. Additionally, to assess further enhancement, air bubbles with flow rate ranging 2–6 LPM were introduced to the central tube while maintaining the superior geometry. The data suggests that incorporating air bubbles can enhance heat transfer up to 142 %, achieving a TEF of 1.17 at an air flow rate of 6 LPM.

Magnetohydrodynamic free convection liquid considering Hall along with ion-slip current has many engineering usages. In addition, boundary layer flow of power-law fluids due to a stretching plane possesses sundry applications in biological sciences, geophysics, and petroleum industries. Further, hybrid nanofluids are important due to their high heat transfer capability. In view of such relevance, the goal of this investigation is to analyze Hall along with ion-slip effects on thermo-fluidic flow of magnetic power-law hybrid nanofluid so as to accomplish effective cooling in the desired thermal systems. Present investigation’s novelty is adding hybrid nanostructure to power-law fluid flow influenced by Hall and ion-slip mechanism and implementation of modified Fourier’s law featured with velocity and temperature gradients. The key results are that fluid velocity amplifies with rise in ion-slip and Hall parameters. Modified Prandtl numbers and Hall parameter ameliorate heat transfer rate while ion-slip parameter diminishes it.

This research delves into the cutting-edge realm of solar-powered dual-temperature refrigeration, adhering to the 3E model emphasizing Energy, Economic, and Environmental considerations with a key focus on financial optimization. The study investigates the implementation of advanced refrigeration technologies, notably the integration of supercritical CO2 and ammonia cycles, tailored for dual-temperature applications. A distinctive aspect of this research is the strategic use of excess thermal energy, enhancing the efficiency of the refrigeration systems under varied climatic conditions. Central to the study is a thorough economic analysis aimed at reducing the Levelized Cost of Cooling (LCOC), while simultaneously enhancing the overall efficiency of the system. With the aid of the Engineering Equation Solver (EES) software, the system is modeled and the preliminary results indicate a promising decrease in cooling expenses (reaching to 90.25 $/GJ) alongside an increase in system efficiency (an improved efficiency of 33.17 %), with the total Coefficient of Performance (COP) demonstrating a significant advancement over traditional refrigeration models. This research underscores the effectiveness of harnessing solar energy in refrigeration technologies, contributing to financially viable and environmentally responsible cooling solutions. It provides valuable insights for the future development of refrigeration systems, which are both economically and environmentally sustainable.

Entropy generation and convection heat transfer in a partially porous chamber with different side wall temperatures using CuO–H2O have been investigated. The importance of this issue is wide application of the results in solar collectors, thermal extrusion systems, heat exchangers, bio-medicine, nuclear waste disposal, etc. The innovation of the present work is related to the investigation of fluid and heat fields and entropy generation by using a matrix with subordination of porosity to the vertical axis and permeability, thermal conductivity, and viscosity with subordination of porosity. To obtain accurate results, the two-phase mixture model was used, and thermal conductivity and viscosity of nanofluid were simulated by experimental models by temperature and volume fraction dependence. Governing equations are solved by the FVM. The main findings indicate that the best and worst optimization factor will occur in the porous matrix ε = ε(y2) and ε = -ε(y2), respectively, which is 113 % and 86 % of NH of the homogeneous matrix, respectively. Also increasing the filling of the cavity, highly improves NH, so that the NH will reach from 1.19 to 1.82 with the increase of S from 0.25 to 1.

In the modern era, Artificial Intelligence (AI) has emerged as a powerful tool that can rapidly generate highly accurate data, offering tremendous potential for optimizing system performance. This study focuses on harnessing the capabilities of an artificial neural network (ANN) to determine optimal parameter values for heat transfer in a mixed convection mechanism. The first step of this research involved conducting CFD simulations to investigate the impact of varying Grashof numbers (102,103,and104), Reynolds numbers (1,10,and100), and MWCNT volume fractions (0, 0.01, 0.02, and 0.03) on the Nusselt number within an elliptical enclosure containing a centrally located rotational cylinder. A total of 48 simulations were performed, generating a comprehensive dataset for training the ANN-Multilayer Perceptron (MLP). In the second step, the trained ANN was utilized to generate an additional 700 data points with remarkable accuracy. This enabled efficient exploration of the parameter space, providing valuable insights into the system behavior and facilitating optimization efforts. The findings of this study revealed a 0.03 vol fraction of MWCNT into the water in Grashof numbers of 102,103,and104, the average Nusselt number increased by approximately 46%, 31%, and 12%, respectively. The ANN-based approach successfully identified optimal values for the variables that maximize the Nusselt number.

This study represents a pioneering investigation into the impact of a punched twisted tape turbulator on the hydrothermal parameters of a pipe operating under constant surface temperature conditions. The punched turbulator was specifically designed by incorporating cuts with diverse geometries, including semicircular, square, and triangular shapes, into the basic twisted tape turbulator. To evaluate the performance of the punched twisted tape, a comparative analysis was conducted with both a smooth tube and a tube equipped with a basic turbulator. The criterion for selecting the optimal cut geometry was the thermal enhancement factor. Subsequently, the influence of the cut area on the hydrothermal parameters was thoroughly elucidated. The enhancement factor was again utilized to identify the most optimal area. Based on the comprehensive evaluations, it was observed that the turbulator with a semicircular cut geometry and a diameter of 5 mm exhibited superior thermal performance compared to all other geometries. By employing this specific turbulator design, a remarkable enhancement in heat transfer and pressure drop within the heat exchanger was achieved, offering improvements of up to 1.63 and 3.65 times, respectively, when contrasted with the plain tube. The maximum enhancement factor value recorded during the investigation reached 1.09.

For the purpose of enhancing the thermal efficiency of double-tube heat exchangers, a new technique has been implemented. By integrating a vibrating turbulator and bubble injection technique, this innovative method produces an added turbulence effect. This research aims to experimentally assess the thermal efficiency of employing two active methods concurrently. Different parameters were analyzed, including water flow rates ranging from 0.5 to 4 kg/min and bubble injection flow rates varying from 2 to 6 l/min, to investigate the effects on heat transfer and pressure drop with and without the magnetic turbulator. The results suggest that by incorporating bubble injection, adopting the magnetic turbulator, and simultaneously utilizing both methods, there is a significant improvement in heat transfer. In optimal scenarios, the heat transfer coefficient is amplified by 150.3% through the injection of bubbles, 328.8% through the implementation of magnetic turbulator, and 586.2% when both techniques are employed in tandem. In comparison to the smooth tube, the friction factor ratios were 6.7, 1.6, and 7.8 times higher in the specified cases. The findings indicated that the concurrent utilization of both techniques can yield an added impact on heat transfer. Ultimately, the integrated approach demonstrated a noteworthy thermal enhancement factor value of 3.49.

The fluctuating nature of wind energy and shortage of biomass resources, as two types of renewables, can be fulfilled via their hybridization. In this respect, present research proposes a hybrid biomass/wind energy driven power generation framework based on combined gas turbine-Rankine cycle scheme. The gas turbine includes a reheat stage where the produced hydrogen is added to the combustion chamber for increasing flue gas temperature to enhance output power. The injected hydrogen is generated via a water electrolyzer which is powered by electricity from the wind turbines. The proposed scheme of biomass/wind powered system leads to a reduction in biomass consumption and will fulfill the fluctuations and non-continuous availability of wind energy. To appraise the feasibility of developed hybrid scheme, thermodynamic first and second law-based analyses were performed. Also, the exergo-environmental evaluation of the hybrid plant is conduced using three exergo-environmental indices. Finally, optimum operation conditions of the proposed hybrid plant is determined based on the minimization of environmental damage index. The results under optimum operation indicate that, the proposed hybrid power generation plant yields exergy efficiency of 47.35 % with environmental damage index of 0.0104.

This study proposes a novel twisted tape turbulator with a unique DNA-like shape, referred to as the special shape twisted tape turbulator (SSTT), to augment the heat transfer efficiency within heat exchanger conduits. This turbulator is composed of segmented components and facilitates the passage of fluid flow through the gaps while inducing swirling motion along the conduit. The pitch ratio of the segments has been examined within the range of 1–4 mm to evaluate its impact on the heat transfer properties. The findings indicate that the novel geometry offers notable benefits compared to a basic twisted tape design. Optimal heat transfer occurs at a pitch ratio of 2 mm, resulting in a 125% improvement over a plain tube. To further improve thermal efficiency, a helical coiled wire turbulator is incorporated alongside the tube, in combination with the chosen SSTT. The findings indicated a 142% rise in the heat transfer coefficient, accompanied by a 960% increase in pressure drop in the presence of these turbulators. Consequently, the thermal performance reached 1.31, representing a 20% improvement compared to a basic twisted tape turbulator.

In this experimental study, a novel approach combining a helical coiled wire (HCW) turbulator and bubble injection (BI) method has been employed to synergistically improve the heat transfer efficiency of double tube heat exchanger. The thermal-frictional characteristics were evaluated by investigating different parameters, including the bubble injection flow rate ranging from 2 to 5 l/min and HCW pitch ranging from 2.5 to 10 mm. For all cases, the thermal enhancement factor (TEF) is employed to determine the optimal configurations. The experimental findings indicate that the introduction of bubble injection, the implementation of the HCW turbulator, and the simultaneous utilization of both methods result in an enhancement of heat transfer by 66 %, 78 %, and 156 % respectively. However, it should be noted that the usage of these methods also leads to an increase in pressure drop. Also, the findings indicate that the integration of two methods yields favorable outcomes in terms of thermal performance when compared to their individual functions. In the optimal scenario, the TEF has the potential to reach a maximum value of 1.28. Furthermore, in order to obtain a more precise comprehension of the relationship between TEF and the parameters under investigation, an empirical equation have been derived and presented.

The reliable supply of electricity and potable water has crucial importance on achieving higher level of human welfare, where the primary energy source to provide these requirements is fossil fuels at present. Since the combustion of fossil fuels has irreparable environmental impacts, thus utilization of clean and renewable energy resources is a promising alternative to overcome the energy-related environmental issues. In this regard, present research aims at development of an effective co-generation of electricity and freshwater plant driven by hybrid geothermal and biomass renewable energy sources. To make a comprehensive system assessment, thermodynamic, exergy, environmental and economic aspects are considered and appraised in detail and multi-objective optimization is used to detect the best performance of the plant. The results indicated feasibility of hybridization of biomass and geothermal resources for efficient co-production of potable water and electricity. Under optimized operation, the plant exergetic efficiency, unit product cost, exergo-environmental index, and CO2 emission are found to be 44.12 %, 66.97 $/MWh, 0.5114 and 0.7105 kg/kWh, respectively. The second law analysis revealed that, from 18302 kW of input exergy, a value of 9357 kW is destructed within the components, where the gasifier owns the largest portion with 3569 kW.

This study probes the effect of connection angle of “L” shaped fin on the melting and discharge process of a vertical PCM unit. The PCM enclosure had dimensions of 50 ×50 mm and the L shaped fin was located at middle of enclosure. The enclosure was heated and cooled by considering constant temperature at the vertical wall. The Lauric acid was considered as the phase change material. Seven different coincidence angles of 0°, 30 °, 60 °, 90 °, −30 °, −60 ° and −90 ° were considered in present investigation. Results indicated that L shaped fin with Teta = −30 ° could provide 14% reduction in the melting process. Furthermore, the case with Teta = 0° provided 45% enhancement in solidification time. The outcomes revealed that maximum charging rate was associated with case with Teta = −30 ° which had the value of 103.41 J/S and provided a 32% enhancement in comparison with the base case. Also, the best discharge rate for the solidification process was about 34.184 J/s which was related to case with Teta = 0° and presented a 2.23 times improvement in the average solidification rate.

Cooling is one of the most important issues for thermal engineers, and the use of simple and inexpensive methods greatly contributes to the efficiency of a thermal system. Also, in recent decades, the development of numerical methods and the advent of computers has led to the emergence of computer simulations. In present numerical study, the natural convection mechanism of nanofluid based on water and titanium oxide (TiO2) were simulated by computational fluid dynamics (CFD) to cool a hot inclined plate inside a square chamber. The considerable innovation in this study is the nanofluids properties depending on temperature, nanoparticle diameter and volume fraction and the cavity is able to incline. The impacts of two Rayleigh numbers (102≤Ra≤104), four volume fractions (0≤φ≤0.06) and four inclined angles (0≤γ≤45) were analyzed on the average convective heat transfer coefficient. This study briefly demonstrated that the optimum values of volume fraction for Rayleigh numbers 102and104 were 0.06 and 0.02, respectively. Moreover, increasing the volume fraction to 6% in low Reynolds number improved the average convective heat transfer coefficient by 21%.

This study has designed and employed computational fluid dynamics to cool lithium-ion batteries (LIBs) to keep the temperature constant between 35and45°C. A duct was designed for installing three hot LIBs to be cooled by water and nano-encapsulated phase change material (NEPCM) flow. for this simulation, n-nonadecane with the fusion temperature of 30.44°C was used for NEPCM's core and also water entered the channel with temperature of 30°C. The impacts of the various surface temperature of LIB, Reynolds numbers, and the concentration of NEPCM were analyzed on flow pattern, dimensionless isotherms, melted NEPCM, and heat transfer rate of each LIB. Increasing Reynolds number from 70 to 100 raised the heat transfer rate of LIBs in order of 12.1–17.2%. Furthermore, increasing the volume fraction from 0 to 0.03 escalated the heat transfer rate by 8.2–13.6%.

MHD natural convection of Fe3O4-water suspension in the presence of magnetic field of solenoid inside a porous enclosure was numerically simulated. Computational fluid dynamic based on finite volume method were exerted to break and solve the PDEs equations. A solenoid was embedded around the cavity for generating a non-uniform magnetic field. The vertical walls of enclosure were maintained at uniform temperatures of Th and Tc and horizontal walls were insulated. Many cases have been simulated to understand the impacts of porous Rayleigh numbers of 10–1000, volume fractions of 0–4%, porosities of 0.5–0.9, and Hartmann numbers 0 to 120. Findings indicate that the presence of magnetic field had a positive effect on heat transfer in low porous Rayleigh number and high Hartmann number, for all porosities. In highest porosity and 4% volume fraction, Nusselt number increased 140%; whereas at high Rap, the presence of a weak magnetic field decreased the heat transfer rate.

The aim of this research is to investigate the impact of major risks such as geopolitical and pandemic risks on tourism industry in selected countries of Asia-Pacific. The results were obtained using a sample of 10 neighboring countries in the period of 1996 to 2018. Diagnostic tests confirmed the existence of spatial interaction between model variables for these countries. According to the results, the economic growth, internally and in neighboring countries, leads to an increase in the influx of tourists. Whereas increased domestic prices will reduce the influx of domestic tourists, rising prices in neighboring countries intensify tourists’ arrival of the country. Furthermore, results reveal that domestic geopolitical and pandemic risks lead to a decrease in tourist arrivals. In addition, whereas pandemic risks in neighboring countries do not have a significant effect on tourist arrivals, geopolitical risks in neighboring countries lead to more domestic tourists’ arrival.

Precise knowledge of the soil organic carbon (SOC) stocks under various land uses is needed to meet the Kyoto Protocol and for the sustainability of natural resources. The purpose of the present study was to (1) gauge the depth and spatial distribution of the soil bulk density (BD), soil organic carbon (OC) stocks, and soil organic matter (OM) among the various land uses in the northern Nile Delta in Egypt; (2) estimate the soil carbon sequestration rate (CSR) under different land uses in the region; and (3) establish baseline data for SOC stocks in future studies on the dynamics of SOC. The study area was divided into ten sampling zones to represent each land use in the northern Nile Delta. Each sampling zone was further divided into four sampling sites to represent virgin lands and fish farms, and twelve sites were used to represent three crop types and four cultivation histories. The crops included clover, (Trifolium alexandrinum L.), sugar beet (Beta vulgaris L.), and rice, (Oryza sativa L.) and the years spanned were 5, 15, 30 and 50. The effects of the crop type on the SBD, SOC content, and SOC stocks were significant. In general, the SOC stocks increase as the number of years of cultivation increased. Thematic maps were produced using Geographical Information Systems (GIS) mapping. The Inverse Distance Weighted (IDW) technique in ArcGIS10.4 software revealed that the spatial pattern of the SBD, OC content, and stocks conformed to the soil analysis results. The SOC stocks of the croplands and fish farms were 1.6 and 1.5 times higher, respectively, compared to those of virgin land. Rice cropland had the lowest SBD (1.34 g cm−3) and the highest OC stocks (7.46 g C kg−1). The conversion of virgin land into croplands or fish farms actively contributed to the carbon storage rate (CSR).

Summary: The aim of this study was to conduct the first comprehensive evaluation of carbon stock in the sediments of Avicennia marina (black mangrove) and Rhizophora mucronata (red mangrove) along the coastline of an arid region (Farasan Islands, Saudi Arabia). Such information is necessary for the development of any management plan for the mangrove ecosystems along the Saudi Red Sea islands and provide a rationale for the restoration of mangrove forests in Saudi Arabia. A. marina and R. mucronata locations showed significant (P < 0.001) differences in sediment bulk density (SBD) and sediment organic carbon (SOC) concentration with higher mean values for both in the sediments of A. marina. Considering the whole depth of sediment sampled (0–50 cm), the highest value of SOC stock (12.3 kg C m−2) was recorded at A. marina locations and the lowest (10.8 kg C m−2) at R. mucronata locations. Thus, the SOC stock of A. marina was greater than that of R. mucronata by 114.3%. Consequently, considering the rate of carbon sequestration and the area of mangrove forests (216.4 ha), the total carbon sequestration potential of mangroves in the Farasan Islands ranged between 10.3 Mg C yr−1 and 11.8 Mg C yr−1 for R. mucronata and A. marina locations, respectively. Thus, it is necessary to protect and restore these ecosystems for the sequestration of carbon and for their other valuable ecosystem services. Keywords: Blue carbon, Carbon sequestration, Carbon stocks, Climate change, Coastal ecosystems

In the current research, the natural convection of water-Al2O3 nanofluid has been simulated inside a cold semi-annulus chamber with a hot block at the its bottom. Also, an oblique magnetic field (MHD) has been implemented to improve and control the flow. The unstructured triangular mesh and FVM with SIMPLE algorithm have been employed for discretization and coupling of pressure and velocity equations. In this simulation, the parameters of Hartmann, Rayleigh numbers and volume fraction of nanoparticles have been investigated on temperature contours, flow pattern, and hot wall Nusselt number. The observations show that, increasing the volume fraction increases the Nusselt number at low Rayleigh numbers. Moreover, the Nusselt number is inversely related to the Hartmann number for high Rayleigh numbers.