Nowadays, many researches are persistently exploring to comprehend the various characteristic of the supercritical fluid natural circulation loop (SCFNCL) such as use of SCFNCL at normal operating condition as well as a passive system for heat removal from the core, steady state and transient behavior of the loop, heat transfer rate, heat transfer coefficient and optimizing mass flow rate of the loop. In last two decade, a significant research has been seen in the form of analytical, computational and experimental works which highlight the notable use of SCFNCL as an active and passive system in nuclear power plant (NPPs). However, very limited state of arts have been reported based on the loop geometry and their effects, different types of supercritical fluids (SCFs) and applications of the loops. Therefore, steady and transient behaviours of loop in single and parallel channels, thermal-hydraulic (TH) instability, effects of the geometrical and operating parameters on SCFNCL and deterioration of heat transfer (DHT) in SCFNCL are the main emphasis of this review. Performance criteria such as instability, transient, and steady-state requirements, along with methods for containing instability, have been covered. It even emphasizes how crucial it is to validate the numerical codes. Since nuclear reactors use coupled SCFNCL as passive cooling systems, different topologies and combinations of fluids are shown. Very limited experimental studies have been reported in the coupled loop, an initial analysis was conducted and the results demonstrated the effectiveness of the system. The review also demonstrated the need for numerical analysis with using different supercritical fluids and combine with the NPP systems as well as experimental investigations, which can be connected to applications in renewable and sustainable energy.

This article aims to evaluate the effect of ceria oxide as rare earth oxides (REOs) on the tribological properties of aluminum hybrid composites with varied concentrations of reinforcing elements such as silicon carbide, aluminum oxide, and ceria oxide. In order to accomplish this, composites were produced by varying the percentage of SiC/Al 2 O 3 in the Al-6061 matrix from 2.5 to 7.5 wt% and the quantity of CeO 2 from 0.5 to 2.5 wt%. The formation of the intermetallic phase (Al 4 Ce 3 ) as a result of the integration of cerium oxide into aluminum composites at concentrations between 0.5 and 2.5 wt% results in a wear rate improvement of up to 87.28%. The objective of developing Levenberg-Marquardt algorithm (LMA) neural networks is to forecast how the tribological behavior of hybrid composites would be altered by the addition of REOs based on data acquired from wear testing. The correlation value (R) and mean square error are found to be 0.987 and 4.3424e −10 , respectively, which is an indication of good fit for the model with high significance. The findings indicate that the LMA neural network models accurately forecast the tribological properties of REOs–aluminum hybrid composites.

The aim of this research is to examine the corrosion characteristics of Al 6061/Al2O3/SiC composites when cerium oxide (CeO2) is incorporated, employing electrochemical analysis and scanning electron microscopy (SEM) techniques.This study investigated the impact of cerium oxide on the corrosion behavior and assessed the hydrophobic properties of the composite surface in corrosive environments using contact angle measurements.The experimental methodology comprised several key components, like the selection of specific materials, the production of hybrid composites by the stir casting technique, the analysis of corrosion using the potentiodynamic polarization method, and the characterization of surface wettability.The metallographic analysis of the composites provided insights into the impact of various reinforcements on the microstructural properties.The incorporation of cerium oxide served to mitigate agglomeration and augment grain refinement within the composites.The utilization of potentiodynamic polarization analysis revealed enhanced corrosion resistance in hybrid composites containing cerium oxide in comparison to the Al 6061 alloy.The corrosion current density exhibited a decrease as the content of CeO2 increased.The findings indicate that cerium oxide can effectively prevent corrosion in aluminum hybrid composites.These composites show potential for use in corrosion-prone applications.

A new kind Al-6061/SiC/Al 2 O 3 hybrid composite was prepared with traces amount of cerium oxide and its corrosion performance was evaluated by potentio-dynamic polarization electrochemical method. A new kind of intermetallic (γ-phase) has been observed in the microstructure with higher content of cerium oxide and Al elements. The corrosion resistance of Al-6061 alloy improved with addition of cerium oxide and this improvement could attribute to depression of the micro-galvanic couples. The corrosion rates were observed as 0.16 and 0.034 mpy corresponding to 3.5 and 2.5 wt% of NaCl corresponding to 2.5 wt% of cerium oxide. Moreover, the formation of cerium oxide and Al enrichment film over the surface of hybrid composites was also found to be main key factor for the inhibition of corrosion resistance. Another key factor that inhibits the further corrosion was observed as hydrophobicity between the aluminium liquid matrix and Al 2 O 3 /SiC reinforcement after incorporation of cerium oxide. Improvement in hydrophobicity of composites with Al 2 O 3 /SiC is due to increase in contact angle up to 100.78° after addition of 2.5 wt% cerium oxide. Micro-hardness and impact strength of the hybrid composites improved significantly after addition of traces amount of REOs from 0.5 to 2.5 wt%.

PurposeThis research aims to examine the impact of friction stir processing (FSP) treatment on an aluminum alloy, especially the AD31T alloy derived from the Al-Fe-Mg-Si system. The aim is to assess the influence of different processing techniques on the microstructure and physical and mechanical characteristics of the material, with a specific focus on structural and bulk imperfections inside the stir zone (SZ).Design/methodology/approachThe study demonstrates that augmenting the linear velocity of the tool within the 25-100 mm/min range results in significant enhancements. The enhancements include a decrease in the heat-affected zone (HAZ), a reduction in the extent of volume defects inside the SZ and a more uniform deformation. The microstructural analysis results are corroborated by data acquired from microhardness and electrical conductivity studies, confirming the beneficial influence of modifying the tool's linear velocity on the material parameters.FindingsThis study provides significant observations on the changes in microstructure and the generation of flaws throughout the process of FSP of AD31T alloy. These results have practical implications for improving the characteristics of the alloy and optimizing the production conditions.Originality/valueAll samples exhibit a distinct reduction in electrical conductivity within the initial third of the sample, aligning with the transitional region between the base metal (BM) and the HAZ. This underscores the importance of understanding the transitional zones during FSP.

Helical coils are commonly employed in a variety of process industries due to their superior fluid mixing capabilities, the flexibility of fabrication, and simple design. Frictional pressure losses occur in flow-through helically coiled tubes, affecting the heat transfer rate across the coils. An inquiry is carried out in the current experimental study to discover friction factors and heat transfer rates within the coil tubes of test fluids flowing in the laminar flow area. Non-Newtonian test fluids comprised ichorous solutions of Carboxy Methyl Cellulose (CMC) at concentrations of 0.5 percent, 1 percent, and 2 percent, whereas Newtonian test fluids consisted of water. With the use of an appropriate viscosity expression, Newtonian consonances are demonstrated to apply to several non-Newtonian fluids with certain constraints. In a laminar flow, the shear stress in a helical coil is greater than in a straight conduit. It has been proved that the experimental data can be fruitfully correlated across a broad extent of fluid data and coil radius stretch. The investigated data obtained has been correlated with Standard a deviation of 15.6% with the range 25<D_e < 2000 and 40<P_r < 226.

In this article the performance study of mustard oil bio-diesel blended with commercially available diesel has been conducted on the single cylinder engine.The bio-diesel was extracted from the mustard oil by transesterification process.The percentage yield of the biodiesel was ≈82%.The extracted bio-diesel was blended with commercially available diesel in different fractions for the study.The performance study and emission analysis were calculated on single cylinder four stroke diesel engine.According to analysis brake specific energy consumption there was decreasedand there is slight increase in brake thermal efficiency.The exhaust analysis showed that there was considerable drop in the engine emission like carbon dioxide, carbon mono oxide and hydrocarbons, resulting in lower smoke opacity.The oxides of nitrogen were present at a higher percentage in the engine emissions when the bio-diesel blend was used.

iston skirts in the cylinder chamber. This covers the way for the examination of multi-pass impacts of graphene nano-powder filled in Al-6063 SCs for investigation of microstructure, hardness, tensile strength, and grain size. The microstructural analysis uncovers the homogenous dispersion of graphene nano-powder particulates in the Al-6063 alloy, and on escalating the numbers of passes during FSP, uniform dispersion of graphene nano-powder in matrix material was observed due to a reduction of grain size in the produced Aluminum metal matrix composites (AMMCs). The results revealed that the superior microhardness of 106.4 VHN along with maximum tensile strength (217 ± 2 MPa) is achieved after the third pass of the tool. The minimum grain size of 23 μm was also observed in 3P- FSP-ed ASCs during friction stir processing.

A new kind of HVAC system is emerging in the building space conditioning market for commercial buildings. This new technology is based on variable refrigerant flow (VRF) or variable refrigerant volume (VRV) technology, which increases effectiveness and efficiency, but these systems are considered new as they have been in existence for only a little over a decade. So these constant improvements and technological upgrades have always kept consumers guessing what new upgrade would be launched and when. This chapter contains a brief discussion of the performance analysis and energy-saving potentials of air conditioning systems with VRV and VRF systems. The initialism VRV can be expanded as variable refrigerant volume, the title that was patented by Daikin. Other brands refer to the system as VRF – variable refrigerant flow. This chapter offers an exploration of the insights, implementation, and the benefits of this system.. For example, through this technology we can make temperature variations in autonomous rooms based on indoor occupancy rates as this technology blends several separate units into one, thereby providing a centralized service. In these systems, during the peak time cycle, compressor power usage can be greatly decreased, and energy bills can be reduced. Due to the potential for energy savings of the VRF system, the downside found in the VRF system is the high initial cost relative to traditional air conditioning systems, so economic VRV/VRF technological systems do need to be built in order to improve business potential and energy quality.

Nowadays, a prime technology in generation IV nuclear reactors, the supercritical water reactor (SCWR), is the main object of focus. The current article aims to develop a thermal hydraulic numerical model for predicting density wave oscillation (DWO) in a supercritical water natural circulation loop (SCWNCL). A one-dimensional thermal hydraulic mathematical model was developed. The numerical model consists of nonlinear mass, momentum, and energy conservation equations, which were discretized by applying the implicit finite difference technique. The numerical model was validated with experimental results, and numerical simulations were carried out to find the marginal stability boundary (MSB) and draw the stability map for the loop. Further, the effects of geometry (i.e., diameter and hot leg length) and operating parameters (i.e., inlet system pressure and friction factor) on the density wave oscillation of the SCWNCL were analyzed.

In this present work mathematical and numerical analysis are carry out to determine the existence of Ledinegg and dynamic instability phenomena in a rectangular shape of natural circulation loop at super-critical condition using super-critical water as a working fluid. A mathematical model has been developed based on the thermal hydraulic (TH) conversion equations of mass, energy and momentum with and without considering the heating structure. Then this dimensional mathematical model has been validated with the SPORT and SUCLIN benchmark model. A rectangular shape with constant diameter of supercritical water natural circulation (RSCWNCL) is investigated and various simulations are performed to find a threshold stability boundary (TSB) at supercritical conditions. Numerical simulations have been carried out to determine the effect of inlet pressure, hydraulic loop diameter and loop riser height on the Ledinegg instability. (C) 2021 Elsevier Ltd. All rights reserved.

In present paper, a mathematical model based on the one dimensional nonlinear mass, momentum and energy conservation equations has been developed to study the density wave instability (DWI) in horizontal heater and horizontal cooler supercritical water natural circulation loop (HHHC-SCWNCL). The one dimensional nonlinear mass, momentum and energy conservation equations are discretized by using finite difference method (FDM). The numerical model is validated with the benchmark results (NOLSTA model). Numerical simulations are performed to find the threshold stability zone (TSZ) and draw the stability map for natural circulation loop. Further, effect of change in diameter and riser height on the density wave instability of SCWNCL has been investigated.

Rare earth particulates are known as the "seed of technology." Due to this in the last few years, the research based on rare earth particulate composite materials and structures (REPCMS) is remarkably increased. In this paper, a review of published papers that are related to mechanical properties along with their microstructure of rare earth composites was done. REPCMS are generally used for a variety of functions apart from primary functions that provide high specific stiffness, superior high-temperature mechanical properties and excellent oxidation resistance. In contrast non-structural functions provide glass polishing, rare earth catalysts used in pollution control, magnets of motors and generators, cell phones and electric vehicle batteries, sports goods and wind turbine magnets for energy harvesting. Many of the recent developments focused on the applications of REPCMS such as predator drones, F-22 fighter jet, Tomahawk Cruise Missile, intelligent bombs, night vision goggles, radar detection, nuclear submarines, nanomaterials, biomechanics, hydrophobicity applications, condensation and evaporation phenomenon. This paper portraits the fabrication of composites with improved mechanical and metallurgical characterization by reinforcing rare earth particulate. Also, the study describes the potential application of aluminum composites with rare earth which suits for automotive, defense and space fields. Some suggestions regarding future research needs are also presented in the paper.

Evaluation of performance parameters, emission and brake specific fuel consumption (BSFC) were made for different blends of solketal in soybean biodiesel with 9%, 10%, 12%, 15% of solketal (volume to volume). These experiments were performed on a single-cylinder water-cooled diesel engine at different speeds and 50% load conditions. In comparison to pure diesel, it was observed that soybean biodiesel and its blends with solketal were higher BSFC. On the addition of solketal to biodiesel higher oxides of nitrogen (NOx) and carbon dioxide (CO 2 ) emissions were reported for all the blends. total hydro carbon (THC) and carbon mono-oxide (CO) emissions were found lower for soybean biodiesel and it’s all four blends as compared to pure diesel and further decreases with the increase in solketal percentage in a blend. A decrease in CO and THC emissions were also observed with the increase in percentage of Solketal fuels. Solketel was found suitable and as an effective additive for biodiesel blends.

The present paper studies the thermal-hydraulic behaviour of the rectangular supercritical natural circulation loop (SCNCL) using numerical model of one dimensional. Then the results of this model is confirmed with experimental and benchmark results. Variations with several geometric parameters like loop diameter, riser length, and heater length and operating conditions like heater inlet enthalpy, pressure, friction factor, and inlet and exit loss coefficient on steady-state performance are investigated for various orientations like HHHC, HHVC, VHVC and VHHC of the heater and cooler. The chances of existing static instability (Ledinegg excursion) has been investigated, which reveals that it can arise only in a low inlet enthalpy condition, far from the suggested various orientations of heater and cooler.

The present paper is to study and explore the possibility of static instability, Ledinegg flow excursion, in a rectangular supercritical natural circulation loop (RSCNCL). Due to drastic change of thermo-physical properties of fluid near the pseudo-critical point, various static and dynamic instabilities might occur in the loop. The instability may be either Ledinegg excursion or density wave oscillations (DWOs). Many previous researchers have analyzed dynamic instability, DWO, in SCNCL, whereas the Ledinegg excursive instability is not studied in depth. In the present research work, a mathematical model will be implemented to predict the Ledinegg instability in SCNCL. The numerical investigation is successful to find whether there would be any Ledinegg instability in the case of SCNCL or not.

Purpose The purpose of the study is to developed the effect of Nusselt number on impeller diameter in agitated vessel, which is beneficial to find out the heat transfer coefficient in the process industry. A comparison has been done between the experimental and calculated Nusselt numbers with standard deviation found to be 8.03 per cent. Design/methodology/approach For studying the effect of impeller diameter on Nusselt Number, the heat transfer measurements were made with three different impellers of diameter. Although the diameter of impeller, D-a shows its effect in Reynolds number, an attempt has been made to find the relationship between the impeller diameter and Nusselt number. A correlation between (N-Nuj/N-Pra('')1/3 N-Rea('')2/3) vs D-a/D-T and (N-Nuoc/N-Pra('')1/3 N-Rea('')2/3) vs D-a/D-c in which data of three fluids [1, 2 and 4 per cent carboxy methyl cellulose solution of A type (CMC-A) solutions] have been plotted. Findings The heat transfer data for agitated Newtonian and non-Newtonian fluids have been successfully correlated by using the viscosity of the fluid evaluated at the impeller tip assuming a cylinder of diameter equal to that of impeller rotating in an infinite fluid. Data of 1, 2 and 4 per cent CMC-A, for three impeller diameters, have been correlated by equations. Using the above concepts of Reynolds and Prandtl numbers, Nusselt Numbers and D-a/D-T, it is also possible to correlate the available published data for other non-Newtonian fluids obtained with different impeller geometries. Originality/value A set up was made for studying the effect of impeller diameter, the heat transfer measurements were made with three impellers of diameter 7.5, 12.7 and 18.35 cm respectively. Although the diameter of impeller, Da shows its effect is Reynolds number, an attempt has been made to find the effect of D-a/D-T ratio on Nusselt number.

In an agitated vessel for finding heat transfer coefficient, few factors play important role. For properly mixing of different fluids, the method of forced convection is used with the help of agitators. For studying the role of agitator diameter and Nusselt Number, calculations of heat transfer were performed with three different agitators of different diameters. It was observed that the diameter of agitator, Da predicts the effect in Reynolds number, an approach has been done for fining the connection between the agitator diameter and Nusselt Number. A link between (Nuj/N″Pra1/3 N″Rea2/3) vs Da/DT and (Nuoc/N″Pra1/3 N″Rea2/3) vs Da/Dc in which data of three fluids (1, 2 and 4% CMC-A solutions) have been plotted. Almost negligible effect of Da/DT is noticed maybe because of very short variation of Da/DT ratio considered in the current work. Nevertheless, an average line between data points gives the implication of Da/DT and Da/Dc equal to 0.1. A comparison has been done between the experimental and calculated Nusselt numbers with standard deviation found to be 8.03%.

In the present stimulated business environment, power sector is playing a major role in the economic growth of India. During the last 20 years, the country had been facing a poor supply of energy and this supply–demand gap is increasing continuously. Therefore, it is important for power plants to improve its power generation capacity drastically by reducing the failure rate. In the present paper, to analyze the causes of poor availability, thermal power plant has divided into six different systems and a system comprising waste gases heating system has been considered. With the help of transition diagram, mathematical equations have been used to find out the availability. After analyzing, it was found that the value of availability is very low and boiler tube failure is one of the most critical factors for this low availability of system. The power plants have low availability causing serious concern and need to identify the responsible factors for this low availability. Boiler tube failure is identified as a responsible factor for low availability, and economizer is the zone where maximum failure occurred. From the maintenance history sheet, it was identified that economizer is a critical zone where maximum tube failures occur and the main cause of economizer failure is due to high-velocity flue gas particle, i.e., erosion. To increase the availability and minimize the failures, erosion process must be reduced in economizer tubes which is mainly responsible for economizer failure and then CFD analysis has been done for this purpose. This results in a decrease in the shutdown period of the plant and an increase in the system availability as well as the power of the system.

In this work a numerical investigation is performed to analyze a rectangular supercritical water natural circulation loop (R-SCWNCL) from thermal-hydraulic point of view with the specific work to predict Ledinegg instability and dynamic instability in a rectangular shape supercritical water natural circulation loop using a thermal-hydraulic model which is based on nonlinear mass, axial momentum and energy conservation equations. The thermal-hydraulic (TH) model has been validated against a result available in the literature. A SCWNCL of rectangular shape is analyzed and numerical simulations are carried out to obtain a marginal stability zone (MSZ) in its operating regime and relevant system. Further parametric studies have been performed to find out the impact of loop riser height (loop height), loop diameter and system pressure on the Ledinegg instability.