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The article widely reviewed the variation of the heat transfer characteristics and fluid flow of various nanofluids based on physical and chemical parameters like velocity, geometry, viscosity, friction factor, and pressure drop. It also shed light on the stability of these nanofluids in various conditions. The article mainly focuses on the effects on Reynolds number and Nusselt number, thermal changes in the environment and the cooling solution used for nanofluids, and the dependency of concentration of nanoparticles in the working fluid. Apart from this, it also discusses the geometry in which the fluid is kept and the motion or forces it experiences and simulations to observe and analyse the flow of fluid and heat through these nanofluids. Also, this article presents the improvement in the pool boiling heat transfer rates through nanofluids with twisted tapes and corrugated patterns such as corrugated double-tube exchangers. This article concluded with the results obtained from experimental analysis and numerical methods. According to the study, as nanofluids get bigger, their velocity increases. When particle size is increased from 10 nm to 100 nm, the alumina-water nanofluid’s velocity rises by 22.22%. For Al2O3/water nanofluid with a particle size of 10 nm, the rate of expansion in wall shear stress when concentration is raised from 0% to 5% is 75%. The geometry of the tubes affects the properties of heat transport. When a triangular tube having a twisted tape is utilized in the system, the Nusselt number is enhanced by 34.7% and 52.5% in turbulent and laminar flow respectively.

The objective of this study was to select an appropriate fuel having different sulfur contents in various coal fuels and optimize the excess air in order to reduce dry flue gas loss, avoid equipment damage due to sulfur dew point corrosion, and reduce maintenance and equipment installation costs. A tri-sector rotary air preheater was employed to exchange heat between dry flue gases and preheat the air (both primary and secondary air). The results showed that coal with 0.6165% sulfur (fuel 2) caused acid dew point temperatures (ADPTs) of 122.38°C and 124.947°C with 15% and 20% excess air, respectively, in a rotary air preheater set at a 30.5° angle, whereas coal with 1.627% sulfur (fuel 1) caused ADPTs of 131.299°C and 133.602°C with 15% and 20% excess air, respectively, in a rotary air preheater set at a 35.99° angle. The experimental results indicate that the use of fuel 2 coal consumption can reduce carbon dioxide (CO2) emission by nearly 4 metric tons (MT)/hour, which is equivalent to a reduction of CO2 emission of 3.8 MT/hour.

In this paper viability of the Nano-refrigerants as a replacement for conventional coolants in bringing down energy consumption and thereby contribute to the green economy has been reviewed. The influence of the % of nanoparticle concentration in thermal conductivity, heat transfer characteristics, and system performance in a refrigeration system is analysed. In this paper, the use of MHD and NEPCM were also discussed and reviewed for their useful impact in the field of nano refrigeration. Review analysis indicated that the maximum coefficient of performance, i.e., 18.75% of enhancement, was observed when the TiO2 nanoparticle was added to the R134a refrigerant. Whereas in the case of the power consumption, Al2O3/R134a gives a 27% reduction in power consumption compared to the conventional fluids. Energy-saving of Al2O3/R134a nano-refrigerant is more than 5 times and 80% more efficient compared to R134a/CuO. Similarly, Al2O3/R134a is 50% more efficient than R134a/SiO2 and 3.4% more efficient than R134a/TiO2. However, R134a/TiO2 exhibited a 54.7% increment in the value of COP compared to R134a/Al2O3. Also, R134a/TiO2 displayed 60% and 35.2% of increment in COP in contrast to R134a/CuO, R134a/SiO2 respectively. The analysis recommends R134a/TiO2 as the best nano-refrigerant as its COP is the highest of all with the energy savings on par with the Al2O3/R134a.

This paper investigates the performance of four nano-refrigerants (CuO-R113a, Al2O3-R134a, ZnO-R152a, and TiO2-R600a) in terms of coefficient of performance and compressor power consumption using a MATLAB-Simulink two-phase flow domain vapor compression refrigeration cycle. The analyses are done for volume concentrations of 0.1%, 0.3%, and 0.5% of nanoparticles in the base-refrigerants. The results are derived mathematically in the Simulink model. The thermophysical properties of base-refrigerants were derived using the NIST chemistry webbook, and various mathematical models were applied to base-refrigerants to calculate the properties of nano-refrigerants. The interpolation of the liquid–vapor region was done using MS Excel. It was found that nano-refrigerants have better heat transfer characteristics and showed the best performance at a lower optimum concentration of 0.1%. Nano-refrigerant combinations have been tested in real-time and model validations; inferences have been duly reported.

In this paper, the thermal management element strategies of the induction motor are developed to assure better endurance and boost efficiency. As the main result, the thermal analysis of an air-cooled and large-capacity induction motor is given considering well-known heat distribution problems. Moreover, this study also presents an integrated approach with two or more cooling strategies to be the need of the hour. The integrated system comprising air- and water-cooled systems are investigated using SolidWorks 2017 and ANSYS Fluent version 2021. Three different flow rates of water 5 LPM, 10 LPM and 15 LPM are analyzed and compared with a conventional air-cooled induction motor, which was validated with the available published resources. Performed analyses indicate that for different flow rates of 5 LPM, 10 LPM and 15 LPM respectively, we have obtained a reduction of temperature accordingly of 2.94%, 4.79% and 7.69%. Hence, the results indicated that an integrated induction motor is efficient in bringing down the temperature compared to air cooled induction motor.

This paper gives a brief review of advanced cooling methods and applications to the permanent magnet synchronous motors (PMSMs), as well as investigates the cooling systems design problem for PMSM systems. Heat sources and losses together with analytical and practical analyses are described. Next, the temperature distribution and its influence on the PMSM is investigated using simulation results. The main part of the paper includes a review of the proposed cooling methods that will release the requirement of heat transfer of the PMSM. The finite element methods (FEM) are applied using the AnSys CFD software to obtain high accuracy thermal model of the PMSM system. The new developed forced air-cooling methods are given in details, which enable to effectively redistribute the temperature and heat transfer increasing the efficiency of the PMSM machine. Examples of CFD simulation are outlined to illustrate the effectiveness and benefits of the strategies developed.

This work discusses the supercritical technology that has been instrumental in reducing pollution levels and quick load response from the thermal plant. Various operating parameters such as main steam pressure and temperature; reheat steam pressure and temperature; excess air ratio for a given fuel, feedwater heater bleed steam pressure and temperature are listed. The influence of their optimization is analyzed to reduce the pollution levels to a certain extent. Primarily, this study deals with utilizing artificial intelligence with the existing plant to predict the optimum thermal plant performance. The input parameters that are used in the artificial neural network (ANN) are evaluated to find the energy input through a mixture of coal and air. The ANN algorithm computes different parameters that initiate the optimization, resulting in the least energy input to the plant, as an algorithm fitness function. The built model could also use online optimization in addition to optimizing the design parameters when further modifications are made. This model is used to determine the effect of various excess air ratios and different types of fuels on the performance of the plant. The different boiler losses of boiler from different coal samples and exergy and exergy losses were analyzed at a particular excess air ratio. Finally, this paper predicts that by using ANN tool optimization, around 30% of coal savings are achieved which is equivalent to CO2 pollution reduction, less reduction of NOx and SOx pollutions, and an increase in plant efficiency by 1.3%.

Vibration is a major issue in turbomachines which causes damage to them and leads to reduction in life and efficiency. This paper reviews various methods to measure the amount of vibration in various turbomachines and also discusses various reasons for the same. This will significantly assist in articulating these vibrations. This paper lists various experiments done, causes, factors, comparison of different turbomachines and their results. Turbomachines which are taken into consideration are Francis turbine, radial turbines, axial turbines, compressors, pumps and fans. The outcome elucidates the changes in vibrations as a function of different input parameters. It can be concluded through various experiments on different types of turbomachines that the major causes of vibrations are cavitation and resonance while excess speed and longer operating periods too contribute to them.

The driving motor is one of the most crucial components of an electric vehicle (EV). The most commonly used type of motor in EVs is the induction motor. These motors generate heat during operation due to the flow of electrical current through the motor’s coils, as well as friction and other factors. For long-run and high efficiency of the motor, cooling becomes more important. This article utilized ANSYS Motor-CAD to map the temperature signature of an induction motor and investigated the thermal efficiency of using nanofluids as a cooling medium. The thermal conductivity of nanofluids has been found to be superior to that of more conventional cooling fluids such as air and water. This research explores the effect of using Al2O3, ZnO, and CuO concentrations in nanofluids (water as a base fluid) on the thermal efficacy and performance of motor. According to the findings, using nanofluids may considerably increase the efficiency of the motor, thereby lowering temperature rise and boosting system effectiveness. Based on the simulation analysis using ANSYS Motor-CAD, the results demonstrate that the utilization of CuO nanofluid as a cooling medium in the induction motor led to a reduction of 10% in the temperature of the motor housing. The maximum reduction in the temperature was found up to 10% when nanofluids were used, which confirms CuO as an excellent option of nanofluids for use as motor cooling and other applications where effective heat transmission is crucial.

Developments in the gas turbine technology have caused widespread usage of the Turbomachines for power generation. With increase in the power demand and a drop in the availability of fuel, usage of turbines with higher efficiencies has become imperative. This is only possible with an increase in the turbine inlet temperature (TIT) of the gas. However, the higher limit of TIT is governed by the metallurgical boundary conditions set by the material used to manufacture the turbine blades. Hence, turbine blade cooling helps in drastically controlling the blade temperature of the turbine and allows a higher turbine inlet temperature. The blade could be cooled from the leading edge, from the entire surface of the blade or from the trailing edge. The various methods of blade cooling from leading edge and its comparative study were reviewed and summarized along with their advantages and disadvantages.

In this work, simulation has been carried out for multipass Gas tungsten Arc Welding of SS316L and their effects were studied for thermal, and residual stresses and compared with experimental results. The sequentially coupled thermo-mechanical, transient thermal and static structural analysis was modelled using ANSYS with relevant Ansys Parametric Design Language coding. Infrared thermography camera was used to obtain the real time temperatures during the welding. The effect of temperatures and the induced residual stresses of the weldment is measured with X-Ray diffraction technique. Tensile residual stresses have been identified at fusion zone and compressive stresses at heat affected zone. Pass wise temperature measurements were taken from analysis and experiment the agreement with 7.24%. The agreement of measured and analysed residual stress had an agreement with 16.66%.

Wind tunnels are built with a certain function in mind and a certain speed range in mind. In this paper, the utility of wind tunnels for varied flow conditions which affect forces on the objects is discussed. As time progresses, more work is being done on wind tunnels which reflects a skilful combination of technology whose roots are based on principles of wind tunnels. Facility characteristics, the principles of operation and therefore the evolution of wind tunnels came to be as they are in today’s world are reviewed. Computational analysis, design criteria and flow physics for subsonic and transonic flows are discussed in this article for closed section testing. Subsonic flow around a circular cylinder and transonic flows over a lambda wing is taken as specific cases. The developed analytical models and closed-circuit wind tunnel tests are compared to validate. The average value of drag coefficient in a circular cylinder subsonic flow indicated a 25–9% variation between the numerical models and the wind tunnel in the specific range of fluid flow (Re). The average value of pressure suction coefficient in a circular cylinder subsonic flow indicated a 27 to − 6% variation between the numerical models and the wind tunnel in the same range of fluid flow. The flow topologies measured using different turbulence models are in good agreement with the schlieren images obtained through the wind tunnel testing for a transonic flow over a lambda wing.

The creation of new age refrigerants might be the answer to the issue of an Earth-wide rise in temperature. Hence, while choosing new refrigerants a careful process is required. The general effect of any refrigerant substance on global warming, energy efficiency, ozone depletion, cost-effectiveness, chemical stability, and safety ought to be assessed. This paper sums up the experimental and numerical investigations directed with the globally accepted R1234yf refrigerant. The paper’s principal points are to assess the capability of the hydro-fluoro-olefin (HFO) refrigerant mainly R1234yf utilized in the refrigeration system (vapor compression systems, domestic refrigeration system) and to explore its utilization as an eco-friendly refrigerant. In the vapor compression refrigeration system, the cooling capacity and coefficient of performance of R1234yf are found to be less, 9% and 11%, respectively compared to that of R134a. But the power consumption of the system with R1234yf increased between 1.6% and 6.7% when compared to R134a. This paper likewise assists with recognizing the gap in the past research works and explores the possibilities for additional works.

Nano-enhanced refrigerant is one of the promising heat transfer fluids in refrigeration systems. It has the capability to boost the efficiency of vapour compression refrigeration and air conditioning systems. In heat transfer application, the density of the fluid plays a crucial role in identifying various heat transfer characteristics such as the Reynolds number, Nusselt number, the friction factor and the pressure loss. Compared to thermal conductivity and viscosity, determining the density of nanofluids has received very less attention in research. The liquid and vapour densities of alumina (Al2O3), titanium dioxide (TiO2) and cupric oxide (CuO) nanoparticles suspended in 2,3,3,3-tetrafluoropropene (R1234yf) are investigated in this study. The Pak and Cho model was adopted to examine the densities of nano-refrigerants as the volume concentration of particles in the base refrigerant and temperature varies from 1% to 5% and 273 to 323 K respectively. The models are validated using the experimental studies conducted by various researchers on different nano-refrigerants. The analysis results indicated that the liquid and vapour densities of CuO/R1234yf nano-refrigerant are 10.3% and 62.93% greater than that of Al2O3/R1234yf at 5% particle concentration. From the liquid and vapour density point of view, the CuO/R1234yf nano-refrigerant is superior over Al2O3/R1234yf and TiO2/R1234yf. Results also indicated that at 308 K the liquid phase density of CuO added with R1234yf nano-refrigerant is higher by 12.99% and 8.65% than R134a and R141b respectively. Hence CuO/R1234yf significantly enhances the performance of refrigeration systems.

Thermal and residual stress distributions induced by the gas tungsten arc welding (GTAW) process on Inconel 625 were studied using numerical simulation and experiments. A multi-pass welding model was developed that uses a volumetric heat source. Thermomechanical analysis is carried out to assess the Thermal and residual stress distributions. Experiments were carried out with 5 mm thick Inconel 625 plates. X-ray diffraction techniques were used to measure residual stresses, and IR thermometry was employed to capture the temperature values on the welded joints. Simulations were performed with ANSYS numerical code, and a close agreement was found between the predicted and experimentally measured residual stress. Thermal measurements were collected pass by pass from the analysis, and the agreement was 9.08%. The agreement between the measured and analysed residual stress was 11%.

In the frame of the circular economy, welding of Ni-based superalloys has gained increasing importance when applied, for instance, to repairing highly expensive components widely used in strategical sectors, such as the defense and aerospace industries. However, correct process parameters avoiding metallurgical defects and premature failures need to be known. To reach this goal, Inconel 625 butt-welded joints were produced by CO2 laser beam welding and different combinations of process parameters. The experimental investigation was carried out with three parameters in two levels with an L4 orthogonal array. Laser power, welding speed, and shielding gas flow rate were varied, and the results were reported in terms of mechanical properties, such as microhardness, tensile strength, distortion, residual stress, and weld bead geometry, and metallurgy. At a lower welding speed of 1 m/min, the full penetration was observed for 3.0 kW and 3.3 kW laser powers. However, sound welds (porosity-free) were produced with a laser power of 3.3 kW. Overall, the obtained full-penetration specimens showed a tensile strength comparable with that of the parent material with residual stresses and distortions increasing with the increase in heat input.

Using TRNSYS software, a comparison of the energy performances of flat-plate collectors (FPCs) and evacuated-tube collectors (ETCs) in domestic solar water heating systems located in different climate areas was carried out in order to ascertain solar energy utilization. Investigations were carried out on single FPCs and ETCs and also for strings of four panels connected in series. Tests were conducted using simulations for water as heat transfer fluid with a fixed fluid flow rate and varying the temperature of the collector’s returning fluid. The maximum power peak decreases with the increase in the inlet temperature of the fluid to the collector in the FPC. The maximum outlet temperature of the FPC is higher than the ETC, most of the time. The evacuated-tube collector performs better only in cold climate areas. Simulations suggest that the use of the FPC is strongly discouraged in cold climatic areas due to thermal losses, whereas the ETC works well with reduced dispersion of heat. In warm seasons, on the contrary, the FPC takes advantage of the high environmental temperature which heats the fluid. The maximum yearly outlet temperature and useful power peak predicted in different climatic areas were investigated by varying the temperature of the fluid inlet fed to the two strings of four FPCs and ETCs. In all cases, the outlet temperature is higher in the ETC technology.

In this paper the attention is focused on introducing the initial experimental results of a comparative experimental investigation on the energy performances of R600a tested as drop-in of R134a in a test-bench refrigeration system developed at the School of Mechanical Engineering of VIT University located in Vellore (India). Moreover, a comparison of the energy performances was pursued also with the system working with and without sub-cooling. The initial experimental investigation is performed respecting the requirement that the two fluids occupy the same volume. The initial energy performances are carried out in terms of evaporator temperature, coefficient of performance and refrigeration effect. The effect of drop-in with R600 a system previously working with R134a, carries an enhancement of the energy performances in terms of COP and refrigeration effect. Moreover, subcooling carries to an additional benefit on the refrigeration effect. The introduced initial experimental results constitute just the first step of a bigger investigation to be conducted in India, focused on analyzing the impact of the drop-in of HFC with new eco-friendly refrigerants.

The electric motor is the mechanism that transforms electrical energy into mechanical energy. Nowadays, electric motors are the cause of a considerable share of the use of electricity and therefore of the energy consumptions (70% in the industrial sector and 25- 30% in the tertiary sector). Faced with ever-increasing energy demand and with a view to adhering to the all-over-the world imperative of adopting measures to reduce energy consumption in all the involved sectors, the use of efficiency enhanced electric motors is required. Generally, the efficiency of an electric motor depends on the type of motor, the size of the motor, the utilization factor, but also on the quality and quantity of the materials employed. Therefore, from all these aspects the need of using energy and costefficient components for developing electric motors arises. This review paper aims to draw a general framework on the methods of increasing efficiency and of reducing weight of the electric motors.

A finite element modelling starts with the heat equation, heat flux input and thermal modelling and the material definition. In this study a laser welding model with heat transfer is defined and analyzed for a 3mm thick SS316LN material, the temperature dependent thermal and structural properties are taken for analysis. The laser has not formed the keyhole, yet lateral conduction forms the weld bead will progress and convection and radiation from the top surface. Modelling of these thermal inputs with symmetric BC's of heat at the fusion zone centre was used in modelling ANSYS solid70 element to obtain the Thermal temperature distribution. Sequentially, this thermal load is given as input to the solid45 to obtain the structural distortion. An orthogonal Array of 9 experiments with three levels of Laser Power, Weld speed and Shield gas flow rate were conducted and analyzed. The optimum levels obtained were 2750Watts, 2500 mm/min and 10LPM. The shield gas flow rate was related to the convective heat transfer coefficient, h in the model. Experimental validation of distortion by experiments had within 8% agreement.

Electric motors are widely used in automobiles and large electric vehicles would be introduced in market in the near future to reduce global warming. Reduction in electric motor weight also reduces the overall weight of automobiles. The use of fiber-reinforced polymer materials reduces the weight of electric motors. Lightweight electric motors promote energy savings owing to the reduction of self-weight. Researchers all over the World are trying to make all parts of electric motors using lightweight materials. This review paper presents the outcome of research carried out by researchers from Germany and UK. Fiber reinforced plastics (FRP) reduce weight and increase mechanical and electrical properties. Phenolic composite materials gave promising results due to its electrical insulation properties and corrosion resistance. Thermosets do not swell when they are exposed to chemicals unlike thermoplastics. Aluminium matrix composites (AMC) are used to improve the motor efficiency resulting in a considerable weight reduction. Electric motors have 90 percent or above, which means that a high mechanical energy is derived from electrical energy. The remaining electrical energy is converted into heat. To prevent overheating, the heat is conducted through housing to a cooling jacket having cold water. Researchers have replaced the circular wire by rectangular flat wire that can be coiled tightly on the stator. Newer cooling concepts are developed for making housings using polymer materials. Carbon fiber reinforced materials with metal pins are used for reducing weight and to increase thermal conductivity. Use of high modulus fibers increase damping properties and reduce noise produced by electric motors. Comparisons between electric motors made of lightweight materials and traditional metals in terms of weight, efficiency, cooling rate are presented.