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Rise in population and industrialisation has significantly impacted the fossil fuel reserves at global scale which has given rise to alarming emission levels in the environment. To address these issues, hydrogen is a favourable alternative owing to its high calorific value, high flame speeds, shorter flame quenching distance and clean burning nature. The present review provides a comprehensive coverage of different hydrogen production methods, hydrogen storage techniques and application of hydrogen in CI engines. Comparative assessment studies illustrated that thermal based hydrogen production methods have higher environmental impact than all other methods but are commercially mature, cost competitive than other hydrogen production routes. Storage techniques of hydrogen includes compression, liquification, cryo-compression, physical and chemical based storage methods. Compression based technology for hydrogen storage offers the advantages of being commercially mature, faster filling and release compared to other technologies offering higher volumetric and gravimetric density than compression-based methods at impractical operating conditions. CI engine studies of hydrogen as dual fuel suggested better performance attributes (high BTE and lower BSFC), lower emissions (such as CO, CO2, HC, smoke with slight increment in NOxemissions) and improved combustion (high HRR, in-cylinder temperature & pressure) owing to high flame speed, wider flammability limits, small quenching zone and high diffusivity of hydrogen.

The addition of natural gas (NG) with diesel fuel is an attempt to increase the combustion efficiency of the diesel engine and to reduce nitrogen-based emissions in this investigation. A three-dimensional computational study has been carried out on the combustion chamber of a NG–dieseldual fuel engine. Standard k-ɛturbulence model was used to incorporate the turbulence inside the combustion chamber. The spray angle inside the combustion chamber was varied from 100° to 150°. The flow characteristics such as pressure, temperature, and velocity distributions, combustion characteristic of apparent heat release rate, and emission characteristic of NO emission of dual fuel engine were investigated at different spray and crank angles. The results show that the maximum pressure inside the cylinder increased from 129 to 131 bar when the spray angle was varied from 100° to 150° at a crank angle of 360°. The maximum temperature was found to be 1602 K at a spray angle of 150° and at crank angle of 360°. The range of velocity inside the cylinder was from 5 m/s to 15.6 m/s. At the spray angle of 150°, the mass fraction of NO emission was 1.15 × 10−09and was the least among the different spray angles. The optimized spray angle was chosen such that the combustion can take place properly with the least emission and was found to be 150°. The results of the present study were compared with the existing literature and are found to be in good agreement.

Due to urbanisation, the reuse of scrap tyres in the form of energy has gained attention for the disposal of waste tyres. Among the numerous methods, pyrolysis appears to be possible, appealing and viable for generating products such as pyrolysis oil, which can be combined with petroleum oils and used as a source of energy. In a prior study, a mixture of jatropha methyl ester (JME) and tyre pyrolysis oil (TPO) was used as a diesel engine fuel, and it was discovered that the JMETPO20 (JME80% + TPO20%) blend gave better results among all the test blends but inferior than diesel operation. Also, it was reported that due to higher viscosity of the JMETPO20 blend, engine gave inferior performance than diesel operated engine. In this context, an attempt has been made to utilize the JMETPO20 blend at different preheating temperatures to substitute conventional diesel. The blend was preheated at three different temperatures, that is, 50, 60 and 70°C and experiments were carried out in a single-cylinder diesel engine with a rated output of 4.4 kW. The results of the investigations were analysed and compared with diesel and presented in this study.

Renewable energy sources are becoming an increasingly viable alternative energy source for the near future due to increased environmental concerns and increasingly strict energy restrictions. Bioethanol and biodiesel are the most promising biofuel options. In the present study effects of spirulina microalgae biodiesel and diesel blends on compression ignition diesel engines at 1500 r/min utilizing various blends B20, B40, B60, B80, and B100, as well as B0(diesel), 23.5° before top dead centre and 18.5 compression ratio (CR) at 220 bar. The extreme peak pressures of the engine for B0, B20, B40, B60, B80, and B100were 103.13, 101.65, 100.25, 98.90, 96.74, and 94.83 bar, respectively. The percentage reduction in ignition delay duration for B20, B40, B60, B80, and B100was 2.57%, 4.17%, 5.28%, 6.60%, and 8.16% compared to pure diesel. B20proves to be the most promising biodiesel blend. Analysis of variance analysis was done for experimental data. The response surface method was used to optimize the engine performance and emission parameters for load, blend, and CR variations. Optimized input conditions were found as load 52.27, CR 18.5, and blend B20. The research dynamic analysis was carried out for the sustainability of biodiesel.

The photovoltaic module only manages to convert around 15% of the incoming light into usable electricity and the rest is lost as heat, reducing the module's overall efficiency. Hybrid photovoltaic thermal systems are therefore the best way to collect thermal and electrical energy. The cooling and heat storage benefits of PV cells are amplified using phase change materials (PCMs). In this article, a simple two-dimensional CFD model to forecast the temperature of the PV where it contacts the PCM. The findings of the numerical simulations show that PV systems equipped with PCM have been studied under a variety of situations. A contemporary thermodynamic study is performed to examine system behaviour under different operating settings by investigating the effect of some rather crucial aspects that have not been taken into account before. The research takes into account three instances, each with its own unique combination of wind speed, ambient temperature, and sun irradiation. It has been shown that the solar radiation is a key component for growth in the PV temperature. The findings show that an increase in PV temperature of 5–7°C is caused by an increase in solar irradiance of 1000 W/m2. The rise in wind velocity, heat dissipation rate increases resulting to the fall in the temperature of the PCM and glass, the decrease in PCM temperature leads to a further drop in glass temperature. More so than wind speed or solar irradiation, ambient temperature determines how quickly PV glass heats up. Furthermore, at an ambient temperature of 35°C, PCM is found to melt entirely in 435 min, whereas at an ambient temperature of 30°C, PCM melts up to a liquid fraction of 0.77 min. Therefore, the efficiency of the PV system improves dramatically as the outside temperature is lowered.

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•Optimizing the geometry of turbulators, thereby increasing their effectiveness in heat transfer rate.•The use of SiO2nanofluid introduces an innovative approach to enhance thermal conductivity, potentially leading to improved heat transfer performance.•The research employs an experimental evaluation of nanofluid, and water to optimize the performance of DPHE.•The findings of this research are expected to contribute to advancements in heat exchanger technology, benefiting a range of industrial applications.•The results of this study show that the heat transfer rate has increased by 87.73 %.

The increased need for renewable energy sources and growing concerns about environmental pollution has driven the need for alternative fuels (particularly biodiesel) in the transportation industry. The most used technique for producing biodiesel is transesterification, which involves the oil reacting with alcohol in the presence of a catalyst. This study looks at the usage of artificial neural network (ANN) and response surface methodology (RSM) to optimize biodiesel synthesis factors for a hybrid oil feedstock (30% cottonseed and 70% spirulina microalgae oil). The parameters that were optimized were the methanol/oil ratio, reaction time, and catalyst concentration. Cottonseed oil was combined with spirulina microalgae oil to minimize its higher free fatty acid content to less than 1% and prevent soap formation during the transesterification process. The optimal biodiesel production was 94.37%, with 106.4 minutes of reaction time, 1.612% catalyst loading, and a methanol/oil ratio of 20:1. The optimized findings, when confirmed with experiments, gave a biodiesel yield of 91.03% with an error of 3.6%. To provide vital insights into the potential environmental benefits of using this alternative fuel, the study further investigates how the optimized biodiesel blend influences engine performance and emission characteristics. Testing was done at 1500 RPM and 17.5 CR for maximum loading conditions, diesel, HBD20, and HBD fuel produced 0.2746, 0.2805, and 0.288 kg/kWh of specific fuel consumption (SFC), respectively. The CO2emissions of HBD and HBD20 were 2.49% and 8.30% lower, respectively, than pure diesel. NOx emissions increased by 14% and 18.3%. The highest cylinder pressure was 66.87 at 363 °C.

Double pipe heat exchanger (DPHE) is a key component of a wide variety of fields where heat trans-mission is a necessity. The numerical simulation was carried out using ANSYS 16.0 within the operating Reynolds number (Re) 6000 to 14,000 to explore and estimate the thermal performance of the heat exchangers (HEs). Computational fluid dynamic (CFD) analysis was performed for the tube tailored with tape twisted (TT) with dimples of Día = 6 mm, D/H Ratio = 1.5, 3 and 4.5, with twist ratio is 5.5. The gathered datasets were subsequently employed validate an artificial neural network (ANN) model, aiming to forecast Nusselt numbers and friction factor within a tube containing dimpled twisted tape inserts. The mean relative errors (MRE) between the predicted results, experimental data and numerical results for the Nusselt numbers and the friction factor were less than 3.30, 0.08 and 2.1 percentage, respectively. Consequently, the study suggests employing the combination of CFD and ANN models as a means to forecast the effectiveness of thermal systems in diverse engineering applications. The efficiency of heat transmission, frictional loss, flow rates and heat transfer rate were all determined using these quantitative simulations.

Significant research is devoted to the transformation of Glycine max oil (soybean oil) into biofuel. An exhaustive investigation into the performance, combustion and emission analyses of glycine max oil biofuel (GMOB) in the context of optimization studies involving variable engine factors such as load, injector timing and so forth, has yet to occur. This study endeavors to fill the gap in the academic literature regarding comprehensive engine investigations of GMOB. In this study, five distinct mixtures of GMOBs are combined with diesel: DS1—0% biofuel with 100% diesel, DS2—5% biofuel with 95% diesel, DS3—20% biofuel with 80% diesel, DS4—40% biofuel with 60% diesel and DS5—100% biofuel and 0% diesel. Using standard ASTM limits, the properties of the biodiesel samples were evaluated and confirmed (the kinematic viscosity at 40°C for GMOB is 4.6 mm2/s, whereas that of unadulterated diesel is 3.0 mm2/s). Utilizing the combustion, emission and performance characteristics of a compression ignition engine, the blend, load and injection timing (IT) were optimized. At 100% load, an upward trend in indicated thermal efficiency is observed for both diesel and biofuel blends. Furthermore, the volumetric efficiency of all biofuel blends was enhanced through the implementation of advanced IT (24.5° b TDC). Additionally, smoke emission is observed to increase by 18.5°–24.5° b TDC across all mixtures. Biofuel mixtures exhibit a negligible minimum rate of pressure increase per degree.

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•Green diesel produces from Clodaphora and Focus algae species.•The effect of fuel injection timing, speeds, CRs on the diesel engine.•Clodaphora and Focus green diesel provide the most concise breakdown of emissions.•Clodaphora and Focus green diesel reduced NOx emissions, according to the findings.

The complex hospital environment requires special attention to ensure healthy indoor air quality (IAQ). It is necessary to protect to patient and healthcare workers against hospital acquired infections and occupational diseases. In a hospital environment, there is a trend of high concentrations of harmful micro-organisms. From an infection control perspective, the primary objective of hospital design is to place the patient at no risk of infection during hospitalization. Many people consider that hospitals are generally clean and free from pathogens which are actually not true. Hospitals are having very complex environment that require effective ventilation for comfort of patients & control from infections. Intensive care represents the highest level of continuing patient care and treatment. Therefore a turbulent airflow study has been performed in Intensive Care Unit (ICU) of hospital. The present investigation stresses preventing airborne infections, protecting the doctor and other patient in ICU, using Computational Fluid Dynamics (CFD) software FLUENT. In which, Navier Stokes and energy equations in three-dimensional co-ordinates have been solved by control volume method. The SIMPLE algorithms are used to solve these equations. Steady state, k-ε turbulence model and incompressible flow of a constant property fluid have been considered. The tracking of massless contaminated particle (infection) has also been carried out by simulation. It is observed that stagnant zone of the room is not healthy for the patients as well as doctor. Therefore suitable ventilation arrangement must be provided for healthy environment in the hospital.

Energy is a basic requirement for development in the world. The continuously rising demand for energy resources and the fast depletion of fossil fuel is raises researcher's concern to focus on alternative sources of energy that can replace the shortage of fossil fuels soon. Biodiesel is recognized as one of the potential alternative renewable energy fuels that can be easily available in a wide range in every part of the world. This paper reviews biodiesel's prospect and focuses on the different fuel properties (physicochemical) of 100 biodiesels from first-, second- and third-generation followed by the evaluation of CI engine characteristics. It has been observed that the fuel properties of first-, second- and third-generation biodiesel are compatible with the ASTM standards. The present paper discussed the potential of various generations of biodiesel feedstocks from production perspectives. This paper also examined many aspects of these feedstocks which include different biodiesel feedstock sources, biodiesel conversion technology, and second-generation biodiesel performance and emission characteristics. Most of the studies showed that biodiesel derived from plant feedstock is costly than diesel. Thus, more influence is to be given to non-edible sources. However, the engine characteristics are shown promising behavior with biodiesel and a slight increase in NOXis also reported on using various biodiesel.

To explore the effect of hybrid fuels containing microalgae, ethanol, methanol and diesel fuel (base fuel) were blends on combustion, performance and emission characteristics and compare with base fuel. The hybrid fuels were calculated using a single-cylinder, four-stroke, naturally aspirated engine, water-cooled, direct injection, diesel engine was used for the experiments under 20%, 50%, 75%, 100% load and simulated by using a thermodynamic engine simulation tool software. The results show that engine brake torque (EBT) of hybrid fuel (ethanol) emulsions were found to be high and exhaust gas temperature to be low compared with that of base fuel. Hybrid fuel (methanol) emulsions helps to increase the cylinder pressure. With the hybrid fuels blend, the ignition delay period and combustion duration of hybrid fuel blends is increased. With the addition of spirulina microalgae, the ignition delay period of spirulina microalgae-diesel blend fuel is shortened. Engine emission results indicated that spirulina microalgae emulsions fuel reduces the specific particulate matter (PM), soot and smoke emissions except nitrogen oxides (NOX) emissions but carbon dioxide (CO2) emission to be higher compared with base fuel.

•AME – diesel blends can be used in a diesel engine without modifications.•Reduction of CO2emission with increase in load, but increasing with increasing percentage of AME biodiesel.•Smoke and PM emission is reduced using AME biodiesel compared to diesel.