RESUMEN
Nanoparticles play a crucial role in enhancing the thermal and rheological properties of nanofluids, making them a valuable option for increasing the efficiency of heat exchangers. This research explores how nanoparticle characteristics, such as concentration, size, and shape, impact the properties of nanofluids. Nanofluids' thermophysical properties and flow characteristics are essential in determining heat transfer efficiency and pressure loss. Nanoparticles with high thermal conductivity, such as metallic oxides like MgO, TiO2, and ZnO, can significantly improve the heat transfer efficiency by around 30% compared to the base fluid. The stability of nanofluids plays a crucial role in their usability. Various methods, such as adding surfactants, using ultrasonic mixing, and controlling pH, have been employed to enhance the stability of nanofluids. The desired thermophysical properties can be achieved by utilizing nanofluids to enhance the system's heat transfer efficiency. Modifying the size and shape of nanoparticles also considerably improves thermal conductivity, affecting nanofluid viscosity and density. Equations for determining heat transfer rate and pressure drop in a double-pipe heat exchanger are discussed in this review, emphasizing the significance of nanofluid thermal conductivity in influencing heat transfer efficiency and nanofluid viscosity in impacting pressure loss. This Review identifies a trend indicating that increasing nanoparticle volume concentration can enhance heat transfer efficiency to a certain extent. However, surpassing the optimal concentration can reduce Brownian motions due to higher viscosity and density. This Review offers a viable solution for enhancing the thermal performance of heat transfer equipment and serves as a fundamental resource for applying nanofluids in heat transfer applications.
RESUMEN
The increasing energy demand has led to the exhaustion of mineral fuel resources and an environmental menace. Biodiesel and alcohol, as oxygenated fuels, offer promising potential for diesel engines. Moreover, the deviation in the fuel injection pressure (IP) favors improvement of the engine performance and reduction of flue gases. The contemporary research aims to explore sustainable biofuel that is an alternative to diesel and to achieve cleaner emissions with enhanced engine performance. The experiment involves testing of a diesel engine tank by quaternary blends comprising diesel, sunflower biodiesel, sunflower oil, and alcohol in the volumetric ratio of 50:25:5:20. The IP was varied from 300, 400, 500, to 600 bar at different engine loads of 10 and 20 N m at 1800 rpm of shaft speed. The quality of the quaternary blend was varied by the inclusion of alcohol having different carbon-chain lengths, namely, ethanol, propanol, butanol, heptanol, and decanol. The effect of alcohol inclusion and variation in the IP led to minimal brake-specific fuel consumption and maximal brake thermal efficiency for blended fuel containing 20% propanol, which was 17.39% lower and 8.70% higher than diesel, respectively. The same composition of the fuel blend offered the lowest smoke and CO2 emissions, which were 92.85 and 27.9% lesser than diesel; moreover, 7.36% lower NO x emission than diesel was achieved.
RESUMEN
This work explores the influence of a pre-engineered notch on the electromagnetic radiation (EMR) parameters in NiTi shape memory alloy (SMA) during tensile tests. The test data showed that the EMR signal fluctuated between oscillatory and exponential, signifying that the specimen's viscosity damping coefficient changes during strain hardening. The EMR parameters, maximum EMR amplitude, and average EMR energy release rate remained constant initially but rose sharply with the plastic zone radius with progressive loading. It was postulated that new Frank-Read sources permit dislocation multiplication and increase the number of edge dislocations participating in EMR emissions, leading to a rise in the value of EMR parameters. The study of the correlation between EMR emission parameters and the plastic zone radius before the crack tip is a vital crack growth monitoring tool. An analysis of the interrelationship of the EMR energy release rate at fracture with the elastic strain energy release rate would help develop an innovative approach to assess fracture toughness, a critical parameter for the design and safety of metals. The microstructural analysis of tensile fractures and the interrelation between deformation behaviours concerning the EMR parameters offers a novel and real-time approach to improve the extant understanding of the behaviour of metallic materials.
RESUMEN
Herein, the performance, emission and physiochemical properties of a soy methyl ester (SME) and its combination with methyl oleate (MO) in a common rail direct injection (CRDI) engine were investigated. Moreover, the performance of the engine in terms of brake power (BP), brake thermal efficiency (BTE), brake specific fuel consumption (BSFC) and NO x emission was assessed to compute the characteristics of the combination of SME with MO; the reasons for using MO in the blending process were the better ignition quality, oxidative stability and low-temperature flow properties of MO, striking a balance between oxidative stability and low flow properties. A remarkable reduction in the BSFC and an increase in the BTE were found in the blended biodiesel (S80-MO20, S70-M30, and S50-M50) as compared to the case of SME. The blended biodiesel was also characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis) and nuclear magnetic resonance (NMR) spectroscopy. In the FTIR spectra, a peak was observed at 1745 cm-1, confirming the presence of a triglyceride ester linkage. Since UV-vis spectroscopy is an affordable technique, herein, it has been employed to detect the presence of conjugated dienes in the oxidized biodiesel. The linear line fitted for absorbance versus the percentage of the blended fuel at 320 nm showed a high coefficient of determination (R 2 = 0.9454). In addition, H NMR spectroscopy was employed to study the oxidative stability of the blended fuel. Different functional groups with their respective peaks (in ppm) are indicated in the NMR spectra.