Empirical investigation of the effect of adding nanoparticles to HB-80 gas turbine oil: Evaluation of thermophysical behaviors.

The current study aims to conduct an empirical investigation on the performance of copper (II) oxide (CuO), Graphene Oxide (GO), and Molybdenum (VI) Oxide (MoO3) nanoparticles as additives for HB-80 base lubricant and their effects on essential characteristics such as density, flashpoint and flammability, cloud point and pour point, viscosity and viscosity indicators, thermal conductivity coefficient, friction coefficient and wear. The test results show that nanoparticles have minor effects on density and viscosity but managed to improve viscosity indicators. Flashpoint, flammability, cloud point, and pour point all increased after the addition of nanoparticles. The increase in the concentration of nanoparticles also improved and increased the lubricant's thermal conductivity coefficient; the highest increase was 11.3 % compared to the base oil with the addition of 1 wt% CuO. Adding nanoparticles to lubricant decreases wear and friction coefficient by creating a lubricant film, especially at lower nanoparticle concentrations, which leads to a more stable lubricant film by nanoparticles. Copper (II) Oxide nanoparticles had the best performance in reducing friction coefficient and wear at 0.2 wt% with 22.86 % and 63.92 % reduction compared to the base oil, respectively.

Taking benefits of using PCMs in buildings to meet energy efficiency criteria in net zero by 2050.

Considering the share of 40% and 35% of buildings in energy consumption as well as CO2 emissions, adding phase change materials (PCMs) is an effective technique to tackle high energy demand and considerable CO2 emissions. When PCMs are injected into the building envelopes, they improved the sensible/latent storage features of the envelopes. In this study, using numerical methods, defining first (no PCM), second (PCM without phase transition), and third building (with phase transition), the importance of sensible storage feature was compared to latent one. It was found that the sensible/latent importance is dependent on the thermal resistance of the envelopes and setpoint. At setpoint 22 °C, it was found that the PCM-enhanced building consumed less power by 32.4 kWhm2. Under this condition, the share of sensible storage as well as latent storage was 54% and 46%, respectively. The reason for the lower share of latent storage was that PCM never participated in phase change about 40% of the year. To boost PCM effectiveness, it was found that the PCM installation near the uppermost layer enhanced energy-saving by 3.72 kWhm2. The presence of phase change in PCM is not always considered a positive point. In one situation, it was observed that if PCM did not undergo phase transition, it reduces energy consumption by 9.4 kWhm2, while for PCM with phase transition this value was 7.1 kWhm2. PCM was also beneficial on CO2 reduction either with phase change or without phase change. In the former, CO2 emissions declined by 34.9 kgm2, and under the latter circumstances it was 23.9 kgm2.

Effectiveness of solar water disinfection in the era of COVID-19 (SARS-CoV-2) pandemic for contaminated water/wastewater treatment considering UV effect and temperature.

Long is the way and hard, that out of COVID-19 leads up to light. The virus is highly contagious and spread rapidly and the number of infections increases exponentially. The colossal number of infections and presence of the novel coronavirus RNA in human wastes (e.g. Excreta/urine) even after the patients recovered and the RT-PCR tests were negative, results in massive load of the viral in water environments. Numerous studies reported the presence of SARS-CoV-2 in wastewater samples. The risk of contaminating water bodies in the regions which suffer from the lack of proper sanitation system and wastewater treatment plants (mostly in developing countries) is higher. Since solar water disinfection (SODIS) is usually used by people in developing countries, there is a concern about using this method during the pandemic. Because the SARS-CoV-2 can be eliminated by high temperature (>56 °C) and UVC wavelength (100-280 nm) while SODIS systems mainly work at lower temperature (<45 °C) and use the available UVA (315-400 nm). Thus, during a situation like the ongoing pandemic using SODIS method for wastewater treatment (or providing drinking water) is not a reliable method. It should be reminded that the main aim of the present study is not just to give insights about the possibilities and risks of using SODIS during the ongoing pandemic but it has broader prospect for any future outbreak/pandemic that results in biological contamination of water bodies. Nevertheless, some experimental studies seem to be necessary by all researchers under conditions similar to developing countries.

Carbon Nanomaterial-Based Nanofluids for Direct Thermal Solar Absorption.

Recently, many scientists have been making remarkable efforts to enhance the efficiency of direct solar thermal absorption collectors that depends on working fluids. There are a number of heat transfer fluids being investigated and developed. Among these fluids, carbon nanomaterial-based nanofluids have become the candidates with the most potential by the heat absorbing and transfer properties of the carbon nanomaterials. This paper provides an overview of the current achievements in preparing and exploiting carbon nanomaterial-based nanofluids to direct thermal solar absorption. In addition, a brief discussion of challenges and recommendations for future work is presented.

Sonication time efficacy on Fe3O4-liquid paraffin magnetic nanofluid thermal conductivity: An experimental evaluation.

In this study, the duration of sonication efficacy on the thermal conductivity of Fe3O4-liquid paraffin nanofluid is investigated. The nanofluid is produced at 0.005, 0.01, 0.015, 0.02, 0.025 and 0.03 vol concentrations by applying two-step method. The sonication process is performed in a temperature range of 20-90 °C. The duration of sonication seems to have two important effects: On the one hand, increasing the duration of sonication breaks the nanoparticles clusters, hence distributes the nanoparticles more uniformly which in turn rises thermal conductivity. On the other hand, an excessive increase in the duration of sonication can impair nanofluid stability. The results of experimental tests proved that the optimal duration of sonication is 3 h. The optimal duration of sonication is not dependent on the nanoparticles volume fraction (φ) and temperature. It was found that at the highest temperature and φ (90 °C,0.03), the greatest thermal conductivity enhancement (28.49%) is obtained. In contrast, at the lowest temperature and φ (20 °C,0.005) the lowest thermal conductivity enhancement was obtained (2.82%).

Numerical simulation of blood flow inside an artery under applying constant heat flux using Newtonian and non-Newtonian approaches for biomedical engineering.

BACKGROUND AND OBJECTIVE: In this paper, different behaviors of blood flow are simulated inside the artery under applying a constant heat flux on the artery boundary walls. METHODS: To simulate the blood flow, the Sisko model is employed. Then, the temperature and Nusselt number of blood flow are reported for different Sisko parameters. Afterward, the effects of different artery radiuses are studied on the Nusselt number. RESULTS: Medical treatment by replenishes fluid and electrolytes in the body vessels can change blood flow properties from non-Newtonian behavior to Newtonian behavior, which increases heat transfer in blood flow and causes to reduce blood flow temperature. In this research, the maximum temperature of Newtonian blood fluid flow is reported as much as 310.0045 K, whereas; maximum flow temperature in non-Newtonian blood fluid is 310.007 K. These results emphasize the effects of the type of Newtonian and non-Newtonian fluid model on the thermal behavior of blood inside body vessels. Since medical science does not permit body temperature to be changed from the normal condition, this small variation can be noticeable and sensible on the health. Hence, medical scientific research centers and institutes of vaccine and serum have to be careful in the mechanical design of drugs for blood fluid. CONCLUSIONS: The results of this research show the application of mechanical engineering for some of the medical concerns in designing the drugs which are effective on the behavior of human body blood.

Analysis and manegement of laminar blood flow inside a cerebral blood vessel using a finite volume software program for biomedical engineering.

BACKGROUND AND OBJECTIVE: Hemodynamic blood flow analysis in the cerebrovascular is has become one of the important research topics in the bio-mechanic in recent decades. The primary duty of the cerebral blood vessel is supplying Glucose and oxygen for the brain. METHODS: In this investigation, the non-Newtonian blood flow in the cerebral blood vessels studied. For modeling the geometry of this problem, we used Magnetic Resonance Image (MRI) approach to take Digital Imaging and Communications in Medicine (DICOM) images and using an open-source software package to construct the geometry, which is a complicated one. The power-law indexes, heat flux, and Reynolds number range in the investigation are 0.6 ≤ n ≤ 0.8, 5 ≤ q ≤ 15Wm-2 and 160≤Re≤310. Effects of Reynolds number, power-law indexes and heat fluxes are investigated. RESULTS: We found that the pressure drop increase with increasing the Reynolds number and power-law index. The maximum Nusselt number in the cerebral blood vessels accrued in the running position of the body in n = 0.8. Also, the highest average wall shear stress occurs in maximum power-law indexes and Reynolds number. CONCLUSION: By increasing the power-law index and Reynolds number, the wall shear stress increases.

Multi-objective optimization of a photovoltaic thermal-compound sensible rotary heat exchanger system using exergo-economic and enviro-economic approaches.

This paper presents exergo-economic and enviro-economic assessment of a novel building integrated photovoltaic thermal-compound sensible rotary heat exchanger (BIPVT-SRHX) system. The innovative BIPVT-SRHX system preheats/precools the outdoor air in winter/summer and generates electric power. The performance of the system are analyzed from the energy/exergy viewpoints for Kermanshah, Iran climatic conditions. Then, the multi-objective genetic algorithm (MOGA) optimization is used to optimize to determine the optimum values of geometric and operating parameters in order to maximize the annual average exergo-economic and enviro-economic aspects of the system. The considered geometric and operating parameters include the length, width and depth of the air channel located underneath the PV modules, the air mass flow rate, and the diameter, rotational velocity and length of the SRHX. Moreover, the annual performance of the optimized and non-optimized BIPVT-SRHX systems are compared. The results showed that the annual average exergo-economic and enviro-economic aspects of the optimized BIPVT-SRHX system are 0.0076 $/annum and 246.9 kWh/$, respectively. Furthermore, it was found that the annual average enviro-economic aspect, annual average exergo-economic aspect, and yearly sum of CO2 mitigation of the optimized BIPVT-SRHX system are respectively 36.8%, 23.1% and 37.7% higher than the non-optimized system.

Effect of sonication characteristics on stability, thermophysical properties, and heat transfer of nanofluids: A comprehensive review.

The most crucial step towards conducting experimental studies on thermophysical properties and heat transfer of nanofluids is, undoubtedly, the preparation step. It is known that good dispersion of nanoparticles into the base fluids leads to having long-time stable nanofluids, which result in having higher thermal conductivity enhancement and lower viscosity increase. Ultrasonic treatment is one of the most effective techniques to break down the large clusters of nanoparticles into the smaller clusters or even individual nanoparticles. The present review aims to summarize the recently published literature on the effects of various ultrasonication parameters on stability and thermal properties of various nanofluids. The most common methods to characterize the dispersion quality and stability of the nanofluids have been presented and discussed. It is found that increasing the ultrasonication time and power results in having more dispersed and stable nanofluids. Moreover, increasing the ultrasonication time and power leads to having higher thermal conductivity and heat transfer enhancement, lower viscosity increase, and lower pressure drop. However, there are some exceptional cases in which increasing the ultrasonication time and power deteriorated the stability and thermophysical properties of some nanofluids. It is also found that employing the ultrasonic horn/probe devices are much more effective than ultrasonic bath devices; lower ultrasonication time and power leads to better results.

A numerical simulation for magnetohydrodynamic nanofluid flow and heat transfer in rotating horizontal annulus with thermal radiation.

The impact of an axial magnetic field on the heat transfer and nanofluid flow among two horizontal coaxial tubes in the presence of thermal radiation was considered in this study. The impact of viscous dissipation was also considered. The well-known KKL (Koo-Kleinsteuer-Li) model was applied to approximate the viscosity of the nanofluid and the effective thermal conductivity. Furthermore, proper transformations for the velocity and temperature were applied in this study to obtain a set of ODEs (ordinary differential equations) for basic equations governing the flow, heat and mass transfer. In addition, the 4th order Runge-Kutta (RK) numerical scheme was applied to solve the differential equations along with the associated boundary conditions. The impacts of different parameters, including Hartmann number, Reynolds number, radiation parameter and aspect ratio, on the heat transfer and flow features were studied. According to the results, the value of the Nusselt number increases with an increase in the radiation parameter, Hartmann number and aspect ratio and a decrease in the Reynolds number and Eckert number.