Experimental Investigation on Stability, Viscosity, and Electrical Conductivity of Water-Based Hybrid Nanofluid of MWCNT-Fe2O3.

The superiority of nanofluid over conventional working fluid has been well researched and proven. Newest on the horizon is the hybrid nanofluid currently being examined due to its improved thermal properties. This paper examined the viscosity and electrical conductivity of deionized water (DIW)-based multiwalled carbon nanotube (MWCNT)-Fe2O3 (20:80) nanofluids at temperatures and volume concentrations ranging from 15 °C to 55 °C and 0.1-1.5%, respectively. The morphology of the suspended hybrid nanofluids was characterized using a transmission electron microscope, and the stability was monitored using visual inspection, UV-visible, and viscosity-checking techniques. With the aid of a viscometer and electrical conductivity meter, the viscosity and electrical conductivity of the hybrid nanofluids were determined, respectively. The MWCNT-Fe2O3/DIW nanofluids were found to be stable and well suspended. Both the electrical conductivity and viscosity of the hybrid nanofluids were augmented with respect to increasing volume concentration. In contrast, the temperature rise was noticed to diminish the viscosity of the nanofluids, but it enhanced electrical conductivity. Maximum increments of 35.7% and 1676.4% were obtained for the viscosity and electrical conductivity of the hybrid nanofluids, respectively, when compared with the base fluid. The obtained results were observed to agree with previous studies in the literature. After fitting the obtained experimental data, high accuracy was achieved with the formulated correlations for estimating the electrical conductivity and viscosity. The examined hybrid nanofluid was noticed to possess a lesser viscosity in comparison with the mono-particle nanofluid of Fe2O3/water, which was good for engineering applications as the pumping power would be reduced.

Resistance to tetracyclines among clinical isolates of Mycoplasma hominis and Ureaplasma species: a systematic review and meta-analysis.

BACKGROUND: Resistance to tetracyclines, the first-line treatment for urogenital infections caused by Mycoplasma hominis and Ureaplasma species, is increasing worldwide. The aim of the present study was to determine the global status of resistance to this class of antibiotics. METHODS: Electronic databases were searched using keywords including 'Mycoplasma', 'Mycoplasma hominis', 'M. hominis', 'Ureaplasma', 'Ureaplasma urealyticum', 'Ureaplasma parvum', 'U. urealyticum', 'U. parvum', 'Ureaplasma species', 'resistance', 'antibiotic resistance', 'antibiotic susceptibility', 'antimicrobial resistance', 'antimicrobial susceptibility', 'tetracycline', 'doxycycline' and 'minocycline'. Finally, after some exclusions, 37 studies from different countries were included in the study and meta-analysis was performed on the data collected. RESULTS: The midrange resistance rates for M. hominis and U. urealyticum/parvum to tetracycline, doxycycline and minocycline were 50.0%, 9.0% and 16.7% and 43.3%, 28.6% and 9.0%, respectively. A high level of heterogeneity was observed in all studies (I2 > 50%, P value < 0.05), except those representing doxycycline resistance in M. hominis isolates (I2 = 39.1%, P  = 0.02). No evidence of publication bias was observed in the studies and neither Egger's test nor Begg's test showed significant publication bias. CONCLUSIONS: The results of the present study show that the overall resistance to tetracyclines is relatively high and prevalent among M. hominis and Ureaplasma species throughout the world. This highlights the importance of and necessity for regional and local antibiotic susceptibility testing before treatment choice as well as development of newer generations of tetracyclines to prevent antibiotic misuse, emergence and spread of resistant strains and, finally, the failure of treatment.

Cooling Performance of a Novel Circulatory Flow Concentric Multi-Channel Heat Sink with Nanofluids.

Heat rejection from electronic devices such as processors necessitates a high heat removal rate. The present study focuses on liquid-cooled novel heat sink geometry made from four channels (width 4 mm and depth 3.5 mm) configured in a concentric shape with alternate flow passages (slot of 3 mm gap). In this study, the cooling performance of the heat sink was tested under simulated controlled conditions.The lower bottom surface of the heat sink was heated at a constant heat flux condition based on dissipated power of 50 W and 70 W. The computations were carried out for different volume fractions of nanoparticles, namely 0.5% to 5%, and water as base fluid at a flow rate of 30 to 180 mL/min. The results showed a higher rate of heat rejection from the nanofluid cooled heat sink compared with water. The enhancement in performance was analyzed with the help of a temperature difference of nanofluid outlet temperature and water outlet temperature under similar operating conditions. The enhancement was ~2% for 0.5% volume fraction nanofluids and ~17% for a 5% volume fraction.

Solar driven Stirling engine - chemical heat pump - absorption refrigerator hybrid system as environmental friendly energy system.

Aim of this paper is to present an alternative environmental friendly energy system consisting of solar driven Stirling Engine, chemical heat pump and absorption refrigeration system. Solar energy is the main energy source and waste heat is rejected by the Stirling engine is utilized by the chemical heat pump and absorption refrigerator. This system presents an alternative environmental friendly energy system that produces electricity, cooling and heating same time. A parametric research is conducted considering power output, energy efficiency and exergy destruction rate. Results are obtained numerically and discussed. According to the results, system operates most efficiently at the high temperature ratio of the working fluids of the Stirling engine and high collector surface temperature. Maximum power output is 9.463 kW, maximum energy efficiency of the hybrid system is 0.337. Comparing these results with Stirling engine, maximum power output of the hybrid system increases 14% and energy efficiency increases 13% for the hybrid system.

Energy and Exergy Analyses of a Solid Oxide Fuel Cell-Gas Turbine-Organic Rankine Cycle Power Plant with Liquefied Natural Gas as Heat Sink.

An exergy analysis of a novel integrated power system is represented in this study. A Solid Oxide Fuel Cell (SOFC), which has been assisted with a Gas Turbine (GT) and Organic Rankine Cycle (ORC) by employing liquefied natural gas (LNG) as a heat sink in a combined power system is simulated and investigated. Initially in this paper, the integrated power system and the primary concepts of the simulation are described. Subsequently, results of the simulation, exergy analysis, and composite curves of heat exchangers are represented and discussed. The equations of the exergy efficiency and destruction for the main cycle's units such as compressors, expanders, pumps, evaporators, condensers, reformers, and reactors are presented. According to the results, the highest exergy destruction is contributed to the SOFC reactor, despite its acceptable exergy efficiency which is equal to 75.7%. Moreover, the exergy efficiencies of the ORC cycle and the whole plant are determined to be 64.9% and 39.9%, respectively. It is worth noting that the rational efficiency of the integrated power system is 53.5%. Among all units, the exergy efficiency of the LNG pump is determined to be 11.7% the lowest exergy efficiency among the other investigated components, indicating a great potential for improvements.