A Comparative Study on Thermal-Hydraulic Performance of Different Non-Newtonian Nanofluids Through an Elliptical Annulus

This paper presents a numerical investigation on heat transfer and flow behavior for non-Newtonian nanofluids with different nanoparticles (Al2O3 and CuO) and carboxymethyl cellulose (CMC) with water as a base fluid. The analysis has been carried out in an elliptical tube. Power-law model is adopted to depict the non-Newtonian nature of nanofluid. The present study has been done with a range of nanosized particles 0–4% by volume, and the variation of Reynolds number is kept under the laminar condition. The physical model covers two concentric tubes used to create an annular space. The effects of volume fraction, particle type, and base fluid have been investigated at different Reynolds numbers numerically. Also, the effect of pressure and heat transfer coefficient on the flow behavior of non-Newtonian nanofluids is analyzed. The results concluded that Al2O3 particles showed 219% and CuO particles give 195% higher heat transfer coefficient as compared with pure water.

Theoretical Design of the Scattering-Based Sensor for Analysis of the Vehicle Tailpipe Emission

Measurement regulations demand, among other requirements, the reduction of particulate matter emissions from diesel engines. Considering this, the establishment of a new measurement instrument for periodic emission control and detection of the Diesel Particulate Filter (DPF) performance after the vehicle exhaust is necessary. To fulfil these requirements, this paper proposes the design of a new, simple, low-weight layout after the vehicle tailpipe. In order to check the operation condition of the proposed sensor, different factors such as the temperature (−10 to 50 ℃) humidity (60%), and flow rate of the sampled emission (laminar condition) are considered. The proposed layout uses an optical particle counter as a portable instrument for real-time detection of the particle concentration after exhaust of the internal combustion engine.

The effect of hydrodynamics on the succession of autotrophic and heterotrophic organisms of biofilms in river ecosystems

Biofilms were cultivated for a 68-day period under different hydrodynamic conditions, and the effect of hydrodynamics on the succession of autotrophic and heterotrophic organisms of biofilms was investigated. Five obvious stages were observed during biofilm formation. At Stage I, the attachment of algae was delayed, especially under turbulent conditions. After Stage II, algal density and heterotrophic biomass of biofilms increased, which were obvious under turbulent flow. Therefore, the algal density and heterotrophic biomass of biofilms were largest under turbulent condition, followed by laminar condition, and then transitional condition. Diatoms were dominant in all flumes and were most abundant under turbulent conditions. The proportion of cyanobacteria was highest under laminar conditions. The ratio of aerobic to anaerobic bacteria decreased and their co-existence could facilitate the nitrification and denitrification in the biofilm. The ratio of monounsaturated fatty acids to saturated fatty acids was highest under turbulent conditions on the 15th day. While the ratio was highest under laminar condition on the 48th day, the high ratio indicates the high ability of biofilm to obtain nutrients, which affect the growth of algae. The regulation of hydrodynamics is a useful technology which can affect the growth of the microorganisms of biofilm, and further improve water quality.

Four Layer Cylindrical Model of Mucus Transport in the Lung: Effect of Prolonged Cough

Background: In this paper, a four layer model of the simultaneous and coaxial flow of moist air, mucus, mixture of mucin and periciliary liquid and serous fluid (assumed to be incompressible and Newtonian fluids) in a circular tube under time dependent pressure gradient representing prolonged cough is analyzed to study the mucus transport in an airway in the presence of prolonged cough. It is assumed that air and mucus flow under quasi steady state turbulent conditions while the mixture of mucin and periciliary liquid and serous layer surrounding mixture layer flows under unsteady laminar condition in presence of immotile cilia carpet. Result: It is shown that the mucus transport increases as the viscosity of serous fluid decreases. Also the mixture and serous fluid flow rates increase as the viscosity of serous fluid decreases. It is also observed that the effect of resistance to flow by serous fluid in the cilia bed is to decrease flow rates. The flow rates of mucus and mixture of mucin and periciliary fluid increase as the viscosity of mixture decreases also air and mixture of mucus and periciliary fluid flow rates increase as the thickness of mixture increases. Conclusion: As the thickness of mucus increases its flow rate increases on the other hand the mixture flow rate, mucus and serous fluid flow rate decreases with the increase of the mixture thickness. Bangladesh Journal of Medical Science Vol.19(1) 2020 p.53-63

Experimental Investigation on the Multi-metallic Cu-Zn NanofluidsHeat Transfer Enhancement and Pressure Losses

Metallic nanofluidsare suspensions of metallic particles of nanometre size in base fluids. The combination of two kinds of metallic particles mixed at the same volume ratio is known as multi-metallic nanoparticles. These multiple metallic particles of nanometre size were suspended in deionized H2Ovia the use of ultrasonic vibratorsat varying volume fractions as well as variations in the ratios of metallic/metallic particles of nanometre size. In our study the dynamic viscosity, the nanofluid’s heat conductivities were determined for varying temperatures and volume fractions. The coefficient of thermal transmissionof the flowing nanofluid in the constant wall heat flux tube were determined experimentally in laminar condition. The results revealedhuge thermal transmission enhancement comparison to the base fluids. The pressure loses were illustrated for all nanofluids. The comparisons of the different metallic and multi-metallic types of the nanofluids were showed that Cu nanofluids have a greater coefficient ofthermal transmission compared with the Cu-Zn, Zn atequal volume fractions.

Numerical Simulation of Radiation Aerosol Collection in Mesoscopic Impactor Filters

Typically, the concentration of natural radioactive aerosols in the containment vessel of nuclear power plant is low and in equilibrium. But when a serious nuclear accident occurred, the massive radioactive aerosols would be rapidly released. In order to ensure the integrality of the containment, the pressure inside the containment must be reduced by reducing the concentration of the aerosol. It can cause a serious damage to the atmospheric environment if such radioactive aerosol directly release. In this paper a new mesoscopic impactor filter has been developed which not only can filtrate and collect the aerosol particles but also can decrease the flowing resistance of gas. This paper intends to make numerical simulation to study the regularity of the deposition of aerosols under the laminar condition at different working condition in mesoscopic impactor filters. The 3D model of the filter was established with the commercial software of ICEM CFD and the meshes were divided accurately. The gas phase uses the laminar model and the particles use DPM (Discrete Phase Model). The detailed modeling method is given and the simulation results are analyzed.

WSS Investigation in Microfluidic FFS Channel at Re 500

Wall shear stress (WSS) is one of the important variables in microfluidic devices. In this paper WSS distribution for a microfluidic device in Forward Facing Step (FFS) configuration has been investigated using Reynolds number 500 and step height 1μm. Numerical simulation was performed usingAnsys-CFX software with the assumption of Newtonian fluid and laminar condition. The simulation result showed that wall shear stress distribution increased after the fluid passing through the step.