Numerical Analysis of The Thermo-Convective Behaviour of an Al2O3-H2O Nanofluid Flow Inside a Channel with Trapezoidal Corrugations

In this present article, a study of the dynamic and thermal behavior of the Al2O3-water nanofluid flow through a channel provided with trapezoidal undulations, under the action of a constant heat flux. To do this, the effect of various volume fractions (0-4%) and that of the nanoparticle diameter (30, 40, 60 nm) on the heat transfer and pressure drop within the channel was analyzed, for a range of Reynolds numbers between 100 to 1000. The equations governing the fluid flow, namely the equations of continuity, momentum and energy were integrated and discretized based on the finite volume method (FVM). The obtained results indicated that using nanofluids with a high-volume fraction and a small nanoparticle diameter makes it possible to improve the performance of the system in terms of heat transfer, pressure drop and friction factor.

Computational Study Regarding CoxFe3−xO4 Ferrite Nanoparticles with Tunable Magnetic Properties in Superparamagnetic Hyperthermia for Effective Alternative Cancer Therapy

The efficacy in superparamagnetic hyperthermia (SPMHT) and its effectiveness in destroying tumors without affecting healthy tissues depend very much on the nanoparticles used. Considering the results previously obtained in SPMHT using magnetite and cobalt ferrite nanoparticles, in this paper we extend our study on CoxFe3−xO4 nanoparticles for x = 0–1 in order to be used in SPMHT due to the multiple benefits in alternative cancer therapy. Due to the possibility of tuning the basic observables/parameters in SPMHT in a wide range of values by changing the concentration of Co2+ ions in the range 0–1, the issue explored by us is a very good strategy for increasing the efficiency and effectiveness of magnetic hyperthermia of tumors and reducing the toxicity levels. In this paper we studied by computational simulation the influence of Co2+ ion concentration in a very wide range of values (x = 0–1) on the specific loss power (Ps) in SPMHT and the nanoparticle diameter (DM) which leads to the maximum specific loss power (PsM). We also determined the maximum specific loss power for the allowable biological limit (PsM)l which doesn’t affect healthy tissues, and how it influences the change in the concentration of Co2+ ions. Based on the results obtained, we established the values for concentrations (x), nanoparticle diameter (DM), amplitude (H) and frequency (f) of the magnetic field for which SPMHT with CoxFe3−xO4 nanoparticles can be applied under optimal conditions within the allowable biological range. The obtained results allow the obtaining a maximum efficacy in alternative and non-invasive tumor therapy for the practical implementation of SPMHT with CoxFe3−xO4 nanoparticles.

Clustering of Diamond Nanoparticles, Fluorination and Efficiency of Slow Neutron Reflectors

Neutrons can be an instrument or an object in many fields of research. Major efforts all over the world are devoted to improving the intensity of neutron sources and the efficiency of neutron delivery for experimental installations. In this context, neutron reflectors play a key role because they allow significant improvement of both economy and efficiency. For slow neutrons, Detonation NanoDiamond (DND) powders provide exceptionally good reflecting performance due to the combination of enhanced coherent scattering and low neutron absorption. The enhancement is at maximum when the nanoparticle diameter is close to the neutron wavelength. Therefore, the mean nanoparticle diameter and the diameter distribution are important. In addition, DNDs show clustering, which increases their effective diameters. Here, we report on how breaking agglomerates affects clustering of DNDs and the overall reflector performance. We characterize DNDs using small-angle neutron scattering, X-ray diffraction, scanning and transmission electron microscopy, neutron activation analysis, dynamical light scattering, infra-red light spectroscopy, and others. Based on the results of these tests, we discuss the calculated size distribution of DNDs, the absolute cross-section of neutron scattering, the neutron albedo, and the neutron intensity gain for neutron traps with DND walls.

Numerical study of the effects of geometric parameters and nanofluid properties on heat transfer and pressure drop in helical tubes

In this research the geometric parameters and nanofluid properties effects on heat transfer and pressure drop in helical tube, by using alumina-water nanofluid as cooling fluid, are numerically investigated. Friction factor and heat transfer coefficient are calculated by considering the effects of nanofluid properties, including nanoparticle diameter, nanofluid temperature, Reynolds number, and volume fraction, on the one hand, and the impact of geometric parameters, including tube diameter, coils diameter and coils pitch, on the other hand. Numerical analysis is performed in the Ansys Fluent 19.2 software using the SST k-ω turbulence model. By increasing the nanofluid volume fraction the heat transfer coefficient and pressure drop in helical coils increase, the same as the nanoparticle diameter reduction. The reduction of nanoparticle diameter causes an enhancement of heat transfer and friction factor, the best results happen in dp = 5 nm and φ = 4%, where the it was ~ 40.64% more efficient than base fluid. This amounts for φ = 3%, φ = 2% and φ = 1% are 31.80%, 18.02% and 8.83%, respectively. Finally, the performance evaluation criteria (PEC) is compared for different cases, the maximum value was happen on φ = 4% and dp = 5 nm, which it is 1.86 times higher than the base fluid. The results indicate that the thermal efficiency of the heat exchanger improve largely by using helical coils and nanofluids, rather than the base fluid, and direct tubes. In addition, increasing coil pitch and curvature ratio enhance heat transfer and reduce friction factor.