Numerical study of a confined slot impinging jet with nanofluids

<p>Abstract</p> <p>Background</p> <p>Heat transfer enhancement technology concerns with the aim of developing more efficient systems to satisfy the increasing demands of many applications in the fields of automotive, aerospace, electronic and process industry. A solution for obtaining efficient cooling systems is represented by the use of confined or unconfined impinging jets. Moreover, the possibility of increasing the thermal performances of the working fluids can be taken into account, and the introduction of nanoparticles in a base fluid can be considered.</p> <p>Results</p> <p>In this article, a numerical investigation on confined impinging slot jet working with a mixture of water and Al₂O₃nanoparticles is described. The flow is turbulent and a constant temperature is applied on the impinging. A single-phase model approach has been adopted. Different geometric ratios, particle volume concentrations and Reynolds number have been considered to study the behavior of the system in terms of average and local Nusselt number, convective heat transfer coefficient and required pumping power profiles, temperature fields and stream function contours.</p> <p>Conclusions</p> <p>The dimensionless stream function contours show that the intensity and size of the vortex structures depend on the confining effects, given by <it>H/</it>W ratio, Reynolds number and particle concentrations. Furthermore, for increasing concentrations, nanofluids realize increasing fluid bulk temperature, as a result of the elevated thermal conductivity of mixtures. The local Nusselt number profiles show the highest values at the stagnation point, and the lowest at the end of the heated plate. The average Nusselt number increases for increasing particle concentrations and Reynolds numbers; moreover, the highest values are observed for <it>H/W </it>= 10, and a maximum increase of 18% is detected at a concentration equal to 6%. The required pumping power as well as Reynolds number increases and particle concentrations grow, which is almost 4.8 times greater than the values calculated in the case of base fluid.</p> <p> <b>List of symbols</b> </p

A Numerical Analysis on Nanofluid Mixed Convection in Triangular Cross-Sectioned Ducts Heated by a Uniform Heat Flux:

In this paper, results obtained by the numerical investigation on laminar mixed convection in triangular ducts, filled with nanofluids, are presented in order to evaluate the fluid dynamic and thermal features of the considered geometry by considering Al 2 O 3 /water based nanofluids. The system is heated by a constant and uniform heat flux also along the perimeter of the triangular duct section in H2 mode as thermal boundary condition and the single-phase model has been assigned for a Reynolds number value equal to 100. Results are given for different nanoparticle volume concentrations and Richardson number values ranging from 0% to 5% and from 0 to 5, respectively. Results, presented for the fully developed regime flow, show the enhancement of average convective heat transfer coefficients values for increasing values of Richardson number and particle fractions. However, wall shear stress and required pumping power profiles increase as expected. The PEC analysis showed that the use of nanofluids in mixed convection seems slightly convenient. It should be underlined that, at the moment, experimental data are not available to compare the numerical proposed model for mixed convection in horizontal triangular ducts with nanofluids

Numerical Analysis of Water Forced Convection in Channels with Differently Shaped Transverse Ribs

Heat transfer enhancement technology has the aim of developing more efficient systems as demanded in many applications. An available passive method is represented by the employ of rough surfaces. Transversal turbulators enhance the heat transfer rate by reducing the thermal resistance near surfaces, because of the improved local turbulence; on the other hand, higher losses are expected. In this paper, a numerical investigation is carried out on turbulent water forced convection in a ribbed channel. Its external walls are heated by a constant heat flux. Several arrangements of ribs in terms of height, width, and shape are analyzed. The aim is to find the optimal configuration in terms of high heat transfer coefficients and low losses. The maximum average Nusselt numbers are evaluated for dimensionless pitches of 6, 8, and 10 according to the shape while the maximum friction factors are in the range of pitches from 8 to 10

A new bioinformatic pipeline allows the design of small, targeted gene panels for efficient TMB estimation

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Dimensional measurements in the shipbuilding industry: on‑site comparison of a state‑of‑the‑art laser tracker, total station and laser scanner

Thanks to recent technological innovations, some large-volume-metrology measuring instruments—that would have been considered out of context one/two decades ago—are now efective for the shipbuilding industry, where dimensional errors of a few millimetres are generally tolerated. This paper considers three state-of-the-art instruments: a laser tracker, a total station, and a laser scanner, all with the latest generation of technology. While the frst instrument type has long been widespread for applications in industrial metrology, the last two have traditionally been used in other felds, such as as-built surveying, civil engineering, architecture and topography. Instruments are compared using experimental tests concerning the dimensional verifcation of cruise-ship modules in the relatively under-explored context of the construction of the hull, which represents the ship’s framework. The comparison is structured based on several qualitative and quantitative criteria, including but not limited to (i) simplicity of use for operator(s), (ii) time of acquisition/analysis of measurement data, (iii) metrological performance, and (iv) cost. The main contribution of this article is the on-site testing of instruments of interest, in the typical (unfavourable) working conditions of shipyards

Strain, Young's modulus, and structural transition of EuTiO3 thin films probed by micro-mechanical methods

EuTiO3 (ETO) is a well-known complex oxide mainly investigated for its magnetic properties and its incipient ferro-electricity. In this work, we demonstrate the realization of suspended micro-mechanical structures, such as cantilevers and micro-bridges, from 100 nm-thick single-crystal epitaxial ETO films deposited on top of SrTiO3(100) substrates. By combining profile analysis and resonance frequency measurements of these devices, we obtain the Young's modulus, strain, and strain gradients of the ETO thin films. Moreover, we investigate the ETO anti-ferro-distorsive transition by temperature-dependent characterizations, which show a non-monotonic and hysteretic mechanical response. Comparison between experimental and literature data allows us to weight the contribution from thermal expansion and softening to the tuning slope, while a full understanding of the origin of such a wide hysteresis is still missing. We also discuss the influence of oxygen vacancies on the reported mechanical properties by comparing stoichiometric and oxygen-deficient samples.Comment: 8 pages, 5 figures; 7 Supplementary Material section