Thermo-Fluid Dynamics of an Array of Impinging Ionic Jets in a Crossflow

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Daniele Testi ◽  
Walter Grassi
Keyword(s):  
High Efficiency ◽  
Fluid Dynamic ◽  
Impinging Jets ◽  
Negative Ion ◽  
Forced Flow ◽  
Heated Wall ◽  
Electrical Currents ◽  
Square Duct ◽  
Nusselt Numbers ◽  
Potential Applications

Laminar to weakly turbulent mixed convection in a square duct heated from the bottom side is highly strengthened by ionic jets generated by an array of high voltage points, opposite to the heated strip. Negative ion injection is activated within the dielectric liquid HFE-7100. Local temperatures on the heated wall are measured by liquid crystal thermography. Distributions of the Nusselt number are obtained at different forced flow rates, applied heat flows, and transiting electrical currents. In correspondence of the point emitters, higher Nusselt numbers in the impingement areas are measured and an analogy with the thermo-fluid dynamic behavior of an array of submerged impinging jets in a crossflow is drawn. The diameter of the ionic jets is evaluated and an electrohydrodynamic Reynolds number is employed for correlation and similarity purposes. Potential applications of the technique are high-efficiency compact heat exchangers and heat sinks.

Thermo-Fluid Dynamics of an Array of Impinging Ionic Jets in a Crossflow

2010 ◽  
Author(s):  
Walter Grassi ◽  
Daniele Testi
Keyword(s):  
Fluid Dynamic ◽  
Impinging Jets ◽  
Negative Ion ◽  
Forced Flow ◽  
Heated Wall ◽  
Electrical Currents ◽  
Square Duct ◽  
Liquid Crystal Thermography ◽  
Nusselt Numbers ◽  
Bottom Side

Laminar to weakly turbulent mixed convection in a square duct heated from the bottom side is highly strengthened by ionic jets generated by an array of high voltage points, opposite to the heated strip. Negative ion injection is activated within the dielectric liquid HFE-7100. Local temperatures on the heated wall are measured by liquid crystal thermography. Distributions of the Nusselt number are obtained at different forced flow rates, applied heat flows, and transiting electrical currents. In correspondence of the point emitters, higher Nusselt numbers in the impingement areas are measured and an analogy with the thermo-fluid dynamic behavior of an array of submerged impinging jets in a crossflow is drawn. The diameter of the ionic jets is evaluated and an electrohydrodynamic Reynolds number is employed for correlation and similarity purposes.

Numerical Study on Mixed Convection in Porous Media in a Channel With an Open Cavity Below

2010 ◽  
Author(s):  
Bernardo Buonomo ◽  
Oronzio Manca ◽  
Paolo Mesolella ◽  
Sergio Nardini
Keyword(s):  
Mixed Convection ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Vertical Wall ◽  
Open Cavity ◽  
Temperature Fields ◽  
Forced Flow ◽  
Heated Wall ◽  
Local Thermal Equilibrium ◽  
Uniform Heat Flux

A numerical analysis of mixed convection in gas saturated metal foam in a horizontal channel with an open cavity heated at uniform heat flux on a vertical wall is studied numerically. Non-local thermal equilibrium and Brinkman-Forchheimer-extended Darcy model are assumed. Boussinesq approximation with constant thermophysical proprieties are considered. Results are carried out for an aluminium foam with 10 PPI and ε = 0.909, the fluid is air and for the assisting case. Results, for different Peclet and Rayleigh numbers, are given in terms of solid and fluid wall temperatures and local Nusselt numbers and stream function and temperature fields. Results show that diffusive effect determined lower temperature values inside the solid and the fluid temperatures are higher in all considered cases. The interaction between the forced flow in the channel and the buoyancy due to the heated wall determines different thermal and fluid dynamic behaviors.

A Numerical and Experimental Investigation on Impinging Round Jets in Channel Partially Filled With Porous Media

2017 ◽  
Author(s):  
Bernardo Buonomo ◽  
Luca Cirillo ◽  
Oronzio Manca ◽  
Sergio Nardini
Keyword(s):  
Experimental Investigation ◽  
Porous Media ◽  
Metal Foam ◽  
Fluid Dynamic ◽  
Heated Surface ◽  
Impinging Jets ◽  
Solid Matrix ◽  
Uniform Heat Flux ◽  
Round Jets ◽  
Nusselt Numbers

In this paper a numerical and experimental investigation on impinging jets with metal foam is carried out. The channel is partially filled with porous media. The physical model and geometry has been made considering that the lower impinging surface is heated at uniform heat flux, qw, and the upper surface is adiabatic. The flow is 2D, unsteady, laminar, and incompressible. The distance between the upper confining surface and the lower heated surface is H (40 mm). Fully developed fluid dynamic and thermal flow is assumed at the outlet sections and the fluid is air. The porous material is considered as homogeneous and isotropic. All the thermophysical properties of the fluid and the solid matrix of the porous medium are assumed constant except for the variation in density with the temperature giving rise to the buoyancy forces. Metal foam of 10 PPI is considered. It was investigated many configuration taking into account the ratio s/H and Dj/H. The values of ratio s/H ranging from 0 to 1 while values of the ratio Dj/H raging from 0.3–1.2. Results in terms of wall temperature profiles, local and average Nusselt numbers are presented for different Reynolds values. For the considered parameters, it is obtained that Nusselt number has a weak dependence of Dj/H, in fact, for the ratio equal to 0.3, it is noted that Nu is higher than the ratio equal to 0.6.

Effects of Curvature and Convective Heat Transfer in Curved Square Duct Flows

2006 ◽  
Vol 128 (5) ◽  
pp. 1013-1022 ◽  
Author(s):  
R. N. Mondal ◽  
Y. Kaga ◽  
T. Hyakutake ◽  
S. Yanase
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Outer Wall ◽  
Heated Wall ◽  
Dean Number ◽  
Square Duct ◽  
Nusselt Numbers ◽  
Wide Range ◽  
Steady Solutions

Non-isothermal flows with convective heat transfer through a curved duct of square cross section are numerically studied by using a spectral method, and covering a wide range of curvature, δ, 0<δ≤0.5 and the Dean number, Dn, 0≤Dn≤6000. A temperature difference is applied across the vertical sidewalls for the Grashof number Gr=100, where the outer wall is heated and the inner one cooled. Steady solutions are obtained by the Newton-Raphson iteration method and their linear stability is investigated. It is found that the stability characteristics drastically change due to an increase of curvature from δ = 0.23 to 0.24. When there is no stable steady solution, time evolution calculations as well as their spectral analyses show that the steady flow turns into chaos through periodic or multi-periodic flows if Dn is increased no matter what δ is. The transition to a periodic or chaotic state is retarded with an increase of δ. Nusselt numbers are calculated as an index of horizontal heat transfer and it is found that the convection due to the secondary flow, enhanced by the centrifugal force, increases heat transfer significantly from the heated wall to the fluid. If the flow becomes periodic and then chaotic, as Dn increases, the rate of heat transfer increases remarkably.

Experimental Investigation on Mixed Convection in a Channel With an Open Cavity Below

2003 ◽  
Author(s):  
Oronzio Manca ◽  
Sergio Nardini ◽  
Ruggero Pitzolu ◽  
Kambiz Vafai
Keyword(s):  
Mixed Convection ◽  
Flow Visualization ◽  
Open Cavity ◽  
Forced Flow ◽  
Heated Wall ◽  
Heated Plate ◽  
Thermal Plume ◽  
Recirculation Flow ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer

Mixed convection in an open cavity with a heated wall bounded by a horizontal unheated plate is investigated experimentally. The cavity has the heated wall on the inflow side. Mixed convection fluid flow and heat transfer within the cavity is governed by the buoyancy parameter, Richardson number (Ri), and the Reynolds number (Re). The results are reported in terms of wall temperature profiles of the heated wall and flow visualization for Re = 100 and 1000, Ri in the range 30–110 (for Re = 1000) and 2800–8700 (for Re = 100), the ratio between the length and the height of cavity (L/D) is in the range 0.5–1.5 and the ratio between the channel and cavity heights (H/D) equal to 0.5 and 1.0. The present results show that the maximum dimensional temperature rise values decrease as the Reynolds and the Richardson numbers decrease. The flow visualization points out that for Re = 1000 there are two nearly distinct fluid motions: a parallel forced flow in the channel and a recirculation flow inside the cavity. For Re = 100 the effect of a stronger buoyancy determines a penetration of thermal plume from the heated plate wall into the upper channel. The dimensionless maximum wall temperatures in terms of L/D had values in ± 5% respect to an average function. Nusselt numbers increase when L/D increase in the investigated range of Richardson numbers.

scholarly journals Experimental Investigation and Comparison of the Thermal Performance of Additively and Conventionally Manufactured Heat Exchangers

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 574
Author(s):  
Ana Vafadar ◽  
Ferdinando Guzzomi ◽  
Kevin Hayward
Keyword(s):  
Surface Roughness ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
High Efficiency ◽  
Cooling System ◽  
Fluid Dynamic ◽  
Dynamic Performance ◽  
Experimental Studies ◽  
Manufacturing Method ◽  
Industrial Sectors

Air heat exchangers (HXs) are applicable in many industrial sectors because they offer a simple, reliable, and cost-effective cooling system. Additive manufacturing (AM) systems have significant potential in the construction of high-efficiency, lightweight HXs; however, HXs still mainly rely on conventional manufacturing (CM) systems such as milling, and brazing. This is due to the fact that little is known regarding the effects of AM on the performance of AM fabricated HXs. In this research, three air HXs comprising of a single fin fabricated from stainless steel 316 L using AM and CM methods—i.e., the HXs were fabricated by both direct metal printing and milling. To evaluate the fabricated HXs, microstructure images of the HXs were investigated, and the surface roughness of the samples was measured. Furthermore, an experimental test rig was designed and manufactured to conduct the experimental studies, and the thermal performance was investigated using four characteristics: heat transfer coefficient, Nusselt number, thermal fluid dynamic performance, and friction factor. The results showed that the manufacturing method has a considerable effect on the HX thermal performance. Furthermore, the surface roughness and distribution, and quantity of internal voids, which might be created during and after the printing process, affect the performance of HXs.

Sub-half-wavelength atom localization via two standing waves

2017 ◽  
Vol 95 (3) ◽  
pp. 305-309 ◽  
Author(s):  
Haifeng Xu
Keyword(s):  
Quantum Interference ◽  
High Efficiency ◽  
Quantum Information Processing ◽  
One Dimensional ◽  
Half Wavelength ◽  
Potential Applications ◽  
Phase Gate ◽  
Quantum Error ◽  
Excited State Population ◽  
Atom Localization

We present a simple scheme of high-efficiency one-dimensional (1D) atom localization via manipulation of excited state population in a four-level inverted-Y atomic system. Because of the joint quantum interference induced by the two standing-wave fields, the 100% detecting probability of the atom in the subwavelength domain appears when the corresponding conditions are satisfied. The proposed scheme may open a promising way to achieve high-precision and high-efficiency 1D atom localization, which provides some potential applications to spatially selective single-qubit phase gate, entangling gates, and quantum error correction for quantum information processing.

Sintering and Hot-Pressing of Ti2AlC Obtained by SHS Process

2010 ◽  
Vol 63 ◽  
pp. 282-286 ◽  
Author(s):  
Leszek Chlubny ◽  
Jerzy Lis ◽  
Mirosław M. Bućko
Keyword(s):  
Hot Pressing ◽  
High Efficiency ◽  
Layer Structure ◽  
Low Cost ◽  
Max Phases ◽  
Fine Powders ◽  
High Temperature Synthesis ◽  
Low Energy Consumption ◽  
Potential Applications ◽  
Xrd Method

Some of ternary materials in the Ti-Al-C system are called MAX-phases and are characterised by heterodesmic layer structure. Their specific structure consisting of covalent and metallic chemical bonds influence its semi-ductile features locating them on the boundary between metals and ceramics, which may lead to many potential applications, for example as a part of a ceramic armour. Ti2AlC is one of this nanolaminate materials. Self-propagating High-temperature Synthesis (SHS) was applied to obtain sinterable powders of Ti2AlC Utilization of heat produced in exothermal reaction in adiabatic conditions to sustain process until all substrates are transformed into product is one of the advantages of the method that result in low energy consumption and low cost combined with high efficiency. Different substrates were used to produce fine powders of ternary material. Phase compositions of obtained powder were examined by XRD method. Than selected powders were used for sintering in various temperature both in a presureless sintering and hot-pressing in argon atmosphere. Properties and phase composition of obtained products were examined.

Tailored 3D printed micro-crystallization chip for versatile and high-efficiency droplet evaporative crystallization

Lab on a Chip ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 767-777 ◽  
Author(s):  
Mingguang Han ◽  
Jin Li ◽  
Gaohong He ◽  
Meng Lin ◽  
Wu Xiao ◽  
...  
Keyword(s):  
High Efficiency ◽  
Interfacial Area ◽  
Drug Preparation ◽  
Evaporative Crystallization ◽  
Potential Applications ◽  
3D Printed

Droplet evaporative crystallization on a micro-structured platform with limited interfacial area has potential applications in crystallization theory, bioengineering, and particle drug preparation.

scholarly journals The Development of Functional Non-Viral Vectors for Gene Delivery

2019 ◽  
Vol 20 (21) ◽  
pp. 5491 ◽  
Author(s):  
Patil ◽  
Gao ◽  
Lin ◽  
Li ◽  
Dang ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Targeted Delivery ◽  
Viral Vectors ◽  
High Efficiency ◽  
Transfection Efficiency ◽  
Cationic Lipids ◽  
Gene Vectors ◽  
Potential Applications ◽  
Low Toxicity ◽  
Low Cytotoxicity

Gene therapy is manipulation in/of gene expression in specific cells/tissue to treat diseases. This manipulation is carried out by introducing exogenous nucleic acids, such as DNA or RNA, into the cell. Because of their negative charge and considerable larger size, the delivery of these molecules, in general, should be mediated by gene vectors. Non-viral vectors, as promising delivery systems, have received considerable attention due to their low cytotoxicity and non-immunogenicity. As research continued, more and more functional non-viral vectors have emerged. They not only have the ability to deliver a gene into the cells but also have other functions, such as the performance of fluorescence imaging, which aids in monitoring their progress, targeted delivery, and biodegradation. Recently, many reviews related to non-viral vectors, such as polymers and cationic lipids, have been reported. However, there are few reviews regarding functional non-viral vectors. This review summarizes the common functional non-viral vectors developed in the last ten years and their potential applications in the future. The transfection efficiency and the transport mechanism of these materials were also discussed in detail. We hope that this review can help researchers design more new high-efficiency and low-toxicity multifunctional non-viral vectors, and further accelerate the progress of gene therapy.

Sign in / Sign up

Export Citation Format

Share Document