In this work, electrically controlled fully reversible wetting-dewetting transitions on superhydrophobic nanostructured surfaces have been demonstrated. Droplet behavior can be reversibly switched between the Cassie-Baxter state and hydrophilic Wenzel by application of electrical voltage current. The nature reversibility mechanism was studied both experimentally theoretically. reported results provide a new method dynamically controlling liquid-solid interactions.

Galinstan, a gallium, indium, and tin eutectic, may be exploited for enhanced cooling of microelectronics because its favorable thermophysical properties. A careful evaluation potential, however, has not been undertaken. Provided here is first-order model to compute the total (i.e., caloric plus conjugate conduction convection) thermal resistance galinstan-based heat sinks. Geometrically optimized minichannel sinks with rectangular channels surface area enhancement minigap, i.e., single...

Superhydrophobic surfaces are known to exhibit reduced viscous drag due slip associated with a layer of air trapped at the liquid-solid interface. It is expected that this will lead turbulent skin-friction in external flows higher Reynolds numbers both laminar and regimes. Results presented from experiments exploring effect. Large-area test have been fabricated tested water tunnel, measuring transitional regimes velocities up 1.4 m/s. Drag reduction approximately 50% observed for flow. Lower...

We analytically and numerically consider the hydrodynamic thermal transport behavior of fully developed laminar flow through a superhydrophobic (SH) parallel-plate channel. Hydrodynamic slip length, length heat flux are prescribed at each surface. first develop general expression for Nusselt number valid asymmetric velocity profiles. Next, we demonstrate that, in limit Stokes near surface an adiabatic shear-free liquid–gas interface, both lengths can be found by redefining existing solutions...

The power density of portable electronic devices continues to increase because packaging advances reduce their size even as features are added and enhanced. Designing thermal management systems accommodate steady-state conditions opposed fixed duty cycles can substantially cost, size, weight. feasibility transient handsets using phase change materials (PCMs) was experimentally investigated an ABS handset mock-up. At selected intervals time, the nonuniform case temperature measured infrared...

A novel framework for the one-dimensional analysis of a thermoelectric module (TEM) in which controlled and uncontrolled sides rather than cold hot it are defined is introduced. Next, heat conduction TEM considered within this framework. Then, operating modes (cooling, generation, etc.) means to compute mode from minimal set parameters provided. Refrigeration depth illustrate application Finally, extended TEMs subjected boundary conditions third kind. Novel aspects indicated Conclusions.

Microchannel heat sinks are a relevant thermal management technology because the combination of surface area enhancement and small length scales results in low wall-to-bulk temperature differences. Previously, resistance 0.09°C/W was achieved when flux 790 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> imposed on 1 cm × footprint portion 400-μm-thick Si substrate utilizing single-phase water-based microchannel cooling 214 kPa...

Analyses of microchannel and microgap cooling show that galinstan, a recently developed nontoxic liquid metal melts at −19 °C, may be more effective than water for direct electronics. The thermal conductivity galinstan is nearly 28 times water. However, since the volumetric specific heat about half its viscosity 2.5 water, caloric, rather convective, resistance dominant. We analytically investigate effect using structured surfaces (SSs) to reduce overall galinstan-based in laminar flow...

The geometry of the semiconductor pellets (i.e., number them and their height) within thermoelectric modules (TEMs) operating in generation mode is optimized order to maximize either performance output power) or conversion efficiency for a specified performance. This accomplished resistive load on TEM as function its effective footprint, i.e., sum cross-sectional areas pellets. resistances which when pellet are also provided. analyses performed absence then presence electrical contact...

Gas-assisted evaporative cooling (GAEC), its advantages in thermal packaging of microelectronics, and implementation a prototype high-performance computer module, are described. Attention is then turned to theoretical considerations the flow gas-liquid-vapor mixtures narrow, parallel plate channels, design operation an appropriate experimental apparatus. Next, results for wall temperature, heat-transfer coefficients, pressure drops presented compared predictions. It shown that this novel...

The design and characterization of monolithic heat sinks, which can take the form complex structures, is reported. designs were conceived to augment transport for enhanced air cooling by exploiting clearly identified physical mechanisms, i.e., streaming flow through a 2-D array polygonal ducts, introducing flow-obstacle-induced local mixing, hydrodynamic instabilities sustain unsteadiness. Fabrication these unconventional was achieved 3-D printing plastic patterns converting them into copper...

We investigate forced convection in a parallel-plate-geometry microchannel with superhydrophobic walls consisting of periodic array ridges aligned parallel to the direction Poiseuille flow. In dewetted (Cassie) state, liquid contacts channel only at tips ridges, where we apply constant-heat-flux boundary condition. The subsequent hydrodynamic and thermal problems within are then analysed accounting for curvature liquid–gas interface (meniscus) using perturbation, assuming small deflection...

For a thermoelectric module (TEM) operating in refrigeration mode, the cooling flux provided by it, its coefficient of performance and voltage per unit footprint are key parameters. They here as function temperatures on both sides TEM, current flow through electrical contact resistance at interconnects geometry, material properties packing density pellets. The pellet heights which maximize TEM (i.e., they can accommodate for specified temperature difference) or efficiency performance)...

Thermoelectric refrigeration offers advantages (e.g., no moving parts) over other technologies. However, because maximum performance (i.e., heat load for a specified temperature drop below ambient or vice versa) and efficiency coefficient of performance) are relatively low, it is important to realize them. It shown that the cross-sectional area semiconductor pellets in thermoelectric module (TEM) operating mode does not affect its efficiency, but may be sized tune current voltage. Then,...

Abstract Solubility and deposition rate experiments were performed in aqueous sodium sulfate potassium solutions at elevated temperatures pressures typical of the supercritical water oxidation (SCWO) process. The test cell was a six‐port chamber form modified 1.91 cm (3/4 in.) diameter Swagelok cross with an internally heated cylinder (hot finger) mounted its center. Solubilities acquired by maintaining surface temperature hot finger about 10°C above gradually increasing bulk solution...

The effects of gas viscosity, meniscus protrusion, and channel aspect ratio are captured in a numerical model for flow through textured microchannels. Spectral accuracy the laminar field is obtained by using Chebyshev collocation method with domain decomposition singularity subtraction.

We semi-analytically capture the effects of evaporation and condensation at menisci on apparent thermal slip lengths for liquids suspended in Cassie state ridge-type structured surfaces using a conformal map convolution. An isoflux boundary condition is prescribed solid–liquid interfaces constant heat transfer coefficient or isothermal one menisci. assume that gaps between ridges, where vapor phase resides, are closed systems; therefore, net rates mass across zero. The reduction length due...

We compute the apparent hydrodynamic slip length for (laminar and fully developed) Poiseuille flow of liquid through a heated parallel-plate channel. One side channel is textured with parallel (streamwise) ridges opposite one smooth. On channel, in Cassie state. No-slip constant heat flux boundary conditions are imposed at solid–liquid interfaces along tips ridges, menisci between considered to be flat adiabatic. The smooth subjected no-slip adiabatic conditions. account streamwise...

The flow rate of a pressure-driven liquid through microchannel may be enhanced by texturing its no-slip boundaries with grooves aligned the flow. In such cases, contain vapour and/or an inert gas and is trapped in Cassie state, resulting (apparent) slip. flow-rate enhancement benefit to different applications including increase throughput lab-on-a-chip, reduction thermal resistance associated metal cooling microelectronics. At any given cross-section, meniscus takes approximate shape...

In this work, we discuss dynamic electrical control of the wetting behavior liquids on nanostructured surfaces spanning entire possible range from superhydrophobic to nearly complete wetting. It is demonstrated that a droplet liquid can be reversibly switched between “rolling ball” state and hydrophilic immobile by application voltage current. The nature transition mechanism studied both experimentally theoretically. reported results provide novel methods manipulating at microscale.

A procedure to optimize the height and number of semiconductor pellets in a thermoelectric generator (TEG) embedded thermal resistance network maximize its performance (output power) or efficiency is provided. Prescribed are thermophysical properties pellets, total footprint material, temperature difference across system, relevant resistances, electrical contact at interconnects between load resistance. When maximized, also prescribed it implied that value below maximum. The imposed TEG...