Droplet Dynamics on a Wettability Patterned Surface during Spray Impact

Wettability patterning of a surface is a passive method to manipulate the flow and heat transport mechanism in many physical processes and industrial applications. This paper proposes a rational wettability pattern comprised of multiple superhydrophilic wedges on a superhydrophobic background, which can continuously remove the impacted spray droplets from the horizontal surface. We observed that the spray droplets falling on the superhydrophilic wedge region spread and form a thin liquid film, which is passively transported away from the surface. However, most of the droplets falling on the superhydrophobic region move towards the wedge without any flooding. The physics of the passive transport of the liquid film on a wedge is also delved into using numerical modelling. In particular, we elucidate the different modes of droplet transport in the superhydrophobic region and the interaction of multiple droplets. The observed droplet dynamics could have profound implications in spray cooling systems and passive removal of liquid from a horizontal surface. This study’s findings will be beneficial for the optimization of efficient wettability patterned surfaces for spray cooling application.

Irreversibility analysis of nanofluid flow in a vertical microchannel with the influence of particle shape

Augmentation of thermal performance in heat transfer system has become research hotspot nowadays. Numerous techniques are carried out to pick up the effective heat transport mechanism for designing high efficient thermal frameworks which has extensive practical uses in industrial process. In the current study, mixture model has been implemented for better describing the characteristics of nanoparticles in a vertical microchannel. The nondimensional equations are computed by using Runge Kutta Fehlberg method. Effect of heat source, buoyancy force and convective boundary on the thermal system has been demonstrated. The role of spheroidal nanoparticles on thermal conductivity of the conventional fluid has been examined. The causes of irreversibilities in a microchannel due to nanoliquid flow has been reported in the current research work. It is obtained that Aluminum foam has higher thermal field compared to Al2 O3. Entropy generation is reduced by lowering Eckert number and Grashof number. It is explored that nanofluid containing oblate shaped nanoparticels has higher thermal conductivity ratio.

Thermal evolution of rocky exoplanets with a graphite outer shell

Context. The presence of rocky exoplanets with a large refractory carbon inventory is predicted by chemical evolution models of protoplanetary disks of stars with photospheric C/O > 0.65, and by models studying the radial transport of refractory carbon. High-pressure high-temperature laboratory experiments show that most of the carbon in these exoplanets differentiates into a graphite outer shell. Aims. Our aim is to evaluate the effects of a graphite outer shell on the thermal evolution of rocky exoplanets containing a metallic core and a silicate mantle. Methods. We implemented a parameterized model of mantle convection to determine the thermal evolution of rocky exoplanets with graphite layer thicknesses up to 1000 km. Results. We find that because of the high thermal conductivity of graphite, conduction is the dominant heat transport mechanism in a graphite layer for long-term evolution (>200 Myr). The conductive graphite shell essentially behaves like a stagnant lid with a fixed thickness. Models of Kepler-37b (Mercury-size) and a Mars-sized exoplanet show that a planet with a graphite lid cools faster than a planet with a silicate lid, and a planet without a stagnant lid cools the fastest. A graphite lid needs to be approximately ten times thicker than a corresponding silicate lid to produce similar thermal evolution.

The Interiors of Jupiter and Saturn

Probing the interiors of the gaseous giant planets in our solar system is not an easy task. It requires a set of accurate measurements combined with theoretical models that are used to infer the planetary composition and its depth dependence. The masses of Jupiter and Saturn are 317.83 and 95.16 Earth masses (M⊕), respectively, and since a few decades, it has been known that they mostly consist of hydrogen and helium. The mass of heavy elements (all elements heavier than helium) is not well determined, nor are their distribution within the planets. While the heavy elements are not the dominating materials inside Jupiter and Saturn, they are the key to understanding the planets’ formation and evolutionary histories. The planetary internal structure is inferred from theoretical models that fit the available observational constraints by using theoretical equations of states (EOSs) for hydrogen, helium, their mixtures, and heavier elements (typically rocks and/or ices). However, there is no unique solution for determining the planetary structure and the results depend on the used EOSs as well as the model assumptions imposed by the modeler. Major model assumptions that can affect the derived internal structure include the number of layers, the heat transport mechanism within the planet (and its entropy), the nature of the core (compact vs. diluted), and the location (pressure) of separation between the two envelopes. Alternative structure models assume a less distinct division between the layers and /or a non-homogenous distribution of the heavy elements. The fact that the behavior of hydrogen at high pressures and temperatures is not perfectly known and that helium may separate from hydrogen at the deep interior add sources of uncertainty to structure models. In the 21st century, with accurate measurements of the gravitational fields of Jupiter and Saturn from the Juno and Cassini missions, structure models can be further constrained. At the same time, these measurements introduce new challenges for planetary modelers.

On the heat transport mechanism and entropy generation in a nozzle of liquid rocket engine using ferrofluid: A computational framework

An investigation has been carried out to demonstrate the performance of heat transfer and entropy generation in a regenerative cooling channel of a rocket engine. The Nanofluid flow in composition with ferrous nanoparticles has been utilized. Foremost equations are reduced to its non-dimensional shape using similarity renovation and sketched out using variational iterative method (VIM). Impression of the pertinent factors on hydrothermal performance has been brought forwarded via tables and graphs. Favourable comparison originates the basis of our present work. Result communicates that non-dimensional entropy generation amplifies in response to the parameter R and Bejan number intensifies for the parameter N. Significance or application of the present literature is to provide kerosene based ferrofluid as a coolant of rocket engine and how pertinent factors affect the entropy inside the system. Parametric study of this investigation will aid aerospace engineers to design the regenerative equipment in an effective way. Highlights Heat transfer and entropy generation in a nozzle of liquid rocket engine has been studied. Ferrous nanoparticles (CoFe2O4) with kerosene as base fluid have been used. Resulting equations has been solved using VIM. Non-dimensional entropy generation amplifies in response to the parameter R. Influence of ϕ reduces the Nusselt number.