5 research outputs found
Rational Micro/Nanostructuring for Thin-Film Evaporation
Heat
management in electronics and photonics devices is a critical
challenge impeding accelerated breakthrough in these fields. Among
approaches for heat dissipation, thin-film evaporation with micro/nanostructures
has been one of the most promising approaches that can address future
technological demand. The geometry and dimension of these micro/nanostructures
directly govern the interfacial heat flux. Here, through theoretical
and experimental analysis, we find that there is an optimal dimension
of micro/nanostructures that maximizes the interfacial heat flux by
thin-film evaporation. This optimal criterion is a consequence of
two opposing phenomena: nonuniform evaporation flux across a liquid
meniscus (divergent mass flux near the three-phase contact line) and
the total liquid area exposed for evaporation. In vertical micro/nanostructures,
the optimal width-to-spacing ratio is 1.27 for square pillars and
1.5 for wires (e.g., nanowires). This general criterion is independent
of the solid material and the thermophysical properties of the cooling
liquid. At the optimal width-to-spacing ratio, as the density of the
pillars increases (i.e., smaller pillar’s dimension), the interfacial
heat flux increases. This study provides a direction for rational
development of micro/nanostructures for thin-film evaporation and
paves the path for development of high-performance thermal management
systems
Decoupled Hierarchical Structures for Suppression of Leidenfrost Phenomenon
Thermal management of high temperature
systems through cooling
droplets is limited by the existence of the Leidenfrost point (LFP),
at which the formation of a continuous vapor film between a hot solid
and a cooling droplet diminishes the heat transfer rate. This limit
results in a bottleneck for the advancement of the wide spectrum of
systems including high-temperature power generation, electronics/photonics,
reactors, and spacecraft. Despite a long time effort on development
of surfaces for suppression of this phenomenon, this limit has only
shifted to higher temperatures, but still exists. Here, we report
a new multiscale decoupled hierarchical structure that suppress the
Leidenfrost state and provide efficient heat dissipation at high temperatures.
The architecture of these structures is composed of a nanomembrane
assembled on top of a deep micropillar structure. This architecture
allows to independently tune the involved forces and to suppress LFP.
Once a cooling droplet contacts these surfaces, by rerouting the path
of vapor flow, the cooling droplet remains attached to the hot solid
substrates even at high temperatures (up to 570 °C) for heat
dissipation with no existence of Leidenfrost phenomenon. These new
surfaces offer unprecedented heat dissipation capacity at high temperatures
(2 orders of magnitude higher than the other state-of-the-art surfaces).
We envision that these surfaces open a new avenue in thermal management
of high-temperature systems through spray cooling
Decoupled Hierarchical Structures for Suppression of Leidenfrost Phenomenon
Thermal management of high temperature
systems through cooling
droplets is limited by the existence of the Leidenfrost point (LFP),
at which the formation of a continuous vapor film between a hot solid
and a cooling droplet diminishes the heat transfer rate. This limit
results in a bottleneck for the advancement of the wide spectrum of
systems including high-temperature power generation, electronics/photonics,
reactors, and spacecraft. Despite a long time effort on development
of surfaces for suppression of this phenomenon, this limit has only
shifted to higher temperatures, but still exists. Here, we report
a new multiscale decoupled hierarchical structure that suppress the
Leidenfrost state and provide efficient heat dissipation at high temperatures.
The architecture of these structures is composed of a nanomembrane
assembled on top of a deep micropillar structure. This architecture
allows to independently tune the involved forces and to suppress LFP.
Once a cooling droplet contacts these surfaces, by rerouting the path
of vapor flow, the cooling droplet remains attached to the hot solid
substrates even at high temperatures (up to 570 °C) for heat
dissipation with no existence of Leidenfrost phenomenon. These new
surfaces offer unprecedented heat dissipation capacity at high temperatures
(2 orders of magnitude higher than the other state-of-the-art surfaces).
We envision that these surfaces open a new avenue in thermal management
of high-temperature systems through spray cooling
Decoupled Hierarchical Structures for Suppression of Leidenfrost Phenomenon
Thermal management of high temperature
systems through cooling
droplets is limited by the existence of the Leidenfrost point (LFP),
at which the formation of a continuous vapor film between a hot solid
and a cooling droplet diminishes the heat transfer rate. This limit
results in a bottleneck for the advancement of the wide spectrum of
systems including high-temperature power generation, electronics/photonics,
reactors, and spacecraft. Despite a long time effort on development
of surfaces for suppression of this phenomenon, this limit has only
shifted to higher temperatures, but still exists. Here, we report
a new multiscale decoupled hierarchical structure that suppress the
Leidenfrost state and provide efficient heat dissipation at high temperatures.
The architecture of these structures is composed of a nanomembrane
assembled on top of a deep micropillar structure. This architecture
allows to independently tune the involved forces and to suppress LFP.
Once a cooling droplet contacts these surfaces, by rerouting the path
of vapor flow, the cooling droplet remains attached to the hot solid
substrates even at high temperatures (up to 570 °C) for heat
dissipation with no existence of Leidenfrost phenomenon. These new
surfaces offer unprecedented heat dissipation capacity at high temperatures
(2 orders of magnitude higher than the other state-of-the-art surfaces).
We envision that these surfaces open a new avenue in thermal management
of high-temperature systems through spray cooling
Antiscaling Magnetic Slippery Surfaces
Scale
formation is a common problem in a wide range of industries such as
oil and gas, water desalination, and food processing. Conventional
solutions for this problem including mechanical removal and chemical
dissolution are inefficient, costly, and sometimes environmentally
hazardous. Surface modification approaches have shown promises to
address this challenge. However, these approaches suffer from intrinsic
existence of solid–liquid interfaces leading to high rate of
scale nucleation and high adhesion strength of the formed scale. Here,
we report a new surface called magnetic slippery surface in two forms
of Newtonian fluid (MAGSS) and gel structure (Gel-MAGSS). These surfaces
provide a liquid–liquid interface to elevate the energy barrier
for scale nucleation and minimize the adhesion strength of the formed
scale on the surface. Performance of these new surfaces in both static
and dynamic (under fluid flow) configurations is examined. These surfaces
show superior antiscaling properties with an order of magnitude lower
scale accretion compared to the solid surfaces and offer longevity
and stability under high shear flow conditions. We envision that these
surfaces open a new path to address the scale problem in the relevant
technologies