MIT researchers help improve plant efficiency
Massachusetts,
US- Research by a team at the Massachusetts Institute of Technology (MIT)
has provided insights into how condensation forms on a surface.
According to the group, the results could
significantly increase the efficiency of the next generation of power and
desalination plants.
Typically, on a condensing surface, droplets grow larger while adhering to the
material through surface tension. When they are large enough, gravity overcomes
the surface tension and droplets rain down into a container.
MIT mechanical engineering graduate student,
Nenad Miljkovic explained that there are ways to make droplets fall from a
surface at smaller sizes, enabling the resulting transfer of heat to be much
more efficient.
One mechanism is a surface pattern that
encourages adjacent droplets to merge together. As they do so, energy is
released, which causes a recoil from the surface.
By incorporating measurements of droplet growth
rates and heat transfer into computer models, the MIT team was able to compare
a variety of approaches to developing a surface pattern.
The researchers found one promising option was to
create a forest of pillars on a surface at nanoscale. They reported that
droplets tended to sit on top of the pillars while only locally wetting the
surface, minimising the area of contact and facilitating easier release.
“We showed that our surfaces improved heat transfer by up to 71% [compared to flat, non-wetting surfaces currently used only in high-efficiency condenser systems] if you tailor them properly,” said Miljkovic.
“We showed that our surfaces improved heat transfer by up to 71% [compared to flat, non-wetting surfaces currently used only in high-efficiency condenser systems] if you tailor them properly,” said Miljkovic.
The enhanced efficiency could improve the rate of
water production in plants that produce drinking water from seawater, or in
solar-power systems.
A similar system could improve heat removal in
computer chips, which is often based on internal evaporation and recondensation
of a heat-transfer liquid through a device called a heat pipe.
MIT is now extending its work to find ways of manufacturing these surfaces rapidly and cheaply on an industrial scale.
MIT is now extending its work to find ways of manufacturing these surfaces rapidly and cheaply on an industrial scale.
