A research team led by Bo Feng from the Georgia Institute of Technology has doubled the heat transfer rate of a metal surface by applying an alumina nano-coating over it.
The research team utilized an atomic layer deposition (ALD) method for controlling the thickness of the alumina coating. Pool boiling is a highly efficient heat transfer technique used widely for heating the contents of a container through heat flux. However, the efficiency of pool-boiling gets affected at a critical point upon which a solid surface becomes too hot.
Feng explained that thermal management of electronics can be advanced and efficiency of several energy systems can be improved by delaying this critical flux. In boiling state, large amounts of heat are carried away from a solid surface by bubbles but these bubbles also behave as an insulator, thus disrupting heat transfer by preventing the surface from getting rewetted by the liquid.
The alumina nano-coating has a high water affinity, thus enabling the solid surface to get rewetted rapidly. This is the major reason for the improvement of heat transfer, informed Feng. The additional alumina nano-layer increases the overall heat transfer rather than increasing the thermal resistance.
G.P. "Bud" Peterson, Director of the Two-Phase Heat Transfer Lab of the Georgia Institute of Technology, explained that the potential contribution of this study depends on customizing the wettability of solid surfaces at nano-scale, thus vastly increasing the transfer of heat during pool boiling. This is particularly promising for applications that use nanowire arrays or nanotubes.
The combination of nano-coating by ALD method and nanowire arrays and/or nanotubes may improve the efficiency of pool boiling even further. The research findings are reported in Applied Physics Letters, a journal of the American Institute of Physics.
Source: http://www.aip.org