Fast mass transport-assisted convective heat transfer through a multi-walled carbon nanotube array

Abstract

The recently reported fast mass transport through nanochannels provides a unique opportunity to explore nanoscale energy transport. Here we experimentally investigated the convective heat transport of air through vertically aligned multi-walled carbon nanotubes (VAMWNTs). The flow through the unit cell, defined as an interstitial space among four adjacent nanotubes (hydraulic diameter = 84.9 nm), was in the transition (0.62 Knudsen number 0.78) and creeping flow (3.83 x 10(-5) Reynolds number (Re) 1.55 x 10(-4)) regime. The constant heat flux (0.102 or 0.286 W m(-2)) was supplied by a single-mode microwave (2.45 GHz) instantly heating the VAMWNTs. The volume flow rate was two orders of magnitude greater than the Hagen-Poiseuille theory value. The experimentally determined convective heat transfer coefficient (h, 3.70 x 10(-4)-4.01 x 10(-3) W m(-2) K-1) and Nusselt number (Nu, 1.17 x 10(-9)-1.26 x 10(-8)) were small partly due to the small Re. A further increase in Re (2.12 x 10(-3)) with the support of a polytetrafluoroethylene mesh significantly increased h (5.48 x 10(-2) W m(-2) K-1) and Nu (2.37 x 10(-7)). A large number of nanochannels in a given cross-section of heat sinks may enhance the heat dissipation significantly. © The Royal Society of Chemistry 2018