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Transcript of CNT
What we are going to talk About ?
Introduction to Carbon Nanotube
Experiment showing the effect of CNT
Influence of carbon nanotubes on deionized water pool boiling performances
University Grenoble France
Rémi Bertossi - Nadia Caney - Jean Antoine Gruss
Received 2 September 2014
Received in revised form 30 October 2014
Accepted 31 October 2014
Available online 7 November 2014
Three parameters can Influence Results
the size of the bubbles
the bubble emission frequency
the number of nucleation sites
For a CNT coated surface
bubbles are observed to be smaller
emission frequency seems to be improved
the number of sites appears to be enhanced.
CNT length influence
For a given heat flux
Superheat is reduced
length of CNT augments
Temperature reduction can reach around 40%
This phenomenon reveals a
better thermal stability
when heat flux augments.
CNT length influence
Heat transfer coefficient
increases with the
specific and interesting result
consists in the evolution of the variation of heat transfer as a function of CNT length
This evolution is quite
0 and 5
lm but the c
urve does not increase so greatly
between 5 and 10 mim
of performance depending on
CNT lengths should exist.
CNT growth techniques on surfaces
can be very different and depend on materials and geometries of desired nanotubes. These techniques are
o they are achieved by specialized laboratories
A major interest of CNT and NW during boiling is their a
bility to increase the critical heat flux (CHF) accordingly to their height
(2011) and R. Chen (2009)
very high increase of CHF
water boiling on silicon NW
It has been shown that
CHF can be multiplied by a factor two
compared to tests led on a plane sample.
increase of the capillarity
in the NW forest, which permits a vaporization of a higher amount of liquid
which are potential nucleation sites.
What is Carbon and what its forms ?
Carbon is one of the most important elements in our planet. Pure carbon is known to us as
, if arranged one way in
arranged in another
, all the carbon atoms have strong chemical bonds to
four other carbon atoms are arranged tetrahedrally
A diamond is
and is formed under
very high temperatures and pressure
All the carbon atoms have strong chemical bonds to
three other carbon atoms
hold the sheets together in stacks that can slide past each other easily
, with a
feel and is formed on
heating coke or coal
interpretation is also shared by Z. Yao, Y.W. Lu
The authors have studied
copper and silicon NW height effects on water
pool boiling on silicon surfaces
SEM pictures have shown that the
larger the NW are, the more the micro cavities are created
These results are totally in agreement with Chen (2009) results
Carbon nanotubes are composed of
sheet of carbon atoms
, which would look like a sheet of
. If you
roll that sheet into a tube
, you'd have a carbon
Carbon nanotube properties depend on how you roll the sheet
In other words, even though all carbon nanotubes are made of carbon, they can be
very different from one another
how you align the individual atoms
Carbon Nanotubes can be categorized by their structures
Single-wall Nanotubes (
Single Tube rolled from graphene sheet
Multi-wall Nanotubes (
of SWNT graphene sheets
Boiling performances of CNT have been studied by
J.P. McHale, S.V. Garimella
) Observed that
CNT are hydrophobic
contrary to copper or silicon
. McHale studied these structures using
different surfaces have been tested: a
bare copper sample
40 lm-long CNT copper coated surface
For deionized water,
CNT allows a superheat decrease for a given heat flux
compared to the
Heat transfer coefficients as well as
are greatly improved
Trapping of gas or vapor
enhancement of capillarity
increase of total heat exchange surface area
Carbon Nanotubes can be categorized by their wrapping Methods
Literature Survey (Conclusion)
The previous results are quite
difficult to compare
because of the
numerous variations of test conditions
nanotubes material and height
. . .).
However, results tend to show that
CNT allows a superheat decrease
at nucleation incipience
Heat transfer coefficient and critical heat flux
Coverage by CNT
Most of authors explain performances enhancement by
creation of numerous nucleation sites
thanks to the wetted CNT gathering.
The Expermient Process
The sample is a
stainless steel surface
CNT growth process has been developed in order
to coat both sides of the samples
CNT thicknesses on the two sides of the sample are
3.5 mim, 5 mim and 10 mim high
iameter is 5 nm
The tested surface is made of
Faces of 100 mm × 5 mm are brazed on two pins
power to heat the surface
maintained in the tank at a temperature of 85 C
The fluid flows at a
very very low flow rate
to avoid forced convection influence
measurements show that surfaces previously
hydrophobic become less hydrophobic or even hydrophilic
after boiling experiments.
CHF is Impoved to nearly 50%
from the bare sample
For a given heat flux, this
reduction in Temperature Difference
can be as high as
40% for 10 lm long
Augmentation of the
number of active nucleation sites
reduction of the bubbles size
 H.S. Ahn, N. Sinha, M. Zhang, D. Banerjee, S.K. Fang, R.H. Baughman, Pool boiling experiments on multiwalled carbon nanotube (MWCNT) forests, J. Heat Transfer 128 (2011) 1335–1342.
 Z. Yao, Y.W. Lu, S.G. Kandlikar, Effects of nanowires height on pool boiling performance of water on silicon chips, Int. J. Therm. Sci. 50 (2011) 2084–2090.
 S. Ujereh, T. Fisher, I. Mudawar, Effects of carbon nanotube arrays on nucleate pool boiling, Int. J. Heat Mass Transfer 50 (2007) 4023–4038.
 M.C. Lu, R. Chen, V. Srinivasan, V.P. Carey, A. Majumdar, Critical heat flux on pool boiling on Si nanowire array-coated surfaces, Int. J. Heat Mass Transfer 54 (2011) 5359–5367.
 R. Chen et al., Nanowires for enhanced boiling heat transfer, Nano Lett. 9 (2009) 548–553.
 J.P. McHale, S.V. Garimella, T.S. Fisher, G.A. Powell, Pool boiling performance comparison of smooth end sintered surfaces with and without carbon nanotubes, Nanoscale Microscale Thermophys. Eng. 15 (3) (2011) 133–150.
 Y. Im, C. Dietz, S.S. Lee, Y. Joshi, Flower-like CuO nanostructures for enhanced surfaces, Nanoscale Microscale Thermophys. Eng. 16 (3) (2012) 145–153.
 H. Hwang, J. Yoon, T. Yeo, H.H. Son, U. Jeong, G. Jeun, W. Choi, S.J. Kim, Enhanced critical heat flux with single-walled carbon nanotubes bonded on metal surfaces, Exp. Therm. Fluid Sci. 60 (2015) 138–147, http://dx.doi.org/ 10.1016/j.expthermflusci.2014.08.015.
 J. Dijon, P.D. Szkutnik, A. Fournier, T. Goislard de Monsabert, H. Okuno, E. Quesnel, V. Muffato, E. De Vito, N. Bendiab, A. Bogner, N. Bernier, How to switch from a tip to base growth mechanism in carbon nanotube growth by catalytic chemical vapor deposition, Carbon 48 (2010) 3953–3963.
 J. Dijon, A. Fournier, P.D. Szkutnik, H. Okuno, C. Jayet, M. Fayolle, Carbon nanotubes for interconnects in future integrated circuits: the challenge of the density, Diamond Relat. Mater. 19 (5–6) (2010) 382–388.
 H.T. Phan, N. Caney, P. Marty, S. Colasson, J. Gavillet, Surface wettability control by nanocoating; the effects on pool boiling heat transfer and nucleation mechanism, Int. Heat Mass Transfer 52 (23–24) (2009) 5459–5471.
 Y. Nam, Y.S. Ju, Bubble nucleation on hydrophobic islands provides evidence to anomalously high contact angle of nanobubbles, Appl. Phys. Lett. 93 (2008) 103115.
 H.T. Phan, N. Caney, P. Marty, S. Colasson, J. Gavillet, Flow boiling of water on
nanocoated surfaces in a microchannel, J. Heat Transfer 134 (2) (2012).
Fullerenes are a form of
that is neither graphite nor diamond
. They consist of a
spherical, ellipsoid, or cylindrical
arrangement of dozens of carbon atoms.
molecules consist of
60, 70, or more carbon atoms
, unlike diamond and graphite, the more familiar forms of carbon.
fullerenes are also called
A spherical fullerene looks like a
ones are called
environmental degradation issues common to
metals—thermal expansion and contraction
Properties of Fullerene
Nanotubes are members of the
They are hollow structure with the walls formed by
CNTs typically have diameters ranging from
1 nm up to 50nm
. lengths are
A very recent study by
G.H. Seo, H. Hwang, J. Yoon(2014)
shows, as previous mentioned by the authors, that bonding a film of SWCNTs to metal surfaces
increases critical heat flux (by an average of 51% compared to bare surfaces
The authors also explain the increase of critical heat flux thanks to increased capillary forces due to a better porosity
Surface temperature Ts
can be estimated from measurements of the electrical resistance by using an
electrical resistance/temperature calibration curve
up to 100
C for one hour to be
Joule effect is imposed
heat transfer coefficient
can be easily determined
The local boiling heat transfer coefficient is defined as
Wettability of CNT
Static contact angles of the CNT coated surface
s have been measured for different lengths of CNT.
CNT Contact angle
Higher than 90
Heat transfer intensification by CNT
given heat flux
, boiling occurs at a
given heat flux
, on coated surface,
heat transfer coefficient
enhancement can reach
compared to bare surface
Let us notice that experimental
uncertainties are about 15%.