ABSTRACT
This article reports the heat transfer data obtained from experimenting a novel functionalized nanodiamond (fND) colloid. In this functionalization technique, the nanodiamonds are coupled with molecules of the host fluid via carboxylic bonds, leading to a de-aggregated and fully stable nanodiamond colloid. The colloid flows through a conduction cold plate where the system cools the electronic component, leading to the resultant heat dissipation. This surface modification on the fully functionalized nanodiamonds ensures ultimate stability of the colloidal suspension of nanodiamond particles. The heat transfer experiments were performed with different concentrations of nanodiamond (0.05, 0.10, and 0.20 wt.%) and under a turbulent flow regime (6,400 < Re < 17,000). The closed-loop heat transfer apparatus utilizes a pump equipped with a variable frequency drive to study the pumping power at various flow rates and fND concentrations. The experimental results of this paper show the remarkable effect of low-concentrated fND additives on enhancing the heat-transfer coefficient of the deionized water. The results show up to a 70% enhancement in the heat transfer coefficient compared to the base fluid at the same pumping power using a 0.20 wt.% fND. The nanodiamond colloid has shown no sedimentation after remaining stored over two years after synthesis.
Acknowledgments
The authors would like to thank International Femtoscience Inc., the Center for Energy Research, Center for Manufacturing Research, and Industrial Assessment Center at Tennessee Technological University for providing the funding materials and support for this study. The authors would also like to thank Dr Lino Costa from the Materials Dept. at the University of Tennessee Space Institute for providing the functionalized nanodiamond colloids for this research.
Disclosure Statement
The authors declared that there is no conflict of interest.
Nomenclature
cp Specific heat (J/kg∙K)
D The inner diameter of the test section tube (m)
DI Deionized water
DNF Diamond nanofluid
EDS Energy dispersive spectroscopy
EG Ethylene glycol
F Friction factor
fND Functionalized nanodiamond
h Heat transfer coefficient (W/m2∙K)
HP Horsepower
K Thermal conductivity (W/m∙K)
L Tube length (m)
ND Nanodiamond
PG Propylene glycol
Pr Prandtl number
Heat flow (W)
r Radius (m)
Re Reynolds number
T Temperature (°C), (K)
TC Thermal Conductivity (W/m∙K)
TEM Transient electron microscopy
Ū Fluid velocity (m/s)
UDD Ultra-dispersed diamond
Volumetric flow rate (m3/s), (LPM)
VFD Variable frequency drive
Greek Letters
Ε Tube roughness (m)
µ Dynamic viscosity (Pa s), (cP)
ρ Density (kg/m3), (g/cm3)
Ф Particle volume fraction
Ψ Particle mass fraction
Subscripts
app Applied
bf Base fluid
cp Cold plate
enh Enhancement
F Fluid
in Inlet
m Mean
ND Nanodiamond
nf Nanofluid
out Outlet