Nanodiamond Colloids heat transfer behavior in electronics thermal management – an experimental study

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.

KEYWORDS:

• Functionalized nanodiamond
• Nanodiamond colloid
• Convective heat transfer
• Electronic cooling
• Variable frequency drive
• Viscosity

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

c_p 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

$\dot{q}$ 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

$\dot{V}$ 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