12-10-2012, 04:34 PM
An Introduction to the NanoFluid
Nano Fluid1[1].pdf (Size: 2.8 MB / Downloads: 498)
Introduction
Nanofluids are a relatively new class of fluids which consist of a
base fluid with nano-sized particles (1–100 nm) suspended within
them. It is introduced by choi on Argonne National Laboratory at
1995.
Advantages of nanofluids
Compared to conventional solid-liquid suspensions for heat transfer
intensifications, properly engineered thermal nanofluids possess the
following advantages:
1. High specific surface area and therefore more heat transfer
surface between particles and fluids.
2. High dispersion stability with predominant Brownian motion of
particles.
3. Reduced pumping power as compared to pure liquid to achieve
equivalent heat transfer intensification.
4. Reduced particle clogging as compared to conventional
slurries, thus promoting system miniaturization.
5. Adjustable properties, including thermal conductivity and
surface wettability, by varying particle concentrations to suit
different applications.
Production of nanoparticles and nanofluids
Nanoparticles
Physical methods (Grinding methods, Inert Gas Condensation, …)
Chemical methods (Chemical precipitation, Chemical Vapor Deposition,
Micro-emulsions, spray pyrolysis, thermal spraying,…)
Nanofluids
The one-step method
simultaneously makes and disperse the nanoparticles directly into a base fluid
prevent oxidation of pure metal particles
non commercial
The two-step method
produced the nanoparticles and dispersed them into a base fluid
Research and industrial applications
Applications of nanofluids
•Transportation (Engine cooling/vehicle thermal management)
•Electronics cooling
•Defense
•Space
•Nuclear systems cooling
•Heat exchanger
•Biomedicine
•Other applications (heat pipes, fuel cell, Solar water heating,
chillers, domestic refrigerator, Diesel combustion, Drilling,
Lubrications, Thermal storage,…)
Challenges of nanofluids
•lack of agreement of results obtained by different researchers
•lack of theoretical understanding of the mechanisms
responsible for changes in properties
•poor characterization of suspensions
•stability of nanoparticles dispersion
•Increased pressure drop and pumping power
•Nanofluids thermal performance in turbulent flow and fully
developed region
•Higher viscosity, Lower specific heat
•High cost of nanofluids
•Difficulties in production process