Nanofluids are engineered colloidal suspensions of nanoparticles in a base fluid. In general the size of these nanoparticles vary from 1-100nm. The type of nanoparticle used is directly dependent on the enhancement of a required property of the base fluid. All physical mechanisms have a critical length scale, below which the physical properties of materials are changed. Therefore particles <100 nm exhibit properties that are considerably different from those of conventional solids. The noble properties of nanophase materials come from the relatively high surface area to volume ratio that is due to the high proportion of constituent atoms residing at the grain boundaries.
The thermal, mechanical, optical, magnetic, and electrical properties of nanophase materials are superior to those of conventional materials with coarse grain structures.
Due to the various speculated uses of nanofluids, it has become important to know more about their properties hence the objective of the present study is to investigate the forced convection of nanofluids.
The investigation was conducted by using double pipe heat exchanger in counter flow arrangement and the flow was turbulent. Water based nanofluids containing Al2O3 nanoparticles of various concentrations will be tested.
Suspended nano particles in conventional fluids are called nanofluids. Recent development of nanotechnology brings out a new heat transfer coolant called 'nanofluids'. These fluids exhibit larger thermal properties than conventional coolants Nanofluids can be considered to be the next-generation heat transfer fluids because they offer exciting new possibilities to enhance heat transfer performance compared to pure liquids.
Micrometer-sized particle-fluid suspensions exhibit no such dramatic enhancement. Nanofluids are expected to have superior properties compared to conventional heat transfer fluids, as well as fluids containing micro-sized metallic particles. The much larger relative surface area of nanoparticles, compared to those of conventional articles, not only significantly improves heat transfer capabilities, but also increases the stability of the suspensions.
In this paper an attempt has been made to discuss about the enhancement of thermal properties in nanofluids especially about the thermal conductivity.
The increase in thermal conductivity of the nanofluids in comparison with the
conventional heat transfer fluids is assumed to be because of the following mechanisms.
1) Brownian motion
2) Interfacial layer(nano layer)
3) Volume fraction
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