The following material is taken from an article titled "NanoFluids" by the Argonne National Laboratory, presented by Julian Edgar, appearing in Issue 462, January 11th, 2008 of the Australian online magazine Autospeed.
Reference:
http://autospeed.com/cms/A_109620/article.html
Introduction
Although it's long been known that the suspension of certain solid particles in a fluid will improve its heat transfer characteristics and make it more thermally efficient, until recently microparticles large enough to be visible to the naked eye were the smallest solids that could be created for this purpose. These microparticles, with a diameter one-thousand times larger than nanoparticles were so large that they would quicly settle out of the fluid and sink to the bottom of a pipe or tank. Even if the fluid containing the microparticles was kept circulating rapidly enough to prevent some of the settling, their relatively large mass would damage the walls of the pipe wearing them thin. Additionally, the abrasive particles would also quickly wear out pumps and bearings.
Creating Nanofluids
The use of nano-sized particles has overcome most of these problems. A nanometer (nm) is one-billionth of a meter (.00000003937008") or ~ 1/50,000 the width of a human hair. Nanofluids are made by suspending nanoparticles of materials such as C, Cu, or CuO in liquids such as oil, water and engine coolant (water + ethylene glycol).
The breakthrough came at the hands of two scientists Steve Choi and Jeff Eastman working at the Argonne National laboratory, a USDOE facility managed by the U of Chicago. Two methods were developed to create the nanoparticles.
The more complex, expensive one-step process utilizes direct evaporation-condensation that results in very small nanoparticles that disperse well in their host fluid. The metal nanofluids it produces are the only ones to date that are extremely stable as a result of particle size alone as no dispersants are needed to achieve long-term stability. The particles are so small that in some cases there is little or no settling even after several months. It is this technique that produces the highly thermally conductive metallic nanofluids.
The simpler, less expensive two-step method produces oxide and non-metallic nanofluids. First, the nanoparticles are produced and second, they are dispersed in the base fluid. This process works with more types of fluids than the one-step process.
Keeping the nanoparticles in suspension is the key to efficient heat transfer. It has been found that in the case of engine coolant, Red Line's Water Wetter aids in this process.
Results
At the Argonne National Laboratory it was found that the addition of 3% (by volume) of CuO nanoparticles to ethylene glycol increased its heat conduction by 15%. However, when only .3% of 10 nanometer diameter spheres of pure Cu were suspended in ethylene glycol, its heat conduction increased by an amazing 40%! Unlike microparticles which tend to sink below the fluid surface where they can't participate in heat transfer, nanoparticles lie closer to the surface enabling them to absorb and transfer heat more efficiently.
Discussion
The improved heat transfer performance due to the addition of nanoparticles into the working fluid is due to several factors. They increase the surface area and heat capacity of the working fluid.They improve the thermal conductivity of the working fluid. There are more collisions and interactions between the working fluid, the particles, and the flow passages. They cause more turbulence and mixing within the working fluid. Additionally, some researchers have found that the lubricating performance of coolant is enhanced. Tests have shown that the above characteristics make nanoparticles ideal for engine cooling systems due to their ability to respond quicly to temperature changes allowing for the dissipation of more heat, using less coolant, in a shorter period of time.
Although currently too expensive to see general use because of production costs, expect to see radiators reduced in size by half when manufacturing costs come down.
Finally, since engine oils and transmission oils and fluids possess relatively poor heat transfer capabilities, they would likely benefit from the high thermal conductivity made possible by nanofluids.
For more information, there is an SAE paper titled "The Effect of Nanoparticle Additions on the Heat Capacity of Common Coolants," by Lukas K Goldenstein and available from the SAE for US $16 for non-members. Document Number: 2002-01-3319. Go to:
http://www.sae.org/technical/papers/2002-01-3319
Happy Motoring!
Reference:
http://autospeed.com/cms/A_109620/article.html
Introduction
Although it's long been known that the suspension of certain solid particles in a fluid will improve its heat transfer characteristics and make it more thermally efficient, until recently microparticles large enough to be visible to the naked eye were the smallest solids that could be created for this purpose. These microparticles, with a diameter one-thousand times larger than nanoparticles were so large that they would quicly settle out of the fluid and sink to the bottom of a pipe or tank. Even if the fluid containing the microparticles was kept circulating rapidly enough to prevent some of the settling, their relatively large mass would damage the walls of the pipe wearing them thin. Additionally, the abrasive particles would also quickly wear out pumps and bearings.
Creating Nanofluids
The use of nano-sized particles has overcome most of these problems. A nanometer (nm) is one-billionth of a meter (.00000003937008") or ~ 1/50,000 the width of a human hair. Nanofluids are made by suspending nanoparticles of materials such as C, Cu, or CuO in liquids such as oil, water and engine coolant (water + ethylene glycol).
The breakthrough came at the hands of two scientists Steve Choi and Jeff Eastman working at the Argonne National laboratory, a USDOE facility managed by the U of Chicago. Two methods were developed to create the nanoparticles.
The more complex, expensive one-step process utilizes direct evaporation-condensation that results in very small nanoparticles that disperse well in their host fluid. The metal nanofluids it produces are the only ones to date that are extremely stable as a result of particle size alone as no dispersants are needed to achieve long-term stability. The particles are so small that in some cases there is little or no settling even after several months. It is this technique that produces the highly thermally conductive metallic nanofluids.
The simpler, less expensive two-step method produces oxide and non-metallic nanofluids. First, the nanoparticles are produced and second, they are dispersed in the base fluid. This process works with more types of fluids than the one-step process.
Keeping the nanoparticles in suspension is the key to efficient heat transfer. It has been found that in the case of engine coolant, Red Line's Water Wetter aids in this process.
Results
At the Argonne National Laboratory it was found that the addition of 3% (by volume) of CuO nanoparticles to ethylene glycol increased its heat conduction by 15%. However, when only .3% of 10 nanometer diameter spheres of pure Cu were suspended in ethylene glycol, its heat conduction increased by an amazing 40%! Unlike microparticles which tend to sink below the fluid surface where they can't participate in heat transfer, nanoparticles lie closer to the surface enabling them to absorb and transfer heat more efficiently.
Discussion
The improved heat transfer performance due to the addition of nanoparticles into the working fluid is due to several factors. They increase the surface area and heat capacity of the working fluid.They improve the thermal conductivity of the working fluid. There are more collisions and interactions between the working fluid, the particles, and the flow passages. They cause more turbulence and mixing within the working fluid. Additionally, some researchers have found that the lubricating performance of coolant is enhanced. Tests have shown that the above characteristics make nanoparticles ideal for engine cooling systems due to their ability to respond quicly to temperature changes allowing for the dissipation of more heat, using less coolant, in a shorter period of time.
Although currently too expensive to see general use because of production costs, expect to see radiators reduced in size by half when manufacturing costs come down.
Finally, since engine oils and transmission oils and fluids possess relatively poor heat transfer capabilities, they would likely benefit from the high thermal conductivity made possible by nanofluids.
For more information, there is an SAE paper titled "The Effect of Nanoparticle Additions on the Heat Capacity of Common Coolants," by Lukas K Goldenstein and available from the SAE for US $16 for non-members. Document Number: 2002-01-3319. Go to:
http://www.sae.org/technical/papers/2002-01-3319
Happy Motoring!
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