Heat Transfer Nanofluids

24 February 2007

Basically heat transfer fluids either take out the excessive heat generated during a chemical process or transfer heat to the system so that the desired chemical reaction takes place. The advantage of the heat exchanger is that it is single and central source that can absorb or supply heat and is more efficient and safe to use and maintain. The conventional heat transfer fluids are based on synthetic or mineral petroleum based and depending on the operating range of temperature, the exact type of heat transfer fluid is selected.

In the recent past carbon nanotubes have been used for various applications and due to their excellent thermal conductivity values, carbon nanotubes has been found suitable for  use in heat transfer fluids. The thermal conductivity of carbon nanotubes is in the range of 2000W/mK, which is approximately 10,000 times greater than the conventional petroleum oil. The only hurdle seems to be incorporation of these carbon nanotubes in to the heat transfer fluid so that the benefit of the carbon nanotubes can be achieved.

It is well known that the thermal conductivity of the heat transfer fluids depends on the particle size and as the particle size goes down the thermal conductivity of the heat transfer fluid increases. If the particle size goes down, it increases the surface area to volume ration, which is responsible for increasing the thermal conductivity. Another factor responsible for heat transfer properties is the particle shape. Non-spherical particles display better heat transfer properties. Carbon nanotubes being spherical in shape are therefore possesses excellent heat transfer properties.

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One Response to “Heat Transfer Nanofluids”

  1. On November 9th, 2007 at 2:54 am, Betty Catalina Rostro Says:

    While carbon nanotubes themselves do posses a high thermal conductivity, suspensions of carbon nanotubes in oil, with the mineral oil having a thermal conductivity of 0.1279 Watts/meter Celcius (W/mC) or poly-alpha-oil having a thermal conductivity of 0.1448 (W/mC), and single-walled carbon nanotubes having a theoretical thermal conductivity of 1000 W/mC, a 1% weight SWNT-oil sample will merely have a conductivity of 0.1645 W/mC and a 10% weight SWNT-oil loading would lead to a 0.2841 W/mC increase. Many people often forget about the interface between the solid and the fluid, if this is bad, then you will never see a great increase in thermal properties. Also, functionalizing the nanotubes will decrease the thermal conductivity, such that you get little or no increase. Plus the solubility of the carbon nanotubes in the oil is quite small, and you need a high loading to get good results, unfortunately the resulting samples are not liquids but more like greases. If you want to see large increases try ceramic nanoparticles which are much cheaper, easier to make and handle and whose thermal properties are significantly higher than those of carbon nanotube structures. Always remember that in the end, you have to stick with what works!

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