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Nanofluids in thermosyphons and heat pipes: Overview of recent experiments and modelling approaches .

Author(s) : BUSCHMANN M. H.

Type of article: Article, Review

Summary

Confronted with limited energy and material resources and undesirable manmade climate changes, science is searching for new and innovative strategies to save, transfer and store thermal energy. Currently, one of the most intensively discussed options are the so-called nano fluids. Nano fluids are suspensions consisting of a liquid base fluid and solid particles of sizes ranging from 10 nm to 200 nm. The higher thermal conductivity of these nanoparticles leads to an increased effective thermal conductivity of the fluid which, the general expectation is, should enhance the heat transfer of the device. This overview aims to compile results of the application of nano fluids in thermosyphons, heat pipes, and oscillating heat pipes. The general goal is to draw conclusions with respect to the potentials for improvement of the thermal performance of these gadgets. Additionally, possible mechanisms which may generate these improvements are discussed. All together 38 experimental studies and 4 modelling approaches are analyzed. While most investigations recognize nano fluids as an advantageous working fluid, some others report negative effects. Performance effects which are related to filling ratio, inclination angle, and operation temperature seem to be similar to those for classical working fluids. Several authors report a decrease of the thermal resistance or an increase of the efficiency with increasing concentration, but also a reversing of this trend if a certain optimal concentration is exceeded. This observation mainly follows with a significant increase of the evaporator heat transfer coefficient. The condenser heat transfer coefficient seems to be not or only weakly affected. Base fluid, nanoparticle material, size and shape, and the stabilization of the suspension have an influence on the thermal performance. However, the limited number of experiments does not allow drawing firm conclusions. The main mechanism responsible for the improved thermal performance seems to be a porous layer built from nanoparticles on the evaporator surface. Additional positive effects may follow from the changed thermophysical properties of the working fluid.

Details

  • Original title: Nanofluids in thermosyphons and heat pipes: Overview of recent experiments and modelling approaches .
  • Record ID : 30010874
  • Languages: English
  • Source: International Journal of thermal Sciences - vol. 72
  • Publication date: 2013/10
  • DOI: http://dx.doi.org/10.1016/j.ijthermalsci.2013.04.024

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