Specific heat capacity of nano- and ionano-fluids


S. Murshed1, C. Nieto de Castro1, A. Ribeiro1, M. Lourenço1 and U. Mardolcar2

1Faculdade de Ciências da Universidade de Lisboa, Portugal
2Instituto Superior Técnico, Lisboa, Portugal

Keywords: nanofluids, Ionanofluids, heat capacity, nanoparticles
property: specific heat capacity
material: nanofluids

Nanofluids have evoked immense interest from the researchers worldwide and extensive research efforts have been made on thermal conductivity of nanofluids [1-2]. However, very little efforts have been made to determine the specific heat capacity of nanofluids, which is especially important in evaluating their thermal performance under flow conditions and in convective heat transfer-based applications. In contrast, the term ionanofluids, which is recently coined by Nieto de Castro and co-workers [3], represents an innovative class of nanofluids where nano-sized particles are dispersed in only ionic liquids. From the pioneering research conducted by the group of Nieto de Castro [3-4] ionanofluids are found to show great promises as advanced heat transfer fluids. Thus, it is of great importance to determine the specific heat capacity of nano- and ionano-fluids for their practical application in thermal system management and green energy-based areas. The volumetric heat capacity of several nanofluids and ionanofluids are measured as a function of particle concentration and temperature. While nanofluids were prepared by suspending 1-5 vol% of TiO2, Al2O3 and Al nanoparticles in ethylene glycol and engine oil, ionanofluids were made by dispersing multi-walled carbon nanotubes (MWCNT) in several ionic liquids such as [C4mim][PF6], [C4mim][NTf2] and [C2mim][EtSO4]. Results show that the volumetric specific heat capacities of these nanofluids decrease substantially with nanoparticle loading. Predictions by the volume fraction mixture rule-based correlation show fairly good agreement with the experimental data. Besides particle volume fraction, particle material and particle shape were found to have influence on this property of nanofluids. On the other hand, the volumetric specific heat capacities of ionanofluids were found to increase significantly with increasing temperature. Unlike nanofluids, there was little increase in heat capacity of ionanofluids with increasing loading of MWCNT. Nevertheless, any increase in heat capacity of such suspensions or fluids is of great importance for their practical applications.

References
  1. S.M.S. Murshed, K.C. Leong, C. Yang, Appl. Therm. Eng. 28, 2109 (2008)

  2. S.M.S. Murshed, K.C. Leong, C. Yang, in Handbook of Nanophysics: Nanoparticles and Quantum Dots, Ed., K.D. Sattler (CRC Press, Boca Raton,USA, 2010), p. 32

  3. A.P.C. Ribeiro, M.J.V. Lourenço, C.A. Nieto de Castro, in 17th Symp Thermophysical Properties, Boulder, CO, USA, 2009

  4. C.A. Nieto de Castro, M.J.V. Lourenço, A.P.C. Ribeiro, E. Langa, S.I.C. Vieira, P. Goodrich, C. Hardacre, J. Chem. Eng. Data. 55, 653 (2010)

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