Experimental study on convective heat transfer of nanofluids in turbulent flow: Methods of comparison of their performance

Ehsan B. Haghighi, Adi T. Utomo, Morteza Ghanbarpour, Ashkan Izadi Tabaei Zavareh, Heiko Poth, Rahmatollah Khodabandeh, Andrzej Pacek, Björn E. Palm

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Turbulent convective heat transfer coefficients of 9 wt% Al2O3/water and TiO2/water nanofluids inside a circular tube were investigated independently at the Royal Institute of Technology, KTH (Sweden) and at University of Birmingham (UK). The experimental data from both laboratories agreed very well and clearly show that Nusselt numbers are well correlated by the equations developed for single phase fluids with the thermophysical properties of nanofluid.
The heat transfer coefficients of nanofluids can be compared with those of the base fluids at the same Reynolds number or at the same pumping power. As the same Reynolds number requires higher flow rate of nanofluids therefore such comparison shows up to 15% increase in heat transfer coefficient. However, at equal pumping power, the heat transfer coefficient of Al2O3 nanofluid was practically the same as that of water while that of TiO2 was about 10% lower. Comparing performance at equal Reynolds number is clearly misleading since the heat transfer coefficient can always be increased by increased pumping power, accordingly, the comparison between the fluids should be done at equal pumping power.
Original languageEnglish
Pages (from-to)378-387
JournalExperimental Thermal and Fluid Science
Early online date12 Jun 2014
Publication statusPublished - Sept 2014


  • Nanofluids
  • Convective heat transfer
  • Turbulent
  • Circular tube
  • Al2O3
  • TiO2
  • Pumping power


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