Effect of nanoparticles in nanofluid on thermal performance in a miniature thermosyphon

Abstract

An experiment was performed to investigate the effect of nanoparticles in the nanofluid on the thermal performance in a miniature thermosyphon. The nanofluids consisted of de-ionized water and CuO nanoparticles having an average size of 30nm. The experimental results show that the water-CuO nanofluids can greatly enhance the boiling heat transfer performance of the evaporator in thermosyphon compared with that using water at subatmospheric pressure conditions. A much lower and more uniform wall temperature of the thermosyphon can be obtained by substituting the nanofluids for water. Boiling heat transfer coefficients and the critical heat flux (CHF) of the nanofluids in the evaporator of the thermosyphon have significant increase compared with those of de-ionized water. There was an optimal mass concentration which was estimated to be 1.0wt% to achieve the maximum heat transfer performance. Operating pressure has very remarkable influences on both the heat transfer coefficients and the CHF of nanofluids, which greatly increase with the decrease of the test pressure. The heat transfer coefficient and the CHF can increase, respectively, about 160% and 120% at the pressure of 7.45kPa compared with those of water. The experimental study confirmed that the heat transfer performance of the miniature thermosyphon can evidently be strengthened by using water-CuO nanofluids.