Thermal conductivity enhancement of nanoparticles in distilled water

This paper provides an overview of the important physical phenomena necessary for the determination of effective thermal conductivity of nanofluid. Increase in the specific area as well as Brownian motion are supposed to be the most significant reasons for the anomalous enhancement in thermal conductivity of nanofluid. Usual heat transfer fluids with suspended ultra fine particles of nanometre size are named as nanofluids, which have opened a new dimension in heat transfer processes. This work presents the increase of thermal conductivity with temperatures for nanofluids with water as base fluid and particles of Al2O3 or CuO as suspension material. Transient hot-wire method is used for the measurement of thermal conductivity. Heat retaining time is introduced and estimated experimentally. The heat retaining time of 0.8% volume fraction of Al22O3 nanofluid increases up to 47.05% of the base fluid and 0.8% volume fraction of CuO nanofluid increases up to 61.7% of the base fluid. The results indicate an increase of enhancement of thermal conductivity with temperature found to be agreeing excellently with a wide range of different models as well as the data published in literature.