Recent studies of nanofluids have shown that the nanoparticles when mixed in fluid medium such as water and ethylene glycol enhance the thermal conductivity of the colloids when compared to the fluid medium. However, numerous experimental studies conducted on the effective thermal conductivity of nanofluids, while using initial particle distribution consisting of range of diameters, have reported their results at volume-weighted average diameters. Here, we use computer simulations to investigate the effect of initial particle distribution or the effect of polydispersivity on the effective thermal conductivity of nanofluids. The study reveals that the simulations performed with multi-sized nanoparticles predict the effective thermal conductivity values of nanofluids closer to the experimental values than the corresponding volume weighted average diameters. Inhomogeneous coagulations in the multi-sized nanofluids were found to be a major factor for the deviation of effective thermal conductivity of the nanofluids in single- and multi-sized nanofluids. Our results suggest that initial distribution of particles has a significant role in predicting the effective thermal conductivity of nanofluids.
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Acknowledgement This work was partially supported by grants from the National Science Foundation (ATM-0332910), National Oceanic and Atmospheric Administration (NA04OAR4310034), and National Aeronautics and Space Administration (NNG04GG46G).
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Materials Chemistry