Myth about nano-fluid heat transfer enhancement

The paper examines a few claims about the merit of using nano-particles to enhance the rate of heat transfer. In the literature, a few mechanisms were put forward to explain the magic of enhancing the rate of heat transfer by many folds compared with a clear fluid by adding a few percentages of nano-particles to the working fluid. In this work, a few introduced mechanisms is examined in the light of classical physics of the thermal diffusion and the fluid mechanics. Yet, no one able to break those simple physics; therefore, they should be valid for particles floating in a fluid. The paper for the first time reports the effect of particle alignment with the direction of heat flow (temperature gradient) effects on the effective thermal conductivity, which is significant. Furthermore, forced and natural convections are examined based on the classical theory of heat transport. We demonstrated the reason of why the rate of heat transfer decreases by adding nano-particles for a fluid experiencing natural convection. (C) 2015 Elsevier Ltd. All rights reserved.