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In this paper, two phase heat transfer of a mixture of nanopaticles in air flow as a type of nanofluid is studied. Volume fraction of the dispersed phase is very low (less than 1%). Nanoparticles travel in the base fluid due to drag, brownian and gravity forces and are tracked according to lagrangian approach. Effect of reduced specific heat of nanofluid on heat transfer is considered. The results show an increase in heat transfer rate which is very much more than that predicted by the Maxwell model.

The effect of different parameters on dispersion of nanoparticles in a microchannel in slip flow regime is studied. The equations of particle motion and energy balance are solved numerically and the effect of particle diameter, starting position of particles in microchannel, and slip coefficient on dispersion of particles is discussed. Radiative heat flux in energy equation and drag force, Saffman lift force, Brownian force and gravitational force in momentum equation are included. The results show that the Brownian force has considerable effect on particle motion in microchannel. Particles temperature at the outlet can be controlled by variation of their diameter and starting position in microchannel.

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