Unexpected technologies for heat transfer enhancement

Innovative strategies for high heat flux dissipation are strongly needed to overcome the intrinsic limitations of the traditional heat transfer schemes. Passive enhancement strategies represent an interesting way to improve the performance of the heat exchangers and, when it is associated to a phase change, it can be very effective. The most common phase change process used in the heat transfer processes is the liquid–vapor one (i.e. boiling), since it can be considered the most effective. On the other hand, the solid–liquid phase change process (as in the case of a Phase Change Material, PCM) is another interesting possibility to reject even high heat loads, especially when they are intermittent as in the case of most electronics cooling, renewable energies, etc.

In the last decades, the development of innovative enhanced heat transfer solutions has involved macro-, mini-, micro- and, more recently, the nano-scale.

This lecture covers the most advanced research activities on two-phase heat transfer enhancement during both liquid-vapor and solid-liquid processes from macro-scale to nano-scales, carried out at the Nano Heat Transfer Lab (NHT-Lab) of the University of Padova.

The use of microfins, porous media, nanoparticles during flow boiling, pool boiling, and solid-liquid phase change will be presented and discussed, highlighting pros and cons of each solution and, finally, showing how the main drawback of nanofluids, can be effectively used to achieve an unexpected, though, groundbreaking result.