HEAT TRANSFER CHARACTERISTICS OF NANOFLUIDS IN TWO-PHASE FLOW BOILING

摘要

The present literature review was focused on the nucleate boiling performance of nanofluids with respect to flow boiling applications. The changes of the thermophysical properties of the base fluid as well as the effects of particle-particle interactions, interactions between the particles and the liquid and between the particles and the boiling surface respectively were considered. The literature survey concludes that nanofluids may significantly enhance the nucleate flow boiling heat transfer and probably delay the occurrence of the critical heat flux. Two main effects of the particles were identified: the improvement of the liquid's thermophysical properties and the deposition of particles on the boiling surface. With regards to the properties of the particles, a high thermal conductivity, a high aspect ratio, a small size and a high specific surface area as well as a low density were found to be most suitable. Furthermore it was pointed out, that the dispersion state and the stability of the solutions seem to be a prerequisite for a sustainable heat transfer enhancement. While non-polar base fluids basically provide the same solubility for all kinds of particles, polar base fluids are most suitable for amphoteric particles, where their dispersion can be considerably increased by electrostatic stabilization.