CHF and heat transfer enhancement by SiO2 nanofluids on a inclined downward facing heating surface

Abstract

In this experiment, the factors affecting critical heat flux (CHF) in the pool boiling research with the heating face down were investigated. Including the type of cooling liquid and the angle of the heating surface. The types of coolants include reverse osmosis (R·O) water and SiO2 nanofluids (0.02 g/L～0.12 g/L). The morphology and types of nanoparticles were characterized by microscope (SEM) and scanning electron X-ray diffraction (XRD) before the experiment. Pool boiling experiments were performed using a specially designed heating block. After data processing, we found that in the horizontal downward heating experiment, the heat flux density increased by 49.68% and the heat transfer coefficient (HTC) increased by 60.73% under nanofluid conditions compared to the case of R·O water when CHF occurred. The increase in the HTC is strongly related to the deposition of nanoparticles on the heating surface. In the heating surface experiment with different tilt angles, both the heat flux density and the HTC increase with the increase of the angle. In the experiment of inclined downward heating surface, the CHF and HTC increase with the increase of heating angle, but the increase is smaller and smaller.