Experiment of CHF Enhancement by Fe3O4 Nanoparticle Coating in Subcooled Boiling Region

Abstract

The subcooled flow boiling CHF experiments were conducted with DI water on bare stainless steel and nanoparticle coated surface at atmospheric pressure. Nanoparticles were deposited sufficiently on test sections by applying deposition process. Experiment was conducted in mass flux range from 1,000 kg/m2s to 5,000 kg/m2s and inlet temperatures of 40, 60 and 80 °C. Overall trend of CHF enhancement was decreased as exit quality decreased and approached to zero in highly subcooled region. In other words, the effect of wettability on CHF improvement decreased in low exit quality region. The CHF enhancement could be decreased due to degradation of active nucleation site density as exit quality decreased in highly subcooled boiling region. The exceptional case is that the CHF enhancement remained about 20 % in high mass flux of 5,000 kg/m2s even in highly subcooled region. CHF enhancement was analyzed by flow boiling CHF mechanism and theoretical CHF model.