Visual experimental study on bubble characteristics near the heating wall in subcooled flow boiling

A visual experiment is conducted to study bubble dimension characteristics during subcooled flow boiling in vertical flow channel with a round heating rod in a squared channel. With the high speed camera, the bubble behavior is captured and bubble dimension characteristics near the heating wall are obtained. In this study, the system pressure is from 0.1 to 1.0 MPa, the mass flux is from 800 to 1900 kg/m2s and the inlet subcooling is from 10 to 30 K. The effect of working conditions on bubble behavior is discussed in detail, such as system pressure, are analyzed in detail. The bubble dimension increases with increasing heat flux, while decreases with system pressure, inlet subcooling and mass flux. In order to predict bubble dimension better, a model is proposed based on important dimensionless numbers in this paper and good agreement is achieved when comparing with the experimental result.