Incipient Boiling of Sodium Flowing in a Single-Pin Annular Channel

This paper deals with an experimental study on incipient boiling of sodium flowing in an annular channel electrically heated by a pin forming the channel core. In the present experiment, the inlet temperature and flow rate were held constant, and the heat flux was gradually increased up to inception of boiling. Measurements were made of the incipient-boiling superheat, and the boiling patterns were observed. The experimental results were compared with analytical calculations The incipient-boiling wall superheat decreased exponentially with increase in flow rate. The boiling patterns observed in the present experiment were not the single-bubble slug expulsion model, as assumed in calculational code, but more similar to multiple-bubble slug expulsion or homogeneous two-phase flow models.