Characteristics of heat transfer inside vertical tube in FBR steam generator

Kurihara, Akikazu ; Monde, Masanori*

An experimental study has been carried out to clarify relationship between flow aspect and heat transfer mode during downward flow in a vertical tube of FBR steam generator. The experiment was done using purified water under the following conditions; initial pressure of 11.2-13.4 MPa, initial water temperature of 200 C and water flow rate of 0.021-1.67 kg/s. The tube was heated by high frequency induction current, where the time averaged heat flux can be estimated using an inverse solution from the measured temperatures at two points on three different positions along the tube wall and then is confirmed to agree with the outer surface measured heat flux within 20% accuracy. It is found that the heat transfer characteristics strongly depend on the flow rate. In high mass flow rate, a stable nucleate boiling is formed on a vertical tube wall with clockwise cycle on - diagram for heat flux changes during 0 at any time. In low mass flow rate, boiling on the wall changes from dq/d0 to dq/d0 during the heating and returns from 0 to 0 during the reduction in heat.