Heat Flux Measurement of Boiling Heat Transfer in a Helically Coiled Tube Heated by Oil Bath

Abstract

This study deals with an experimental investigation of the flow boiling heat transfer characteristics of water in a helically coiled tube heated in a high temperature oil bath in relation to the steam generator of LMFBR. Time variations of the external and internal tube wall temperatures were measured under low quality conditions and the heat fluxes across the tube were calculated from the difference between the external and internal temperatures. A simple numerical analysis was made to evaluate the heat transfer coefficients at the external and internal tube walls and their time variations. The results show that the heat flux change is caused by the heat capacity of the tube and that its temporal behavior is quite different from the wall temperatures. This suggests that the deterioration of heat transfer caused by local dry-out on the wall surface results in peculiar changes of the wall temperatures and the heat fluxes.