Burn-out phenomena of a liquid nitrogen forced convective flow in a tube heated in cosine-distribution

Forced convective critical heat flux was experimentally studied. Liquid nitrogen was used for the working fluid in a vertical tube the heat flux of which had a cosine distribution. It was examined the rise of the tube wall temperature, the fluctuation of the pressure and the flow pattern for the critical heat flux based on the averaged critical heat flux of the tube. Two phenomena on the critical heat flux were found. One was a burn-out phenomenon occurred when flow pattern changed from slug or churn flow to annular flow at higher heat flux. The other was a DNB phenomenon just after the boiling at lower heat flux. The phenomena on the critical heat flux were experimentally studied and discussed. (author)