Orientation Effects on Critical Heat Flux due to Flooding in Thin Rectangular Channel

Abstract

Forced convective critical heat flux (CHF) in a rectangular channel that depended on an inclination angle was investigated. The experiment has been performed with a one side-heated thin rectangular channel under the atmospheric pressure with the inclination angle varying from 10° to 90° and mass flux from 0 to 400 kg/m²·s. The CHF was found to decrease with the inclination angle remarkably at low mass flux. Flooding CHF analysis was carried out based on the result of flow visualization in the channel, and the incorporation of inclination angle into a model was proposed. A comparison of the model prediction with experimental results showed good agreement between the measured and predicted CHF with varying inclination angle. The model was combined with a conventional CHF correlation for evaluation of mass flux, and finally a forced convective CHF correlation for an inclined thin rectangular channel was proposed.

KEYWORDS:

• critical heat flux
• flooding
• countercurrent flow
• thin rectangular channel
• narrow gap
• flow orientation
• channel inclination
• severe accidents