Study on safety boundary of flow instability and CHF for parallel channels in motion

The safety boundary of flow instability and critical heat flux(CHF) for parallel channels was theoretically investigated in static and motion. For flow instability, a parallel-channel instability mechanistic model was adopted. For CHF, the liquid sublayer dryout mechanism model was used. Also, a unified form of additional forces caused by motion was derived for both flow instability and CHF model. An in-house code was developed combining the flow instability model and the CHF model in motion. The safety boundary of twin rectangular parallel channels with length of 40 mm, width of 2 mm and height of 1 m was calculated in static, inclination, heaving, pitching and rolling motions. The results show that the safety boundary consists of CHF lines and instability boundary. The heating power of the parallel channels is limited by flow instability or CHF depending on the mass flux. All the motions have little influence on the instability boundary. The effects of longitudinal inclination, heaving and pitching motions on the safety boundary are no more than 1%. However, the CHF is obviously reduced in transverse inclination due to flow maldistribution and in rolling motion due to pulsating flow.