Can flow oscillations during flow boiling deteriorate the heat transfer coefficient?

Two-phase flow instabilities have been identified as one of the impediments for achieving high heat flux in boiling systems due to their potential heat transfer deterioration. However, most of the fundamental characteristics of two-phase flow instabilities and the mechanisms leading to the heat transfer deterioration remain uncharted. In particular, up to what extent self-induced oscillations can deteriorate the heat transfer coefficient is not well understood. Here, we measure the flow boiling heat transfer coefficient under controlled oscillatory flow conditions. We show that flow oscillations can deteriorate the heat transfer coefficient significantly, but the deterioration depends on the amplitude and period of the oscillations. In particular, the deterioration is primarily a consequence of the dry-out at the wall that in turn increases the averaged wall temperature.