The overlooked role of pressure oscillations on heat transfer deterioration during self-sustained flow oscillations

Abstract

The naturally occurring oscillations during flow boiling inside a heated pipe under specific conditions are known to hinder the system performance. Although substantial research has been done to reveal the occurrence and control mechanisms of such oscillations, the heat transfer mechanism remains a puzzle to be solved. In particular, it is believed that the heat transfer deterioration can be attributed to the flow velocity variation, namely, the amplitude and period of the oscillations. Here, we show that the heat transfer deterioration does not necessarily depend on the flow velocity variation. Using controlled experiments, we investigate the underlying mechanisms of the heat transfer deterioration during flow oscillations. We show that the associated pressure oscillations play a dominant role in triggering the heat transfer deterioration. In the absence of pressure oscillations, even a high amplitude flow velocity oscillation does not deteriorate the heat transfer rates in the studied conditions.