Flow boiling characteristics in microchannels with half-corrugated bottom plates

This study investigates the two-phase heat transfer performance of half-corrugated micro-channels with bottom sinusoidal structured surfaces. The boiling curves, heat transfer coefficients, flow morphologies and temperature and pressure oscillation have been obtained over a range of effective heat fluxes (350 KW-950 KW/m2) and mass flux of 400 kg s−1 m−2. The half-corrugated micro-channels can achieve higher heat transfer coefficients and lower superheat temperatures for the same effective heat flux than plain bottom micro-channels during the boiling process. The flow in saturated boiling regions begins with bubbly flow. The bubbly flow evolves to slug flow, churn flow and annular flow with the increase in effective heat flux. The churn flow and annular flow are observed together with bubbly flow at higher effective heat flux. Bubbly flow can contribute to relieve dry-out and enhance film-styled boiling. Bubbly flow may also result in fluid going forward and backward rapidly. The upstream flow reduces energy output. A sinusoidal half-corrugated structure is a help in not only storing more liquid for evaporation and nucleating bubbles, but also impeding the upstream flow of liquid in a round movement. Thermal-hydraulic performance of micro-channels is influenced by the geometric characteristics of corrugation. Different from conventional micro-channels with sinusoidal structures on both the upper and bottom plate, all half-corrugated micro-channels except micro-channels with wave length of 1 mm and wave amplitude 0.3 mm have a smaller pressure drop than plain bottom micro-channels. The experiments show that the sinusoidal half-corrugated micro-channels with wave length 3 mm and wave amplitude 0.2 mm or with wave length 5 mm and wave amplitude 0.3 mm have better heat transfer performance and smaller pressure drop.