Dissipative evaporation through a permeable mini-space

• A semi-active dissipative evaporation is proposed to address heat penetration. • Water-membrane evaporator is proposed to achieve large-area thermal protection. • Vapor-liquid flow patterns and thermal responses of the evaporator are obtained. • Three heat transfer regimes are identified by vapor-liquid flow patterns. • Heat flux for the regimes transition increases with ambient pressure increases. Aerothermally-induced heat penetration poses a severe challenge to the thermal protection design of long-endurance hypersonic aircraft. Here, dissipative evaporation inside the inner wall of the flight cabin is proposed for the efficient thermal protection. The dissipative evaporation heat transfer mechanism and flow pattern in a water-membrane evaporator are investigated by a visualized experiment. The effects of the heat flux and ambient pressure on the heat transfer regime of dissipative evaporation are experimentally examined and analyzed. The characteristics of dissipative evaporation heat transfer in a permeable mini-space are further characterized by a regime diagram based on the heat flux and ambient pressure. The results indicate that the dissipative evaporation through a permeable mini-space sequentially undergoes surface evaporation, nucleate boiling and convection evaporation as the heat flux increases. Surface evaporation features a stable meniscus where the phase change occurs on the vapor-liquid meniscus. The nucleate boiling features the formation and growth of bubble, and the flow patterns of bubble flow, bubble-slug complex flow, bubble-slug-annular complex flow are observed. Convective evaporation is characterized by the appearance of continuous wavy annular flow. As the ambient pressure increases, the transitional heat flux density corresponding to the transition of heat transfer mechanisms and flow patterns tends to increase.