Inception of evaporative dryout for CO2 in milliscale pipe flows

作者：Giulio Cantini, Desiree Hellenschmidt, Camila Pedano, P. Petagna, Carl M. Sangan, Mauro Carnevale · 发表于：International Journal of Heat and Mass Transfer · 年份：2025 · DOI：10.1016/j.ijheatmasstransfer.2025.127299 · 被引用次数：1 · 研究领域：Heat Transfer and Boiling Studies、Heat Transfer and Optimization、Refrigeration and Air Conditioning Technologies

Carbon dioxide is a cost-effective, reliable and environmentally-friendly refrigerant with increasing employment in evaporator design. A clear understanding of the underlying flow physics, coupled with robust prediction of phase change through boiling, is necessary to enable widespread uptake of CO 2 as a coolant. In scenarios such as nuclear reactors or thermal management in silicon detectors ( e.g. , Large Hadron Collider at CERN), employing saturated CO 2 in milliscale pipes introduces further uncertainties in the design process, particularly regarding its behaviour at high vapour quality. During the phase change process, the fluid exhibits an abrupt decrease in the heat transfer coefficient. Such a condition, known as the onset of dryout , can lead to potentially catastrophic overheating. Two opposing behaviours are observed in the available literature concerned with the onset of dryout, coined in this study as the δ − and δ + regimes. The δ − regime exhibits decreasing dryout vapour quality with mass flux, while the δ + regime, which is more relevant to CO 2 in millichannels , yields an increasing dryout vapour quality with mass flux. A detailed experimental campaign was conducted at CERN providing unprecedented insight into the phenomena resulting in the inception of dryout. A new theoretical model based on small perturbation theory was developed to accurately predict the dryout phase in the δ + regime. This study provides general theory to predict dryout, which is vali...