2-PHASE FLOW IN SMALL-SCALE RIBBED AND FINNED PASSAGES FOR COMPACT EVAPORATORS AND CONDENSERS

Complex small-scale finned and ribbed passages are being used with inc reasing frequency in compact high-performance evaporators and condense rs. The complexity and small scale of these passages causes the flow a nd transport mechanisms to differ substantially from those in larger s impler tubes more commonly used in power, process and refrigeration ap plications. Special features of two-phase and transport in ribbed and finned passages are described. Results of recent investigations which have illuminated some of the very different mechanisms that arise in t hese circumstances are also summarized. The effects of liquid shedding from discontinuous structures, the strong role of surface tension for ces, and the existence of recirculation zones and lateral nonuniformit y of the flow are especially important in these small-scale passages. The impact of these features on modeling of two-phase transport in eva porators and condensers is also discussed.