HEAT-TRANSFER CHARACTERISTICS IN PARTIAL BOILING, FULLY-DEVELOPED BOILING, AND SIGNIFICANT VOID FLOW REGIONS OF SUBCOOLED FLOW BOILING

Subcooled flow boiling covers the region beginning from the location w here the wall temperature exceeds the local liquid saturation temperat ure to the location where the thermodynamic quality reaches zero, corr esponding to the saturated liquid state. Three locations in the subcoo led flow have been identified by earlier investigators as the onset of nucleate boiling, the point of net vapor generation, and the location where x = 0 is attained from enthalpy balance equations. The heat tra nsfer regions are identified as the single-phase heat transfer prior t o ONB, partial boiling (PB), and fully developed boiling (FDB). A new region is identified here as the significant void flow (SVF) region. A vailable models for predicting the heat transfer coefficient in differ ent regions are evaluated and new models are developed based on our cu rrent understanding. The results are compared with some of the experim ental data available in the literature.