SUMMARY

This study investigated flow boiling of water in a closed flow loop system at reduced pressure experimentally with a wide range of heat fluxes, mass fluxes and inlet fluid temperatures. Two microgaps, with sparse pin fins, and the other with dense pin fins, were studied and compared. A new two phase heat transfer correlation and pressure drop correlation was proposed based on current study. Two phase flow instabilities were observed and discussed. High speed visualization was utilized to characterize two phase flow patterns. Effects of spatially non-uniform surface heating on two phase flow were studied. The heat transfer and pressure drop performance of dielectric liquid HFE-7200 was tested and compared with water.