Enhanced Surface Spary Cooling With Embedded and Compound Extended Surface Structures

Experiments were conducted to study the effects of enhanced surface structures on heat flux using spray cooling. The surface enhancements consisted of embedded structures (dimples, pores, and tunnels) and compound extended surface enhancements (straight fins, cubic pin fins and dimples) machined on and within the top surface of copper heater blocks. Each copper block had a projected cross-sectional area of 2.0 cm². Measurements were also obtained on a heater block with a flat surface for baseline comparison purposes. A 2times2 nozzle array was used with PF-5060 as the working fluid. Thermal performance data was obtained under nominally degassed (chamber pressure of 41.4 kPa) and gassy conditions (chamber with N² gas at 101 kPa) with a bulk fluid temperature of 20.5 degC. Results for both the nominally degassed and gassy cases show that the highest critical heat flux (CHF) was attained using straight fins and porous tunnels. For the nominally degassed case, both had a CHF of ap142 W/cm² while for the gassy case their CHF values increased to 175 W/cm² . This gave an enhancement relative to the respective flat surface degassed/gassy cases of ap 77% and 62% respectively