Flow boiling critical heat flux of FC-72 from flush-mounted and protruded simulated chips in a vertical rectangular channel

Experiments on flow boiling heat transfer and critical heat flux (CHF) of the dielectric coolant FC-72 are carried out for four in-line simulated electronic chips of 10 mm × 10 mm, for both flush-mounted and protruded chips on one wall of a vertical rectangular channel. The fluid velocity and subcooling are varied from 4.2 to 78 cm/s (ReL=1.0×103 to 3.0 × 104), and from 15 to 33°C, respectively. The fully-developed nucleate boiling regime is not affected by changes in flow velocity and subcooling, whereas the surface temperatures decrease with increasing flow velocity and subcooling in the partial boiling regime. CHF generally increases with the degree of subcooling and with velocity at higher inlet velocities, but velocity has little effect at values less than 20 cm/s. The surface temperatures for the flush-mounted chips are lower than those for protruding chips, and the CHF data for the flush-mounted chips are higher than those for protruding chips; the differences between these two cases increase with increasing velocity.