The enhancement of a critical heat flux — CHF — in pool boiling was investigated by supplying liquid-jets to a heating surface, as a proposal of the high heat removal technology for the future industrial field. The mechanism on the enhancement of CHF was examined through measurement of void fraction near the heater by using a void probe and macrolayer model of CHF by Haramura-Katto.
Experiments were conducted using a copper block and saturated water for a pool condition at 0.1 MPa. One, two or three jet-nozzles were set away a certain distance from the test surface, 1 or 6 mm, for supplying liquid-jets to the heating surface. The effects of the distance, the diameter of jet-nozzles, 0.9, 0.5 or 1.5 mm, the liquid flow rate and the jet-velocity on the enhancement rate of the CHF were examined experimentally.
The CHF was enhanced by supplying three liquid-jets a factor of about three for 6 × 10−6 m3/s in the flow rate. The enhancement rate increased with the liquid flow rate and jet-velocity. The void fraction near the heating surface was a lower value by the supplying liquid-jets when the heat flux was similar to the normal CHF without the supplying liquid. These results suggests that the enhancement of the CHF is affected additionally by the quantity of supplied liquid to the macrolayer on the heating surface.