Subcooled Pool Boiling in Variable Gravity Environments

Abstract

Virtually all data to date regarding parametric effects of gravity on pool boiling have been inferred from experiments performed in low-g, 1g, or 1.8g conditions. The current work is based on observations of boiling heat transfer obtained over a continuous range of gravity levels (0g–1.8g) under subcooled liquid conditions (n-perfluorohexane, ΔTsub=26°C, and 1 atm), two gas concentrations (220 ppm and 1216 ppm), and three heater sizes (full heater-7×7 mm2, half heater-7×3.5 mm2, and quarter heater-3.5×3.5 mm2). As the gravity level changed, a sharp transition in the heat transfer mechanism was observed at a threshold gravity level. Below this threshold (low-g regime), a nondeparting primary bubble governed the heat transfer and the effect of residual gravity was small. Above this threshold (high-g regime), bubble growth and departure dominated the heat transfer and gravity effects became more important. An increase in noncondensable dissolved gas concentration shifted the threshold gravity level to lower accelerations. Heat flux was found to be heater size dependent only in the low-g regime.

Experimental study of the heater size effect on subcooled pool boiling heat transfer of FC-72 in microgravity

“…Raj [5] found that if the gravitational acceleration is larger than 0.3 g e the heat fluxes for three heater sizes are similar. But for the acceleration values smaller than 0.3 g e , it is obvious that the heat transfer performance changes with the heater size.…”

Bubble dynamics and heat transfer on a wettability patterned surface

“…The heater size effects were studied extensively by Kim et al [33,34]. According to their research, relative small heater size has poorer heat transfer than that of a large size.…”

Phase distributions of boiling flow in helical coils in high gravity

“…Recently, He et al [9] studied the non-uniformity of the temperature field in a closed cavity with centrifugal acceleration in simulations and experiments. On the other hand, extensive research focusing on microgravity [10][11][12] also introduced valuable data of the boiling flow in high gravity more or less. However, their mutual limitation is that the experiments are conducted in the on-board parabolic flight, so their maximum accelerations of 2 g is insufficient for manned or unmanned flight vehicles.…”