vacuum cooling process, degree of superheat is fundamentally
caused by the pressure drop; b) the increasing of bubble
size depends largely on the pressure drop from the tube bottom
to water surface during immersion vacuum cooling; c) the
bubbles at the tube bottom are more difficult to grow up than
the upper ones, which is different from the phenomenon in
cooking process (Ahmadi et al., 2012). Consequently, controlling
the pressure drop rate seems to be one of the fundamental
methods to improve the effect of vacuum cooling.