  In this research, a novel method to investigation the transient heat transfer
coefficient in a channel is suggested experimentally, in which the water flow,
itself, is considered both just liquid phase and liquid-vapor phase. The
experiments were designed to predict the temporal and spatial resolution of
Nusselt number. The inverse technique method is non-intrusive, in which time
history of temperature is measured, using some thermocouples within the wall to
provide input data for the inverse algorithm. The conjugate gradient method is
used mostly as an inverse method. The temporal and spatial changes of heat
flux, Nusselt number, vapor quality, convection number, and boiling number have
all been estimated, showing that the estimated local Nusselt numbers of flow
for without and with phase change are close to those predicted from the
correlations of Churchill and Ozoe (1973) and Kandlikar (1990), respectively.
This study suggests that the extended inverse technique can be successfully
utilized to calculate the local time-dependent heat transfer coefficient of
boiling flow.
