  Bubble growth, departure and sliding in low-pressure flow boiling has
received considerable attention in the past. However, most applications of
boiling heat transfer rely on high-pressure flow boiling, for which very little
is known, as experimental data are scarce and very difficult to obtain. In this
work, we conduct an experiment using high-resolution optical techniques. By
combining backlit shadowgraphy and phase-detection imaging, we track bubble
shape and physical footprint with high spatial (6 $\mu$m) and temporal (33
$\mu$s) resolution, as well as bubble size and position as bubbles nucleate and
slide on top of the heated surface. We show that at pressures above 1 MPa,
bubbles grow in a heat-diffusion controlled regime and retain a spherical shape
throughout the growth and sliding process. We analytically derive
non-dimensional numbers to correlate bubble velocity and liquid velocity
throughout the turbulent boundary layer and predict the sliding of bubbles on
the surface, solely from physical properties and bubble growth rate. We also
show that these non-dimensional solutions can be leveraged to formulate
elementary criteria that predict the effect of pressure and flow rate on bubble
departure diameter and growth time.
