  We explore steady state and transient heat transfer from a narrow,
rectangular stainless steel heater strip cooled from one side by an open bath
of He~II. Setup validation is done by fitting the Kapitza heat transfer
expression $Q = a_\mathrm{K} \left( {T_\mathrm{s}}^{n_\mathrm{K}} -
{T_\mathrm{b}}^{n_\mathrm{K}} \right)$ to steady state measurements, finding
fit parameters within the expected range; $a_\mathrm{K}$ = 1316.8$\pm10\%$
$\mathrm{W}\mathrm{m}^{-2}\mathrm{K}^{-1}$, $n_\mathrm{K}$ = 2.528$\pm10\%$. We
find critical heat flux in line with estimates from literature, and the time
between a step in heating and the onset of film boiling follows the expected
$\propto Q^{-4}$ dependence. During the first millisecond after a step in
applied heating power density our measurements show a slower thermal rise time
than that found by a time-dependent one-dimensional model of our setup using
the steady state Kapitza heat transfer expression as the cooling boundary
condition. However, the results compare favourably with transient measurements
in literature. After the first millisecond, agreement between measurement and
model is excellent. We do not find conclusive evidence of an orientation
dependence of the Kapitza heat transfer mechanism, nor heat transfer
differences that can be attributed to local surface variations along the same
heater.
