KURENAI : Kyoto University Research Information Repository

As mentioned above, the transient boiling curve had a portion where
Zhe wall superheat shifts to the right of the steady state boiling
curve. A similar phenomenon is reported to have been observed in pool
boiling of water [13] .
I.3.2.c Transient Maximum Heat Flux
Figures 19 through 27 are correlative representations of the experi-
mental transient maximum heat flux vs. exponential period. Solid lines
in these figures represent an empirical correlation, Eq.(17) and will
be discussed later. The boundary between A-type and B-type boilings is
also indicated in some of these figures by dot-dash-line. Unless bound-
aries are indicated in the figure, A-type boiling is meant. Effects of
period, pressure, subcooling, velocity and heater size on the transient
maximum heat flux will be discussed individually.
Effect of exponential period on transient maximum heat flux is given
in Fig.26(a) for 0.8 mmdiam, 7 cm long heater at pressure 0.396 MPa, sub-
cooling 30 K and velocity from 1.35 to 4.04 m/s. In this figure, the right
hand side of the dot-dash-line is a region of A-type transient boiling and
the left hand side a region of B-type. In the A-type region, the transient
maximum heat flux increases with decreasing period at constant velocity,
whereas,in the B-type region, the transient maximum heat flux , decreases
with the period and then increases. •
Effects of velocity, subcooling and pressure are seen in Figs.26(a),
(b) and (c), respectively. Results thus indicate that the transient max-
imum heat flux increases as the period is decreased and, for a constant period
it increases with increasing velocity, subcooling and pressure.
25