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the transient maximum heat flux. It might be possible to assume expo-
nential period, T, for TO for exponentially increasing heat generation.
We further assume the following nondimensional expression for the transient
maximum heat flux because , the transient maximum heat•flux
approaches the steady state maximum heat flux at the period for exponential
power increase being infinity
gmax
,tr gmax,st —)(____)() Pva6PLbLO cHidTGe ( (—)(------) =C
-(15) GH
fgPLGL0,dhe Hfg P LL0
The experimental data for A-type boiling were used to determine a - e in
Eq.(15). This showed that (q- q) had little dependence on
LOPH
1 max max,st (
d)and(H--=), h
efg
i.e. c and d are zero.a, b And e
have been determined by least squares fitting , giving
gmax
,trgmax,stPVo
GH .2038 ( —)(~-)()(16) •s26PLo19TGo63 0
=
fgpLG LOP LL0 .
Figure 28 shows plots of the transient maximum heat flux in terms of
gmax ,tr - gmax,stPvGPL, •TO (GH)()_o•sz
-(GL)-019vs.() for subcooling
f gPL0PLLO
from 0 to 40 K, velocity from 1.35 to 4.04 m/s , pressure from 0.143 to 1.503
MPa, heater diameter from 0.8 to 1.5 mm and heater length from 3 .93 to 10.04
cm and for A-type boiling. The data lie within ±30 % of Eq .(16).
By substituting Eq.(10) into Eq .(16), we finally obtain Eq .(17)
for the transient maximum heat flux
gmax ,tr= 0.3740(pv)0.66 P•
GH f (L)0.40
gPL0
PAH .
x [ 1 + {0.03648 (d0)-0.20 ( PL)-o.79 +e}}I_27•heLfg
+ 0.2038 (
PL—)o.52(6L16)0.19 (TO)-0.63 (17)
27
P1 .110 ,