Critical heat flux has been measured during natural circulation boiling of water and R113 on a uniformly heated outer tube in a vertical annular tube. The experiment was carried out using water at atmospheric pressure and R113 at a pressure of 0.1–0.4 MPa for the annular gap width of $S=1.0-4.0 mm,$ the heated tube diameter of 9–17 mm, and the annular tube length of 100–1000 mm. The similarity of critical heat flux between annular configurations of either inner or outer heated tubes and a simple heated tube can be clearly elucidated based on the characteristics of the heated equivalent diameter. The critical heat flux measured for $S=1 mm$ can be predicted accurately by existing correlation for the annular tube and for clearance larger than $S=4 mm$ by existing correlation for the single tube. A new correlation for medium clearances from $S=1$ to 4 mm has been developed to connect between both the existing correlations. [S0022-1481(00)01901-0]

1.
Islam
,
M. A.
,
Monde
,
M.
,
Hasan
,
M. Z.
, and
Mitsutake
,
Y.
,
1998
, “
Experimental Study of critical heat flux in Concentric-tube Open Thermosyphon
,”
Int. J. Heat Mass Transf.
,
43
, pp.
3691
3704
.
2.
Monde
,
M.
, and
Yamaji
,
K.
,
1990
, “
Critical Heat Flux During Natural Convective Boiling in a Vertical Uniformly Heated Tubes Submerged in Saturated Liquid
,”
J. Heat Transfer
,
2
, pp.
111
116
.
3.
Monde
,
M.
,
Mitsutake
,
Y.
, and
Kubo
,
S.
,
1994
, “
Critical Heat Flux During Natural Convective Boiling on Uniformly Heated Inner Tubes in Vertical Annular Tubes Submerged in Saturated Liquid
,”
Wa¨rme-Stoffu¨bertragung
,
29
, pp.
271
276
.
4.
Park
,
K. A.
, and
Bergles
,
A. E.
,
1988
, “
Effect of Size of Simulated Microelectronic Chip on Boiling and Critical Heat Flux
,”
ASME J. Heat Transfer
,
110
-
3
, pp.
728
734
.
5.
Monde
,
M.
,
Kusuda
,
H.
, and
Uehara
,
H.
,
1982
, “
Critical Heat Flux During Natural Convective Boiling in Vertical Rectangular Channels Submerged in Saturated Liquid
,”
J. Heat Mass Transf.
,
104
, pp.
300
303
.
6.
Monde
,
M.
,
Inoue
,
T.
, and
Mitsutake
,
Y.
,
1997
, “
Critical Heat Flux in Pool Boiling on Vertical Heater
,”
Heat Mass Transfer
,
32
, pp.
435
440
.
7.
Katto
,
Y.
,
1981
, “
Generalized Correlations of Critical Heat Flux for the Forced Convection Boiling in Vertical Uniformly Heated Annuli
,”
Int. J. Heat Mass Transf.
,
24
, pp.
541
544
.
8.
Shah
,
M. M.
,
1980
, “
A General Correlation for Critical Heat Flux in Annuli
,”
Int. J. Heat Mass Transf.
,
23
, pp.
225
234
.
9.
Collier, J. G., 1981, Convective Boiling and Condensation, 2nd Ed., McGraw-Hill, New York, p. 135.