Boiling Heat Transfer in a Small Diameter Tube below Atmospheric Pressure on a Natural Circulation Condition.pdf

B114
Boiling Heat Transfer in a Small Diameter Tube below Atmospheric
Pressure on a Natural Circulation Condition
*CHOWDHURY Feroz MD Fumito KAMINAGA Koji GOTO Kunihito MATSUMURA
Department of Mechanical Engineering , Faculty of Engineering,
Ibaraki University, Hitachi 316, Japan.
ABSTRACT
Boiling heat transfer is experimentally examined in a vertical small diameter tube(ID= mm) using water, ethanol and
Freon R-113 working fluids over a wide low pressure range of to bar. Comparisons of the measured heat transfer
coefficients with existing pool boiling correlations and a boiling correlation developed for a thermosyphon show that the
measured coefficients are a little larger than the pool boiling correlations and lower than thermosyphon correlation. But for
ethanol and Freon R-113 the measured coefficients at high pressure are larger than the thermosyphon correlation. The effect of
pressure on the boiling heat transfer for water is found to be less than that in a pool boiling condition. But for ethanol and
Freon R-113 the measured heat transfer coefficients increase with increase in pressure. Finally correlations are developed that
show good agreement with the experimental data.
Key Words: Boiling heat transfer, Natural circulation, Low pressure, Small diameter tube.

NOMENCLATURE affected only by flow behavior in the microlayer adja