Experiments were conducted to investigate the forced convection heat transfer of water with high temperature and pressure in an inclined upward tube with an inclination angle of 22° and an inner diameter of 26 mm at pressure of 23-28 MPa
mass velocity of 600-1 500 kg/(m
2
·s)
and heat flux at inside wall of 200-600 kW/m
2
. The results show that the circumferential wall temperatures of the inclined tube were not uniform
and the wall temperature at the top was the highest while the lowest temperature occurred at the bottom. The top-bottom temperature difference decreased with an increase in pressure and mass velocity but increased with the heat flux. Moreover
the low-density hot water gathered at the top of the inclined tube because of natural convection caused by buoyancy effect
leading to the deterioration of the heat transf
er condition
and thus the temperature at the top was higher than that at the bottom. The relationship between buoyancy and top-bottom wall temperature difference was obtained by Petukhov's criterion
and the predictions with Jackson's criterion agree well with the experimental data
indicating that both of the two criteria can be used to judge the buoyancy effect in an incline tube. The heat transfer correlations of the forced convection heat transfer of supercritical water were achieved from the experimental data
which can be used to predict heat transfer coefficients of inclined upward flow in tubes.
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references
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