Predicting the onset of nucleate boiling in a vertical thermosiphon reboiler

Analysis of incipience of nucleate boiling in a reboiler tube

“…This corresponds to the saturated boiling regime as exhibited by the slowly decreasing wall and liquid temperature profiles. Further details are given elsewhere by Kamil 19 and Kamil et al 20,21 Boiling incipience in a vertical thermosiphon reboiler From the wall and liquid temperature distributions as discussed earlier, it is observed that there exists a point at which the bubbles start appearing at the surface, though the liquid is still below its saturation value. This may be the onset of subcooled/surface boiling, and its effect is exhibited in deviation of wall temperature curves from straight-line behavior, characteristic of single-phase convection.…”

“…These transient phenomena create a quenching effect on the nucleation process, which is further complicated by liquid submergence. A few workers, such as Agarwal, 17 Ali and Alam, Kamil, 19 and Kamil et al, [19][20][21] have investigated the effect of inlet liquid subcooling and submergence on heat transfer, circulation rate, and boiling incipience in a vertical thermosiphon reboiler. In a natural circulation reboiler, the induced flow is established due to the differential head between the cold and hot legs.…”

“…Reed and Mudawar 16 examined the effectiveness of the zero-angle cavities created by curved contact with a flat surface in promoting vapor embryo capture, low temperature boiling incipience, and reduction or elimination of the incipience temperature overshoot with highly wetting liquids. Agarwal, 17 Ali and Alam, 18 Kamil, 19 and Kamil et al 20,21 experimentally determined the boiling and nonboiling zones for the heating surface and superheat for incipient boiling in a vertical tube thermosiphon reboiler with wide ranges of submergence. A dimensionless correlation relating the values of heat flux, inlet liquid subcooling, and submergence was proposed for predicting Z OB /L and wall superheat relating the heat flux with thermophysical properties of test liquids as given in Table 1.…”

“…The validity of the criterion was proven in many practical applications. Incipience based on r tan criteria for natural convection system was studied by Agarwal, 17 Ali and Alam, 18 Kamil,19 and Kamil et al [20][21][22][23][24] Sudo et al 9 and Hino and Ueda 10 used a different hypothesis in their forced convection study. They predicted incipience based on the maximum cavity radius (r max ) available for nucleation on the heated surface.…”

Effect of submergence on boiling incipience in a vertical thermosiphon reboiler

“…Wu et al [23] studied the surfactant effects on boiling incipience. Agarwal [24], Ali and Alam [25], Kamil [26], and Kamil et al [27,28], experimentally obtained the boiling and non-boiling zones (Z OB /L) for heating surface and wall superheat for incipient boiling for different liquids in a vertical tube thermosiphon reboiler with wide range of submergence. A dimensionless correlation relating the values of heat flux, inlet liquid subcooling and submergence was proposed for Z OB /L and for wall superheat relating the heat flux with thermophysical properties of test liquids.…”