Bubble behaviour and Critical heat flux on circular tubes during pool boiling process

Abstract

In recent years pool boiling heat transfer has been a focus of study due to high heat dissipation capability corresponding to small temperature differences. The utilization of the aforementioned technique is widely implemented for thermal management in nuclear industries. This research primarily emphasises analysing the effect of length and diameter of tubes on bubble behaviour and CHF during pool boiling in saturated water under atmospheric pressure. The tubes are made of SS 304 and kept in a horizontal orientation. The tube diameters varied from 1.2 mm to 9 mm. The length of the tubes is varied from 50 mm to 1000 mm. It is observed that for the same length, lower diameter tubes exhibit a higher magnitude of CHF. For the same diameter, the smaller the length higher the CHF. The study shows that irrespective of diameter, beyond the length of 500 mm, CHF variation is insignificant. The study shows the nucleation and bubble behaviour for different dimensions of tubes under different heat fluxes. It is inferred from the experiment that for smaller curved surface areas, active nucleation sites are less. So, the bubble formation and coalescence are less. An empirical correlation, including the effect of tube length and diameter, is suggested for the pool boiling CHF. The experimental data are tabulated to contribute towards pool boiling CHF databank.