Experimental investigations on bubble departure diameter and frequency of methane saturated nucleate pool boiling at four different pressures

In this work, bubble departure diameters and bubble departure frequencies on saturated nucleate pool boiling of methane were studied. The experiments were conducted on the upper surface of a smooth vertical copper cylinder, at pressures of 0.15 MPa, 0.2 MPa, 0.3 MPa and 0.4 MPa with heat fluxes varying from 10.64 kW m−2 to 79.25 kW m−2. Bubble departure diameters were measured from the images captured by a high-speed digital camera at lower heat fluxes less than 79.25 kW m−2, at which isolated bubbles were obtained. Bubble departure frequencies were calculated by counting the numbers of the detachment bubbles and the corresponding time intervals. Their relationship with Jacob number (Ja) was analyzed. With an increase in Ja at a given pressure, bubble departure diameter increases while bubble departure frequency tends to decrease. After the comparisons with six most used correlations for bubble departure diameter, a new correlation was developed within ±20% deviation from most of the experimental data. Additionally, a new correlation for the relationship between bubble departure diameter and departure frequency was also proposed within ±20% deviation from most of the experimental fDd2.