Experimental consideration for contact angle and force acting on bubble under nucleate pool boiling

Pool boiling experiments are performed within an isolated bubble regime at inclination angles of 0 degrees and 45 degrees. When a bubble grows and departs from the heating surface, the pressure, buoyancy, and surface tension force play important roles. The curvature and base diameter are required to calculate the pressure force, the bubble volume is required to calculate the buoyancy force, and the contact angle and base diameter are required to calculate the surface tension force. The contact angle, base diameter, and volume of the bubbles are evaluated using images captured via a high-speed camera. The surface tension force equation proposed by Fritz is modified with the contact angles obtained in this study. When the bubble grows, the contact angle decreases slowly. However, when the bubble departs, the contact angle rapidly increases owing to necking. At an inclination angle of 0 degrees, the contact angle is calculated as 82.88 degrees at departure. Additionally, the advancing and receding contact angles are calculated as 70.25 degrees and 82.28 degrees at departure, respectively, at an inclination angle of 45 degrees. The dynamic behaviors of bubble growth and departure are discussed with forces by pressure, buoyancy, and surface tension.(c) 2022 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).