An Overall Bubble Diameter Model for the Flow Boiling and Numerical Analysis through Global Information Searching

Bubble diameter is important for the three-dimensional nucleate boiling two-phase flow simulation. However, the bubble diameter is rarely considered as a variable because it is difficult to estimate. In this paper, a novel bubble diameter model is proposed for the boiling flow. The heat transfer growth, the breakup or coalescence of collision and the liquid impacting separation are considered as the factors affecting the bubble diameter, and three bubble diameter sub-models are developed to calculate the overall bubble diameter based on a departure diameter. In the model, the heat transfer growth is calculated after estimating the bubble location. The collision variation is deduced from the interfacial area concentration equation. The liquid impacting variation is calculated through phase interaction force and gas viscous force. The proposed model is conducted through global information searching in the flow boiling simulation and validated using the void fraction and temperature data from the literature. The effects of the heat transfer growth, the collision, and the separating volume on the bubble diameter are discussed.