Mechanism study of bubble maximum diameter in the subcooled boiling flow for low-pressure condition

Bubble characteristic sizes are important parameters for the heat transfer and critical heat flux. Compared to the empirical correlation and force analysis model, the heat balance model is an effective method to calculate the bubble maximum diameter. In this paper, a detailed evolution process is described for the growth of the bubble in the subcooled boiling flow. Based on the heat balance theory, a new mechanistic model is developed for bubble maximum diameter under the low-pressure condition. Three heat fluxes are taken into account which include heat from thin liquid film, heat from superheated liquid layer and heat dissipated to the surrounding subcooled liquid. The area fractions of heat fluxes are adjusted to satisfy physical reality. Liquid Reynolds number is used to describe the effect of velocity instead of velocity itself. Four experimental databases and one independent database on the low-pressure conditions are used for the validation of the present model. Results show a good agreement with an average relative error about 35.80% in a wide range of boiling flow conditions. (C) 2020 Elsevier Ltd. All rights reserved.