A SIMPLIFIED FORCE-BALANCE MODEL TO PREDICT BUBBLE DEPARTURE DIAMETER IN HORIZONTAL FLOW BOILING

摘要

In this paper, a simplified force-balance model in horizontal flow boiling is proposed by introducing several dominant dimensionless parameters. Forces acting on a bubble attached in the direction parallel to the heating surface are analyzed completely, which include quasi-steady drag force, surface tension force and growth force in x-direction. When the force balance is broken in the x-direction before the y-direction, bubble will departure from the nucleation site immediately. Based on the force-balance analysis, bubble departure diameter is formulated to be a function of Jakob number, Reynolds number and Prandtl number. By analyzing the effects of dimensionless parameters, it is found higher Jakob number indicates larger bubble departure diameter, while the increase of Reynolds number will reduce the departure diameter. Besides, the simplified model is able to enlarge application of force-balance model under various dimensionless parameters and make the calculation of bubble departure diameter much easier. Finally, comparing with the experimental data reported in literature, the error between simplified force-balance model and experimental is about 25%.