NUMERICAL STUDY OF EFFECT OF CONTACT ANGLES ON FLOW BOILING EMPLOYING THERMAL LBM SIMULATION

摘要

The influence of contact angle on bubble growth and detachment is investigated in this paper. The phase-change Lattice Boltzmann Method (LBM) which includes a SRT pseudo-potential LB model and a thermal LB model is used to simulate the flow boiling in vertical tube. To verify the correctness of the model, the coexistence curve obtained from the LBM simulations is compared to the analytical one. Then the relation between the diameter of bubble detachment and the wall superheat is compared with the empirical relation. The effect of contact angle on the bubble growth is investigated. The bubble growth with different contact angles is calculated. The bubble growth processes with different contact angles and the detached shape are shown in this paper. The bubble equivalent diameter and the length of contact line is investigated. The bubble equivalent diameter curve shows that bubble growth can be divided into two stages, initially isothermal growth stage, followed by isobaric growth stage. Bubbles show different characteristics at those two stages. The length of contact line curve shows there is a period of stagnation in the process of bubble growing up. This phenomenon can be explained by the theory of dynamic contact angle.