In terms of direct-contact heat transfer process between cold air bubbles and immiscible liquid

the convection heat transfer equation was established and solved numerically. A correlation between Nu and Re as well as Pr was obtained

and the validation of the model was verified by comparing the theoretical value and the experimental data. Entropy generation during the heat transfer process was studied. The variation of entropy generation rate was presented regarding Re. An optimal Re would lead to a minimum entropy generation during the heat transfer process. The research provides a theoretical basis of optimizing the direct-contact heat transfer process.