A detailed description of the heat transfer and mass transfer during ammonia-water bubble absorption in air-cooled vertical finned tube is presented.The tube is externally finned.The ammonia-water absorbent and ammonia vapor enter the absorber at the bottom and leave at the top.A differential mathematical model for the heat and mass transfer is proposed based on mass and energy balances.The changes of the two-phase flow

such as churn flow

slug flow

and bubble flow

are analyzed.The heat and mass transfer between the vapor phase and the liquid phase in different two-phase flow

and the heat transfer from the two-phase flow to the air outside the tube are considered.Solving the differential equations

local values of some important parameters temperature

molar ratio and their variations along the absorber length are obtained.