Falling film pyrolysis can improve the quality of pyrolysis products of waste plastics. The pyrolysis process of molten plastics is a complex process and the interphase force has an important influence on the flow and heat transfer process of the liquid film. Based on OpenFOAM (R) and considered the interphase drag force, the flow behaviors and heat transfer characteristics of the liquid film during the falling film pyrolysis of molten plastics were numerically simulated by VOF (Volume of Fluid) method. The results show that the surface of the liquid film is a wavy structure and the liquid film presents a comprehensive flow pattern of film, rivulet and droplet. With the increase of pyrolysis temperature, the length of liquid film and the average apparent heat transfer coefficient decrease, and the average thickness increases slightly. With the increase of the liquid film inlet velocity, the liquid film thickness and the average apparent heat transfer coefficient increase. (C) 2018 Elsevier Ltd. All rights reserved.