Effect of impinging jet angle and offset on the heat transfer characteristics of a liquid falling film on a rotating cylinder

The jet impingement on a horizontal rotating tube is widely used in various engineering applications. However, an uneven distribution of the liquid film on the rotating tube can substantially impact the hydrodynamic and heat transfer properties of the thin liquid film. Thus, this study employs 2-D numerical simulations using the Volume of Fluid method to investigate the hydrodynamics and thermal characteristics of a thin liquid film on a rotating cylinder, exploring the effects of rotational speeds, jet tilt angles, and offset distances. The numerical results reveal that with an increase in rotational speed, the location of the jet departure position shifted in the direction of the angular motion and the local heat transfer coefficient at the impingement zone significantly decreased. However, there is no substantial difference in the value with respect to the jet velocities investigated. Deviations in the jet impingement angle cause the liquid film thickness to increase on one side of the cylinder, however, the jet departure point does not alter significantly, emphasizing the governing role of rotational motion. Additionally, for a given rotational speed, there exists a critical jet offset distance beyond which the film experiences severe unsteadiness, particularly in the liquid film departure zone at the bottom side of the cylinder.