Methodology for Modeling Spray Cooling Of a Cylindrical Tube Heated In the Film Boiling Regime

This work focuses on the physics related to spray cooling of horizontal, circular tubes under film boiling conditions, i.e. when the substrate temperature exceeds the Leidenfrost point.The main objective is to express the steady state heat removal rate from the heated surface, with a focus on understanding heat transfer and drop impact on a complex geometry.The characteristics of the spray, which include drop size, velocity (assumed constant), and spatial distribution, are expressed in terms of local number flux.To account for drop-drop interactions on the cylinder, an effective coverage in terms of coverage efficiency is considered at higher mass flow rates.Results are presented as the average heat transfer coefficient.The findings highlight the importance of liquid mass flow rate and droplet diameter as the most influential parameters affecting heat transfer.Additionally, the non-normal impact angles caused by the spray angle and the curvature of the cylindrical surface lead to dramatically reduced heat transfer rates.This reduction of the heat transfer can be mitigated by placing multiple nozzles at various longitudinal and circumferential positions around the tube.