Experimental Measurements and Numerical Modeling for the Air-Mist Cooling of a Heated Cylinder

Experimental measurements and numerical simulations are conducted to investigate the effect of mist on the spray heat transfer and fluid dynamics in the cooling of a low-carbon steel cylindrical surface heated to the nucleate boiling temperature range. Multiple tests are performed to investigate the effect of the droplet size, and liquid-to-air loading on the spray heat transfer along the circumference of the annulus cylinder. Infrared imaging is used to capture the effect of the spray flow conditions on the droplets transportation process around the heated cylinder. A computational fluid dynamics model is also developed to simulate the spray transportation process, droplets impaction and evaporation over the cylinder surface. The model takes into consideration droplet-to-surface interaction and water-film accumulation on the surface. Simulation results show the wetting of the cylinder depends on the droplet size and liquid-to-air loading. The smaller the droplets, the closer to the surface they remain. For high liquid-to-air loadings and high air velocities, droplet wetting of the cylinder back surface dramatically increases due to the increase in the flow turbulence. An overall good agreement is observed between the experimental measurements, numerical simulations and the thermal images. The results of this study shall lead to a better understanding of the multiphase heat transfer enhancement that plays an important role in the design of heat exchangers using multiphase cooling.