Experimental investigation of heat transfer performance in gas-atomized spray cooling

Abstract

Spray cooling has substantial potential for wide application, given its unique characteristics, including high heat transfer coefficient, absence of contact thermal resistance, and the elimination of cooling hysteresis. In this study, a visualized experimental system featuring a gas-liquid two-phase cyclonic nozzle was constructed to study both the heat transfer and fluid morphology features pertaining to the wall. With the increase of wall superheat, a progressive transition across four distinct stages of heat transfer – liquid film, stream flow, droplet flow, and mist flow can be found. Of these, the droplet flow stage outperforms others in terms of heat transfer performance and is thus advocated as the preferred mode of application. In response to increasing spray pressure, the droplets generated on the wall during the droplet flow stage undergo a reduction in size, yet become more densely distributed. A notable increase in critical heat flux by 59.5 % is observed when spray pressure is elevated from 0.2 to 0.4 MPa. While raising the spray flow rate leaves the heat transfer performance during the liquid film stage largely unchanged, it effects a significant augmentation in critical heat flux. Our experimental results ultimately obtain the optimal operating parameters that facilitate the wall surface's retention in the droplet flow stage. These experimental results are poised to contribute meaningfully to the engineering practices associated with spray cooling applications.