LAUSR

Jet impingement boiling has been widely used in industrial facilities as its higher heat transfer coefficient (HTC) and critical heat flux (CHF) can be achieved in comparison with the pool boiling. By covering beads packed porous layer on the heated wall surface, the enlarged heat transfer area and rise of nucleation sites for boiling occur, thus, the heat transfer performance of boiling can be enhanced. For the jet impingement boiling with brass bead packed porous layers, the heat transfer performance is crucially influenced by the characteristics of porous layer and working fluid flow, so the experiments were conducted to investigate the effects of the jet flow rate, fluid inlet subcooling, number of porous layer and brass bead diameter of porous layer. Comparison study shows that impingement boiling promotes the HTC and CHF as 1.5 times and 2.5 times respectively as pool boiling at similar conditions. Higher heat transfer performance can be obtained in the cases of a higher jet flow rate and a higher fluid inlet subcooling, and there exist the optimal layer number and bead diameter for heat transfer. Particularly, a double-layer porous layer results in an increase of 39% in heat flux at superheat of 30 K compared with a single-layer case; a single porous layer at d =8 mm brings an increase of 23% in heat flux at superheat of 30 K compared with that of bare plain surface. Besides, the actual scene of jet impingement boiling was recorded with a camera to investigate the behavior evolution of vapor bubbles which is highly correlated to the heat transfer process.