Performance of pool boiling with 3D grid structure manufactured by selective laser melting technique

3D thin wall grid structures were manufactured with selective laser melting (SLM) technique for boiling enhancement. To precisely control the structure parameters and investigate their influences on boiling heat transfer characteristics, the scan line spacing method was adopted to manufacture various grid width and wall height structures. The stainless steel was chosen as the building material. Pool boiling experiment results showed that grid structures could significantly influence nucleate boiling behavior and enhance critical heat flux (CHF). The nucleate boiling heat transfer coefficient generally decreased with grid width except for the 0.4 mm grid width samples, the grid channels of which were blocked. The decrease trend was caused by the decreasing effective heating area. The CHF increased with grid width until 1.1 mm, then slightly decreased when the grid width was greater than 1.1 mm. The maximum CHF on the grid structure surface achieved at the transition point was 303 W/cm2, which was three times that of the plain surface. The enhancement was attributed to the grid structure's “partition effect” that inhibited Helmholtz instability, confined bubble and hot spot expansion in the near surface region. The results provide important guidance for the design of future 3D structured surfaces for boiling enhancement. SLM technique provides a new and effective way for the manufacturing of innovative structured surfaces with controllable parameters and opens a new direction for boiling heat transfer mechanism research.