Pool boiling cooling of high heat generating devices is examined experimentally. Influence of surface shape on subcooled boiling heat transfer in low degree of superheat at surface of dummy CPU is investigated. The heat transfer surfaces used are minute pyramid-like types. Effects of apex angle, pyramid pitch and addition of sodium myristate as a surfactant on the pool boiling heat transfer performance are examined. It is found that optimum pitch is about 0.5 mm. And also, the steeper the slope of pyramid, the more heat transfer evaluated at projected surface area is promoted. Pyramid 30° type with pure water improves heat transfer coefficient at heat flux of around 0.3 W/m2 about 5 times compared to that of smooth surface. Furthermore, pyramid 30° type with sodium myristate at above heat flux improves heat transfer coefficient about 9 times compared to that of smooth surface with pure water.
Non-equilibrium molecular dynamics(NEMD) simulations were conducted for a coexistence system of water and ice on a solid surface in order to elucidate effects of solidification phenomena on the water molecules in the vicinity of the solid surface. First, the initial state for the simulation was investigated by varying the temperature of the system, and the melting point of the system was estimated. Then, the state at the estimated melting point was adopted as the initial state, and the NEMD simulation was conducted. The results show that the density of the water molecules in the vicinity of the solid surface changes when the solidification front of water reaches close the solid surface, in the case of the relatively low solid-liquid interaction strength.