Effects of cylindrical wall attachment on nucleate boiling

This paper reports on a pool boiling experiment with either water or Freon-113 that was conducted to investigate nucleate boiling from a vertical heated wall with a horizontal cylindrical attachment. The result revealed that nucleate boiling is enhanced due to a favorable thermal environment characterized by a unique liquid temperature profile within the restricted regions between the attachment and the heated wall. Nucleate boiling is enhanced in terms of a lower wall superheat required for incipient boiling and more bubbles generated than from an open heated wall. As a result of the enhanced nucleate boiling, heat transfer of the vertical heated wall above the attachment was improved due to excess bubbles moving upward along the heated wall, causing removal of the thermal layer near the wall and evaporation of the thin liquid film between the bubbles and the wall. The boiling curve hysteresis with Freon-113 was significantly reduced as a result. The influences of diameter, length, and surface roughness of the cylindrical attachment were also investigated. The result of this study can be applied to enhancement of boiling heat transfer through surface attachment