Researchers at Oregon State University developed novel heterogeneous surface structures tailored to enhance bubble dynamics and nucleate boiling heat transfer, at the liquid and heated surface interface. The patterned heterogeneous surface structures utilize hydrophobic and hydrophilic properties to encourage bubble nucleation and transport fluid to specific bubble release sites. The release sites are specifically tailored for desired bubble size, coalescence, and departure rate. Modification of bubble nucleation and departure rate is needed to control the onset of nucleate boiling and to limit interfacial heat transfer resistance from accumulating vapor films. The microstructure patterns are printed and created without multi-stage lithographic techniques; enabling precise, inexpensive, and scalable manufacture.
Features & Benefits
Background of Invention
Heat transfer is a fundamental design consideration for energy management, equipment sizing, and safe operation of heat generating equipment. Powerful lasers, radars, reactors, and power electronics require new technologies and design techniques to dissipate ultra-high heat fluxes. Historically, boilers have been used to effectively remove large quantities of heat through liquid vaporization. The boiling process begins with bubble formation at the liquid and heated surface interface. Therefore, engineering bubble formation and dynamics plays a critical role in boiling onset and heat transfer performance. Recent developments in nano and micro-fabrication techniques provide a new platform for the modification of boiling surfaces for improved heat transfer. Advanced heat dissipation enables smaller heat exchanger design and provides rapid cooling for equipment with ultra-high heat flux. Developments in boiler heat transfer technology will improve the performance of boilers frequently used in the food, chemical, and energy industry.
Figure 1. Bubble nucleation of heterogeneous surfaces in 80 C water: Figure (a) shows an untreated surface with no visible bubbles. Figures (b) and (c) both have bubble formations with different surface microstructure patterns.