A new microstructure for pool boiling

Combining electrocoating and etching processes, we have developed a new type of microstructure for nucleate boiling. The basic elements of the structure are cylindrically shaped; their density ranges up to 10(7) cm(-2). To test the efficiency of the structure, the outer surface of a tube has been provided with such a structure and used in pool boiling experiments with the refrigerant R141b at atmospheric pressure. The results obtained show the heat flux to remain independent of the wall superheat in the fully developed boiling region. The behavior is novel. It is most probably associated with the density of active bubble nucleation sites. Activated at a certain wall superheat, the density of the sites generating bubbles remains apparently unaffected by raising the heat flux. Given that these preliminary results should be confirmed by further experiments, the microstructure developed will be suitable for nucleate boiling in general, but for keeping the heating surface largely isothermal, despite the variation of the heat flux, in particular. (C) 2004 Elsevier Ltd. All rights reserved.