Once-Through contactless flow boiling in a micro evaporator

Equipment miniaturization offers several opportunities such as an increased surface-to-volume ratio combined with high heat transfer coefficients. However, moving towards small-diameter channels demands extra attention to fouling, reliability and stable operation of the system. The present investigation explores the possibilities of hot gas flow through the porous wall of a pipe as a means to evaporate a liquid flowing in the pipe fully. A reduction of the pressure fluctuations of about 30 to 40% is obtained with this so-called contactless boiling. Because of the injected gas, wall temperatures measured are higher. The reduction in heat transfer coefficient corresponds to an insulating gas layer at the wall with an estimated thickness of 20 um.