Convective Condensation in Small Diameter Channels

This work presents an experimental and analytical study on the convective condensation in small diameter channels. Two different types of heat exchangers were tested: one with conventional channels and one where a porous boundary was present. Tests were performed for low and high flow rates and two saturation temperatures. For low flow rates, the condensers with small diameter channels presented excellent heat dissipation capability, with high Nusselt numbers. For the condenser with a porous boundary, the Nusselt number was even higher when compared with the condenser with conventional channels, even for the same channel size. For high flow rates, the Nusselt number presented higher levels than those observed for low flow rate, and the pressure drop was also high. Equations for Nusselt number and pressure drop predictions were obtained, which showed excellent degree of correlation. During the tests, four different flow patterns could be observed: annular, bubbly, plug and stratified. An analytical model for the heat transfer process in small diameter channels was developed, where the liquid film thickness and the meniscus curvature could be calculated.

Autorentext

Research Engineer and Faculty at the Space Mechanics and Control Division at the National Institute for Space Research in Brazil. Degrees: B.Sc UNESP-Brazil (1992), Mechanical Engineering; M.Sc USP-Brazil (1996), Mechanical Engineering; Ph.D (2000), joint program between USP and Clemson University (USA), Mechanical Engineering.