Flow Boiling of Lithium Bromide-water Solution in Microchannels, with Application to Desorption

Download or read book Flow Boiling of Lithium Bromide-water Solution in Microchannels, with Application to Desorption written by Kurt Fackrell and published by . This book was released on 2004 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent studies of flow boiling within microchannels have shown high heat fluxes, leading to successful design and testing of compact heat exchangers, cooling systems for electronics and other high efficiency, miniature components. An experimental study of flow boiling of a concentrated salt solution in microchannels is presented. Experiments examined flow in single, circular microchannels, with a length of 25 mm and diameters of 0.127 mm and 0.25 mm, and in arrays of five rectangular microchannels, each with a length of 8.5 mm and a hydraulic diameter of 0.133 mm. Inlet concentrations of lithium bromide were varied from 47% to 57% by mass, heat inputs from 2.2 to 7.0 W per channel, and flow rates from 0.60 to 0.80 g/min per channel. Single channel tests yielded as much as 0.05 g/min of water vapor for the conditions examined. If an array of channels could produce vapor at a similar rate, it may be possible to apply microchannel flow boiling in a compact desorber or evaporator. Unequal flow distribution in the microchannel arrays limited testing to heat input rates too low to verify array desorption. Infrared visualization of flow at the exit of the microchannel was performed to document solution exit condition based on flow rate, heat input rate, and lithium bromide concentration. Visualization identified four basic exit conditions: steady dripping at low heat input rates, unsteady dripping with occasional vapor at moderate heat input rates, continuous droplet spraying at high heat input rates and flow rates, and long period oscillation between unsteady dripping and droplet spraying at high heat input rates and low flow rates.