Heat/mass transfer enhancement of an exothermic absorption utilizing a spinning disk reactor

Abstract

An effective way to improve the performance of absorption cooling systems is to enhance heat and mass transfer in the absorber unit. To enhance heat and mass transfer, one process intensification method that can be used is centrifugal acceleration. In centrifugal acceleration, rotation of the heat transfer surface thins and mixes the solution film and thereby decreases film-side thermal resistance. In this study, a flat disk spinning at up to 625 rpm was experimentally investigated for use as the absorber in an absorption cooling system. Aqueous lithium bromide was used as the working fluid, and the heat of absorption was rejected to cooling water. Overall and film-side heat transfer coefficients were 3.3 and 5.5 times higher, respectively, compared to conventional horizontal tube banks. Average power consumption rate of the electric motor powering the rotation was 3.1% of cooling capacity. This study suggests that the absorption process can be intensified by enhancing the transfer processes, which could lead to more economical absorption chillers. Spinning disk absorbers may be especially useful for a new generation of absorbents that exhibit high viscosity, but promise to substantially improve the overall system efficiency.