Heat and mass transfer models for horizontal-tube falling-film ammonia-water absorption

Abstract

An experimental investigation of heat and mass transfer in a horizontal-tube falling-film ammonia-water absorber, operated as part of a complete ammonia-water absorption test facility, is presented. A tube bank consisting of four columns of six 9.5 mm nominal outer diameter, 0.292 m long tubes was installed in an absorber shell that allowed flow visualization and heat and mass transfer measurements at component- and local-levels. The Falling-film mode was found to account for a major portion of the absorber. The effects of operating conditions on the heat and mass transfer coefficients were investigated. While the solution Nusselt number increased, the vapor and liquid Sherwood numbers remained relatively insensitive to the solution Reynolds number. Heat and mass transfer models were developed to predict the absorber performance over a wide range of operating conditions in air-conditioning and heat pumping modes (solution concentration: 5–40%, pressures: 150, 345, 500 kPa, and solution flow rates: 0.019–0.034 kg s−1).