Measurement of absorption rates in horizontal-tube falling-film ammonia-water absorbers

Heat and mass transfer in a horizontal-tube falling-film ammonia-water absorber was investigated. A tube bank consisting of four columns of six 9.5 mm nominal OD, 0.292 m long tubes was installed in a shell that allowed heat and mass transfer measurements and optical access for flow visualization. This absorber was installed in a test facility consisting of all the components of a chiller, fabricated to obtain realistic operating conditions at the absorber to account for the influence of the other components in the system. Tests were conducted over desorber solution outlet concentrations of 5–40% for three nominal absorber pressures of 150, 345 and 500 kPa, for solution flow rates of 0.019–0.034 kg s−1. Measurement and analysis techniques, heat transfer rates, and solution- and vapor-side heat and mass transfer coefficients are described. Trends in heat and mass transfer coefficients are discussed, highlighting the effects of solution flow rate and concentration, and absorber pressure.