Novel geometries for air-cooled condensation of ammonia-water mixtures

•Air-cooled condensers for ammonia-water mixtures modeled and tested.•Round-tube corrugated fin and multi-pass tube array designs compared.•Model predictions within 5% of experimental data.•Improved multi-pass design meets design duty with 33% size reduction. An analytical and experimental investigation of air-cooled condensers for small-scale ammonia-water absorption heat pumps is presented. Conventional round-tube corrugated fin design and a novel multi-pass tube array design are considered for a condenser operating at severe ambient conditions within a compact footprint. Segmental heat and mass transfer models are developed to gain a deeper understanding of the characteristics of each design. Predicted heat duties are within 5% of the measured values. The limitations of correlations to predict air-side pressure drop in corrugated fins are identified. The performance of the novel multi-pass tube array condenser was comparable to that of conventional condensers, but is determined to be air-side limited throughout length of the heat exchanger. An improved multi-pass condenser design with fins for increased air-side area is proposed using the insights gained from the modeling and experiments. This design meets the heat duty requirements at severe ambient conditions, while decreasing the size of the heat exchanger by 33%.