Develops a design model of an ammonia-water condenser in absorption heat pump systems. An ammonia-water mixture enters the condenser through a helically coiled fluted tube as a superheated vapour, cools, and then condenses into a liquid, which is further subcooled. The hydronic fluid flows in the annular channel around the coiled tube in confined cross-flow. The helically coiled fluted tube was used to enhance heat and mass transfer in the mixture and heat transfer in the hydronic side. The ammonia-water condenser was divided into four different regions according to the characteristics of the heat transfer mechanisms - superheated vapour, rectification, condensation, and subcooled liquid regions. Studies the effects of heat transfer coefficients in each region, the inlet concentration of vapour, and the geometric details of the fluted tube on the heat exchanger size. Presents the design results.

KEYWORDS: year 1996, designing, condensers, ammonia, water, extended surfaces heat exchangers, heat exchangers, heat transfer coefficient, heat flow, properties