TUBE AND FIN GEOMETRY ALTERNATIVES FOR THE DESIGN OF ABSORPTION-HEAT-PUMP HEAT-EXCHANGERS

The present study investigates the possibility of using highly compact , flat-tube/multilouver fin heat exchangers as replacements for conven tional round-tube hydronic fluid-to-air heat exchangers used in space- conditioning applications. The advantages of these novel heat exchange rs such as smaller frontal obstruction to air flow compared to round t ubes (drag and fan power reduction), larger heat transfer coefficients due to the interrupted multilouver fins, and larger surface areas per unit volume can benefit absorption space-conditioning systems. A comp arison of the performance of this new geometry versus conventional rou nd-tube heat exchangers was performed through the quantification of th e decrease in heat exchanger mass for equivalent heat duties. Within t he limitations of the available heat transfer and friction factor corr elations, round-tube heat exchangers with flat,wavy, louvered and annu lar fins, and flat-tube heat exchangers with multilouver fins were des igned to meet typical absorption cycle design conditions. The effect o f design variables such as parallel/serpentine flow arrangements of tu bes, fin densities, core depth, and other parameters on heat transfer performance and tube-and air-side pressure drops was investigated. It was shown that hat-tube heat exchangers can transfer equivalent heat d uties while meeting pressure drop constraints with a significant reduc tion in the overall mass and size.