Effect of hydraulic diameter on condensation of R-134A in flat, extruded aluminum tubes

This paper addresses the effect of hydraulic diameter on single-phase and c ondensation heat transfer and pressure gradient for R-134a in multi-port fl at extruded aluminum tubes. The hydraulic diameter range of the four tubes tested is between 0.44 and 1.56 mm. This work is believed to provide conden sation data on the smallest hydraulic diameters reported in the literature. The modified Wilson plot method was used to determine the heat transfer co efficient for water-side flow in the annulus. The data span 300-1000kg/m(2) -s mass velocity and approximately 15-to-90% vapor qualities. The condensat ion coefficient and pressure gradient increases with decreasing hydraulic d iameter for all tubes. The effect of hydraulic diameter on condenser design and operation is also discussed. The ability of existing correlations to p redict the single-phase and condensation coefficients are evaluated.