THE EFFECT OF FIN DENSITY ON THE HEAT TRANSFER AND PRESSURE DROP PERFORMANCE OF LOW-FINNED TUBE BANKS

Heat transfer and pressure drop data are presented for equilateral-triangular pitch tube bundles containing low-finned tubes with fin counts between 0.4 and 1.06 fins per mm. Two types of finned tubes were tested. The first was a 19-mm O.D. integral finned tube with a 1.65-mm fin height and with 0.75 and 1.06 fins per mm. The second was a 31.75-mm O.D. plain tube wound with 3.18-mm soldered fin stock and containing 0.4, 0.71, and 0.98 fins per mm. A new low-fin heat transfer correlation was developed which predicted these new data and additional data from five other sources within an error range from minus 20 percent to plus 31 percent. A necessary dimensionless group required to obtain this accuracy was the fin diameter/fin spacing ratio. Existing friction factor correlations were not successful in predicting these new pressure drop results. A new low-fin friction factor correlation was developed which predicted these data and additional published data within an error range from minus 19 percent to plus 27 percent.