Heat transfer and pressure drop during condensation of refrigerant 134a inan axially grooved tube

Condensation experiments have been performed over a mass flux range of 75-4 50 kg m(-2) s(-1) in an 8.91 mm inside diameter, axially grooved, micro-fin tube with R134a. At 75 kg m(-2) s(-1), the axially grooved tube performs m arginally better than a smooth tube, but worse than a similarly grooved tub e with an 18 degrees helix angle. Mass fluxes at 150 kg m(-2) s(-1) and gre ater show broad quality ranges in which the axially grooved tube performs s ignificantly better than both smooth and helically grooved tubes. Pressure drop characteristics of the axially grooved tube are similar to those found in an 18 degrees helix angle tube. (C) 1998 Elsevier Science Ltd. All righ ts reserved.