An experimental study was carried out in order to investigate the heat transfer performance of falling film outside a single horizontal tube with a new test facility. Two types of commercial evaporation tubes were tested: a plain tube and an enhanced tube

which have the same outer diameter of 19 mm and the same effective test length of 2500 mm. Refrigerant 404A was used as working fluid to transfer heat with heating water inside the tube. Spraying feeding method was adopted by using 21 spray nozzles with the equivalent diameter of 2 millimeters. Experiments were performed at saturation temperatures of 0

5

10 and 15 oC

heat fluxes from 8 to 30 kW/m2 and mass flow rate per unit length of tube from 0.07 to 0.11 kg/ms. The regularity of falling film heat transfer performance of R404A outside a horizontal tube was obtained which is meaningful for the design and application of falling film evaporator.