Two-phase flow pattern data were obtained with 12-mm-bore sight glasses for five refrigerants - R123, R134a, R502, R402A, and R404A. The existing flow pattern maps of Taitel and Dukler (1976) and Hashizume (1983) poorly represented the data, while, with the exception of mist flows, the VDI map identified the flow patterns successfully. Methods used in horizontal flow boiling correlations to determine the threshold between all wet wall and partially wet wall flows were shown to be unreliable.

KEYWORDS: year 1995, measuring, calculating, fluid flow, heat flow, refrigerants, replacing, horizontal, tubes, accuracy, R123, R134a, R502, R402A, R404A, visualising, comparing