Condensation heat transfer and pressure drop data of R-134a in annular helical pipes is of significant importance to the effective design and reliable operation of helical pipe heat exchangers for refrigeration, airconditioning, and many other applications. This paper presents the experimental investigation on condensation heat transfer and pressure drop characteristics of R-134a in an annular helical pipe. The average condensation heat transfer coefficients and pressure drops were experimentally determined for R-134a at three different saturated temperatures (35 8C, 40 8C, and 46 8C). The experimental results are compared with the data available in the literature for helical and straight pipes.

This article presents an experimental investigation on condensation heat transfer of R-134a in horizontal straight and helically coiled tube-in-tube heat exchangers. The experiments were carried out at three saturation temperatures(35℃, 40℃ and 45℃) with the refrigerant mass flux varying from 100kg/m-s to 400kg/m-s and the vapor quality ranging from 0.1 to 0.8. The effects of vapor quality and mass flux of R-134a on the condensation heat transfer coefficient were investigated. The results indicate that the condensation heat transfer coefficients of the helical section are 4%-13.8% higher than that of the straight section. The experimental results were compared with the data available in literature for helical and straight pipes.