Saturated vapor condensation of R1234ze(Z) inside a 4 mm ID horizontal smooth tube

R1234ze(Z), cis-1,3,3,3-tetrafluoroprop-1-ene, has been proposed as a refrigerant for high temperature heat pumps. The application of this molecule is still not widespread and its heat transfer performance is still poorly investigated, in comparison to other HFO refrigerants. This paper presents the experimental heat transfer coefficient and frictional pressure drop measured during R1234ze(Z) saturated vapour condensation inside a 4 mm ID horizontal copper smooth tube. New experimental tests were carried out at 40 °C of saturation temperature, with refrigerant mass flux in the range 75–300 kg m −2 s −1 at decreasing vapour quality. The new data are then compared against some well-known literature correlations and, finally, against other experimental data collected by using isobutane as two-phase fluid under the same working conditions.