Flow boiling heat transfer of R1234yf inside a 3.4 mm ID microfin tube

• The flow boiling heat transfer of R1234yf inside a mini microfin tube is studied.
• The heat transfer coefficients and the frictional pressure drops are measured.
• The vapour quality at the onset dryout is estimated.
• The reliability of two recent models for flow boiling heat transfer and pressure drop is addressed.

This paper presents experimental results about the flow boiling of R1234yf inside a mini microfin tube. R1234yf is a Hydro Fluoro Olefin with a GWP < 1, and thus it has recently been proposed as one of the possible substitutes of the common R134a. This study was carried out in a facility located at the Dipartimento di Ingegneria Industriale of University of Padova. The microfin tube has an inner diameter at the fin tip of 3.4 mm, an outer diameter of 4.0 mm, it has 40 fins and each fin is 0.12 mm high. From the experimental measurements, it was possible to calculate the heat transfer coefficients, frictional pressure drops, and vapour qualities at the onset of the dryout phenomenon. The mass velocity was varied from 190 to 940 kg m−2 s−1, the heat flux from 10 to 50 kW m−2, the vapour quality from 0.10 to 0.99, and the saturation temperature at the inlet of the test section was kept constant and equal to 30 °C. The experimental results were also compared against the values predicted by empirical correlations available in the open literature.