Experiments on boiling heat transfer and pressure drop of lowpressure, low-GWP refrigerants inside a horizontal microfin tube

摘要

This study experimentally investigated the boiling heat transfer characteristics of low-pressure and low-GWPrefrigerants, including R1224yd(Z), R1233zd(E), R1336mzz(E), and R1336mzz(Z), which are expected to beused as alternative refrigerants to R245fa in high-temperature heat pumps, inside a horizontal microfin tube.The test tube was a copper tube with an equivalent inner diameter of 8.9 mm, a fin height of 0.12 mm, a helixangle of 16.5°, and a number of 65 fins. The experiments were conducted under a mass velocity range of 50–300 kgm~(-2)s~(-1) and a saturation temperature of 40 °C. The boiling heat transfer coefficients and pressure dropswere measured. Additionally, the applicability of correlations for microfin tubes, proposed in our previousstudy, was verified. It was found that the boiling heat transfer coefficients in the high mass velocity range aswell as pressure drops were relatively in agreement with previously reported correlations.