An experimental study of flow boiling frictional pressure drop of R134a in a horizontal 1.002 mm tube under hypergravity

An experimental study with a horizontal 1.002 mm inner diameter mini-tube is conducted to investigate the two-phase frictional pressure drop of R134a flow boiling under hypergravity. Totally 1718 data points under the gravity from 1 to 3.16g were obtained, with mass fluxes of 400-1075 kg/m2 s, vapor qualities of 0.05-0.85, heat fluxes of 24.0 and 31.5 kW/m2, and saturation pressures of 0.6 and 0.7 MPa. The hypergravity conditions were achieved using a centrifugal acceleration machine. The results show that with increasing gravity the flow boiling frictional pressure drop increases at high vapor quality but decreases at low vapor quality, and the trend reversals take place roughly in the range of 0.07 < x < 0.45, depending on saturation pressure and mass flux. The comparison between the experimental data and the predictions of 28 correlations of two-phase frictional pressure drop is made, and the results show that the best correlation has a mean absolute deviation of 12.8% for the entire data, 10.6% for normal gravity, and 13.7% for hypergravity.