EXPERIMENTAL INVESTIGATION ON PRESSURE DROP CHARACTERITICAL OF SUPERCRITICAL-PRESSURE R134a FLOWING IN HEATED CHANNELS
In this study,the pressure drop of supercritical R134a fluid are tested in heated circular tubes with inner diameter of 2 mm.The test parameter ranges are as follows:fluid pressure p=4.3-4.9 MPa,mass flux G=550-1650 kg/(m2·s),and heat flux q=25-75 kW/m2(simulated by electrical heating).According to the typical features of friction pressure drop curve,it can be divided into three regimes,namely the liquid-phase-like regime,two-phase-like regime,and gas-phase-like regime.The influence of operating parameters(pressure,mass flux and heat flux)on friction pressure drop and friction factor are both analyzed in the above-mentioned three regimes.In two-phase-like regimes,there is an obvious peak in friction factor curves.Typical friction factor correlations for supercritical fluids are compared with the experimental data,and are quantitatively evaluated.The results show that the prediction errors of these correlations are generally large,especially in two-phase-like regimes.Therefore,a modified friction factor correlation is proposed for supercritical fluid,in which a density term,a viscosity term,and an average Prandtl number are included.The new correlation is compared with the experimental data,and 97%of the predicted data are within the error range of±20%.
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