Two phase flow maps of R1233zd(E) at near critical saturation temperature

The authors present a study on flow maps and flow structures of refrigerant R1233zd(E) in the range of high saturation temperatures and medium and high reduced pressures. Emerging technologies such as high-temperature heat pumps or Organic Rankine Cycle systems operate at saturation temperatures above 100 °C necessitating the precise knowledge of flow boiling and flow condensation data. The experiment was conducted with a vertical transparent tube of d = 3 mm internal diameter for reduced pressure ranging from 0.2 to 0.8, and mass velocities, G ranging from 180 [kg/(m 2 ·s)] to 445 [kg/(m 2 ·s)]. The collected experimental database consists of 302 data points. In addition to the typical mass velocity flow map authors presented the reduced pressure flow map, to highlight the effects observed with the variation of saturation pressure. The effect of saturation pressure is significant because transition lines between flow regimes are shifting alongside increasing saturation temperature. Annular flow can occur even 0.4 quality later for reduced pressure 0.8 in comparison to reduced pressure 0.2. The authors report the mass velocity flow maps in a function of vapor quality for constant values of reduced pressure or constant mass velocities. A new flow pattern prediction method is proposed which divides flow structures into three parts: bubbly, intermittent and annular flow. Postulated correlation estimates the transition between bubbly flow and intermittent flow and between intermittent flow and annular flow. The prediction method is compared against 7 well-established literature correlations. The new prediction method showcases the best results among analyzed correlations.