Ammonia single-phase and two-phase local pressure losses on sudden expansion and contraction

The manuscript presents a significant experimental study on single-phase and two-phase ammonia flow in ID 4 and ID 6 mm smooth tubes with expansion and contraction. This study, conducted in six configurations with the geometrical factor of expansion and contraction between 0.08 and 0.56, has provided valuable insights at saturation temperatures of 45 and 65 °C, mass velocity of 300 to 500 kg·m-2·s-1 and vapour quality of 0.1 to 0.9. The findings have confirmed the validity of the homogeneous approach [1], which defines the local pressure losses in the channel on expansion and contraction. The homogeneous model fits the ammonia test data with an accuracy of ±20 % at the considered boundary conditions. Chisholm's heterogeneous model with the marginal empirical coefficients (B = 0.5 and 1.5) provides conservative minimal and maximal estimations, which could be helpful in engineering applications.