# Calculation Methods - Reducer/Expander

For all phase states, the pressure loss across reducers/expanders is calculated from the following expressions: Expanders Equation 1: Enlargements where the included angle of divergence is in the range: θ ≤ 45 o. K = 2.6 sin θ/2 (1 - β2)2 / β4. Equation 2: Enlargements where the included angle of divergence is in the range: 45 o < θ ≤ 180 o. K = (1 - β2)2 / β4. Contractions Equation 3: Contractions where the included angle of convergence is in the range: θ ≤ 45 o. K = 0.8 sin θ/2 (1 - β2) / β4. Equation 4: Contractions where the included angle of convergence is in the range: 45 o < θ ≤ 180 o. K = 0.5 (sin θ/2)0.5 (1 - β2) / β4. where: β = the ratio of small to large pipe diameter. θ = the included angle of divergence for enlargements and convergence for contractions. Note, FluidFlow calculates the angle (θ) automatically based on the small and large pipe diameters and transition length. Note, FluidFlow applies a correction to the above equations depending on the reducer/expander type, i.e., Concentric or Eccentric. For a more detailed discussion and explanation refer to Crane [13].