Momentum and Heat Transfer Analogy (continued) Define the Stanton number St. St= h Nu pVcp Re Pr The analogy takes the form CL-SI Reynolds analogy 2 The restrictions:the validity of the boundary layer approximations,dp/dx=0and Pr1. The modified Reynolds,or Chilton-Colburn, analogy has the form CL=St Pr213 =j (0.6<Pr<60) 2 Colburn j factor For laminar flow,it's only appropriate when dp/dx0Momentum and Heat Transfer Analogy (continued) • Define the Stanton number St, • The analogy takes the form • The restrictions: the validity of the boundary layer approximations, and . The modified Reynolds, or Chilton-Colburn, analogy has the form RePr Nu Vc h St p    St Cf  2 Reynolds analogy / 0 * dp dx  Pr 1     2 / 3 Pr (0.6 Pr 60) 2 f c St j Colburn j factor For laminar flow, it’s only appropriate when / 0 * dp dx 