# Calculation Methods - Tube Bundle (Flow through tubes)

The pressure loss for flow through a tube bundle is composed of 2 contributing parts: Δ P = Tube Friction Loss + Tube Entrance/Exit Loss The tube friction loss is calculated assuming a tube roughness of 0.05mm, using the pipe equation calculation methods. The tube entrance and exit losses are: For laminar flow: KTubes := 3.25 NTubePasses - 1.5. For turbulent flow: KTubes := 2.00 NTubePasses - 1.5. The tube Entrance/Exit Loss is then 0.5 G2 KTubes / ρ. The variables used in the above equations are described below. G is the mass flux. KTubes is the K factor determined as noted above. ρ is the fluid density. KTubes is the entrance/exit loss coefficient.