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Equivalent Length Of Return Bends & Elbows: Method used in WinHeat Software

The equivalent length of a return bend may be obtained from the following curves based on Maxwell table and corrected using the Reynolds number correction factor.

Lequiv = FactNre*Lrb
Where,
 FactNre = Reynolds number correction Lrb = Equivalent length of return bend, ft  Where,
 G = Mass velocity, lb/sec-ft2 Di = Inside tube diameter, in Visc = Viscosity, cp
Equivalent Length Of Return Bends & Elbows: Alternate Method

 Description Velocity Heads Equivalent Length, Tube Dia Long Radius 90° Elbow 0.30 16.5 Short Radius 90° Elbow 0.50 27.5 Long Radius 180° Return 0.50 27.5 Short Radius 180° Return 0.75 41.25 Velocity Head 1.00 55

Calulations based on above data:

Friction Loss:
Dp = 0.00517/di*G2*Vlm*F*Lequiv
Where,
 Dp = Pressure drop, psi di = Inside diameter of tube, in G = Mass velocity of fluid, lb/sec-ft2 Vlm = Log mean specific volume correction F = Fanning friction factor Lequiv = Equivalent length of pipe run, ft
And,
Vlm = (V2-V1)/ln(V2/V1)
For single phase flow,
 V1 = Specific volume at start of run, ft3/lb V2 = Specific volume at end of run, ft3/lb

 Pressure Drop with Alternate Fitting Equivalent Length Methods Calculator Coil Data Pipe schedule: Schedule 10 Schedule 30 Schedule 40 Schedule 80 Nominal pipe dia, in: Pipe straight length, ft: Fitting type: Short Radius Elbow Long Radius Elbow Short Radius Return Long Radius Return Number of fittings: Process Data Mass vel., lb/sec-ft2: Viscosity, cp: Spec. vol. at start, ft3/lb: Spec. vol. at end, ft3/lb: Friction factor, Fanning: Inside diameter, in: Maxwell equiv fitting lgth, ft: Alternate equiv fitting lgth, ft: Maxwell total lgth, ft: Alternate total lgth, ft: Maxwell pressure drop, psi: Alternate pressure drop, psi: