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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
FactNre = Reynolds number correction
Lrb = Equivalent length of return bend, ft
Return Bend Equivalent Length Reynolds Correction

G = Mass velocity, lb/sec-ft2
Di = Inside tube diameter, in
Visc = Viscosity, cp
Equivalent Length Of Return Bends & Elbows: Alternate Method

DescriptionVelocity HeadsEquivalent Length, Tube Dia
Long Radius 90 Elbow0.3016.5
Short Radius 90 Elbow0.5027.5
Long Radius 180 Return0.5027.5
Short Radius 180 Return0.7541.25
Velocity Head1.0055

Calulations based on above data:

Friction Loss:
Dp = 0.00517/di*G2*Vlm*F*Lequiv
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
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: Nominal pipe dia, in:
Pipe straight length, ft:
Fitting type: 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: