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.

L_{equiv} = Fact_{Nre}*L_{rb}

Where,

Fact_{Nre} = Reynolds number correction

L_{rb} = Equivalent length of return bend, ft

Where,

G = Mass velocity, lb/sec-ft^{2}

D_{i} = 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:

D_{p} = 0.00517/d_{i}*G^{2}*V_{lm}*F*L_{equiv}

Where,

D_{p} = Pressure drop, psi

d_{i} = Inside diameter of tube, in

G = Mass velocity of fluid, lb/sec-ft^{2}

V_{lm} = Log mean specific volume correction

F = Fanning friction factor

L_{equiv} = Equivalent length of pipe run, ft

And,

V_{lm} = (V_{2}-V_{1})/ln(V_{2}/V_{1})

For single phase flow,

V_{1} = Specific volume at start of run, ft^{3}/lb